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Photochemistry of Triptycene-1,4-Quinone and the control of reaction multiplicity in the solid state Gamlin, Janet Nathalir 1996

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PHOTOCHEMISTRY OF TRIPTYCENE-1,4-QUINONE AND T H E CONTROL OF REACTION MULTIPLICITY IN T H E SOLID STATE By Janet Nathalie Gamlin B.Sc. (Hons), University of British Columbia, 1991 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF CHEMISTRY) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA JUNE 1996 © Janet N. Gamlin, 1996 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. i Department The University of British Columbia Vancouver, Canada DE-6 (2/88) A B S T R A C T Three triptycene-l,4-quinoiie derivatives were synthesized and their photochemical rearrangements investigated in solution and in the solid state. The substituents at the 9,10-bridgehead positions affected the 63 R = H 69 R = CH3 outcome of the photochemical reactions in some novel and unexpected 72 R = CH2OCH3 ways. Upon direct irradiation of triptycene 63 in acetonitrile in the absence of oxygen, formation of the corresponding dibenzosemibullvalene derivative arising from the di-71-methane rearrangement was observed. Photolysis of the methyl substituted compound 69 led to the formation of the corresponding dibenzosemibullvalene compound as well as a dark blue norcaradiene derivative resulting from a carbene intermediate. Triptycene 72 also rearranged to a small extent to a norcaradiene derivative, but primarily underwent a y-hydrogen abstraction reaction giving a colorless dihydroiuran derivative. Additionally, a dark orange benz[tf]aceanthrylene derivative was isolated. Photolysis of triptycene 63 in the presence of oxygen gave a unique triketone derivative. Irradiation of triptycene 63 in chlorinated solvents resulted in chlorinated triptycene quinones. A l l three starting triptycene-1,4-quinones were found to be photo chemically inert in the crystalline state. The photoproduct structures were supported by X-ray crystallographic analysis, and possible mechanisms for their formation are presented and discussed. The ability to enhance triplet photochemical behavior of a probe molecule in the solid state was tested by introducing either heavy atoms, which enhance intersystem crossing, or i i sensitizers, which promote triplet-triplet energy transfer. The efficiency of intersystem crossing as well as triplet-triplet energy transfer was studied by forming salts between photochemically reactive carboxylic acids and either alkali metal hydroxides or organic amines containing an acetophenone moiety. Promising triplet-triplet energy transfer results were established by irradiating salts formed between a P,y-unsaturated keto-acid and several different sensitizer amines. The singlet/triplet photoreactivity of a series of monosubstituted dibenzobarrelene carboxylates (probe molecules) was also analyzed in the crystalline state and in solution. The L i + , Na + , K + , Rb + and Cs + salts of the carboxylates as well as salts with various ammonium ion sensitizer components were prepared in order to control the reaction multiplicity in the solid state by the heavy atom effect or by triplet-triplet energy transfer. By monitoring the ratio of singlet photoproduct (dibenzocyclooctatetraene) to triplet photoproduct (dibenzo-semibullvalene), the effects of heavy atoms linked to a probe molecule were studied. A general explanation for the increase in triplet product formation in the solid state upon the introduction of heavy atoms was suggested. Solid state triplet-triplet energy transfer was also successfully demonstrated in the salts containing the amine sensitizers. The X-ray crystal structures of the salts were studied in order to establish a correlation between the geometric arrangement of the donor and acceptor and the increase in triplet state reactivity. The observed difference in efficiency of the sensitizers was proposed to result from different excited states. iii T A B L E O F C O N T E N T S Abstract ii Table of Contents iv List of Figures x List of Tables xvi List of Graphs xviii Acknowledgments xix Dedication xx I N T R O D U C T I O N 1 CHAPTER 1 PHOTOCHEMICAL INTRODUCTION 1 1.1. General 1 1.2. Solid State Organic Photochemistry 2 1.2.1. The Topochemical Principle 3 1.2.2. Topotactic Reactions 6 1.2.3. Solid State Reaction Efficiency 7 1.2.4. Photochemical Reactivity of Organic Salts 8 1.3. The Di-7i-Methane Rearrangement 9 1.3.1. Reaction Mechanism 10 1.3.2. Reaction Multiplicity 14 1.3.3. Regio selectivity of the Di-7t-Methane Rearrangement 15 1.3.4. Photochemistry of Dibenzobarrelene Derivatives 17 1.3.5. The Oxadi-7i-Methane Rearrangement 20 1.4. The Norrish Type JJ Reaction 22 1.5. The Excited State 25 1.5.1. Triplet-Triplet Energy Transfer 26 1.5.2. The Heavy Atom Effect 29 iv 1.5.3. The Heavy Atom Effect in Zeolites 33 1.6. Objectives of Present Research 35 R E S U L T S A N D D I S C U S S I O N 41 P A R T I P H O T O C H E M I S T R Y O F T R D ? T Y C E N E - 1 , 4 - Q U I N O N E 41 CHAPTER 2 GENERAL ORGANIC SYNTHESIS 41 2.1. Preparation of 9,10-DihydJO-9,10[l\2']benzenoanthracene-l,4-dione (63) 41 2.2. Synthesis of Anthracene Derivatives 42 2.3. Preparation of 9,10-Disubstituted-9,10-dihydro-9,10[l',2']benzeno-anthracene-l,4-dione Derivatives 43 2.4. Preparation of 5- and 6-Chloro-9,10-dihydro-9,10[l',2']benzeno-anthracene- 1,4-diones 45 CHAPTER 3 PHOTOCHEMICAL STUDIES OF 9,10-DfflYDRO-9,10[l',2'] BENZENOANTHRACENE-1,4-DIONE (63) 47 3.1. Photochemical Results Upon Direct Irradiation of 63 48 3.1.1. Structure Elucidation of Sernibulrvalene 80 49 3.1.2. Regioselectivity of Semibulrvalene Photoproduct Formation 51 3.2. Photochemical Results Upon Irradiation of 63 in Acetone 53 3.2.1. Structural Assignment of Triketone 81 53 3.2.2 Mechanistic Speculation on the Formation of Triketone 81 57 3.3. Photolysis of Quinone 63 in Chlorinated Solvents 61 3.3.1 Structural Assignment 62 3.3.2 Mechanism for Formation of Chlorinated Product 75 65 3.3.3 Mechanism of Formation of Chlorinated Photoproduct 74 68 3.4. Solid State Reactivity of Triptycene- 1,4-quinone (63) 71 CHAPTER 4 PHOTOCHEMICAL STUDIES OF 9,10-DfflYDRO-9,10-DIMETHYL-9,10[1',2']BENZENOANTHRACENE-1,4-DIONE (69) 77 4.1. Photochemical Results Upon Direct Irradiation 77 4.1.1. Photoproduct Structure Elucidation 77 4.1.2. Mechanism of Formation of Semibullvalene 102 and Norcaradiene Derivative 103 83 4.1.3. The Midnight- Blue Color of Norcaradiene 103 86 4.1.4. Solvatochromic Effect of Norcaradiene 103 90 CHAPTER 5 PHOTOCHEMICAL STUDIES OF 9,10-BIS(METHOXYMETHYL) -9,10-DfflYDRO-9,10[l',2']BENZENOANTHRACENE-l,4-DIONE (72) 93 5.1. Photorearrangement of 72 in Acetonitrile 93 5.1.1. Structure Elucidation of Photoproducts 103,110 and 111 94 5.1.2 Mechanism for Formation of Dihydrobenzofuran 111 99 5.1.3 Structure-Reactivity Analysis of Quinone 72 102 5.1.4 Structure Elucidation of Product 112 104 5.1.5. Mechanism for the Formation of Benz[a]aceanthrylene 112 107 P A R T H T H E C O N T R O L O F R E A C T I O N M U L T I P L I C I T Y I N T H E S O L I D S T A T E : I O N I C S E N S I T I Z E R S A N D I O N I C H E A V Y A T O M E F F E C T S i l l CHAPTER 6 GENERAL ORGANIC SYNTHESIS 112 6.1. Prep aration of (3, y-Unsaturated Ketones 112 6.2. Preparation of p-Acetyl-AyV-dimethylbenzylamine (128) 113 6.3 Preparation of 9,10-Dihydro-9,10-ethenoanthracene Acids 114 vi CHAPTER 7 THE PHOTOCHEMISTRY OF 0, y-UNSATURATED KETONES 116 7.1. The Solution Phase Photochemistry of Pentanone Derivative 121 116 7.2. The Solid State Photochemistry of Pentanone Derivative 121 and its Alkali Salts 117 7.3. The Photochemistry of Ionic Sensitizer Salts of Pentanone Derivative 121 118 7.4. The Solution Phase Photochemistry of Hexanone Derivative 125 121 CHAPTER 8 THE PHOTOCHEMISTRY OF 9,10-DHTYDRO-9,10-ETHENO ANTHRACENE DERIVATIVES 127 8.1. Photolysis of ll-Hydroxymethyl-9,10-(lihydro-9,10-ethenoanthracene (131).. 127 8.2. Triplet-Triplet Energy Transfer in Zeolites 129 8.3. Photolysis of 13-(ll-Methyl-9,10-dihydro-9,10-ethenoanthracenyl) succinate (132) 131 8.4. The Heavy Atom Effect in the Photochemistry of Succinate 132 133 8.5. Photolysis of 13-(ll-Methyleneoxy-9,10-dihy(ko-9,10-ethenoanthracenyl) acetic Acid (133) 135 8.6. The Heavy Atom Effect in the Photolysis of Acetic Acid Derivative 133 137 8.7. Structural Elucidation of Cyclooctatetraene and Semibulrvalene Photoproducts 143 CHAPTER 9 TRIPLET-TRIPLET ENERGY TRANSFER IN A TWO-COMPONENT CRYSTALLINE SYSTEM 146 9.1. Photochemical Results Upon Irradiation of Salts 164,166, and Complex 165 146 9.2. Structure-Reactivity Analysis of Salts 164, 166, and Complex 165 151 9.3. UV/VIS Analysis of Salts 164,166, and Complex 165 157 9.4. Energy State Analysis of Salts 164,166 and Complex 165 159 vii E X P E R I M E N T A L 161 CHAPTER 10 PREPARATION OF SUBSTRATES 161 10.1. General Procedures 161 10.2. Preparation of Photochemical Substrates 165 10.2.1. 9,10[r,2']Benzenoanthracene-l,4-dione Derivatives 165 10.2.2. 2-(l-Cyclopentenyl)cyclopentanones and 2-(l-Cyclohexenyl) cylohexanones 186 10.2.3. 9,10-Dihydro-9,10-ethenoanthracene Derivatives 198 10.3. Salt Formation of Photochemical Substrates 207 10.3.1. Sensitizer Salts Formed with 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 207 10.3.2. Alkali Metal Salts Formed with 9,10-Dihydro-9,10-ethenoanthracene Derivatives 210 10.3.2.1. Alkali Metal Salts Formed with Succinate Derivative 132.... 210 10.3.2.2. Alkali Metal Salts Formed with Acetic Acid Derivative 133 213 10.3.3. Sensitizer Salts Formed with Acetic Acid Derivative 133 218 CHAPTER 11 PHOTOCHEMICAL STUDIES 223 11.1. General Procedures 223 11.2. Photolysis of Substrates 225 11.2.1. Photolysis of 9,10[r,2']Benzenoanthracene-l,4-dione Derivatives in Solution 225 11.2.2. Photolysis of 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 in Solution 237 11.2.3. Photolysis of 9,10-Dihydro-9,10-ethenoanthracene Derivatives in Solution 239 11.2.4. Photolysis of 9,10-Dihydro-9,10-ethenoanthracene Derivatives in the Solid State 252 viii 11.3. Photochemical Studies of Salts 253 11.3.1. Photolysis of Sensitizer Salts Formed with 2-(l-Cyclopentenyl)cyclo-pentanone Derivative 121 253 11.3.2. Photolysis of Alkali Metal Salts of 9,10-Dihydro-9,10-ethenoanthracene Derivatives 255 11.3.3. Photolysis of Sensitizer Salts Formed with Acetic Acid Derivative 133 258 R E F E R E N C E S 260 ix L I S T O F F I G U R E S Figure Caption Page 1.01. Photochemistry of trans-Cinnamic Acid (1) in the Crystalline State and Solution 4 1.02. Cohen's Concept of Reaction Cavity 5 1.03. Photodimerization of Cyclopentanone 5 6 1.04. Plots of Changes in Quantum Yield as a Function of Reaction Progress 8 1.05. Photodimerization of Acridizinium Salt 7 9 1.06. Mechanism of the Di-7r-Methane Rearrangement 10 1.07. Experimental Exploration of Biradical I in the Di-7t-Methane Rearrangement 12 1.08. Deuterium Labeling Experiment 13 1.09. Multiplicity-Dependent Photochemistry of Barrelene 15 1.10. Regio selective Di-7t-Methane Rearrangements 16 1.11. Photorearrangement of Dibenzobarrelene Derivative 27 18 1.12. Enantio selective Photorearrangement of Dibenzobarrelene 30 19 1.13. Photorearrangements of 3, y-Unsaturated Ketones 20 1.14. State- Selectivity of P, y-Unsaturated Ketone Photochemistry 21 1.15. Reaction Pathways for ODPM Rearrangement and [1,3]-Acyl Shift 22 1.16. Norrish Type n Reaction Mechanism 23 x 1.17. Representation of Hydrogen Abstraction Geometry and Arrangement of Atomic Orbitals 24 1.18. Energy Diagram for Selected Transitions 25 1.19. Benzoyl (Donor)-Naphthyl (Acceptor) Systems 43 and 44 28 1.20. Experimental Example of the External Heavy Atom Effect 30 1.21. Exp erimental Example of the Internal Heavy Atom Effect 30 1.22. Photolysis of P, y-Unsaturated Ketone 51a and 51b 31 1.23. Photolysis of Enone 54 32 1.24. Xanthone 33 1.25. 1 l,12-Diester-9,10-ethenoanthracene Derivatives 36 1.26. Series of Triptycene-l,4-quinone Studied 37 1.27. P, y-Unsaturated Ketone and Sensitizers Selected for the Study of Triplet-Triplet Energy Transfer 38 1.28. Series of 9,10-Dihydro-9,10-ethenoanthracene Derivatives and Sensitizers 39 2.01. Preparation of 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63) 41 2.02. Preparation of 9,10-Bis(chloromethyl)anthracene (64), 9,10-Dimethyl-anthracene (65) and 9,10-Bis(methoxymethyl)anthracene (66) 42 2.03. Preparation of 9,10-Dihydro-9,10-dimethyl-9,10[l',2']benzeno-anthracene-l,4-dione (69) 43 2.04. Preparation of 9,10-Bis(methoxymethyl)-9,10-dihydro-9,10[1 ',2']benzeno-anthracene-l,4-dione (72) 44 xi 2.05. Structures of 5-Chlorotriptycene- 1,4-quinone (73) and 6-Chlorotriptycene-l,4-quinone (74) 45 2.06. Possible Chlorinated 2 : 1 Adducts 77a-d 46 2.07. Preparation of 5-Chloroanthracene (79a) and 6-Chloroanthracene (79b) 46 3.01. Numbering System for Triptycene- 1,4-quinone (63) and its Charge-Transfer Excited State (63a) 47 3.02. Dibenzosemibullvalene 80 from the Irradiation of Triptycene-1,4-quinone (63) 48 3.03. lH NMR Spectrum of Dibenzosemibullvalene 80 50 3.04. Regio selectivity of the Di-7i-Methane Rearrangement of 63 52 3.05. Triketone 81 from the Irradiation of Triptycene- 1,4-quinone (63) 53 3.06. Cyclopenten-3,5-dione (82) 54 3.07. lH NMR Spectrum of Triketone 81 55 3.08. X-ray Crystal Structure of Triketone 81 56 3.09. Proposed Mechanism for Formation of Triketone 81 57 3.10. Carbene Mechanism for Formation of Triketone 81 58 3.11. Reaction Pathway Between Carbene 87 and Molecular Oxygen 59 3.12. Carbene Trapping Mechanism 60 3.13. Chlorinated Photoproducts from the Irradiation of Triptycene-1,4-quinone (63) 61 3.14. lH NMR Spectrum of Triptycene- 1,4-quinone (63) 63 xii 3.15. *H NMRNOE Experiment for Triptycene- 1,4-quinone (63) 64 3.16. Addition of Hydrogen Chloride to 1,4-Benzoquinone (60), Followed by Oxidation 66 3.17. Proposed Mechanism for Formation of Chlorinated Product 75 67 3.18. Addition of Chlorine Atom at Carbon 4a of Intermediate 96 68 3.19. Proposed Mechanism for Formation of Chlorinated Photoproduct 74 69 3.20. Proposed Mechanism for Hydrogen Chloride Formation 70 3.21. Packing Diagram for Triptycene-1,4-quinone (63) 72 3.22. X-ray Crystallographic Structure of Triptycene-1,4-quinone (63) 73 3.23. Intramolecular Distances between Ring Centers 1, 2 and 3 74 3.24. Example of an Unreactive Photoreaction in the Solid State 75 3.25. Crystal Lattice Steric Effects in Compound 100 76 4.01. Photolysis of 69 in Acetonitrile 77 4.02. T i NMR Spectrum of Norcaradiene 103 79 4.03. X-ray Crystallographic Structure of Norcaradiene 103 82 4.04. Photolysis of Triptycene 104 83 4.05. Trapping of Carbene 104a 84 4.06. Proposed Mechanism for Formation of Photoproducts 102 and 103 85 4.07. Charge-Transfer from an Excited Donor (D*) to Acceptor (A) 87 4.08. Naphth[2,3-a]azulene-5,12-dione (108) and Norcaradiene 103 88 4.09. Example of a Photochromic 9,10-Ethenoanthracene Derivative 109 89 xiii 4.10. UV/VIS Absorption Spectrum of 103 in Acetonitrile and Chloroform 91 5.01. Photolysis of 72 in Acetonitrile 93 5.02. ' H N M R Spectrum of Dihydrofuran Derivative 111 96 5.03. Mechanism for the Formation of Dihydrofuran Derivative 114 100 5.04. Mechanism for the Formation of Dihydrofuran Derivative 111 101 5.05. X-ray Crystal Structure of Quinone 72 103 5.06. Tf N M R Spectrum of Benz[a]aceanthrylene Derivative 112 105 5.07. Photoreaction of 1,4-Dimethoxytiptycene (115) 108 5.08. Proposed Mechanism for the Formation of Benz[a]aceanthrylene 112 109 6.01. Preparation of 2-(l-Cyclopentyl)cyclopentanone (121) 112 6.02. Preparation of 2-( l-Cyclohexenyl)cyclohexanone (125) 113 6.03. Preparation of/?-Acetyl-AyV-dimethylbenzylamine (128) 114 6.04. Preparation of 9,10-Dihydro-9,10-ethenoanthracene Acid 132 and 133 115 7.01. Photolysis of Keto-Acid 121 116 7.02. Photolysis and Work-Up of Salts 138,139 and 140 119 7.03. l(l-Cyclohexen-l-yl)-2-oxocyclohexaneacetic Acid (125) 121 7.04. Rearrangement of 2-Cyclohexenylidenecyclohexanone (123) and 2-(l-Cyclohexenyl)cyclohexanone (123a) 122 7.05. Dieneone 142 Studied by Direct Irradiation 123 xiv 7.06. X-ray Crystallographic Structure of Keto-Acid 125 124 7.07. Stereo Diagram of Keto-Acid 125, Showing Hydrogen Bonding 125 8.01. Photolysis of Dibenzobarrelene 131 127 8.02. Photolysis of Succinate 132 132 8.03. Photolysis of Acetic Acid Derivative 133.. 136 8.04. Tub-shape of Cyclooctatetraene (163a) 144 9.01. Photolysis of Salts 164,166 and Complex 165 146 9.02. Stern-Volmer Equation 147 9.03. Packing Diagram and Stereoview of Salt 164 152 9.04. Packing Diagram and Stereoview of Complex 165 153 9.05. Packing Diagram and Stereoview of Salt 166 154 9.06. Different Representation of Packing Diagrams for Salts 164 and 166 156 9.07. UV/VIS Absorption Spectrum of Salt 166 in Methanol 157 9.08. Structural Comparison of 4'-Aminobutyrophenone (168) and 4'-Piperazinoacetophenone (167) 158 9.09. Examples of Different States for Aryl Ketones 160 xv L I S T O F T A B L E S Figure Caption Page I Angles Between the Quinone and Benzene Moieties 71 JJ Intermolecular and Intramolecular Distances Between Ring Centers 75 m *H N M R (500 MHz) and 1 3 C N M R (125 MHz) Data for Norcaradiene 103 80 IV *H N M R Data (500 MHz) for Norcaradiene 103 81 V UV/VIS Absorption Data for Norcaradiene 103 90 V I UV/VIS Absorption Data for Benzoquinone 90 VII J H N M R (500 MHz) and 1 3 C N M R (125 MHz) Data for Dihyfaofuran 111 97 Vm *H N M R Data (500 MHz) for Dihydrofuran 111 98 DC Crystallographically Determined Angles for Quinone 72 104 X *H N M R (500 MHz) and 1 3 C N M R (125 MHz) Data for Benz[fl]aceanthrylene Derivative 112 106 X I *H N M R Data (500 MHz) for Benz[a]aceanthrylene Derivative 112 107 XII Hydrogen Abstraction Geometric Parameters for 125 126 X m Photolysis Results of Alcohol 131 128 X I V Zeolite Photolysis Results 130 X V Photolysis Results of Succinate 132 133 X V I Photolysis of Acetic Acid Derivative 133 137 X V I I Relationship between Lifetime and Concentration of a Quencher 148 xvi X V m Solid State Photolysis Results of Sensitizer Salts 164, 166 and Complex 165 149 XDC Distances (< 7.5 A) Between Chromophores 155 X X Photoproduct Mixture Composition of Derivatives 131,132 and 133a 252 X X I Photoproduct Mixture Composition of Salts 138, 139 and 140 254 X X I I Photoproduct Mixture Composition of Salts 153 and 154 255 X X m Photoproduct Mixture Composition of Salts 158 to 162 257 X X I V Photoproduct Mixture Composition of Salts 164,166 and Complex 165 258 xvii L I S T O F G R A P H S Figure Caption Page I Irradiation Results of Alkali Salts of Succinate 132 135 TJ Irradiation Results of Alkali Salts of Acetic Acid 133 138 in Conversion versus Irradiation Time Experiments 141 IV Irradiation Results of Methyl Ester of Acid 133 in Alkah-Containing Zeolites 142 V Reactant Conversion of Salts 164,166 and Complex 165 versus Irradiation Time 150 xviii A C K N O W L E D G M E N T S I would like to thank my research supervisor Professor John R Scheffer for his valuable guidance, his encouragement and the many helpful suggestions he has offered. His expertise and dedication in the field of photochemistry have been a source of inspiration to me. I would also like to extend my gratitude to Professor James Trotter and the members of his research group, Dr. Gunnar Olovsson, Dr. Bozena Borecka and Dr. Tai Y u Fu, who are responsible for the X-ray structures in this thesis. Also, special thanks go to the members of the N M R laboratory, Mass-Spec faculties, Mr. Peter Borda and the attentive staff of the departmental services. Furthermore, I would like to express my thankfulness to my co-workers in the lab, especially Matt Netherton and Dr. Heiko Ihmels for proof-reading my thesis. Their thoroughness, promptness and invaluable comments were very much appreciated. Special recognition also goes to Jeffery Raymond for his encouragement. Finally, I am also grateful for all the help I have received from my friends in the department, who have made my life at U.B.C. a zestful and memorable experience. xix D E D I C A T I O N To my parents xx Introduction I N T R O D U C T I O N CHAPTER 1 PHOTOCHEMICAL INTRODUCTION 1.1. General In the early 20th century, photochemists made use of the sun as a radiation source in order to induce chemical reactions, as demonstrated by Ciamician, who conducted his research on the roof of the chemical research building in Bologna.1 Nowadays, experiments are more carefully controlled and the use of narrower bands of electromagnetic radiation enables researchers to investigate photochemical reactions systematically. There are many areas of photochemistry that have been addressed increasingly over the years. Among them is synthetic organic photochemistry. Light can be remarkably selective causing chemical reactions. A structurally simple molecule may be converted by the process of irradiation into a rather complex structure, which might be otherwise difficult to synthesize. Another more recent area of interest that photochemists are concerned with is the development of devices that can be reversibly written and read by light.2 Compounds that exhibit photochromism, a photoinduced transformation photochemically or thermally reversible, resulting in molecules with different electronic properties,3 are used in the development of Photochromic Microimage Processing leading to ultrairncrofihris.4 Through this technique a standard size book page can be reduced to less than 1 mm in height. Further development in the field of organic photochemistry may offer promising advancements in the field of computers and electronics. 1 Introduction 1.2. Solid State Organic Photochemistry The history of solid state chemistry dates back to 1828 when Friedrich Wohler observed the thermal transformation of crystalline ammonium cyanate into urea.5 Combining photochemistry and solid state reactivity, Trommsdorff5 showed in 1834 that crystals of santonin, much later shown to have the skeleton of a sesquiterpene, turned yellow and cleaved when exposed to sunlight. During the late 19th and early 20th centuries, a greater understanding of the interaction of matter with light was obtained as a wide variety of photochemical reactions were investigated by the pioneers of photochemistry.7 As technology advanced, X-ray crystallography was used as a tool to explore molecular conformation and packing arrangements of starting materials and products in the crystal, providing a greater insight into structure-reactivity relationships. Extensive research in the field of solid state organic photochemistry has shown that the molecular crystal lattice plays an important role in controlling organic photoreactivity.8 This work has demonstrated that photoreactions are capable of giving different products in the solid and solution states as a result of changes in reaction regio-, stereo- and enantioselectivity. Entirely different photoproducts may arise from solid state irradiation experiments as a result of physical restraints restricting the movements found in the solution phase. Reactions in the solid state are governed by two important factors, namely the conformation and the packing arrangement of the reacting molecules. In isotropic phases, a flexible molecule may adopt many conformations due to fast equilibrium between them. However, in the crystalline state, the molecule will rarely take up 2 Introduction more than one conformation and most commonly crystallizes in or near its miriimum energy conformation.9 Increased selectivity arises from the limited motion in crystals which consequently affects reactions that are sensitive to the conformation of the reactant. Furthermore, the packing of the reactant in a crystal is important, since the anisotropic environment of the crystal lattice can affect the course of the reaction by restricting the movement within the crystal. Using X-ray crystallography, mechanistic information on the preferred interatomic distances and angles required for a reaction to proceed can be determined. A number of review articles dealing with differential reactivity in solution and the solid state have appeared in recent years.10 1.2.1. The Topochemical Principle The topochemical principle was proposed in 1918 by Kohlshutter,11 who stated that "reactions in solids are dependent on the constraining three dimensional environment in which the molecules exist". This first principle of solid state chemical reactivity recognized the restrictive environment a crystal may impose on a given reaction. More than 40 years later, the topochemical postulate was reinvestigated with the introduction of X-ray crystallography by Schmidt and co-workers,12 who examined the [2+2] photocycloaddition reaction of trans-cinnamic acid derivatives in the crystalline phase. Figure 1.01 illustrates the three packing forms (a, |3, y) for unsubstituted and/or substituted trans-cinnamic acids. In order for a photocycloaddition to occur, the center-to-center distance between the two neighboring double bonds was proposed to be less than 4.2 A. Furthermore, the parallel ahgnment of the reacting double bonds played an important role in the reaction. 3 Introduction cis-trans isomerization Figure 1.01. Photochemistry of trans-Cinnamic Acid (1) in the Crystalline State and Solution. Hence, by determining the intermolecular distances and orientations between the reactive centers of frtf^-cinnamic acid, Schmidt demonstrated that solid state reactions are controlled by strict size and shape limitations. A "reaction cavity" can be thought of as arising from the non-bonding repulsive interactions between a reacting molecule and its closest neighbors. This concept was first introduced by Cohen,1 3 who visualized a reacting molecule in a crystal as a substance 4 Introduction that was residing in a cavity created by its neighboring molecules, whose shape resembled the packing of the crystal. As the reaction would proceed, the surface of the cavity walls could become distorted as a result of pressure exerted by atomic movement. According to Cohen,1 3 the closely packed crystal lattice restricted the degree of distortion of the cavity wall. Solution Products Transition States Figure 1.02. Cohen's Concept of Reaction Cavity. As indicated in Figure 1.02, the reaction proceeding from within the cavity walls is not only limited by the number of reaction partners (if any) but also by the extent of molecular displacement and conformational motions.14 Hence, a reaction is predicted to be topochemically feasible i f the shape and size of the transition state resembles the cavity. 5 Introduction The concept of the reaction cavity has further been explored by Ramamurthy et al,15 who investigated the reactivity in a variety of organized and constrained media such as organic inclusion hosts, zeolites, micelles and liquid crystals. 1.2.2. Topotactic Reactions One goal of research in organic solid state photochemistry is the discovery of single crystal-to-single-crystal transformations, known as topotactic reactions.16 This rare phenomenon occurs when a single crystal of the reactant retains its singularity while being smoothly and continuously transformed into a single crystal of the product. One reaction that has been extensively studied by Jones et al.11 is the photodimerization of 2-benzylidene-5-benzyl cyclopentanone (5) in the solid state. Photolysis of crystalline compound 5 resulted in a complete conversion to the [2+2] adduct 6 with the retention of molecular single crystallinity. The packing arrangement of the reactant and product showed that the reaction involved relatively small amounts of molecular and atomic motion, which was demonstrated by following the topotactic process by X-ray crystallography. 5 6 Figure 1.03. Photodimerization of Cyclop entanone 5. 6 Introduction 1.2.3. Solid State Reaction Efficiency The photochemical conversion of a reactant to a photoproduct in the solid state is usually limited, as the reactivity often changes as a function of reaction progress. The quantum yield of a photochemical reaction is defined as the number of moles of product formed divided by the number of photons absorbed by the system.18 Ideally, the quantum yield in a solid state reaction remains unaltered from the lowest to the highest conversion values as shown in the first order plot in Figure 1.04 (a).14 However, most commonly, the environment and/or crystal phase may continuously change, leading to a decrease in quantum yield as a function of time (Figure 1.04 (b)). Once the product formation begins, the reacting species in the lattice may absorb the light resulting in poor photon penetration through the crystal. The light absorbing properties of the reactant may also be diminished by the generation of defects in the lattice. These are formed by the different three-dimensional geometries corresponding to the reactants and products. Scattering of light back to the surface will take place and the reaction of the crystal will be inhibited. Reaction efficiency may also be reduced by prolonged photolysis as a result of the crystal cracking or becoming cloudy. Melting of the crystal may facilitate the reaction leading to fewer constraints on molecular motion (Figure 1.04 (c)), or even result in the formation of different products. 7 Introduction irradiation Time Irradiation Time Irradiation Time R = Reactant Figure 1.04. Plots of Changes in Quantum Yield as a Function of Reaction Progress. 1.2.4. Photochemical Reactivity of Organic Salts Research in solid state organic photochemistry has concentrated primarily on the chemical reactivity of molecular crystals. An attractive system that has not received much attention is a crystal that is ionic in nature, such as a salt of the type RCOOTVT or RNHs^" . Whereas molecular crystals are held together by relatively weak dipole-dipole and van der Waals attractive forces, and sometimes by hydrogen bonding, ionic crystals are held together by relatively strong Coulombic attractive forces. This difference gives salts the advantage of being not only high melting solids, reducing the chances of crystal breakdown, but may also lead to higher conversions without the loss of crystallinity and topochemical control. Jones and co-workers19 showed, for example, that acridizirmim salts underwent topotactic transformations upon irradiation in the solid state yielding the [4+4] photodimer 8. 8 Introduction 2 X = C1, Br, I Figure 1.05. Photodimerization of Acridizinium Salt 7. Upon photolysis, single-crystal-to-single crystal conversion was observed in the halide salts of 7 resulting in the corresponding dimer 8. X-ray structure analysis showed that the dimerization process requires a substantial amount of movement in the crystal lattice. 1.3. The Di-71-Methane Rearrangement The photoreaction investigated in this thesis is the di-7C-methane rearrangement, a photo-induced unimolecular process, recognized as one of the most general and thoroughly studied of all organic photoreactions.20 This photochemical reaction is known to occur in compounds possessing two 7i-bonds separated by an sp3 hybridized carbon atom. Upon irradiation, the compounds can be converted into products containing a vinylcyclopropane moiety. The mechanism was first proposed by Howard Zimmerman in 1967, who postulated that the initial step involves bonding between C2 and C4 to afford a 1,4 biradical (9a), followed by a homolytic cyclopropane ring cleavage to give a 1,3 biradical (9b) and subsequent ring closure to the vinylcyclopropane unit (10).21 Figure 1.06 shows the mechanism for the simplest case of 1,4-pentadiene. 9 Introduction Methane Carbon V Y •• • r : 9 9a 9b 1,4-Diene Biradical I Biradical JJ Figure 1.06. Mechanism of the Di-7t-Methane Rearrangement. The 7t-moieties may be either isolated or conjugated and may be part of a cyclic or an acyclic system. The biradical species 9a and 9b were first considered by Zimmerman as approximations of species involved, but recently Zirnmerman et al.22 provided evidence that biradical 9a is a true thermally equilibrated intermediate. 1.3.1. Reaction Mechanism Despite extensive investigations of the di-7C-methane rearrangement over the last three decades, the mechanistic pathway has still not been completely delineated. In order to confirm the existence of the cyclopropyldicarbinyl biradical 9a (Figure 1.06), Zimmerman chose to explore the di-7t-methane rearrangement of dideuterio-m-cyanodibenzobarrelene 11.23 The irradiation experiment with acetophenone in benzene was shown to be regioselective giving sermbultvalene 12 as the sole product. Figure 1.07 depicts the four possible reaction pathways. The experimental results indicated that the reaction followed pathway I demonstrating that the initial bridging step was favored by the cyanobenzo ring, rather than the benzo ring. Also, in reaction pathway I the 10 5 10 Vinylcy clopr op ane Introduction cyano-group stabilized biradical I (11a). Conversely, pathway JJ resulted in the cyano-stabilization of biradical II ( l i d ) . Reaction pathways in and IV did not apply as they did not afford an odd-electron stabilization by the cyano-substituent. The regioselectivity was proposed to be controlled by the formation of the lowest-energy biradical I. Zirnmerman23 also conducted ab initio theoretical calculations in order to explore the existence of biradical I further. 11 Introduction Figure 1.07. Experimental Exploration of Biradicals I in the Di-7t-Methane Rearrangement of Cyanodibenzobarrelene 11. 12 Introduction In order to verify the 1,3-biradical JJ (9b, Figure 1.06) in the di-71-methane rearrangement of bicyclic barrelene systems, Zimmerman conducted deuterium labeling experiments.21b'21c The results showed that triplet-sensitized irradiation of barrelene 16 led to a 1 : 1 ratio of semibuhvalenes 17 and 18 as a result of radical coupling reactions occurring in the biradical resonance structures of 16b and 16c. This evidence supported the presence of the 1,3-biradical, acting as an actual intermediate. 18 Figure 1.08. Deuterium Labeling Experiment. 13 Introduction 1.3.2. Reaction Multiplicity Another aspect to be considered is the multiplicity-dependency of the di-7t-methane rearrangement.24 Generally, acyclic compounds rearrange via their singlet excited states, whereas cyclic compounds undergo the rearrangement efficiently through their triplet excited states.25 This can be explained in terms of how the geometry of the diene unit favors a particular reaction pathway. The competing pathways consist of cis-trans isomerization26 and [2+2] cycloaddition.27 A comparison of the rate constants for each of these processes203 shows that the triplet state of an acyclic system favors cis-trans isomerization over the di-u-methane rearrangement. However, a cyclic system that is unable to cis-trans isomerize prefers the latter pathway. Singlet State : ^ C A > ^ D P M > ^ c n Triplet State : 1kCTi > ^ D P M > ^ C A where C A = Cycloaddition Reactions D P M = Di-7i-Methane Rearrangement CTI = Cis-Trans Isomerization Hence, the di-7t-methane rearrangement of acyclic diene systems generally occurs from the singlet excited state and is often in competition with cycloaddition reactions. The barrelene system (Figure 1.09) illustrates distinct reactivity of a substrate based on the multiplicity of the excited state. This cyclic di-7t-methane system rearranges to semibuhValene 20 upon triplet-sensitized photolysis as shown by Zimmerman and co-workers,21 whereas direct irradiation results in a [2+2] 14 Introduction cycloaddition forming the quadricyclene-hke intermediate 19c, followed by the thermally allowed [4+2] retrocycloaddition to give 19d. This intermediate then rearranges to produce cyclooctatetraene 21.28 19 Barrelene T l Si 19a 19b Ti = Sensitized Irradiation, Triplet Reaction Si = Direct Irradiation, Singlet Reaction 19c Not Isolated 19d Not Isolated 20 Semibullvalene 21 Cyclooctatetraene Figure 1.09. Multiphcity-Dependent Photochemistry of Barrelene. 1.3.3. Regioselectivity of the Di-7i-Methane Rearrangement In addition to the formation of distinct photoproducts arising from different excited states, the di-7t-methane rearrangement can also yield regioisomeric products resulting from two differentially substituted 7t-bonds, as shown in Figure 1.10.20a Regioselectivity studies have played an important role in understanding and estabh'shing the reaction mechanism. For instance, the regioselectivity has been correlated with different stabilities of the two possible biradical species that can be formed in the initial step of the reaction mechanism.20 If the n-bonds of the diene 15 Introduction system are part of an aromatic unit, the reaction will proceed in such a manner that the aromaticity will be re-established in the final product. Additionally, initial bonding usually gives the more stable intermediate. Figure 1.10. Regioselective Di-7t-Methane Rearrangements. Hence, an electron withdrawing group will likely be part of the final cyclopropyl ring (23), whereas an electron donating group will be attached to the double bond of the product (25), due to the reduced ability of the radical to delocalize.20a The carbinyl carbons of the cyclopropyldicarbinyl biradical (22a or 24a) are believed to be electron rich. Opening of the 16 Introduction cyclopropyl ring was proposed to result in the transfer of this negative charge onto the carbon which participates in the double bond formation. An electron withdrawing substituent may aid the neighboring carbinyl carbon in rmintaining its electron-rich character and in not taking part in the formation of the 7t-bond (23). On the other hand, an electron donating group may act as a chiving force for the adjacent carbinyl carbon to participate in the ring opening step, converting it into the %-bonded carbon(25). 1.3.4. Photochemistry of Dibenzobarrelene Derivatives The study of barrelenes has been expanded to include the photoreactions of benzobarrelenes,29 3 0 dibenzobarrelenes31 and notably to various ester derivatives32'33'34 of the same. The possibility of obtaining different regioisomers from photoreactions of unsymmetrically substituted dibenzobarrelenes has also been explored. The first report of a photochemical study of this type, by Ciganek,32 dates back to 1966. As seen from Figure 1.11, dibenzobarrelene ester 27 has four initial bonding possibilities. The reaction pathway involving initial benzo-benzo bridging may be ruled out, due to the loss of aromaticity in two phenyl rings as opposed to the disruption of only one aromatic ring occurring in benzo-vinyl bonding. This leaves two reaction pathways, the first involving benzo-vinyl bonding on the unsubstituted side, the second benzo-vinyl bonding on the ester side. Pathway "a" is preferred as a result of the radical stabilization by the ester carbonyl group leading to the formation of the dibenzosemibuHvalene derivative 28. 17 Introduction Figure 1.11. Photorearrangement of Dibenzobarrelene Derivative 27. The mechanism postulated for this transformation is in agreement with Zirnmerman's proposal. Ciganek also demonstrated that solution irradiation of the dimethyl dibenzobarrelene diester derivative resulted in a dibenzosemibullvalene photoproduct. More recent studies investigating the photolysis of dibenzobarrelene diesters in the solid state have been carried out by Scheffer, Trotter and co-workers,35 who conducted structure-correlation experiments. Dibenzobarrelene derivative 30 was investigated in solution and the solid state.353 One interesting aspect of this compound was that it was found to crystallize in two different dimorphic forms, belonging to the achiral space group Pcba or the chiral space group P2i2i2i. 18 Introduction Figure 1.12. Enantio selective Photorearrangement of Dibenzobarrelene 30. Photolysis of diester 30 in solution or in a single Pcba crystal gave a racemic rriixture of sernibullvalene 31, whereas single crystal photolysis of the chiral P2i2i2i morphology led to the formation of photoproduct 31 with >95% enantiomeric excess. The initial bridging step was suggested to be the source of enantio selectivity resulting in different reaction pathways. Crystallographic analysis was used to determine the absolute configuration of the starting material and its photoproduct in order to differentiate between the different pathways. Furthermore, the lattice environment of the starting material was analyzed showing that steric crowding would hinder one of the bonding routes. 19 Introduction 1.3.5. The Oxadi-7t-Methane Rearrangement Another example of a di-7t-methane rearrangement is the structurally analogous oxadi-7t-methane (ODPM) rearrangement.36 This rearrangement takes place upon triplet excitation of a P, y-unsaturated ketone 32, and leads to a cyclopropyl ketone 34 formed via a formal 1,2-sigmatropic acyl shift accompanied by ring closure. Upon direct irradiation of the same ketone, a 1,3-sigmatropic acyl shift37 is often observed, resulting in photoproducts of general structure 33. The competition between the 1,2-acyl shift pathway occurring from the lowest excited triplet state (71, 7t*) and the 1,3-acyl shift from the lowest excited singlet state (n, 7i*) is dependent on the structure of the molecule. A' 33 32 34 Figure 1.13. Photorearrangements of P, y-Unsaturated Ketones. The current state of understanding of the mechanism of the above processes is summarized in Figure 1.14, according to Demuth.3 8 Investigations showed that the 1,3-acyl shift arises not only from the singlet state, but also through intersystem crossing from the singlet ( S i ) to the triplet state (T 2). The O D P M rearrangement is thought to proceed through the Ti state involving an initial 1,2-acyl shift. 20 Introduction 1,2-acyl shift (ODPM) S 2 (j-,7-*) 1 R l . . R 2 1,3-acyl shift Si (n,7t*) T 2 (n,7t*) T l (71 ,71*) 3 1.3-R l • • R2 ~~~~»~.»-~vt> acyl shift 1,2-acyl shift (ODPM) Figure 1.14. State-Selectivity of P, y-Unsaturated Ketone Photochemistry. The O D P M rearrangement and the 1,3-acyl shift have been the subject of many reviews 3 9 ' 4 0 and the possible reaction mechanisms are illustrated in Figure 1.15. The O D P M reaction pathway is analogous to the di-7t-methane rearrangement suggesting the presence of biradicals 35a and 35b. However, the 1,3-acyl shift has been proposed to involve two competitive routes via either a free radical pair 35c (i.e. a fragmentation-recombination mechanism) or via a quasi-concerted process demonstrated by intermediate 35d. Recent theoretical studies have been conducted by Wilsey et al.41 who explored the reaction pathways of the 1,3- and 1,2-acyl shifts by investigating the existence and nature of the "classical" proposed reaction intermediates computationally. Their results supported the reaction pathways represented in Figure 1.15. 21 Introduction v° v° V f f O H ' f L ^ ' CT 35c . / \ ^ H • i r f \ f' *f H - f f-H H 35a / < H 35b H H 36 H H H ODPM product \ | H ^ > 35 X . H H O H H H 35d Figure 1.15. Reaction Pathways for O D P M Rearrangement and [1,3]-Acyl Shift. [l,3]-acyl shift 1.4. Norrish Type II Reaction Another common type of photochemical reaction is the Norrish type II reaction, which involves the intramolecular abstraction of a y-hydrogen atom by a carbonyl oxygen atom.42 The hydrogen abstraction by the excited carbonyl group is suggested to result in the formation of a 1,4-hydroxybiradical intermediate 38a, which may either cyclize to the cyclobutanol 39 (Yang reaction) or fragment to the alkene 42 and enol 40 products (Figure 1.16).42 22 Introduction 41 40 42 Figure 1.16. Norrish Type JJ Reaction Mechanism. The Norrish type JJ reaction has been widely used to create relatively strained ring systems in natural product synthesis,43 and much attention has been devoted to the mechanistic aspects of the process, particularly those concerning the 1,4-biradical intermediate.44 The determination of the geometric requirements for the initial hydrogen abstraction was also of interest. Wagner et al.45 suggested that the geometry for the y-hydrogen abstraction would involve a strain-free, chair-like, six-membered transition state. However, later work by Scheffer, Trotter and co-workers46 4 7 demonstrated that a chair-like transition state is not essential in the crystalline state. Irradiation of a-cycloalkylacetophenones in the solid state showed three types of y-hydrogen abstraction geometries: - chair-like, boat-like and half-chair-like.47 Four parameters were proposed to describe the hydrogen abstraction geometry: (i) d, the distance between the carbonyl oxygen and the y-hydrogen; (ii) co, the angle between the O Hy vector and the carbonyl mean 23 Introduction plane; (iii) 9, the angle between the carbonyl oxygen, the y-hydrogen and the y-carbon; and (iv) A, the angle between the carbonyl carbon, the carbonyl oxygen and the y-hydrogen. (c) Figure 1.17. (a) Representation of Hydrogen Abstraction Geometry, (b) and (c) Arrangement of Atomic Orbitals. The optimal values of these four parameters for a hydrogen abstraction involving the n,7t* excited state of a carbonyl compound have been suggested by Scheffer et al.47 The ideal value for the distance is ca. 2.7 A , which originates from the sum of the van der Waals radii for hydrogen and oxygen (2.72 A ) . 4 8 The preferred value of A lies between 90° and 120° and depends on the nature of the atomic orbitals containing the n-electrons, that can be represented by two types of models. The Kasha Model 4 9 (Figure 1.17 (b)) demonstrates the involvement of a 2p orbital, 24 Introduction forming an angle of 90° with the C=0 axis. Alternatively, the second model, the "rabbit ear" model30 (Figure 1.17 (c)), has an sp2 hybridized atomic orbital leading to an orientation of 120° with respect to the C=0 axis. In the case of the angle co, the most favorable value is co = 0°, in which case the hydrogen is coplanar with the n-orbital on oxygen. The abstracting orbital is thought to be the non-bonding py orbital on oxygen, which lies in the 7i-bond nodal plane, represented by the Kasha Model (Figure 1.17 (b)). In the case of the angle 0, a linear arrangement is thought to be preferred (6 = 180°), however, departures from this value have been observed.51 1.5. The Excited State When an organic molecule absorbs light, a molecular excited state is produced. In the ground state of most organic molecules, electrons exist in pairs with anti-parallel spins. This is referred to as the ground singlet state ( S c ) . Upon irradiation with ultraviolet or visible light, a photon may be absorbed, promoting an electron to the first excited singlet state ( S i ) . hv Y ISC LUMO HOMO Si Ti Figure 1.18. Energy Diagram for Selected Transitions. 25 Introduction As a result of spin-orbit coupling, an electron can flip its spin, resulting in a configuration with parallel spins called the triplet excited state (Ti). This non-radiative transition between vibronic states is referred to as intersystem crossing (ISC), a process that is formally spin-forbidden. Spin-orbit coupling results from the rnbdng of an electron's spin-magnetic moment (s = ± Vz) with the electron's orbital angular moment (1 = 0, 1, 2,...) and depends on the relative orientation between the spin and orbital magnetic moments. Furthermore, spin-orbit coupling is most effective between states which involve both changes in electron spin and orbital types —> 3(n,n*) and can be enhanced by the presence of either paramagnetic compounds (i.e. 0 2 , NO, etc.), or heavy atoms (I, Br, K , Rb, etc.). Other photochemical processes a molecule can undergo after excitation include chemical reaction, fluorescence (Si —?• S 0 + hv), phosphorescence (Ti -» S 0 + hv) or internal conversion (e.g. Si -> SG + heat), a non-radiative process that occurs between two electronic states of equal multiplicity. 1.5.1. Triplet-Triplet Energy Transfer Sensitization methods provide a powerful technique leading to products from the triplet state without obtaining the competing products arising from the singlet state. A triplet-triplet energy transfer (triplet sensitization) involves the transfer of triplet energy from an electronically excited molecule (donor) to its ground state neighbor (acceptor), which then becomes electronically excited. D*(Tj) + A (S0) -> D (S0) + A*(Ti) where D = donor, A = acceptor. 26 Introduction This bimolecular process is more likely to occur i f the excited state of the donor is long-lived (e.g., T T = 10"4 s for acetophenone). The use of a triplet sensitizer (donor) will enable an acceptor molecule to be excited to its triplet state without having directly absorbed a photon. Compounds containing carbonyl groups, such as acetone (E T = 78 kcal/mol),5 2 acetophenone (E T = 74 kcal/mol) and benzophenone (Ex = 69 kcal/mol), have high-energy triplet states and are examples of commonly used sensitizers. The donor triplet state must be of higher energy than the acceptor triplet state to provide for successful exothermic energy transfer. Effective exchange interactions are also facilitated if the donor and acceptor molecules come into close proximity on the order of 10-15 A . 5 3 Intramolecular energy transfer has been investigated by Zimmerman et al.,54 amongst others, who conducted experiments involving the excitation (k > 350 nm) of the benzoyl (donor)-naphthyl (acceptor) system 43. At this wavelength only the benzoyl moiety (n-7t*) was excited, leading to through space energy transfer to the naphthyl group, from which phosphorescence was detected. A triplet-triplet energy transfer efficiency of 100% was observed when the average separation between donor and acceptor, created by a spacer group, was 7 A. Steroid 44, 5 5 although not as efficient = 35%), is another example of a compound that can undergo intramolecular triplet-triplet energy transfer. In this case the estimated distance between donor and acceptor lies around 14 A, thus giving evidence that triplet-triplet energy transfer is distance dependent. 27 Introduction 28 Introduction 1.5.2. The Heavy Atom Effect A n alternative method for generating triplet state-derived photoproducts is by taking advantage of the heavy atom effect. In this case, the triplet state results from intersystem crossing (ISC) from the singlet state. For compounds with large S1-T1 energy gaps, such as alkenes, ISC is very inefficient by itself. Although ISC is spin forbidden, these radiative and radiationless transitions may be enhanced in the presence of atoms possessing a high atomic number. This is referred to as the heavy atom effect and is brought about by the interaction between spin-orbit coupling, among the spin magnetic moment and the orbital angular moment, and a nuclear charge.56 By directly relating the magnitude of the nuclear magnetic field from the motion of the nucleus to the size of the nuclear charge, and therefore atomic number, spin-orbit coupling is found to increase with increasing atomic number.57 The heavy atom may either be attached to the molecule (internal)58 or be located in the reaction medium (external).59 One of the first examples of an external heavy atom effect was given by Cowan and Drisko, 6 0 who investigated the photochemistry of acenaphthylene 45 in different solvents. Compound 45 was shown to dimerize to the trans dimer 47 from the Ti state, whereas the cis dimer 46 was obtained from the Si state. Photolysis in benzene or cyclohexane yielded the cis dimer as the major product. However, irradiation in n-propyl bromide, a heavy atom solvent, resulted in an increase of the triplet-derived trans dimer. This data indicated an increase in ISC from Si -> Ti due to external heavy atom perturbation. 29 Introduction heavy atom hv 45 46 47 cis dimer from S i trans dimer from T1 Figure 1.20. Experimental Example of the External Heavy Atom Effect. A great number of investigations of the heavy atom effect involve halogens. However, other atoms of high atomic weight have been shown to lead to similar results. A n internal heavy atom effect was found when a-methylmercuridiazoacetonitrile 48 was photolyzed.61 Direct irradiation in C7s-2-butene resulted in a non-stereospecific 1:1 ratio of the cis and trans products of 50. However, the reaction of diazoacetonitrile with c/s-2-butene was known to be stereospecific resulting from a singlet carbene. As a result, compound 48 was believed to undergo ISC to the triplet state in the presence of the mercury as the heavy atom. 48 49 50 Figure 1.21. Experimental Example of the Internal Heavy Atom Effect. 30 Introduction An internal heavy atom effect has also been observed by Givens et al., who detected an increase in Ti -> S0 radiationless decay. The author reported on the photochemistry of the halogenated 3,y-unsaturated ketones 51a or 51b. These compounds are known to undergo either an oxadi-7t-methane rearrangement (ODPM) from the Tx (n, %*) state or a 1,3-acyl shift (AS) from Si(n, 7 i * ) or T2(n, n*). Upon irradiation, the quantum yields of the sensitized ODPM reactions were decreased with the introduction of the heavy atoms chlorine or bromine. Furthermore, the triplet-sensitized reaction also resulted in less 1,3-acyl shift product formation. These results, which were supported by phosphorescence quenching studies, led to the conclusion that the heavy atom effect increases the radiationless decay rate for the triplet states. R=C1 51a Br 51b hv 52a 52b ODPM 53a 53b 1,3-AS Figure 1.22. Photolysis of 3,y-Unsaturated Ketones 51a and 51b. An example of an external heavy atom-induced Si -> T 2 intersystem crossing process was provided by Schuster et al.,63 who irradiated 3-methyl-3-(l-cyclopentenyl)butan-2-one (54) in the presence of xenon. Enone 54 is known to undergo the 1,3-acyl shift to give product 56 upon direct or sensitized irradiation from the Si(n, 7 t * ) or T2(n, TC*) states. Additionally, upon 31 Introduction sensitization, the O D P M rearrangement has been observed, resulting in product 55 from the Ti (TC, TC*) state. Irradiation of 54 in xenon led to an increase in product 56 and no formation of product 55. H 3 C \ =o CH3 CH3 55 O D P M hv sensitized 54 hv sensitized or direct Cf II o 56 1,3-AS Figure 1.23. Photolysis of Enone 54. In this case, the heavy atom effect was believed to enhance intersystem crossing from the Si(n , 71*) to the T2(n, 7C*) state rather than to the T x (TC, TC*) state (Figure 1.14). These results were not in agreement with the earlier formulated El-Sayed's rules,64 stating that ISC in ketones, nitrogen heterocycles and related compounds is favored to occur between singlet and triplet states of different electronic configuration (i.e. between l(n,iz*) and 3(7C, 7C*)). A referee for Schuster's paper63 suggested that El-Sayed's rules might not apply to bichromophoric systems as a result of extensive interaction between the excited states, which may result in a highly mixed configurational character of the lowest singlet and triplet excited states. 32 Introduction 1.5.3. The Heavy Atom Effect in Zeolites The heavy atom effect has also been investigated in zeolite environments. These molecules may be viewed as an open structure of silica in which a number of tetrahedral sites have been substituted with aluminum.65 Hence, the framework consists of pores, channels and cages. As a result of the substitution of trivalent aluminum ions for a fraction of tetravalent silicon ions at lattice positions, a negatively charged network is obtained. This must be balanced by other counterions. The pioneers in this area, Turro and Ramamurthy et al.66 studied the photophysics and photochemistry of molecules in zeolites, focusing on the changes in electronic excited states and reactivities of guest molecules. Recently, the phosphorescence properties of xanthone have been investigated in alkali metal cation-exchanged zeolites by Anpo et al.67 A weak fluorescence spectrum was observed with L i + and Na + cations. However, by changing the alkali metals to Rb + and Cs +, phosphorescence increased remarkably. Overall, an enhancement of the phosphorescence of xanthone was observed by changing the alkali metal cations from L i + , Na + , K + , Rb + to Cs +. Anpo et al. suggested that intersystem crossing in xanthone was enhanced by the presence of the alkali metals. O 57 Figure 1.24. Xanthone (57). 33 Introduction Another example of the heavy atom cation effect in zeolite systems was demonstrated by Ramamurthy et al.,6S who exarnined the photophysical properties of aromatic and olefinic compounds in these environments. The effect that heavy atoms exert on the guest molecule was established by monitoring the phosphorescence to fluorescence ratio from several aromatics (naphthalene, anthracene, phenanthrene) and olefins (/ra«s-stilbenes). The intensity ratios were observed to increase as lighter cations were substituted by heavier ones in the order of L i + < Na+ < K + < Rb+ < Cs+ < Tl +. The results showed that it is possible to control the extent of the excited singlet and triplet interconversion of the guest molecule by introducing different exchange cations into the zeolites. Ramamurthy et al.69 also reported on the study of a bimolecular photoreaction within the zeolite framework in the presence of heavy atoms. By varying the exchangeable cations, the multiplicity of the reactive state could be controlled. The chosen molecule for these studies was acenaphthylene (45), which was known to dimerize in solution forming the cis 46 and trans 47 dimers (Figure 1.20). The singlet excited state yields mainly the cis dimer, whereas the triplet state gives both the cis and trans dimers. The triplet yields and lifetimes of acenaphthylene in the zeolite were obtained by monitoring the intensity of the T-T absorption at 470 nm via flash photolysis techniques.70 Zeolites containing the Li + and Na+ cations did not show any triplet absorption, indicating that the dimerization originated from the excited singlet state. However, high triplet yields were obtained in the zeolites containing, K + , Rb+, Cs+ and Tl + which could be attributed to the heavy atom effect. Although this paper demonstrated an increase in the intensity of the T-T absorption with increasing mass of the cation, the product distribution of cis and trans dimers was not as expected, leading to a decrease in trans dimer yield for Rb+, Cs+ and Tl + zeolites. The different product ratios were proposed to result from the limited space in the zeolite 34 Introduction cavity. In contrast to the cis dimer with a length (7 A) that could occupy a single cage, the trans isomer was thought to be too extended (14 A) taking up two cages within the zeolite. 1.6. Objectives of Present Research As previously mentioned, solid state organic photochemistry is an area that is receiving an increasing amount of attention, as it is important and interesting to understand how a molecular crystal lattice affects organic photoreactivity. The overall objective of this thesis is to investigate how different media, either solution or the solid state, influence the photoreactivity of a probe molecule. By preparing a number of related compounds and applying X-ray crystallography, a correlation may be drawn between the reactivity in the solid state and the structure. Before fully exploring the solid state reactivity of a compound, the photochemistry in an isotropic medium needs to be investigated. This thesis is divided into two parts: (I) the photochemistry of triptycene-1,4-quinone and (II) the control of reaction multiplicity in the solid state, which discusses triplet-triplet energy transfer and the heavy atom effect. In Part I, the photoreactivity of triptycene-1,4-quinone is presented and discussed. The carbon skeleton of this compound (63) resembled that of previously investigated dibenzobarrelene diesters.71 7 2 For example, compound 58a (Figure 1.25) is known to undergo the di-rc-methane rearrangement in solution and the solid state.71 Introducing 9,10-substituents at the bridgehead positions72 resulted in dibenzobarrelenes exhibiting photochromism, changing them from colorless to dark blue or green as a result of irradiation in the solid state. One possible explanation for the 35 Introduction photochromism is photoinduced electron transfer between electron donating and electron accepting groups in the molecule. 58 (a-d) a R = H 7 i b R=CH0 72a,b C R=CH 2 Cl72a ,b d R = CC>2Me72c Figure 1.25. ll,12-Diester-9,10-ethenoanthracene Derivatives. Triptycene-1,4-quinone was chosen to study photoinduced electron transfer further in such systems. By investigating the photoreactions or lack thereof in the solid state, it was anticipated that some insight would be gained on the influence of crystal packing on the availability of reaction pathways. With the intention of comparing the reactivity of triptycene-1,4-quinone and two of its derivatives in solution and the solid state, experiments in solution were carried out first. 36 Introduction 63 R = H, Chapter 3 69 R = C H 3 , Chapter 4 72 R = C H 2 O C H 3 ; Chapter 5 Figure 1.26. Series of Triptycene-1,4-quinones Studied. Part I of this thesis is divided into three chapters discussing the photorearrangements of triptycene- 1-4-quinone and two 9,10-dialkyl-substitued derivatives. The photoreactivity of triptycene-1,4-quinone in solution was examined, as it brought about some unexpected and interesting results. Irradiation of the triptycene-1,4-quinones led to the isolation and characterization of different photoproducts depending on the solvents used and the absence or presence of oxygen. Mechanistic pathways leading to the formation of the various photoproducts are presented and discussed. Furthermore, the photoreactivity of the substituted quinones provides insight into the solid state photochromism of certain 9,10-ethenoanthracene derivatives. Part II of the thesis deals with the control of singlet/triplet photoreactivity of two different probe molecules in the solid state. Up to now, studies of the chemical reactivity of organic crystals have been primarily concerned with materials involving one pure component only. This may be explained by the fact that two-component solid solutions existing over a wide concentration range are relatively uncommon. In solution phase photochemistry, reaction 37 Introduction multiplicity can often be directed by the use of sensitizers. In the crystalline state, however, this is difficult to achieve. This obstacle could be overcome by forrning a salt between a probe molecule that would exhibit a differential singlet/triplet reactivity and a counterion that would selectively populate the triplet excited state. This project was aimed at controlling the reaction multiplicity of an electronically excited probe molecule in the solid state by introducing heavy atoms or sensitizers. The first section of Part II reports on the results obtained by applying the "ionic sensitizer" concept to the carboxylic acid of a (3,y-unsaturated ketone 121 (Figure 1.27) through salt formation with a number of appropriate sensitizers containing an amine functionality. 136 128 137 Figure 1.27. P,y-Unsaturated Ketone and Sensitizers Selected for the Study of Triplet-Triplet Energy Transfer. Additionally, the solid and solution state photochemistry of three 9,10-dihydro-9,10-ethenoanthracene derivatives (Figure 1.28) has been investigated in order to establish their singlet and triplet photoreactivity. The later part of the thesis is concerned with the effects that heavy 38 Introduction atoms (Li+, Na+, K + , Rb+, Cs+) and three different sensitizers exert on the photochemical behavior of 9,10-dihydro-9,10-ethenoanthracene derivative 132. X-ray crystallography was employed to investigate the geometric relationship between the sensitizer and the probe molecule in order to explain the efficiency of triplet-triplet energy transfer. 131 R = H 132 R = COCH 2 CH2C02H 133 R = CH 2 CU2H Ph -C-C H 2 C H 2 N(CH 3 ) 2 N ^ " ~ ^ ~ ^ C H 3 H \ / N ~ ^ ~ y ~ % H 1 3 6 137 167 Figure 1.28. Series of 9,10-Dihydro-9,10-ethenoanthracene Derivatives and Sensitizers. The successful experiments demonstrating the control of reaction multiplicity in the solid state expand the field of organic photochemistry in this medium. Triplet as well as singlet excited state properties can now be investigated in the solid state by applying X-ray crystallography as a tool to correlate structure and reactivity. These positive results open up the possibility of perforrning triplet energy quenching studies in the crystalline state, an area that has yet to be explored. Furthermore, as already accomplished in solution,73 Stern-Volmer type kinetic studies could be carried out in the solid state through quantum yield detenninations. By studying the 39 Introduction photochemical and photophysical behavior of organic compounds in a variety of solid environments, such as salts, zeolites and polymers, more may be learned about controlling chemical reactivity in ordered media. 40 Results and Discussion R E S U L T S A N D D I S C U S S I O N P A R T I P H O T O C H E M I S T R Y O F T R I P T Y C E N E - 1 , 4 - Q U I N O N E CHAPTER 2 GENERAL ORGANIC SYNTHESIS 2.1. Preparation of 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63) 9,10-Dihydro-9,10[r,2']benzenoanthracene-l,4-dione (63), also known as triptycene-1,4-qinone, was first synthesized by Clar74 in 1931 and later by Bartlett.75 This sequence involved an initial Diels-Alder addition between /?-benzoquinone and anthracene to give adduct 61, followed by aromatization with hydrobromic acid to 1,4-dihydroxytriptycene 62 and an oxidation with potassium bromate (Figure 2.01). Figure 2.01. Preparation of 9,10-Dihydro-9,10[r,2']benzenoanthracene-l,4-dione (63). 41 Results and Discussion 2.2. Synthesis of Anthracene Derivatives 9,10-Dimethylanthracene (65) was prepared by reduction of 9,10-bis(chloromethyl)-anthracene (64) with hthium aluminum hydride according to the procedure by Kirby et al.16 9,10-Bis(methoxymethyl)anthracene (66) was obtained by refluxing 9,10-bis(chloromethyl)anthracene (64) in a solution of methanol with potassium hydroxide according to Miller et al.11 The parent compound for both syntheses was prepared by adding anthracene and paraformaldehyde to a solution of dioxane and concentrated hydrochloric acid saturated with hydrogen chloride gas.77 CH2OCH3 66 Figure 2.02. Preparation of 9,10-Bis(chloromethyl)anthracene (64), 9,10-Dimethylanthracene (65) and 9,10-Bis(methoxymethyl)anthracene (66). 42 Results and Discussion 2.3. Preparation of 9,10-Disubstituted-9,10-dmydro-9,10[l',2']benzenoanthracene-l,4-dione Derivatives 9,10-Dihycfro-9,10-dimemyl[r,2']be (69), otherwise known as 9,10-dirnethyl triptycene-1,4-quinone,78 and 9,10-bis(methoxyrnethyl)-9,10-dihydro-9,10[l',2']-benzenoanthracene-l,4-dione (9,10-bis(methoxymethyl)triptycene- 1,4-quinone) (72), were synthesized by oxidation of the corresponding hydroquinones (68 and 71) with potassium bromate. The hydroquinones were prepared according to the literature procedure through the Diels-Alder addition of /?-benzoquinone to either 9,10-dimethylanthracene or 9,10-bis(methoxymethyl)anthracene, followed by base-catalyzed aromatization.79 13 ^ n 3 8 69 Figure 2.03. Preparation of 9,10-Dihya^o-9,10-a^ethyl-9,10[r,2']benzenoanthracene-l,4-dione (69). 43 Results and Discussion In the case of 72, difficulties arose in the base-catalyzed aromatization step and the concentration of the base had to be reduced. The aromatization of the Diels-Alder adduct 70 was also attempted with hydrobromic acid, but this did not result in the desired hydroquinone 71. 13 CH2OCH3 8 72 Figure 2.04. Preparation of 9,10-Bis(methoxymethyl)-9,10-dihydro-9,10[1 ',2'] benzenoanthracene-l,4-dione (72). The Diels-Alder addition between 9,10-bis(methoxymethyl)anthracene and benzoquinone proceeded in high yield (90%), although the reaction time to form 70 was prolonged (7 h) compared to the adduct formation times of 61 (2 h) and 67 (1 min). Although not as efficient as the methyl groups, the methoxymethyl substituents apparently act as electron donating groups, to promote the cycloaddition. Since 9,10-bis(chloromethyl)anthracene (64) had already been prepared, an experiment was also conducted to add this diene to the dienophile benzoquinone. 44 Results and Discussion However, this reaction led to no distinct product formation for reasons that are unclear at this point. 2.4. Preparation of 5- and 6-Chloro-9,10-dihydro-9,10[l',2,]benzenoanthracene-l,4-diones Two chlorinated derivatives of triptycene-1,4-quinone were prepared in order to confirm the structure of an isolated photoproduct and verify the position of the chlorine atom (see Chapter 3.3). The synthesized compounds were 5-chlorotriptycene-1,4-quinone (73) and 6-chlorotriptycene-1,4-quinone (74), a compound that had been prepared by a six step synthesis described by Hashimoto et al.80 Improving upon this lengthy synthesis, both chlorinated quinones were obtained by the same procedures as for tripycene-1,4-quinone 63, giving 5-chlorotriptycene-1,4-quinone (73) and 6-chlorotriptycene-1,4-quinone (74). The spectral data of 74 was found to be identical to that reported in the literature.80 45 Results and Discussion The reduced yield in the case of 74 can be attributed to the formation of one or a mixture of the 2 : 1 adducts 77a-d (i.e. two molecules of anthracene and one molecule of benzoquinone, Figure 2.06). The structural elucidation was based on comparing the spectral data to the corresponding 1 : 1 adduct 74. The mass spectrum shows the characteristic pattern of a structure with two chlorine atoms with a peak ratio of 9 : 6 : 1 corresponding to the molecular ion peak at m/e 528 , M+2 at m/e 530 and M+4 at m/e 532. The disappearance of the quinone vinyl hydrogens in the *H NMR gave a clear indication that a second cycloaddition had occurred. However, the exact position of the second chlorine atom could not be determined. Rl R2 R3 R 4 a Cl H H H b H Cl H H c H H Cl H A H H H Cl Figure 2.06. Possible Chlorinated 2 :1 Adducts 77a-d. The required chlorinated anthracene derivatives were obtained by reduction of the corresponding anthraquinone with zinc powder and acetic acid (Figure 2.07).81 8 2 0 % R, 78a 78b Zn/pyridine acetic acid 79a 79b Ri Rz a Cl H b H Cl Figure 2.07. Preparation of 5-Chloroanthracene (79a) and 6-Chloroanthracene (79b). 46 Results and Discussion CHAPTER 3 PHOTOCHEMICAL STUDIES OF 9,10-DfflYDRO-9,10[l',2']BENZENOANTHRACENE-1,4-DIONE (63) In the past, 9,10-dihydro-9,10[r,2']benzenoanthracene-l,4-dione (63) has received a great deal of attention concerning its photophysical properties. Iwamura and Makino83 as well as Murata et al.u and Kitaguchi85 have demonstrated that this compound, along with several derivatives, possesses a charge transfer excited state (Figure 3.01) resulting from intramolecular electron transfer from one of the aromatic rings to the quinone ring. 3 Figure 3.01. Numbering System for Triptycene-1,4-quinone (63) and its Charge-Transfer Excited State (63a). Photochemically, triptycene-1,4-quinone (63) has been studied by Kitaguchi,86 who investigated its photoreduction in the presence of xanthene as a hydrogen atom donor and determined the quantum yield (<1> = 0.35). However, Kitaguchi did not report any unimolecular photoreactivity of this system. Triptycene-1,4-quinone possesses the skeleton of a di-TC-methane reactant in which the 1,4-pentadiene moiety is replaced by a benzene and quinone ring 47 Results and Discussion respectively. This prompted the question whether a dipolar CT excited state would interfere with the photochemistry of quinone 63. 3.1. Photochemical Results Upon Direct Irradiation of 63 Irradiation of triptycene-1,4-quinone through Pyrex (k > 290 nm) in deoxygenated acetonitrile, methanol or ethanol led to a single photoproduct isolated as yellow needles (80%), and assigned as the di-TC-methane rearranged product 80 (Figure 3.02) based on its spectroscopic properties. Figure 3.02. Dibenzosemibullvalene 80 from the Irradiation of Triptycene-1,4-quinone (63). This conversion of triptycene quinone to photoproduct 80, a oibenzosemibullvalene, is analogous to the well established di-rc-methane rearrangement of other 9,10-ethenoanthracene derivatives as discussed in the Introduction. 48 Results and Discussion 3.1.1. Structure Elucidation of Semibullvalene 80 The ^Ji NMR spectrum of diberizosemibullvalene 80 (Figure 3.03) was compared to structures containing the semibullvalene skeleton that had been investigated previously.87 The multiplet at 8 8.05-7.97 ppm can be assigned to the aromatic hydrogen H-l (Figure 3.03). The downfield position of this hydrogen may be explained by the deshielding effect of the anisotropic cone88 of the carbonyl group, situated closest to the aromatic ring at this position. The remaining seven aromatic hydrogens are represented by a multiplet at 8 7.35-7.03 ppm. The vinyl hydrogens H-2' and H-3' are observed at 8 6.63 ppm as a singlet. The singlet at 8 5.13 ppm is assigned to hydrogen H-4b at the doubly benzylic position. This downfield position may result from the deshielding effect of the two aromatic rings. The more shielded hydrogen at 8 4.37 ppm is attributed to the cyclopropyl methine H-8b. Such chemical shifts are characteristic of dibenzosemibultvalenes and the assignment of the structure was supported by correlation of 1 H NMR spectral interpretation to X-ray crystal structures reported by Scheffer et al. 8 9 The IR spectrum, with a carbonyl band at 1677 cm1, and the mass spectrum, with a parent mass of m/e 284, also support the structure assigned to photoproduct 80. 49 Results and Discussion 50 Results and Discussion 3.1.2. Regioselectivity of Semibullvalene Photoproduct Formation The formation of semibullvalene 80 may be rationalized by comparing the relative stabilities of intermediates 63b and 63e (Figure 3.04) that would result from the two possible bridging pathways: (a) benzo-benzo bridging [i.e. bonding between C(8a) and C(12)] and (b) benzo-quinone bridging [i.e. bonding between C(4a) and C(10a)]. If the reaction proceeds through pathway (a) the aromaticity would be lost in both benzenoid rings, as seen in biradical 63b. However, if the benzo-quinone bridging pathway (b) would be followed, only one benzenoid ring would be disrupted, whereas the second odd electron would be stabilized by the adjacent carbonyl group of the quinone ring. Reaction pathway (b) is preferred since it involves the more stable biradical 63e affecting only one of the benzenoid rings instead of two. This regiochemistry is in accord with the work of Zimmerman et al.,90 who showed that initial bridging to form the more stable cyclopropyldicarbinyl 1,4-biradical intermediate is product-deterrnining in such compounds. There appears to be no need to invoke a CT excited state for this process, although its participation cannot be ruled out. 51 Results and Discussion Figure 3.04. Regio selectivity of the Di-rc-Methane Rearrangement of 63. 52 Results and Discussion 3.2. Photochemical Results Upon Irradiation of 63 in Acetone The photolysis of triptycene-1,4-quinone (63) in deoxygenated acetone resulted in the formation of the dibenzosemibulfvalene product 80, the same photoproduct that had been obtained from direct irradiation experiments. However, when air was present, a different photoproduct was detected by gas chromatographic (GC) analysis. Optimization of the experimental conditions in air-saturated acetone led to a rmximum isolated yield of 18% of triketone 81 (Figure 3.05). Figure 3.05. Triketone 81 from the Irradiation of Triptycene-1,4-quinone (63). 3.2.1. Structural Assignment of Triketone 81 The structure of triketone 81 was initially assigned by spectral analysis and then confirmed by X-ray crystal analysis. In order to obtain a mass spectrum of triketone 81, desorption chemical ionization (DCI + NH3) was used to ionize the sample resulting in a base peak of M+18 at m/e 318. The M+l peak at m/e 301 indicates that an additional oxygen atom has been added to the initial skeleton, which has an M+l peak at m/e 285. The infrared spectrum also reveals the 53 Results and Discussion presence of two types of carbonyl stretches: a strong band at 1709 and a medium band at 1760 cm1. The lower stretching frequency was compared to the vibrations of the carbonyl groups of cyclopenten-3,5-dione (82), which occur at 1718 cm"1 (nujol).91 82 Figure 3.06. Cyclopenten-3,5-dione (82). Peak assignment of the lH NMR spectrum was done by comparing the triketone 81 to the starting material 63. A noticeable change was observed in the chemical shift of the vinyl hydrogens, initially at 8 6.59 ppm, which moved further downfield to 8 7.38 ppm. This chemical shift can be compared to the shift of the vinyl hydrogens of cyclopenten-3,5-dione (82) at 8 7.31 ppm.92 The bridgehead hydrogens shifted upfield from the initial singlet at 8 5.79 ppm to two distinct singlets at 8 4.98 and 4.47 ppm. 54 Results and Discussion Results and Discussion Figure 3.08. X-ray Crystal Structure of Triketone 81. Space Group Pnal\ (#33); a = 12.274(3) A, b = 7.957(3) A, c = 15.444(3) A, Z = 4, R - 3.7%. 56 Results and Discussion 3.2.2. Mechanistic Speculations on the Formation of Triketone 81 A possible mechanism for the photochemical reaction leading to the formation of triketone 81 is depicted in Figure 3.09. The reaction pathway is believed to proceed through the cyclopropyldicarbinyl biradical 63e, which could either undergo the di-TC-methane rearrangement in the absence of oxygen to give semibullvalene 80 (Figure 3.04, pathway (b)), or be trapped by dissolved oxygen from an air-saturated acetone solution. Intermediate 83 could then abstract a hydrogen from the solvent, followed by homolysis and rearrangement of biradical 85 to triketone 81. Figure 3.09. Proposed Mechanism for Formation of Triketone 81. 57 Results and Discussion A n alternative mechanism could involve the participation of the charge transfer excited state species 63a (Figure 3.01), which could capture dissolved oxygen at positions C(4a) or C(9a). The reaction pathway would then progress by a mechanism similar to that described above and be completed by an electron return step to the benzene ring. However, the proposed mechanism described in Figure 3.09 appears to be more promising, as it involves the already established biradical 63e. The possibility of the reaction proceeding through a carbene mechanism was also considered as shown in Figure 3.10. 81 Figure 3.10. Carbene Mechanism for Formation of Triketone 81. 58 Results and Discussion This mechanism may either involve zwitterion 63g (Figure 3.10) or its biradical counterpart 63e (Figure 3.09) forming the carbene 63h followed by a reaction with dissolved oxygen. The reaction between carbenes and molecular oxygen has been established over the years. Early research by Bartlett et al.93 showed that benzophenone (89) could be produced by irradiating diphenyldiazomethane (86) in the presence of oxygen. The isolation of the cyclic peroxide 90 led to the suggestion of intermediate 88. Furthermore, experiments with 3 6 0 2 showed that cyclic peroxide did not decompose into benzophenone and oxygen. P h 2 C N 2 hv 0 2 [ P h 2 0 0 - 0 -* + P h 2 C = 0 - 0 ] + -P h 2 c: 86 87 88 P - Q / Y j - d 89 90 Figure 3.11. Reaction Pathway Between Carbene 87 and Molecular Oxygen. 59 Results and Discussion Although not completely ruled out, the carbene mechanism (Figure 3.10) for the formation of triketone 81 is less likely, as a carbene trapping experiment failed to produce positive results. This was conducted by irradiating triptycene 63 in methanol. The resulting photoproduct was determined to be cubenzosemibullvalene 80 as mentioned in Section 3.1, after isolation by chromatography. Trapping experiments are often performed in order to determine the presence of a carbene. The mechanism, involving the insertion of methanol into the arylcarbene 92, generated by the photolysis of diazo compound 91 is illustrated in Figure 3.12. This experiment provided evidence for the involvement of the carbene 92 in the product formation step.94 hv CH 3 OH ,CH 3 Ar 2 CN 2 A r 2 C : *- Ar 2C—O, *• Ar 2 CH-OCH 3 H 91 92 93 94 Figure 3.12. Carbene Trapping Mechanism. 60 Results and Discussion 3.3. Photolysis of Quinone 63 in Chlorinated Solvents Photolysis (300 nm or 350 nm, Rayonet Photoreactor) of triptycene-1,4-quinone (63) in deoxygenated chloroform or carbon tetrachloride led to the formation of three products, two monochlorinated isomers 75 (25%), 74 (24%) and one dichlorinated 76 product (1%), (Figure 3.13). After 8 h and about 50% conversion by GC, no di-rc-methane product 80 could be detected. Figure 3.13. Chlorinated Photoproducts from the Irradiation of Triptycene-1,4-quinone (63). 61 Results and Discussion 3.3.1. Structural Assignment The mass spectra of compounds 75 and 74 clearly indicate that one hydrogen atom has been substituted by a chlorine atom, resulting in the characteristic isotopic pattern for chlorine. The relative abundance of the peaks occurs in a 3 : 1 ratio corresponding to the molecular ion peak at m/e 318 and the M+2 peak at m/e 320. Compound 76 shows a molecular ion peak at m/e 352, an M+2 peak at m/e 354 and an M+4 peak at m/e 356 in the ratio of 9 : 6 : 1, a characteristic pattern for a compound containing two chlorine atoms. The structure of the benzoquinone ring was not altered, since the carbonyl absorption bands remained in the typical range of 1675-1655 cm"1, established by the IR spectra. In order to determine at what position the addition of the chlorine atoms occurred, the lH N M R spectra of the chlorinated products were compared to the spectrum of the starting material triptycene-1,4-quinone (63). The J H N M R spectrum of 75 clearly shows the loss of one of the vinyl hydrogens. The X H N M R spectrum of 74, however, indicates the loss of one hydrogen at an aromatic position. In order to determine the assignments of the aromatic hydrogens, an N O E N M R experiment was performed with triptycene-1,4-quinone (63) (Figure 3.15). On the one hand, irradiation of the bridgehead hydrogens H-9 and H-10 at 8 5.79 ppm led to the disappearance of the multiplet at 8 7.10-6.95 ppm. On the other hand, irradiation at 8 7.01 ppm resulted in the disappearance of the peak at 8 5.79 ppm. Irradiation at 8 7.4 ppm had no effect on the multiplet at 8 7.01 ppm and singlet at 8 5.79 ppm. Hence, the multiplet at 8 7.50-7.35 ppm can be assigned to the hydrogen atoms at the a-position of the aromatic rings, whereas the multiplet at 8 7.10-6.95 ppm corresponds to hydrogen atoms P on the aromatic rings. 62 Results and Discussion g.o • i • B.O 7 . 0 ' I 16 . 0 5 . 0 PPM 4 .0 ' I 1 ' 3 . 0 2 . 0 1 T — T 1 . 0 0 . 0 Figure 3.14. ! H NMR Spectrum of Triptycene-1,4-quinone (63). 63 Results and Discussion i) Figure 3.15. ] H NMR NOE Experiment for Triptycene- 1,4-quinone (63), (i) No Irradiation, (ii) Irradiation at 8 5.79 ppm, (iii) Irradiation at 8 7.01 ppm, (iv) Irradiation at 8 7.4 ppm. 64 Results and Discussion The X H NMR spectrum of the chlorinated product 74 lacks one hydrogen in the upfield aromatic region, positioning the chlorine atom beta (P) on the aromatic ring. In order to establish the structure further, two triptycene-1,4-quinone adducts were synthesized with chlorine atoms at either the a or p positions on one of the benzene rings (see Chapter 2, Figure 2.05, p 45). Comparing the spectral data of the authentic samples to the spectral data of photoproduct 74 confirmed the assignment. 3.3.2. Mechanism of Formation of Chlorinated Product 75 The photoreaction of 63 in chloroform was monitored by gas chromatography, which showed that the dichlorinated species 76 only formed after the appearance of mononchlorinated products 75 and 74 in solution. Furthermore, upon irradiation in either chloroform or carbon tetrachloride, the solution tested positive for the presence of hydrogen chloride. A control experiment was conducted by stirring triptycene-1,4-quinone (63) dissolved in acetone in a 15% aqueous hydrogen chloride solution and monitoring the reaction by GC. After one hour product 75 could be detected and hence the possibility that 75 or 76 could be true photoproducts was ruled out. 65 Results and Discussion Based on the assumption that hydrogen chloride is formed during the photolysis, the formation of 75 can be explained in terms of the analogous reaction between 1,4-benzoquinone (60) and hydrogen chloride which dates back to the 19th century.95 Detailed mechanistic studies on the hydrogen chloride reaction with quinonoid systems were later pursued by Adams.96 As seen from Figure 3.16 (a), the electrophilic part of hydrogen chloride was proposed to bind to the carbonyl group and the nucleophilic part attaches to the P-carbon. This results in the hydroxydienone 60a which enohzes to the phenol 60b. Upon oxidation by an unreacted quinone molecule in the reaction mixture, as described by Cason et al.,91 quinone 60c will be obtained (Figure 3.16(b)). 60b 60 60c 60(1 Figure 3.16. Addition of Hydrogen Chloride to 1,4-Benzoquinone (60), Followed by Oxidation. 66 Results and Discussion The above reaction pathways may be applied to triptycene-1,4-quinone (63), which possesses the quinone moiety. During the photolysis hydroquinone 95a is believed to be oxidized by an unreacted quinone 63 molecule to give product 75. 75 Figure 3.17. Proposed Mechanism for Formation of Chlorinated Product 75. As illustrated by Figure 3.17, the chlorine addition is only observed at position C3. This may be explained by the lack of a hydrogen atom at position C4a, which is required for the enolization step to form the corresponding hydroquinone. If the addition did occur, ehmination of the chlorine atom would likely result, driven by the ketonization step (Figure 3.18). 67 Results and Discussion Figure 3.18. Addition of CMorine Atom at Carbon 4a of Intermediate 96. 3.3.3. Mechanism of Formation of Chlorinated Photoproduct 74 The unusual chlorination of the aromatic ring of triptycene-1,4-quinone (63) was quite puzzling and a control experiment was conducted showing that benzene could not be chlorinated under the same irradiation conditions. The chlorinated photoproduct 74 may originate from the cyclopropyldicarbinyl biradical 63e (Figure 3.19) which was proposed earlier in this thesis as a common intermediate for sermbullvalene 80 and triketone 81. A chlorine atom from the solvent could be abstracted by intermediate 63e resulting in radical 99. In chloroform, the hydrogen could then be abstracted by the solvent radical giving dichloromethane and photoproduct 74. A gas chromatographic analysis of the volatile reaction product, dichloromethane, was not performed as it would have been very difficult to trace such minute quantities in the chloroform reaction mixture. In the case of carbon tetrachloride, the abstraction of a chlorine radical would result in a *CC13 radical. Upon the abstraction of a hydrogen atom from intermediate 99, chloroform would be the obtained byproduct. The lack of substitution at position C(5) of the benzene ring may be explained by sterically hindering interactions between the incoming chlorine atom and the bridgehead hydrogen at the position C(10) of 63. 68 Results and Discussion As previously noted, the participation of a charge-transfer excited state is not required for the reaction to proceed, but can not be excluded at this point. + C H 2C1 2 Figure 3.19. Proposed Mechanism for Formation of Chlorinated Photoproduct 74. 69 Results and Discussion The above reaction pathway leading to photoproduct 74 may also give an insight into the presence of hydrogen chloride in the reaction mixture. As illustrated by Figure 3.20, the chlorinated intermediate 99 is proposed to undergo a reversible loss of the chlorine atom forming quinone 63. If this is the case, the resulting chlorine atom may abstract a hydrogen from chloroform yielding hydrogen chloride.98 The presence of hydrogen chloride in the carbon tetrachloride reaction mixture may result from the small quantities of chloroform being formed during the photolysis reaction. + ' C H C b \ HC1 Figure 3.20. Proposed Mechanism for Hydrogen Chloride Formation. 70 Results and Discussion 3.4. Solid State Reactivity of Triptycene-l,4-quinone (63) The photochemistry of 9,10-ethenoanthracene derivatives in the solid state has been well documented by Scheffer et al." as these molecules possess interesting photochemical reactivity. In view of further exploring these systems, the solid state reactivity of triptycene-1,4-quinone (63) was investigated. Unexpectedly, however, irradiation of triptycene-1,4-quinone in the solid state through Pyrex (A. > 290nm) for 8 h led to no reaction. In order to provide insight into this lack of reactivity in the solid state, the X-ray crystal and molecular structure was deterrnined and analyzed. As seen from the packing diagram in Figure 3.21, the bridgehead carbons (C9 and CIO) of the individual molecules are tetrahedral (109.5°). These angles, between each V-shaped cleft, are shghtly deviated (4°) due to strain (Table I). Cyclopropyldicarbinyl biradical 63e formation would require that one of the aromatic rings and the quinone ring would move together to approximately 60°. Table I Angles Between the Quinone and Benzene Moieties (see Figure 3.23) Atoms Angles (°) C8a, C9, C12 106.2 C9a, C9, C8a 105.5 C9a, C9, C12 105.4 71 Results and Discussion Figure 3.21. Packing Diagram for Triptycene- 1,4-Quinone (63). 72 Results and Discussion Figure 3.22. X-ray Crystallographic Structure of Triptycene-1,4-quinone (63). Space Group Prima (#62), a = 13.979(2)A, b = 12.608(7)A, c - 8.024(2)A, Z = 4, R = 5.9%. The structure is represented, showing its crystallographic numbering system, which takes the symmetry of the molecule into account. This numbering system differs from the up-to-now applied IUPAC system 73 Results arid Discussion As shown by Figure 3.23 and Table JJ, the center-to-center (represented as RC) intramolecular distances between the separate rings range between 4.45 and 4.58 A , permitting initial di-7t-methane bridging. However, the illustration of the molecular stacking of 63 (Figure 3.21), indicates that each molecule is very close to its neighbors with distances ranging between 3.65 to 4.80 A (Table JJ). The quinone and aromatic rings of adjacent molecules in the crystal appear to be almost interlocked, which may explain the possible hindrance of the benzo-quinone bridging step. Figure 3.23 depicts the two possibilities for the initial bonding process: (i) bonding between the quinone ring RC1 and benzene ring RC2 and (ii) bonding between the quinone ring RC1 and the benzene ring RC3. The packing diagram of quinone 63 (Figure 3.21) reveals that pathway (i) may be sterically impeded by the short distance between benzene ring RC3 and benzene ring RC2 of adjacent molecules (4.74 A) and the even smaller intermolecular distance between benzene ring RC3 and quinone ring RC1 (3.65 A). Additionally, process (ii) may be hindered by the vicinity of the intruding hydrogens of the aromatic ring RC2 to quinone ring RC1 and benzene ring RC3 of the neighboring molecule, given by the distances 3.37 A and 3.28 A, respectively (Figure 3.21). 3 4.45 A Figure 3.23. Intramolecular Distances between Ring Centers 1, 2 and 3. 74 Results and Discussion Table II Intennolecular and Intramolecular Distances Between Ring Centers Ring Centers Intennolecular Distances (A) Ring Centers Intramolecular Distances (A) RC1-RC2 4.80 RC1-RC2 4.52 RC1-RC3 3.65 RC1-RC3 4.58 RC2-RC3 4.74 RC2-RC3 4.45 Previous research by Scheffer et al. has demonstrated that bridging motions in the solid state may be hindered by the presence of aromatic rings from adjacent molecules in the clefts. 100 101 Figure 3.24. Example of an Unreactive Photoreaction in the Solid State. The initial reaction step in compound 100 was believed to be hindered by the presence of a methyl group from an adjacent molecule, which was at a distance of 4.12 A and 4.75 A from the center of either aromatic ring. The center-to-center distances between the two aromatic rings was shown to be 6.48 A (Figure 3.25). After the reaction, the aromatic center-to-center distance was estimated from Dreiding models to have decreased to 4.1 A, reducing the distances between the methyl carbon and the aromatic rings to 2.6 and 3.0 A respectively. Adding the van der Waals radii of the methyl group (2.0 A ) 1 0 1 and the van der Waals half "thickness" of an aromatic ring 75 Results and Discussion (1.7 A) together resulted in a sum (3.7 A) greater than the distances between the methyl group and the rings, prohibiting the photoreaction in the solid state. before reaction after reaction Figure 3.25. Crystal Lattice Steric Effects in Compound 100. Applying this hypothesis to triptycene-1,4-quinone (63) may explain the lack of reactivity. The already relatively short distances between the hydrogen attached to carbon 14 at RC2 with respect to RC1 and RC3 are believed to decrease considerably upon the bridging process, rmking it difficult to accommodate the aromatic ring RC2, resulting in the photostability of 63. 76 Results and Discussion CHAPTER 4 PHOTOCHEMICAL STUDIES OF 940-DmYDRO-9,10-DIMETHYL-9,10[l',2']BENZENOANTHRACENE-l,4-DIONE(69) 4.1. Photochemical Results Upon Direct Irradiation Irradiation at X > 300 nm of 9,10-dimethyltriptycene-1,4-quinone (69) in deoxygenated acetonitrile resulted in a purple solution (4.5 h). Two photoproducts were isolated, the di-7t-methane photoproduct 102 (yellow needles, 28%) and the norcaradiene photoproduct 103 (blue black prisms, 23%). 69 102 103 ° Figure 4.01. Photolysis of 69 in Acetonitrile. 4.1.1. Photoproduct Structure Elucidation The elucidation of the structure of photoproduct 102 was facilitated by its similarity to the di-7i-methane photoproduct analogue 80 (Figure 3.02). The *H NMR spectrum shows the presence of one aromatic hydrogen as a doublet at 8 7.80 ppm («/ - 7 Hz), and a multiplet at 8 77 Results and Discussion 7.20-7.02 ppm, corresponding to the rernaining seven hydrogens. The vinyl hydrogens of the quinone ring can be assigned to the A B system at 8 6.74 ppm ( J = 10Hz). The rermining two singlets at 8 2.13 and 1.98 ppm represent the methyl substituents. The IR spectrum displaying the carbonyl band at 1668 cm"1 and the mass spectrum with a parent mass of m/e 312 are also consistent with the assignment of the proposed photoproduct 102. The structure of norcaradiene 103 was elucidated on the basis of the spectral data collected. The IR spectrum shows the presence of two carbonyl bands (1664 cm"1 and 1645 cm"1), with the latter being shifted to lower frequencies due to extended conjugation with the diene ring. The mass spectrum of compound 103 has a base peak at m/e 297, which results from the loss of one methyl group from the molecular ion peak at m/e 312. The Tf N M R spectrum of norcaradiene 103 (Figure 4.02) reveals the presence of one aromatic ring. The quinone vinyl hydrogens H-3 and H-4 are represented by an A B system at 8 6.65 ppm (J= 10 Hz). The former second aromatic ring, however, is replaced by a diene system. The assignments of the hydrogens of the diene ring are based on the coupling constants (J), corresponding to the doublet at 8 6.98 ppm (H-17, J= 6 Hz), the doublet of doublets at 8 6.31 ppm (H-18, J= 9 Hz and J= 6 Hz) and the doublet of doublets at 8 6.03 ppm (H-19, J = 9 Hz and J= 5 Hz). The doublet at 8 2.55 ppm represents the cyclopropyl hydrogen (H-20, J = 5 Hz). Due to the lack of symmetry of the molecule a single peak is observed for each methyl group (Me-21 at 8 1.50 ppm and Me-22 at 8 1.06 ppm). To further verify the structure, an H M Q C N M R experiment (Heteronuclear Multi-Quantum Correlation) as well as an H M B C N M R experiment (Heteronuclear Multi-Bond Correlation) were conducted. The assignments are given in Table HI. 78 Results and Discussion 79 Results and Discussion Table m *H NMR (500 MHz) and 1 3 C NMR (125 MHz) Data for Norcaradiene 103a 11 103 F. HMQC lYL-uC HMBC Carbon Assign-Spectrum (125 MHz) 8 ppm, APT1' 'Fl NMR Correlations Long-range Correlations R Y ment (500 MHz) 8 ppm (Assignment) a 1 141.89 H-3 & 4, H-17 I) 2&5 186.11, 185.87 H-3 &4 c 3 &4 137.87(-ve), 136.19(-ve) 6.03 & 6.31 (H-3 &4) d 6 149.51 H-3 & 4, Me-21 e 7 61.01 H-19, Me-21 f 8 146.45 H-9, H-10 & 11, Me-21 g 9 & 12 124.97(-ve), 126.74(-ve) 7.78-7.69 & 7.40-7.30 (H-9 &12) H-10, H - l l h 10 & 11 127.14(-ve), 128.01(-ve) 7.28-7.19 (H-10 &11) H-9, H-12 i 13 148.17 H-10& 11, H-12, H-20, Me-22 i l l ! 14 21.99 Me-22 k 15 56.88 H-19, H-20, Me-21, Me-22 1 16 134.89 H-18 m 17 121.84(-ve) 6.98 (H-17) H-18 n 18 126.32(-ve) 6.31 (H-18) H-17, H-20 0 19 126.65(-ve) 6.02 (H-19) H-17, H-20 1> 20 37.82(-ve) 2.55 (H-20) H-19 q 21 23.88(-ve) 1.50 (Me-21) r 22 10.77(-ve) 1.06 (Me-22) H-20 a -The assignments and chemical shifts of the 1 3 C N M R spectrum are listed in columns II and III, respectively. Column IV shows the *H N M R signal(s) which correlate(s) with the carbon of columns II and III, as obtained from the H M Q C experiment (1 bond correlation). The last column lists the hydrogen(s) which correlate(s) with the 1 3 C N M R signal of column II and III as obtained from the H M B C experiments (2 and 3 bonds correlation(s)). b - The results of the APT experiments are given in parentheses (-ve for C H and C H 3 carbon signals). 80 Results and Discussion Table TV *H NMR Data (500 MHz) for Norcaradiene 103 Liitry Hydrogen Assignment *H-NMR (500 MHz) 8 ppm (mult., J (Hz)) C O S Y Correlations a H-3 & 4 6.65 (AB system, J= 10) b H-9 & 12 7.78-7.69 (m), 7.40-7.30 (m) H-10& 11 c H-10& 11 7.28-7.19 (m) H-9 & 12 d H-17 6.98 (d, J=6) H-18 e H-18 6 .31(dd , J=6&9) H-17,H-19 f H-19 6.03 (dd,J = 9 & 5 ) H-18, H-20 g H-20 2.55 (d,J=5) H-19 h Me-21 1.50 (s) i Me-22 1.06 (s) 81 Results and Discussion The proposed structure of norcaradiene 103 was later corifirrned by X-ray crystal analysis. The X-ray structure shown in Figure 4.03 demonstrates that the methyl groups C21 and C22 are anti to each other, and the methyl group C21, which is closer to the quinone ring, is syn to the cyclopropyl hydrogen H10. Figure 4.03. X-ray Crystallographic Structure of Norcaradiene 103. Space Group Pl\/n (#14), a = 8.114(3) A, b = 11.966(3) A, c = 16.694(3) A, (3 = 95.53(2)°, Z = 4, R = 3.7%. 82 Results and Discussion 4.1.2. Mechanism of Formation of Semibullvalene 102 and Norcaradiene Derivative 103 Photoproduct 102 is analogous to the previously discussed photoproduct 80, which resulted from the di-7r-methane rearrangement of triptycene-1,4-quinone (63). As shown by Scheffer and co-workers,102 9,10-bridgehead substitution can have a profound effect on the photochemistry of 9,10-ethenoanthracene derivatives. This is also the case for the irradiation of quinone 69. The formation of photoproduct 103 can be related to the work of Walsh103 and Turro et al.,104 who in 1969 studied the photochemical behavior of triptycene (104) and isolated a similar norcaradiene derivative (106) upon irradiation in solution. These results contrasted former photochemical results with barrelene and its benzo derivatives, which were found to rearrange to semibullvalene and cyclooctatetraene derivatives upon irradiation, as discussed in the Introduction. Figure 4.04. Photolysis of Triptycene 104. Initially, Turro104 proposed that photoproduct 106 was formed by a 1,5-sigmatropic rearrangement of semibullvalene 105, which was not isolated by him or Walsh. Iwamura and co-83 Results and Discussion workers 1 0 5 ' 1 0 6 later proposed that this reaction proceeds through a carbene mechanism. This hypothesis was supported by trapping of the carbene intermediate 104a with methanol, leading to the isolation of compound 107. Additionally, molecular models were used to demonstrate the favorable position of the divalent carbon atom with respect to the aromatic carbons of the fluorene ring 104a. 84 Results and Discussion The formation of norcaradiene 103 can be rationalized by applying Iwamura's mechanism to quinone 69 (Figure 4.06). Figure 4.06. Proposed Mechanism for Formation of Photoproducts 102 and 103. The suggested reaction pathway involves an initial di-Ti-methane rearrangement giving the well established 1,3-biradiacal 69b of the Zimmerman mechanism, which may either ring-close to semibullvalene 102, or rearrange to the carbene intermediate 69c. The carbenic center may then add internally to the aromatic ring resulting in norcaradiene 103. This mechanism may also provide an explanation for the lack of norcaradiene formation for the previously discussed unsubstituted triptycene-1,4-quinone (63). In the case of quinone 69, the methyl substituent is believed to stabilize the carbenic center of intermediate 69c, thereby facilitating its formation from 85 Results and Discussion biradical 69b. Also, the ring closure of biradical 69b to semibullvalene 102 could be sterically hindered by the same methyl group. A second possible mechanism could involve carbene 69c as the common intermediate for formation of semibullvalene 102 and norcaradiene 103. Trapping experiments were conducted showing that upon irradiation of quinone 69 in methanol, the yield of photoproduct 103 decreased significantly (4%), whereas an increase in the amount of di-TC-methane product 102 was observed (40%). The reduced formation of norcaradiene derivative 103 leads to the tentative conclusion that successful trapping of intermediate 69c occurred, and that semibullvalene 102 was less likely to result from intermediate 69c. Control experiments were also conducted in order to rule out the possibility of interconversion between 102 and 103 under the photolysis conditions. 4.1.3. The Midnight-Blue Color of Norcaradiene 103 Although 69 is more commonly referred to as a triptycene-1,4-quinone derivative, it can be viewed as a 9,10-ethenoanthracene derivative. Classified as such, it is believed to be the first example to form a photostable norcaradiene product upon photolysis. A l l previous examples of this reaction have been produced by triptycene derivatives.107 One of the unusual observations of this reaction is that norcaradiene 103 is midnight-blue in color, whereas the previously analyzed norcaradiene analogues from the triptycene reaction were reported as being yellow. The blue color results from a very broad absorption band, centered around 570 nm, as indicated by the 86 Results and Discussion UV7VJ.S absorption spectrum (Figure 4.10). This can be explained by a charge-transfer interaction between the norcaradiene and quinone chromophores. This interaction often occurs in molecules that possess a low ionization potential (electron donor) or a high electron afEnity (electron acceptor), giving a broad absorption spectrum as a result of an electron-donor-acceptor complex. Within this complex the formation of an ion pair in the excited state results. This type of electron transfer, which must be exothermic, more commonly occurs between a ground and excited state compound than two ground state molecules. The LUMO of the electron acceptor must be at a lower energy than the LUMO of the excited electron donor.108 Hence, an increase in the energy difference between the LUMO of the ground and excited state would lead to a decrease in the activation energy barrier of the charge-transfer process. LUMO-HOMO LUMO HOMO D* + D« A-Figure 4.07. Charge-Transfer from an Excited Donor (D*) to Acceptor (A). If both molecules are in the ground state, an electron transfer can only take place if the HOMO of the donor is higher-lying than the LUMO of the acceptor. 87 Results and Discussion A n example of a compound that exhibits a pronounced charge-transfer absorption band at Amax (CH 3 CN) 655 nm and possesses similar structural components to norcaradiene 103 is naphth[2,3-a]azulene-l,12-dione (108).109 This can be explained by the interaction between the quinone which possesses acceptor properties and the cycloheptatriene which has donor properties (Figure 4.08). Figure 4.08. Naphth[2,3-a]azulene-5,12-dione (108) and Norcaradiene 103. Similar colors, which however were transient, have been detected in the crystalline state photochemistry of several 9- or 9,10-disubstituted 9,10-ethenoanthracene derivatives with electron-withdrawing esters or carboxyhc acid substituents on the bridging double bond. 1 1 0 These compounds were shown to be photochromic, a process whereby a substance changes color upon absorption of light. This appearance is by definition either thermally or photochemically reversible.111 Compounds displaying photochromism have been studied since the end of the last century112 and this process has been observed for various compounds in different media, including examples of photochromism in the solid state.110 88 Results and Discussion A compound that exhibits photochromism is 9,10-ethenoanthracene derivative 109 (Figure 4.09), which turns dark blue upon irradiation in the crystalline state and gradually loses its color over several hours at room temperature in the dark.113 Heating as well as dissolving the colored crystals also resulted in a loss of color. Figure 4.09. Example of a Photochromic 9,10-Ethenoanthracene Derivative 109. In the case of norcaradiene 103, the blue-colored crystals were thermally as well as photochemical stable. The diffuse reflectance UV7VIS absorption spectrum of the irradiated crystals of compound 109 resembles the corresponding spectrum of norcaradiene 103. Hence, it is possible that irradiation of 109 leads to the formation of a small amount of the analogous norcaradiene derivative, which may break down to form colorless products. Although norcaradiene 103 was only formed under irradiation conditions in solution, and 69 was shown to be unreactive in the solid state (k > 290 nm, 8 h), the isolation of norcaradiene 103 might have solved the up-to-now unsolved mystery of solid state photochromism of 9,10-substituted-ethenoanthracene derivatives. However, in order to fully understand why the coloration of triester 109 is unique to the crystalline state, and quinone 69 is photo stable upon irradiation in the solid state, the medium effects have to be investigated further. CO2CH3 CDjCHg 109 89 Results and Discussion 4.1.4. Solvatochromic Effect of Norcaradiene 103 A solvent effect was observed when norcaradiene 103 was dissolved in acetonitrile and in chloroform. The color of the solution of norcaradiene 103 in acetonitrile was violet, whereas in chloroform a deep blue color was obtained. This is known as the solvatochromic effect, resulting from changes in the wavelengths, intensities and shapes of the absorption band of chromophores due to the effect of the solvent. 1 1 4 Table V UV/VIS Absorption Data for Norcaradiene 103a Band d i m ) icetonitril l l i l i l iiliiiiiiii ( (nm) ^hloroforn 1 fkmax (cm1) a £ max 1 569 17,570 2,066 594 16,840 2,423 2 316 31,650 3,577 324 30,860 4,157 3 232 43,100 9,756 256 39,060 8,889 (a) Concentrations of 103 in acetonitrile and chloroform were 4.10xlO"4M and 4.49xlO"4M, respectively. Table VI UV/VTS Absorption Data for Benzoquinone Band Acetonitrile l A m a x (Cm"') Dichloroethane 1/^ max (Cm" 1) 1 (n -> TC*) 29,540 29,370 . 2 (TC -> TC*) 39,920 39,600 90 Results and Discussion The UV/VIS absorption spectrum of 103 in chloroform shows a red shift (bathochromic shift), which can be attributed to an increase in solvent polarity. In comparing the UV/VIS absorption spectra of 103 to the spectra of benzoquinone in similar solvents, a correlation between the absorption bands is observed.115 In both cases, the n -> n* and n —> n* absorption bands of the carbonyl compounds undergo a red shift as the polarity of the solvent increases. Figure 4.10. UV/VIS Absorption Spectrum of 103 in Acetonitrile and Chloroform. 91 Results and Discussion By increasing the polarity of the solvent, the TC — » TC* transitions of aromatic carbonyl compounds undergo a red shift, whereas the n -> TC* transitions undergo a blue shift.115 The blue shift observed for the n —> TC* absorption bands of carbonyl compounds may result from cooperating effects of both electrostatic and hydrogen bonding interactions with the solute molecule.115 Protic solvents are thought to hydrogen-bond more strongly to the more polar ground state of the molecule than the excited state, which only has one available n-electron.116 This lowers the energy of the ground state more than the energy of the excited state. As a consequence the energy of the n — » TC* transition is raised. The red shift is believed to be caused by a greater stabilization of the excited state than the ground state. In this case the excited state is thought to be more polar than the ground state, resulting in the energy lowering of the TC —> TC* transition. In the case of compounds 103 and benzoquinone, the n —> TC* absorption band does not undergo a blue shift in dichloroethane or chloroform. This may be explained by the lack of hydrogen bonding interaction between solvent and the solute molecules. Hence, the general effect on the n —> TC* absorption of these polar solvents is also a red shift. As seen from Figure 4.10 a pronounced solvatochromic effect is observed for the absorption bands of norcaradiene 103. As before, quinone 103 can be compared with naphth[2,3-a]azulene-l,12-dione (108) (Figure 4.08), which demonstrates sorvatochromism in acetonitrile and benzene, ? i m a x (CH3CN) = 655 nm, A^ax (Ct^h) = 672 nm, as a result of the quinone moiety which has acceptor properties and the cycloheptatriene moiety which has donor properties. 92 Results and Discussion CHAPTER 5 PHOTOCHEMICAL STUDIES OF 9,10-BIS(METHOXYMETHYL)-9,10-DfflYDRO-9,10[l',2']BENZENOANTHRACENE-1,4-DIONE (72) 5.1. Photorearrangement of 72 in Acetonitrile Photolysis of 9,10-bis(methoxymethyl)triptycene- 1,4-quinone (72) at X > 300 nm, in deoxygenated acetonitrile, led to the formation of three photoproducts which, after column-chromatographic separation, were identified as the dark-blue norcaradiene 110 (3%), the colorless dihydroberizofuran 111, (19%) and the dark red benz[a]aceanthrylene 112 (18%). However, the corresponding semibullvalene derivative was not isolated. When a solution of 72 was irradiated at X > 300 nm in benzene, the isolated product yields changed to 10% of (iihydrofuran 111 and 33% of benz[a]aceanthrylene 112. 112 Figure 5.01. Photolysis of 72 in Acetonitrile. 93 Results and Discussion 5.1.1. Structure Elucidation of Photoproducts 103,110 and 111 The structural assignment of the blue norcaradiene photoproduct 110 was simplified not only by its blue color, which had been observed earlier in the case of norcaradiene 103, but also by comparing its X H NMR and TR spectra to those of 103. The JR spectrum supports the structure by the presence of two carbonyl bands at 1665 and 1646 cm"1. The base peak of the mass spectrum is at m/e 372, which is equivalent to the mass of the starting material. Similarities between norcaradiene 110 and 103 are mainly established by the X H NMR spectrum. This shows the presence of one aromatic ring between 8 7.66 and 7.19 ppm and the quinone vinyl hydrogens as an AB system at 8 6.64 ppm {J = 8 Hz). Furthermore, the assignment of the diene moiety was based on the coupling constants represented as a doublet at 8 6.90 ppm (J = 6 Hz), a doublet of doublets at 8 6.31 ppm (J = 9 Hz and 6 Hz), and a doublet of doublet at 8 6.16 ppm (J = 9 Hz and 5 Hz). Additionally, the doublets at 8 4.05 (J = 9 Hz) and 3.30 ppm ( J = 9 Hz) are representing the two hydrogens of one of the methoxymethylene groups, whereas the AB system at 8 3.28 ppm (J = 9 Hz) depicts the reiriaining methoxymethylene hydrogens. The methoxymethyl substituents are corifirmed by a singlet at 8 3.21 ppm and 3.17 ppm. The doublet at 8 2.85 ppm (J = 5 Hz) corresponds to the hydrogen at the cyclopropyl ring. As previously discussed (Chapter 4), the formation of norcaradiene derivative 110 is believed to proceed through a carbene intermediate, analogous to that of norcaradiene 103, as suggested by Iwamura.105 94 Results and Discussion The structure of dihydrobenzofuran 111 was assigned on the basis of the spectral data collected. The TR absorption at 3270 cm"1 clearly indicates the presence of an O H group. A molecular ion at m/e 372, the same as that of the starting material, was observed in the mass spectrum, suggesting that a rearrangement had occurred. The J H N M R spectrum of 111 is shown in Figure 5.02. Assignment of the peaks was confirmed by H M Q C and H M B C N M R experiments (Table W ) as well as by a COSY N M R experiment (Table V1TJ). The disappearance of the C H 2 -signal of one of the methoxymethylene groups and the appearance of one hydrogen singlet at 8 6.87 ppm instead, supported the proposed formation of an acetal group involving one of the methoxymethyl substituents. Also of note is the presence of two singlets at 8 3.98 ppm and 8 3.91 ppm corresponding to two different methoxy groups, indicating a loss of symmetry. As a result of the incorporation of one of the former quinone oxygens into the dihydrobenzofuran ring, the second quinone oxygen was reduced to a phenol group corresponding to the peak at 8 8.28 ppm 95 Results and Discussion 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 < i ' i pp* 9 B 7 6 S 4 3 2 1 0 Figure 5.02. lH NMR (CDC13) Spectrum of Dihydrofuran Derivative 111. 96 Results and Discussion Table V H *H NMR (500 MHz) and 1 3 C NMR (125 MHz) Data for Dihydrofuran 111" 20 n i "C NMR HMQC 'H- , 3 C HMBC N Carbon Spectrum(.125 MHz) ] H NMR Long-range 1 Assign- Correlations Correlations R ment (500 MHz) 5 ppm Y (Assignment) a 1 138.24 H-2,H-3 b 2&3 107.83(-ve),116.61(-ve) 6.48 (H-2 & H-3) c 4 126.00 H-3 d 5&16 121.3 l(-ve), 121.81(-ve) 7.22-7.17 (H-5 & H-7 or 6 or 14 or 15 16) e 6&7, 125.16(-ve), 124.97(-ve) 7.08-6.97 (H-6 & 14&15 124.82(-ve), 124.59(-ve) 7&14&15) f 8&13 120.48(-ve), 124.82(-ve) 7.40 & 8.22-8.16 H-7 or6 or 14 or 15 (H-8 & 13) S 9 57.60 H-13 or 8 h 10 53.91 CH2-19 i 11 & 10a 145.03, 145.03 j 8a & 12 146.15, 146.17 H-8 or 13, H-13 k 17 112.06(-ve) 6.87 (H-13) Me-18 1 18 58.22(-ve) 3.91 (Me-18) H-17 m 19 71.43 4.96 (CH2-19) n 20 59.60(-ve) 3.98 (Me-20) CH2-19 a -The assignments and chemical shifts of the 1 3 C N M R spectrum are listed in columns II and III, respectively. Column IV shows the *H N M R signal(s) which correlate(s) with the carbon of columns II and III, as obtained from the H M Q C experiment (1 bond correlation). The last column lists the hydrogen(s) which correlate(s) with the 1 3 C N M R signal of column II and III as obtained from the H M B C experiments (2 and 3 bonds correlation(s)). b - The results of the APT experiments are given in parentheses (-ve for C H and C H 3 carbon signals). 97 Results and Discussion Table VHI *H NMR Data (500 MHz) for Dihydrofuran 111 F.ntry Hydrogen Assignment 1H-NMR(500 MHz) 5 ppm (mult., J (Hz)) COSY Correlations a H-2&3 6.48 (AB system, J= 8 Hz) b H-5 & 16 7.22-7.17 (m) H-6,H-15 c H-6, 7, 14, 15 7.08-6.97 (m) H-5, H-8, H-16, H-13 d H-8 & 13 7.40 (d,J=7), 8.16-8.12 (m) H-7,H-14 e H-17 6.87 (s) f Me-18 3.98 (s) g CH2-19 4.96 (s) h Me-20 3.91 (s) i OH 8.28 (s) 98 Results and Discussion 5.1.2. Mechanism for Formation of Dihydrobenzofuran 111 Earlier investigations of the photochemistry of quinones containing tert-butyl side-chains have resulted in photorearrangements sirnilar to that found for quinone 72. One example is the photochemical conversion of tert-butyl- 1,4-quinone 113 into the corresponding dihydrobenzofuran derivative 114, reported by Orlando et al.117 The proposed mechanism involves an initial intramolecular y-hydrogen abstraction resulting in a semiquinone biradical 113a (Figure 5.03). Biradical 113a is suggested to undergo intramolecular cyclization to give spirocyclopropane 113b, followed by an electron demotion to yield zwittterion 113c. The cyclopropyl ring opening is believed to be initiated by a strong tendency to aromatization. Dihyoiobenzofuran derivative 114 is formed as a result of a hydrogen transfer. In order to confirm the reaction pathway, Farid118 conducted trapping experiments of biradical 113a with sulfur dioxide. Several products were isolated, and explained by the formation of the corresponding sulfuric acid benzoquinone precursor resulting from the initial addition of sulfur dioxide to the radical side-chain of 113a followed by a hydrogen transfer. 99 Results and Discussion 114 113d 113c Figure 5.03. Mechanism for the Formation of Dihyoiofuran Derivative 114. Based on the structural similarities between photoproducts 114 and 111, quinone 72 is believed to undergo a photorearrangement by a mechanism analogous to that proposed by Orlando et al.117 as illustrated in Figure 5.04. 100 Results and Discussion CH2OCH3 111 Figure 5.04. Mechanism for the Formation of Dihydrofuran Derivative 111. The more favorable y-hydrogen atom abstraction (Norrish type JJ photoreaction) involving one of the methoxymethyl groups and a quinone oxygen of 72 (Figure 5.04) may explain the low yield of norcaradiene 110 (Section 5.1). The pathway, giving rise to photoproduct 111, is believed to be preferred due to the radical-stabilizing effect of the methoxymethyl substituent. The activating effect that alkoxy groups possess in promoting hydrogen abstractions in the Norrish 101 Results and Discussion type U photoreaction has clearly been demonstrated by Wagner and co-workers in arylalkyl ketones.119 Wagner showed that a hydrogen abstraction will be favorable if the y-substituent stabilizes the resulting radical site. In the case of the methoxymethyl group of quinone 72, the avanability of the lone pairs on the oxygen is believed to contribute to the resonance stability of radical 72b. The mechanism is assumed to proceed through dispiro compound 72c, which is thought to be formed by an intramolecular cyclization of biradical 72b. An electron demotion is believed to occur, resulting in zwitterion 72d. This is proposed to undergo cyclopropyl ring opening to yield 72e. Finally, a hydrogen transfer is suggested to take place leading to photoproduct 111. 5.1.3. Structure-Reactivity Analysis of Quinone 72 As demonstrated by the X-ray crystal structure of quinone 72 (Figure 5.05), the intramolecular distances between the y-hydrogen (hydrogens 6 and 7) and the quinone oxygen (oxygen 1) are within the proposed abstraction distance of 2.72 A (sum of the van der Waals radii for hydrogen and oxygen).120 The involvement of the Norrish type II photoreaction leading to dihydrofuran 111 is geometrically favorable as indicated by the two abstractable hydrogens at C=0 H distances of 2.44 and 2.53 A and angle values in Table LX. As discussed earlier (see p 24, Introduction), the optimum range for the angle A is between 90-120°. Thus in quinone 72, with A angles at 89.0 and 102.7°, n-orbital abstraction is favored. Angles co, at 13.02 and 24.69°, are also close to the optimum value of zero. As noted earlier, the angle 0 may differ from the preferred 102 Results and Discussion value of 180°, as seen in this case. This analysis is based on the assumption that the reactive excited state geometry in solution is close to the ground state geometry as determined by X-ray crystallography.121 Figure 5.05. X-ray Crystal Structure of Quinone 72. Space group Cl/c (#15), a = 15.772(1) A, b = 8.000(1) A, c = 14.7883(9) A , B = 98.430 (6)°, Z = 4; R = 4.0%. 103 Results and Discussion Table TX Crystallographically Determined Angles for Quinone 72 Angle Value (°) A C2, 01, H7 98.0 A C2, OI, H6 102.7 0 C l l , 01, H7 92.1 0 C l l , 01, H6 97.5 CO C2, OI, H7 13.0 CO C2, OI, H6 24.7 5.1.4. Structure Elucidation of Product 112 Compound 112 was proposed as a phenolic aldehyde having the benz[a]aceanthrylene carbon skeleton, based on its spectral data. The IR spectrum indicates the presence of an O H group at 3332 cm"1 and a carbonyl group at 1643 cm"1. As a result of the conjugated TC-system, the absorption of the aldehyde is shifted to a lower frequency. Structure 112 was further supported by the mass spectrum with a base peak of m/e 296. This mass corresponds to the loss of a methoxymethyl group as well as the loss of a methoxy group from the original quinone 72. The strongest spectral evidence supporting the structure 112 came from the J H N M R , COSY NMR, as well as from H M Q C and H M B C N M R experiments. The absence of the methoxymethyl groups was confirmed by the presence of hydrogens in the aromatic region only. Correlating the carbon and hydrogen atoms as seen from Table X , led to the proposed assignment of benz[a]aceanthrylene 112. The singlet at 5 11.55 ppm is in agreement with the general region of chemical shifts expected for an aldehyde hydrogen. 104 Results and Discussion 105 Results and Discussion Table X *H NMR (500 MHz) and 1 3 C NMR (125 MHz) Data for Benz[a]aceanthrylene Derivative 112" 6 112 E 1 3 C N M R 'H- 1 3 C HMBC lllll Carbon Assign-Spectrum (125 MHz) 6 ppm. APT1' Correlations Long-range Correlations < 7* ment (500 MHz) 8 ppm (Assignment) a 1 154.34 H-2 b 2 128.47(-ve) 8.85 (H-2) c 3 125.99(-ve) 7.55-7.46 (H-3) d 3a 129.12 e 4 126.07 r 4a 130.01 H-5, H-7(4-bonds) g 5 126.47(-ve) 9.28 (H-5) H-7 h 6 127.90(-ve) 7.73-7.70 (H-6) H-8 i 7 128.32(-ve) 7.84-7.80 (H-7) H-5 j 8 125.35(-ve) 9.02 (H-8) H-6 k 8a 133.21 H-8, H-6(4bonds) 1 9 125.12(-ve) 8.26 (H-9) in 10 & 11 127.31(-ve), 128.83(-ve) 7.55-7.46 (H-10,H-11) H-12 n 12 125.68(-ve) 8.62 (H-12) H - l l 0 12a 140.10 H-12 P 12b 138.03 q 12c 136.36 H-8 12d 117.12 12e 132.48 H-2 13 193.26(-ve) 11.55 (H-13) a -The assignments and chemical shifts of the C N M R spectrum are listed in columns II and III, respectively. Column IV shows the *H N M R signal(s) which correlate(s) with the carbon of columns II and III, as obtained from the H M Q C experiment (1 bond correlation). The last column lists the hydrogen(s) which correlate(s) with the 1 3 C N M R signal of column II and III as obtained from the H M B C experiments (2 and 3 bonds correlation(s)). b- The results of the APT experiments are given in parentheses (-ve for C H and C H 3 carbon signals). 106 Results and Discussion Table XI *H NMR Data (500 MHz) for Benz[a]aceanthrylene Derivative 112 Entry Hydrogen Assignment 1H-NMR(500MHz) 8 ppm (mult., J (Hz)) COSY Correlations a H-2 8.85 (d,J= 8.5) H-3 b H-3 Part of mat 7.55-7.46 H-2 c H-5 9.28 (d, J=9) H-6 d H-6 7.73-7.70 (m) H-5 e H-7 7.84-7.80 (m) H-8 f H-8 9.02 (d,J=8.5) H-7 g H-9 8.26 (dd, J=7&6) H-10 h H-10 Part ofm at 7.55-7.46 H-9 i H - l l Part ofm at 7.55-7.46 H-12 j H-12 8.62 (dd, J=6&7) H - l l k OH 10.20 (s) 1 CHO 11.55 (s) 5.1.5. Mechanism for the Formation of Benz[a]aceanthrylene Derivative 112 Benz[a]aceanthrylene derivatives have been commonly observed as by-products in the photochemistry of triptycenes as demonstrated by Iwamura et al.122 The photochemistry of 107 Results and Discussion triptycenes was also of interest to Wheeler et al.123 who investigated the photochemical isomerization of 1,4-dimethyoxytriptycene (115) in methanol (Figure 5.07). Instead of the expected norcaradiene derivative similar to that found by Iwamura (Section 4.1.2), Wheeler obtained benz[a]aceanthrylene 117. Wheeler suggested that triptycene 115 formed norcaradiene 116, followed by a thermal conversion to compound 117, accompanied by the loss of methanol. 108 Results and Discussion Applying the proposed thermal rearrangement step to a mechanism which involves dihydrofuran derivative 111 may explain the formation of benz[a]aceanthrylene 112 (Figure 5.08). + C H 3 O H f Figure 5.08. Proposed Mechanism for the Formation of Benz[a]aceanthrylene 112. 109 Results and Discussion Although compound 118 was not detected in the reaction rjoixture, it is possible that the acetal ring of 111 could open under the photolysis conditions. Compound 118 could then react further, forming the carbene intermediate 118a as discussed earlier for the formation of norcaradiene 113. Opening of the cyclopropyl ring, elimination of the methoxymethyl substituent, and loss of the hydroxy group could then give benz[a]aceanthrylene derivative 112. Two control experiments were conducted in order to detennine i f dihydrofuran derivative 111 was a potential precursor. Treatment of 111, dissolved in acetone, with aqueous hydrochloric acid (15%) followed by stirring the reaction mixture overnight, did not result in the formation of any major product, as the reaction contained a mixture of compounds, which could not be identified. The possibility exists that hydroquinone 118 is not a stable intermediate, as it is in equilibrium with dihydrofuran 111. Likewise, irradiation (2 h) of dihydrofiiran derivative 111 under the same photolysis conditions as described at the beginning of this section, did not lead to photoproduct 112. Based on these results, it may be concluded that either the reaction conditions are very specific and were not reproduced in the control experiments, or a different pathway may explain the photoreaction. The tentative mechanism will have to be evaluated and more studies will have to be conducted in this area to fully determine the reaction pathway for the formation of photoproduct 112. As was the case for quinones 63 and 69, quinone 72 was found to be unreactive upon irradiation (8 h) through Pyrex (k > 290 nm) in the solid state. The lack of reactivity may be explained by reasoning analogous to the rationalization proposed in Section 3.4. 110 Results and Discussion P A R T H T H E C O N T R O L O F R E A C T I O N M U L T I P L I C I T Y I N T H E S O L I D S T A T E : I O N I C S E N S I T I Z E R S A N D I O N I C H E A V Y A T O M E F F E C T S Although the control of the multiphcity of a photochemical reaction in solution has been well established over the years by sensitization and quenching techniques, not much attention has been devoted to this area of research in the solid state. In order to enhance the photochemical triplet behavior of a probe molecule in the solid state, heavy atoms, which enhance intersystem crossing or sensitizers, which promote triplet-triplet energy transfer, could be introduced. The two components would have to be in close proxknity to one another. This may be achieved by combining two functionally different molecules in the crystalline state by forming a salt. The auxiliaries chosen for this study are either inorganic cations (heavy atoms), or triplet energy sensitizer arnines to populate the triplet excited state in a probe molecule containing a carboxyhc acid functionality. The differential singlet/triplet reactivity of the probe molecule would then be monitored to detennine the success of the energy transfer. The application of the ionic auxiliary concept would permit the investigation of how distances and orientations, determined by X-ray crystallography, affect the efficiency of energy transfer in the solid state. I l l Results and Discussion CHAPTER 6 GENERAL ORGANIC SYNTHESIS 6.1. Preparation of 3, y-Unsaturated Ketones: 2-(l-Cyclopentenyl)cyclopentanone (121) and 2-(l-Cyclohexenyl)cyclohexanone (125) The 3, y-unsaturated keto-acid 121 was first synthesized by Givens et al.124 a by alkylating 2-cyclopentylidene cyclopentanone (119) with methyl bromoacetate to yield ester 120, followed by hydrolysis with methanolic KOH. The procedure for the preparation of 2- cyclop entylidene cyclopentanone (119) was described by Varech et al.125 and involves a based-catalyzed aldol condensation between two molecules of cyclopentanone (118). 2 121 Figure 6.01. Preparation of 2-(l-Cyclopentyl)cyclopentanone (121). 112 Results and Discussion The 6, y-unsaturated keto-acid 125 was prepared in an analogous manner to 121, except for the initial aldol condensation step between two cyclohexanone molecules (122), which was carried out under acidic conditions according to procedures described by Gault et al.126 125 Figure 6.02. Preparation of 2-(l-Cyclohexenyl)cyclohexanone (125). 6.2. Preparation of /j-Aceryl-iV^-dimethylbenzylamine (128) The synthesis of /?-acetyl-AyV-cumethylbenzylaniine (128) involved the initial preparation ofp-(dimethylaminomethyl)benzonitrile (127) from a-bromo-/>-toluonitrile (126) as described by Norman et al.127 This entails an initial nucleophilic substitution reaction of a-bromo-/?-toluonitrile (126) with dimethyl amine at -78°C and was followed by a Grignard reaction with methyl-magnesium iodide to give compound 128. 113 Results and Discussion 126 127 128 Figure 6.03. Preparation of/?-Acelyl-AyV-(limethylbenzylamine (128). 6.3. Preparation of 9,10-Dihydro-9,10-ethenoanthracene Acids Dibenzobarrelene ester 130, originally prepared by Vaughan et a/.,1 2 8 was obtained by a Diels-Alder reaction between anthracene and ethyl propiolate in a sealed Carius tube. The ester was then reduced by hthium aluminum hydride-aluminum trichloride to the corresponding alcohol.129 The introduction of the extended side-chain to obtain acid 132 was achieved by addition of succinic anhydride to a refluxing pyridine solution of alcohol 131, a procedure described for a different system by Aries.130 Acid 133 was prepared by reacting alcohol 131 with bromoacetic acid in the presence of sodium hydride under reflux conditions, a reaction adapted from Brady et a/.1 3 1 114 Results and Discussion Figure 6.04. Preparation of 9,10-Dihydro-9,10-ethenoanthracene Acids 132 and 133. 115 Results and Discussion CHAPTER 7 THE PHOTOCHEMISTRY OF p, y-UNSATURATED KETONES 7.1. The Solution Phase Photochemistry of 2-(l-Cyclopentenyl)cyclopentanone Derivative The first type of probe molecule chosen for testing the success of energy transfer was the P, y-unsaturated ketone 121. The photochemistry of this acid has been investigated by Givens et al.,132 who showed that compound 121 undergoes primarily a 1,3-acyl shift (1,3-AS) reaction from the excited singlet state upon direct irradiation in solution to form P, y-unsaturated ketone 135. However, upon triplet-sensitized photolysis, the cyclopropyl ketone derivative 134 is formed by the oxadi-TC-methane (ODPM) rearrangement from the triplet excited state. Compound 121 would hence serve as a good candidate for investigating the chemical effects that a series of increasingly heavy alkali metal cations and various ionic sensitizers containing an arnine functionality would have on promoting triplet state reactivity in the solid state. 121 sens hu direct hu O CH2COOH 134 121 135 Figure 7.01. Photolysis of Keto-Acid 121. 116 Results and Discussion 7.2. The Solid State Photochemistry of 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 and its Alkali Metal Salts The direct irradiation of keto-acid 121 in the crystalline state was first investigated by Scheffer and Ramamurthy et al.,133 who detected the same characteristic 1,3-acyl shift reactivity that had been observed in solution, yielding photoproduct 135. The same communication describes an investigation of the heavy-atom effect by preparing the Li + , Na+, K + , Rb+ and Cs+ salts of compound 121 and subjecting them to direct photolysis both in the crystalline state and solution. A significant cation effect was observed in the solid state but not in solution. The results were intriguing, showing that the Li + salt afforded 9% of the ODPM product 134, the Na+ salt 52%, the K + salt 65%, the Rb+ salt 60% and the Cs+ salt 40%. Hence the greatest perturbation of the photoproduct ratio did not result from the heaviest metal ion. This was attributed to the different crystal structures with different distances and orientations between metal ions and organic moieties. For instance, the closest contact distances between the K + and oxygen atom of the ketone group of keto-acid 121 was determined to be 2.79 A, whereas the X-ray crystal structure of the Rb+ salt showed a distance of 3.43 A . The similar amounts of product arising from the triplet state were proposed to result from the nearly identical conformations of the potassium and rubidium salts in the solid state. Additionally, it was suggested that intersystem crossing was enhanced by the heavy atoms as a result of the coordination of the metal ions to the ketone oxygen atoms. This paper also demonstrated the first example of the perturbation of uriimolecular photochemical behavior as a result of heavy metal-containing zeolites. Ramamurthy investigated the photophysical behavior and photoproduct distribution of methyl ester 121 in heavy metal-117 Results and Discussion containing zeolites. The fluorescence and phosphorescence emission intensities were measured, and the photoproduct ratios were determined by gas chromatography. The decrease in singlet lifetime and fluorescence intensities and the increase in the phosphorescence intensities were observed as a result of the heavy atom effect. Furthermore, the photoproduct ratios in the zeolite systems confirmed the effects that the alkali metals exerted on the photorearrangement of the salts in the crystalline state. 7.3. The Photochemistry of Ionic Sensitizer Salts of 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 The employment of ionic sensitizers to bring about triplet state reactions was the next target of investigation. The amines chosen for study were 3-(dimemylamino)propiophenone (136), commercially available as the hydrochloric salt from Aldrich, p-acetyl-NJf-dimethylbenzylamine (128), a synthesized compound, and 4-acetylpyridine (137), a compound that is obtainable from Aldrich. The selected amines contained an acetophenone group, which is a good sensitizer for most O D P M reactions.134 This is important in order to achieve selective excitation of the sensitizer, as it is impossible to use a large excess of a sensitizer in the crystalline state compared to solution state photolysis experiments. Reaction of the keto-amines with keto-acid 121 afforded salts 138, 139 and 140 as white powders. The samples were irradiated in the solid state through a uranium glass filter (A, > 330 nm) at a wavelength where only the aryl ketone of the sensitizer absorbs, followed by acidic work-up and treatment with diazomethane (Figure 7.02). 118 Results and Discussion ' k 1. hv, crystal 2. acidic workup 3. C H 2 N 2 no reaction Figure 7.02. Photolysis and Work-Up of Salts 138,139 and 140. 119 Results and Discussion As shown above (Figure 7.02), amines 136 and 128 acted as ionic sensitizers, giving the ODPM ester 134a exclusively, as no singlet-mediated 1,3-AS reactivity was observed. Only traces of ODPM product 134a could be detected as a result of photolysing salts 138 and 139 in methanol. The solutions were probably too dilute (10"2M) for energy transfer to occur during the excited state lifetime of the sensitizer, as the ionic pair would now be separated. Amine 137, however, did not act as an ionic triplet energy donor, leading to no reaction after irradiation (24 h) both in the solid state and solution. The detailed results of these experiments are summarized in Table XXI (Experimental, p 254). The poor quality of the crystals, even after successive recrystalhzations, made it impossible to obtain X-ray crystal structures of salts 138, 139 and 140. This may be attributed to decomposition, possibly, of the sensitizer amine component to the amine oxide. However, the decomposition products were never characterized. Therefore, a correlation between the structures of the individual salts and the reactivity was difficult to establish. Although the potential of utilizing ionic sensitizers to bring about a triplet state reaction in the solid state has been demonstrated by the above examples, the full interpretation of these preliminary results had to be postponed until a more suitable probe molecule could be found. 120 Results and Discussion 7.4. The Solution Phase Photochemistry of l-(l-Cyclohexen-l-yl)-2-oxocyclohexaneacetic Acid (125) The promising results brought about by the alkali salts of the 5-membered ring keto-acid 121, encouraged us to study its 6-membered counterpart (125). 125 Figure 7.03. l-( 1-Cyclohexen- l-yl)-2-oxocyclohexaneacetic Acid (125). The photochemistry of 2-(l-cyclohexenyl)cyclohexanone 123a had previously been analyzed by Cookson and Rogers,135 who demonstrated that irradiation of a rnixture of isomers 123a and 123 in cyclohexane gave cyclobutanol 141 as the major photoproduct (Figure 7.04). Hence, compound 123a undergoes a y-hydrogen abstraction (Norrish type JJ reaction). However, irradiation of 123 in acetone yielded only a small amount of cyclobutanol 141, with the major product being the isomer 123a as the result of an a, p to P, y isomerization. There was no evidence of products arising from 1,3- or 1,2-acyl shifts. Cookson and Rogers later showed136 that upon direct irradiation, compound 123 isomerizes to 123a via the lowest excited triplet state, followed by a singlet state reaction to give cyclobutanol 141. The failure of the oxadi-7i-methane reaction upon acetone-sensitized irradiation of 123a was believed to result from loss of triplet energy by ring-twisting or reaction from a different inactive lowest triplet state. 121 Results and Discussion 123a Figure 7.04. Rearrangement of 2-Cyclohexenylidenecyclohexanone (123) and 2-( l-Cyclohexenyl)cyclohexanone (123a). The direct irradiation of P,y,(3',y'-dienones had been studied by van der Veen and Cerfontain,137 whose results revealed that dieneone 142 was photostable at X > 300 nm. The observed photostabihty was rationalized in terms of rapid radiationless decay of the excited singlet state, enhanced by CT-interactions between the carbonyl 1(n,%*) state and the homoconjugated 1,4-diene moiety.137 122 Results and Discussion 142 Figure 7.05. Dieneone 142 Studied by Direct Irradiation. Although these results indicated that the 6-membered ring keto-acid 125 would not react in the same manner as the 5-membered ring keto-acid 121, keto-acid 125 was nevertheless irradiated in the solid state (Pyrex, X > 290 nm, 44 h) as well as in acetonitrile or acetone (2 h). The results in solution were analogous to dieneone 142, as no reaction was observed. An X-ray crystal structure of 125 was obtained in order to determine the distances between the carbonyl oxygen and the y-hydrogens that could be abstracted (Figure 7.06). The X-ray crystal structure of keto-acid 125 represented in Figure 7.06 shows the most probable orientation of the disordered molecule. The stereodiagram is also given, illustrating intermolecular hydrogen bonding (Figure 7.07). 123 Results and Discussion Figure 7.06. X-ray Crystallographic Structure of Keto-Acid 125. Space Group C2/c (#15), a = 26.516(2) A,b = 6.9831 (3) A, c = 18.503(2) A, P = 131.394(4)°, Z = 8, R = 5.2%. 124 Results and Discussion Figure 7.07. Stereo Diagram of Keto-Acid 125, Showing Hydrogen Bonding. 125 Results and Discussion Despite the presence of three potential y-hydrogens, a closer look at the distances led to only one y-hydrogen (H17) which was within the proposed abstracting distance of 2.72 A 1 3 8 from the oxygen (01). Table XU shows the abstraction parameters obtained from the X-ray structure of 125 for non-bonded contacts less than 3.60 A. Table XU Hydrogen Abstraction Geometric Parameters for 125 Oxygen y-Hydrogen d(C=O....H)(A) A O G O 01 H17 2.67 64.43 62.25 116.50 01 H16 3.32 76.45 52.22 76.45 As shown in Table XU, the angle between the carbonyl carbon (Cl), the carbonyl oxygen (01) and y-hydrogen (H17), defined as A, is outside the favorable range of 90-120°. The same holds true for the angle co, representing the degree to which the abstractable hydrogen lies outside the mean plane of the carbonyl group, which has an ideal value of 0°. In addition, angle 9, defined as the angle between the carbonyl oxygen, the y-hydrogen, and the y-carbon, which has an ideal parameter of 180°, is also relatively unfavorable. The lack of reactivity of 125 may therefore be explained by these geometric parameters, which do not favor a y-hydrogen abstraction in the solid state. Hence, to study multiplicity effects in the solid state, a different system had to be chosen, in order to establish structure-reactivity relationships between a particular ionic sensitizer and a probe molecule. 126 Results and Discussion CHAPTER 8 THE PHOTOCHEMISTRY OF 940-DrHYDRO-9,10-ETHENOANTHRACENE DERIVATIVES 8.1. Photolysis of ll-Hydroxymethyl-9,10-dihydro-9,10-ethenoanthracene (131) Mono substituted dibenzobarrelenes containing a methylene group at one of the vinyl positions were chosen for the study of the heavy atom effect and triplet-triplet energy transfer. In the past, 11-alkyl substituted dibenzobarrelenes have been shown to undergo the di-7t-methane rearrangement upon triplet-sensitized irradiation and dibenzocyclooctatetraene formation upon direct irradiation.139 Before carboxylic acid-substituted derivatives of the dibenzobarrelene system were prepared, the photochemical behavior of the corresponding hydroxymethyl compound 131 was determined in solution and the solid state. CH2OH 5 144 4 CHjOH CHjOH CH2OH hv direct via Si 1 131 8 via T\ 145 143 CHO Figure 8.01. Photolysis of Dibenzobarrelene 131. 127 Results and Discussion Direct irradiation of dibenzobarrelene 131 in acetonitrile with the Rayonet Photoreactor (254 nm) led to exclusive formation of the dibenzocyclooctatetraene derivative 143. However, changing the light source to a 450-W Hanovia lamp equipped with a Vycor filter (k > 240 nm) resulted in the formation of 143 as well as a small amount of (ubenzosermbulrvalene regioisomers 144 and 145 (Table XHI). In comparison, triplet-sensitized irradiation of alcohol 131 in acetone through a Pyrex filter (k > 290 nm) gave the corresponding dibenzosernibulrvalene regioisomers 144 and 145, as well as the dibenzosemibullvalene aldehyde 146. The aldehyde formation, which occurs only in acetone, may be explained by the presence of the potentially reactive C — H bond a to the oxygen in alcohol 131. Such oxidation reactions are commonly observed in the liquid phase photochemistry of alcohols, as a result of abstraction by a radical or a photo-activated ketone, which could be acetone in this case.140 Solid state irradiation of alcohol 131 with the Hanovia lamp gave cyclooctatetraene 143 as the sole product. Table XD3 Photolysis Results of Alcohol 131a Medium (wavelength) Alcohol 131 (%) Photoproduct 143 (%) Photoproduct i i i i i i i i i i i i i i i s Photoproduct Photoproduct 146 (%) Acetonitrile (k > 240 nm) 11 84 4 i 0 Acetonitrile (254 nm) 11 89 0 0 0 Acetonitrile (254 nm) 13 69 0 0 0 Acetone (k > 290 nm) 0 0 55 34 11 Acetone (?,> 290nm) 0 0 38 24 6 Solid State (k > 200 nm) 92 8 0 0 0 (a) A l l non-highhghted yields were determined by gas chromatography with an estimated error of ± 2%. The highUghted rows correspond to isolated yields. 128 Results and Discussion These results differ slightly from the data obtained by Cristol et al.,141 who showed that direct (254 nm) irradiation of the corresponding acetate derivative of 131 in acetic acid or benzene led to a 4 : 1 mixture of the acetate derivatives of cyclooctatetraene 143 and semibullvalene 144. 8.2. Triplet-Triplet Energy Transfer in Zeolites In collaboration with Dr. V. Ramamurthy and co-workers at Tulane University in New Orleans, the triplet state reactivity of alcohol 131 in the presence of a variety of sensitizers was investigated in a zeolitic environment by selectively irradiating through Pyrex (X > 290 nm). The sensitizers chosen for study were acetophenone (147), /j-methoxyacetophenone (148) and a-aminoacetophenone hydrochloride (149). The incorporation of the sensitizer and probe molecule 131 within the zeolite cage was achieved by stirring the sensitizer or probe molecule in a hexane solution with zeolite K-Y, followed by filtration, washing with hexane and vacuum drying the complex. Among the numerous naturally occurring and synthetically induced zeolites, zeolite K-Y is one of two synthetic forms of zeolites, X and Y, also known as faujasites, which differ by the typical unit cell composition: X type = M86(AlO2)86(SiO2)i06 • 264 H 2 0, Y type = M56(A102)56(Si02)i32 • 253 H 2 0 . 1 4 2 The K-Y complexes were irradiated in the solid state and as a hexane slurry. Triplet-triplet energy transfer was achieved in all cases, and p-methoxyacetophenone (148) proved to be the most effective sensitizer as shown by the increased triplet product formation of 144 and 145 (Table XIV). 129 Results and Discussion Table X I V Zeolite Photolysis Results3 Medium Irradiation Medium Photoproduct 143 Photoproduct 144 Photoproduct 145 K Y slurry0 77 19 4 solidc 84 15 1 K Y + O M slurry 20 54 26 solid 7 65 28 147 K Y + O if slurry 7 59 34 148 sohd <1 54 45 K Y + O J f slurry 51 21 28 r ^ N ^ ^ C H 2 N H 3 + a " 149 sohd 32 32 36 (a) A l l yields were determined by gas chromatography with an estimated error of + 2%. The average loading of material in the zeolite was 25, indicating the presence of one sensitizer molecule and one probe molecule for every 25 supercages. These results were obtained by Ramamurthy et al. (b) Samples were irradiated for 2.5 h in a suspension of hexane. (c) Samples were irradiated as powders for 20 h. These results may be explained by the different low-lying triplet states of the sensitizers. Compared to acetophenone, with a low-lying n, Tt* triplet state at 26,900 cm"1, the lowest energy state of/?-methoxyacetophenone is the 7t, TC* triplet state.143 This can be attributed to the methoxy substituent which raises the energy of the n, TC* triplet state to 27,800 cm"1 and lowers the energy 130 Results and Discussion of the TC, TC* triplet state (25,600 cm"1). The TC, TC* triplet state is more desirable than the n, TC* triplet state since it is relatively chemically inert towards a photochemical reaction with the acceptor molecule (i.e. alcohol 131), a process that may interfere with triplet-triplet energy transfer. Furthermore, the relatively long radiative lifetime of the TC, TC* state of p-methoxyacetophenone (xrad = 0.38 s) versus that of acetophenone (T r ad = 0.005 s) contributes to the ability of compound 148 to be the better sensitizer.143 Additionally, the dry powder technique resulted in an enhanced triplet-triplet energy transfer compared to irradiation in the slurry. This may be explained by an increase in triplet lifetime in the solid state or a decrease in mobility between the probe molecule and sensitizer as the zeolite channels are filled with solvent. 8.3. Photolysis of 13-(ll-Methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132) The first carboxylic acid that was chosen for the heavy atom investigation was dibenzobarrelene 132. In order to confirm that this compound would lead to similar photochemical results as alcohol 131, it was irradiated in acetonitrile, acetone and in the solid state. The results are surnmarized in Table X V . 131 Results and Discussion 132 Results and Discussion Table XV Photolysis Results of Succinate 132a Medium (wavelength) Succinate 132b (%) Photoproduct 150 (%) Photoproduct 151 Photoproduct 152 (%) Acetonitrile (X > 240 nm) 3 80 17 0 Acetonitrile (254 nm) 3 83 14 0 Acetonitrile (254 nm) 2 66 11 0 Acetone (X > 290 nm) 5 0 75 11 Acetone (X>290 nm) 4 0 58 12 Solid State (X > 240 nm) 87 6 7 0 (a) All non-highlighted yields were determined by gas chromatography with an estimated error of ± 2%. The highlighted rows correspond to isolated yields, (b) Succinate 132 was identified as the methyl ester derivative. The methylated succinate derivative was also subjected to the same photolysis conditions and the jesults were determined to be equivalent to those of acid 132. As seen from Table XV, direct irradiation of 132 in acetonitrile also produces a small amount of the triplet product sernibulfvalene 151. Furthermore, the reaction in the solid state results in an almost equal distribution of the singlet and triplet products. 8.4. The Heavy-Atom Effect in the Photochemistry of Succinate 132 Difficulties arose in the preparation of the alkali metal salts of succinate 132, as the side chain had a tendency to cleave during treatment with sodium or potassium hydroxide. Milder conditions had to be applied, and the salts were formed by mixing equimolar amounts of sodium 133 Results and Discussion or potassium bicarbonate with succinate 132. Graph I represents the results of irradiation of the sodium and potassium salts in the sohd state and in solution. The cations have a significant effect on the reaction in the crystalline state, leading to a product distribution favoring the triplet-derived dibenzosermbulfvalene regioisomers 151 and 152. This behavior can be attributed to an increase in the rate of intersystem crossing from Si to Ti resulting from enhanced spin-orbit coupling. In solution, however, no significant effect was observed. As the salts are sotvated and separated in the methanol solution, the heavy atom effect is expected to be weak, as it operates only over relatively short distances as shown by Chandra et al.144 X-ray crystal structures of the sodium and potassium salts could not be obtained due to the amorphous, hygroscopic quality of the solids obtained. 134 Graph I Irradiation Results of Alkali Salts of Succinate 132 Results and Discussion H (132) Na (153) K (154) 8.5. Photolysis of 13-(ll-Methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetic Acid (133) As a result of the hruitations inherent in the use of acid 132, a different side chain had to be utilized, which would be able to withstand treatment with alkali hydroxides, and later arnines to make sensitizer salts. Dibenzobarrelene derivative 133 was prepared and subjected to irradiation experiments in solution and the solid state in order to determine the photoproducts. The results of 135 Results and Discussion irradiation in solution were analogous to those found for dibenzobarrelene 132. However, in the sohd state, less triplet-derived sernibulivalene 156 and 157 formed, resulting in an increase of singlet-derived cyclooctatetraene 155 (Table XVI). 155 156 157 Figure 8.03. Photolysis of Acetic Acid Derivative 133. 136 Results and Discussion Table X V I Photolysis Results of Acetic Acid 133a Medium (wavelength) Acid 133b (%) Photoproduct 155 Photoproduct 156 (%) Photoproduct 157 (%) Acetonitrile (X > 240 nm) 0 76 21 3 Acetonitrile (254 nm) 0 77 23 0 Acetonitrile (254 nm) 0 40 10 0 Acetone (A, > 290 nm) 0 0 72 28 Acetone (>>>290 nm) 0 0 46 15 Sohd State (X > 240 nm) 93 6 1 0 (a) A l l non-highhg ited yields were determined by gas chromatography with an estimated error of ± 2%. The highhghted rows correspond to isolated yields, (b) Acid 133 was identified as the methyl ester derivative. 8.6. The Heavy-Atom Effect in the Photolysis of Acetic Acid Derivative 133 The L i + , Na + , K + , Rb + and Cs + salts of acid 133 were prepared from the corresponding alkali hydroxides and subjected to direct photolysis (Vycor, X > 240 nm) both in the crystalline state and as a methanol solution. Graph II is a representation of the irradiation results (2 h), showing the combined percentage of triplet-derived photoproducts 156 and 157. 137 Results and Discussion Graph JJ Irradiation Results of Alkali Salts of Acetic Acid 133 0 I i | i i i i Hor Li Na K Rb Cs Me (158) (159) (160) (161) (162) The results summarized in Graph II reveal a strong cation effect in the solid state, but not in solution, similar to the earlier findings with succinate 132. This demonstrates again that in solution, the interaction or association between alkali ions and the organic substrate is reduced significantly, hence affecting the photochemical behavior of the probe molecule. Contrary to predictions,145 the greatest perturbation of the photoproduct ratio does not result from the salt with the heaviest alkali metal ion. The Uthium cation, even though it is not a heavy atom, led to a large increase in triplet-derived product formation, whereas the cesium cation effect is less than that due to rubidium. It is possible that these unexpected results may be due to differences in the 138 Results and Discussion distances and orientations between the metal ions and organic moieties in the crystal structures of the salts. This concept was supported by Scheffer et al.146 who interpreted the X-ray structures for the potassium and rubidium salts of keto-acid 121 (Figure 7.01). Hence, the observed enhancement of ISC may be explained by the more favorable positioning of the L i + cation in salt 158, compared to the Cs + ion with respect to the probe molecule 133. The deviation of these results may depend on the orientation of the heavy atom with respect to the chromophore orbital. Another factor that could contribute to the enhanced triplet-derived product formation, apart from the heavy atom effect, could be the manner of coordination between the metal ions and the ethenoanthracene carbonyl oxygen. Triplet enhancement resulting from a hthium cation was also observed by Ramamurthy et al.147 who investigated the Norrish type I and II reactions of macrocyclic ketones in the cavities of alkali metal-containing zeolites. The Uthium cation was believed to bind more strongly to the carbonyl chromophore. Hence, the electronic interaction between the cation and the probe molecule is of importance. The strength of the bonding interaction between the cation and probe molecule is suggested by Anpo et al.148 to be directly dependent on the charge density or electrostatic potential of the cation. The electrostatic potential in e/r (charge/radius) decreases with increasing atomic number of the cation ( L i + (1.67), Na + (1.05), K + (0.75), Rb + (0.67) and Cs + (0.59).1 4 8 Ramamuthy et al.149 demonstrated that higher charge densities (i.e. charge per unit volume of the cation) led to stronger bmding (AH binding: Na + , 14.9; K + , 11.0; Cs +, 7.9 kcal mole"1). In this case, the light L i + atom would have more influence on the reaction than the heavier Cs + atom. This is known as the light atom effect.149 Anpo et al.148 have also observed that the phosphorescence lifetimes of xanthone molecules in 139 Results and Discussion alkali-metal cation-exchanged Y-zeolites are affected by the cations. The singlet-triplet transitions were proposed to be affected by alkali metal cations resulting in a prolongation of the lifetimes of the excited triplet states in the order L i + (0.30 s), Na + (0.28 s), K + (0.15 s), Rb + (0.04 s) and Cs + (0.03 s). Applying this observation to acid 133, the presence of the L i + cation may lead to a longer triplet lifetime, hence increasing the di-TC-methane rearrangement product formation. The conversion of each reactant to photoproducts was kept below 15%, as a result of 2 h of irradiation, in order to minimize changes in the crystal environment, which may lead to altered reaction selectivity. However, the photolysis experiments were conducted over a period of 22 h (Graph m ) in order to detect any changes in the reaction rate resulting from changes in the crystal structure. A l l alkali salts followed approximately a first-order plot indicating a constant rate of conversion with time. 140 Results and Discussion Graph UI Conversion versus Irradiation Time Experiments 1.95 H L O G [R] 1.9 1 1.85 H 1.8 -\ 1.75 ^ - L i - • - N a K - * - R b ^ - C s 2 4 5 Irradiation Time (h) ~i 6 —i— 11 22 R is the percentage of starting material rernaining at the different irradiation time intervals. To confirm the heavy atom effect results, the photochemistry of the methyl ester of 133 was also investigated in alkali metal-containing zeolites in collaboration with Ramamurthy et al. The photochemical outcome in IN/TX zeolites in the sohd state or in a hexane slurry verified the strong effect earlier observed for the L i + cation. Overall, the results in the slurry display a similar trend in triplet product formation as shown previously (Graph JJ). However, in the sohd state in the zeolites, the K + cation only exerts a minute heavy atom effect on the ester of 133. The sohd state reactions in the zeolites were carried out over 20 h compared to 2 h of photolysis of the 141 Results and Discussion alkali salts. However, the irradiation of the ester of 133 as a slurry in the heavy metal containing zeolites was performed over a period of 2.5 h, leading to somewhat more comparable results. 142 Results and Discussion 8.7. Structure Elucidation of Cyclooctatetraene and Semibullvalene Photoproducts All photoproducts were isolated and fully characterized by spectroscopic and analytical methods. The [ H NMR spectra of the cyclooctatetraene photoproducts 143, 150 and 155 are quite similar, differing only in the side-chain. The aromatic hydrogens appear as a multiplet integrating for eight hydrogens between 5 7.20 and 7.00 ppm. The vinyl hydrogens closest to the side chain are represented by a broad singlet at 8 6.8 ppm. For alcohol 143 and succinate 150, the rermining two vinyl hydrogens, appear as an AB system (J= 12 Hz) at 8 6.78 ppm. The coupling interaction between these chemically ^equivalent protons results in the splitting by the adjacent protons. In the case of acid 155, the vinyl protons give a singlet at 8 6.72 ppm, indicating that they are chemical shift equivalent. The multiplicity of the CH^O-group at the vinyl position of the three distinct cyclooctatetraenes also differs. An AB system (J = 14 Hz) is observed in the spectra of alcohol 143 and acid 155 at 8 4.42 ppm and 8 4.39 ppm respectively, compared to a doublet (J = 1 Hz) in the spectrum of succinate 150 at 8 4.88 ppm. This doublet may actually be an AB system with the outer transitions being indistinguishable from the noise of the base line of the spectrum. Structure determination of cyclooctatetraene has shown that the molecule is tub-shaped,150 and NMR studies have revealed that two dynamic processes may occur in solution, namely a conformational flip or rc-bond migration (Figure 8.04).151 More recently, Paquette et al.152 have investigated the dynamics of conformational mobility of chiral cyclooctatetraenes. As a result of the substituents, the tub-shaped cyclooctatetraene derivatives 143, 150 and 155 become chiral molecules with no plane of symmetry. Hence, the pair of hydrogens in the CH^O-group which give rise to the AB system can be interpreted as two diastereotopic geminal hydrogens. 143 Results and Discussion 163a 163b re-bond migration 163a 163c Figure 8.04. Tub-shape of Cyclooctatetraene (163a). The lH N M R spectra of photoproducts 144, 151 and 156 are typical of the diberizoserm^ullvalene skeleton. The multiplets in the region 8 7.25-6.85 ppm are assigned as the aromatic hydrogens. The pentalene hydrogens at carbons 4b, 8b and 8d respectively appear as two singlets in the ratio 1 : 2 at 8 4.5 ppm and 8 3.05 ppm. The spectrum of aldehyde 146 is similar to the spectrum of semibullvalene 144, differing only in the aldehyde peak at 8 9.24 ppm. The structure of the aldehyde was further corifirmed by the IR spectrum with a carbonyl peak at 1686 cm'andthe aldehyde C - H stretch at 2831 cm"1. 144 Results and Discussion The lH N M R spectra of the regioisomers 145, 152 and 157 vary slightly as a result of the loss of symmetry of the semibullvalene. The aromatic hydrogens produce a multiplet centered around 8 7.36 ppm representing one hydrogen and a multiplet corresponding to the remaining seven aromatic hydrogens centered at 8 7.18 ppm. The pentalene hydrogens are assigned as a doublet (J = 6 Hz, HUb) at 8 4.5 ppm, a triplet near 8 3.5 ppm (J = 6 Hz, Ihc) and a doublet at 8 3.14 ppm (J = 6 Hz, Hgb). The CH^O-group at carbon 8d is represented by an A B system (J = 12 Hz) indicating that the protons are diastereotopic. 145 Results and Discussion CHAPTER 9 TRIPLET-TRIPLET ENERGY TRANSFER IN A TWO-COMPONENT CRYSTALLINE SYSTEM 9.1. Photochemical Results Upon Irradiation of Salts 164,166 and Complex 165 After estabhshing the photochemical reactivity of carboxylic acid derivative 133 in solution and the sohd state, arnines linked to a sensitizer moiety were selected in order to study triplet-triplet energy transfer in the resulting crystalline organic salts. o R 164 155 O CH2OCH2 [2OD—] 1. hv, crystal 2. acidic workup 3. CH 2 N 2 R 156 R 166 157 R= CH2OCH2CO2CH3 Figure 9.01. Photolysis of Salts 164,166 and Complex 165. 146 Results and Discussion The selected amines were chosen on the basis of possessing an acetophenone moiety and their commercial availabihty from Aldrich. These included 3-(dimemylamino)propiophenone (136), 4-acetylpyridine (137) and 4'-piperazinoacetophenone (167). The salts 164, 166 and complex 165 were prepared as described in the Experimental Section (p 218-222) by adding equimolar amounts of acid 133 dissolved in ethyl acetate to the selected amines in ethanol. Irradiation of salts 164, 166 and complex 165 in methanol through a uranium glass filter (k > 330 nm) led to the detection of 1-2% of photoproducts 156 and 157 after 6 h, following work-up. The extent of dilution (10"2 M) may account for the reduced efficiency of the energy transfer between the sensitizer and the probe molecule. The amine-containing acetophenone moiety, finictioning as the sensitizer (donor), and the dibenzobarrelene operating as a quencher (acceptor), must be in close proximity for the triplet-triplet energy transfer to take place. Quenchers are known to accelerate the deactivation of the excited state, suppressing the photochemical reaction.153 The relationship between quantum yields and quencher concentrations is given by the Stern-Volmer equation.154 A plot of quantum yields in the absence (<J»°) and presence (<D) of the quencher versus the concentration of the quencher should lead to a straight line with a slope of kqT, where kq is the quenching constant and T the lifetime of the excited donor molecule. Figure 9.02. Stern-Volmer Equation. 147 Results and Discussion The quenching constant (kq) is usually assumed to be diffusion-controlled.155 If the lifetime of the donor is relatively short-lived, the concentration of the quencher will need to be higher to lead to efficient quenching, assigning the common value of 101 01/mol s to the quenching constant (kq).156 This is illustrated by Table X V U , which suggests that quencher concentrations of greater than 10"3 M lead to quenching of all species with a lifetime longer than 10"5 s. Hence, in solution the quencher (dibenzobarrelene component) concentration is assumed to be too dilute to give rise to an efficient energy transfer during the excited state lifetime of the sensitizer (acetophenone moiety). Table X V U Relationship between the Lifetime and Concentration of a Quencher that will lead to > 99% Quenching Lifetime (T) of D * (s) Quencher Concentration (M) IO-9 10 10"8 1 IO"7 0.1 IO"6 IO"2 I O 5 IO"3 IO"4 IO"4 IO"3 IO"5 Solid state photolysis of the two salts 164, 166 and the complex 165 resulted in the exclusive formation of photoproducts 156 and 157 (Table XVIJI). A control experiment showed that dibenzobarrelene 133 does not react under the same irradiation conditions in the solid state. 148 Results and Discussion Table XVJTI Solid State Photolysis Results of Salts 164,166 and Complex 165a Sensitizer Salt lllllililllll Complex Sensitizer 133 Ratio Phot 133b olysate Co i i i l l l l i i mposition 157 (%) 155 0 Ph-C-CH 2CH 2N(CH3)2 136 164 1 : 1 93 6 1 0 r=\j \ / / C ^ C H : ; 137 165 1 : 2 94 5 1 0 HWNH0"^CH, 167 166 1 : 1 81 15 4 0 (a) A l l yields were determined by gas chromatography with an estimated error of ± 2%. (b) Compound 133 was identified as the methyl ester derivative. A comparison of the results between salt 164 and complex 165 suggests that the ratio between the probe molecule and sensitizer does not seem to affect the efficiency of the triplet-triplet energy transfer. However, further experimentation in this area is needed. Conversions were kept below 20% in order to minimize the possibility of melting the sample. The reaction was monitored over 23 h and the conversion of starting material is illustrated in Graph V. Salt 166 was the most reactive. In order to achieve consistent results, the reaction time was kept at 9 h. After this time, a slight increase of reactivity of 166 was observed. These results may suggest possible melting of the crystal, a process that would bring about an increase in conversion as a result of fewer physical restraints in the crystal lattice. 149 Results and Discussion Graph V Reactant Conversion of Salts 164,166 and Complex 165 versus Irradiation Time 0 1 165 164 166 Irradiation time (h) 15 23 R is the percentage of starting material rerriaining at the different irradiation time intervals. 150 Results and Discussion 9.2. Structure-Reactivity Analysis of Salts 164,166 and Complex 165 Triplet-triplet energy transfer between the sensitizer and probe molecule clearly occurred in the sohd state in all three cases as illustrated by Table XVTII. Furthermore, amine 167 proved to be the most effective sensitizer. In order to help understand the triplet-triplet energy transfer between the sensitizers and probe molecule, the X-ray crystallographic structures of the two salts and one complex were examined. In principle, the orientation of the sensitizer amine relative to the probe molecule should be important for the energy transfer process and is represented by the stereoviews and packing diagrams of salts 164, 166 and complex 165 (Figures 9.03-9.05). The stereoviews illustrate the position of the aromatic ring of the sensitizer with respect to the ethenoanthracene double bond. The orientation is most favorable in the case of salt 166, where the aromatic ring of the sensitizer points directly at the ethenoanthracene double bond of the probe molecule with a center-to-center distance of only 4.11 A. The packing diagrams also show the ratio of probe molecule to sensitizer arnine within the crystal, which is one to one for salts 164 and 166 and two to one for complex 165. 151 Results and Discussion Figure 9.03. Packing Diagram and Stereoview of Salt 164. Space Group C2/c (#15), a = 37.712(3) A, b = 8.977(1) A, c = 15.922(1) A, p = 92.055(6)°, Z = 8, R = 4.5%. 152 Results and Discussion o II CHJOCHJCO — H Figure 9.04. Packing Diagram and Stereoview of Complex 165. Space Group Pi (#2), a = 12.344(1) A, b = 18.439(3) A, c = 8.2721(7) A, a = 101.789(9)°, (3 = 94.525(8)°, y = 95.05(1)°, Z = 2,R=5.1%. 153 Results and Discussion Figure 9.05. Packing Diagram and Stereoview of Salt 166. Space Group PI(#2), a = 9.760(1) A, b = 16.254(2) A, c = 9.114(1) A , a = 99.47(1)°, p = 109.17(1)°, y = 88.101(1)°, Z = 2, R = 4.4%. 154 Results and Discussion The minimum distances between the centers of the chromophores were measured with the following results: Table X f X Distances (< 7.5 A) Between Chromophores Chromophores Dibenzobarrelenea-Amine Sensitizer0 Distance 164 j (A) in Salts or ( 165 Complex 166 4.62 5.01 6.08 6.67 6.78 7.00 4.59 5.19 > € ) 4.03 5.95 6.97 5.38 5.48 5.72 7.48 4.11 6.79 (a) Vinylic double bond, (b) carbonyl and aromatic functionality, where X = C, N . The distances between the chromophore moieties were of importance, as these units are responsible for the absorption of light by the molecule. A l l of these distances are small enough for an efficient energy transfer to occur between the probe molecule and the sensitizer. Intramolecular triplet-triplet energy transfers were shown to take place at separations of 7 and 15 A as discussed in the Introduction (Section 1.5.1, p 27). The positioning of the probe molecule with respect to the acetophenone moiety of the amine was also investigated. A different representation of the packing diagrams for salts 164 and 166 (Figure 9.06) illustrates the interaction between the dibenzobarrelene (white circles) and the acetophenone (black circles) groups. Salt 164 demonstrates that the probe molecules are sandwiched between two layers of sensitizer amines, whereas the illustration of salt 166 indicates that the sensitizer molecules are sandwiched between layers of the probe molecules. In the case of 155 Results and Discussion complex 165, where two dibenzobarrelene carboxylic acids crystallized with one amine functionalized sensitizer, a similar arrangement, as described above, was not observed. Whether the reversed pattern between salts 164 and 166 affect the triplet-triplet energy transfer efficiency is not clear at this point. Figure 9.06. Different Representation of Packing Diagrams for Salts 164 and 166. (The white circles represent the dibenzobarrelene moiety and the black circles acetophenone). Interactions of less than 10 A between atoms are represented by the connected lines. 156 Results and Discussion 9.3. UV/VIS Analysis of Salts 164,166 and Complex 165 The increase in triplet product formation in the case of salt 166 compared to salt 164 and complex 165 may be due in part to its pronounced absorption spectrum. Examination of the UV/VIS absorption spectrum of salt 166 in methanol shows a very high molar extinction coefficient (e = 20,700) at A^ax of 325 nm This is not the case for salt 164 and complex 165, which exhibit extinction coefficients at Xmax of 319 nm similar to that of acetophenone (s = 50, in cyclohexane).157 Wavelength (nm) Figure 9.07. UV/VIS Absorption Spectrum of Salt 166 in Methanol. 157 Results and Discussion In agreement with the results for salt 166 is the absorption spectrum of the free arnine sensitizer moiety 167 in methanol, demonstrating an extinction coefficient (s) of 22,600 at a Amax of 326 run. This value may be compared to the absorption spectrum of 4'-arninobutyrophenone (168) in methanol, which exhibits a similarly strong molar extinction coefficient (e = 20,200) at a A , m a x of 316 nm.1 5 8 Figure 9.08. Structural Comparison of 4'-Aminobutyrophenone (168) and 4'-Piperazinoacetophenone (167). These features of the absorption spectra are characteristic of charge transfer (see Section 4.1.3, p 86), which results from the intramolecular interaction of the electron-withdrawing and electron-donating substituents with the 7t-system of the aromatic ring. Furthermore, salt 166, which was initially light yellow compared to the colorless salt 164 and complex 165, turned slightly pink after one hour of irradiation. This color disappeared when the crystals were left in the dark (1 h). Hence, the crystals exhibited photochromism. Irradiation of the crystals of sensitizer arnine 167 did not lead to these results. However, this was not further investigated, as it was outside the scope of the present project. O 168 167 158 Results and Discussion 9.4. Energy State Analysis of Salts 164,166 and Complex 165 The efficiency of the triplet-triplet energy process also depends on the relative energies of the states involved in the transfer step. These may either be n ,TC*, TC,TC* or CT states. Each sensitizer contains an acetophenone moiety, which possesses a carbonyl chromophore and an aromatic ring chromophore in conjugation. In such cases, the lowest energy excited state of a molecule is determined by the chromophore with the lowest energy excited state.159 Experiments conducted by Lamola,160 showed that acetophenone demonstrates a short-lived phosphorescence, characteristic of n, TC* triplet aromatic carbonyl compounds. The orbital composition of the Ti state of any ketone can be represented by the following equation : Ti = a (n, TC*) + b (TC, T C * ) , where "a" and "b" are the extent to which each configuration contributes to the state.161 The configuration of three different ketones and their corresponding excited states are illustrated in Figure 9.09.161 If a reaction proceeds through an n, TC* state, the triplet-excitation energy should be localized mainly on the carbonyl group (169). If the TC, TC* state is involved, this implies that the excited carbonyl oxygen is not as electron deficient as in the n, TC* state and the electron density of the excited state may be partially delocalized (170). Aryl ketones that contain strong electron donating substituents and undergo efficient electron transfer from a heteroatom substituent to the carbonyl group will give rise to a more nucleophihc carbonyl oxygen. States which follow this model, are referred to as charge transfer excited states (171). 159 Results and Discussion Q. 6 c — o o' CH3 c — o + 169 170 171 T i ~ n,TC* T l ~ TC,TC* T i ~ C T Figure 9.09. Examples of Different States for Aryl Ketones. From the irradiation results it appears that the energy transfer for salt 164 and complex 165 occurs between the n, Tt* (keto-amine) and the Tt, Tt* (dibenzobarrelene-acid) excited states, whereas in the case of salt 166, transfer results from either the T C , T C * state or CT state to the dibenzobarrelene T C , T C * triplet. Electronic excitation of 4'-piperazinoacetophenone (167) could result in a transfer of charge from the electron-donating nitrogen group to the carbonyl group, as in the case of p-aminobenzophenone (171). Both TC, T C * and CT states involve mainly TC-type orbitals. However, the difference lies in the occupation of space. In the case of T C , T C * states, the TC and T C * electrons are commonly presumed to be positioned in similar or the same vicinity of space, whereas in the CT state, the TC and T C * electrons may have different locations, resulting in a charge separation.161 Additionally, the ability of amine 167 to act as a more efficient triplet-triplet sensitizer may relate to its longer TC, T C * triplet lifetime (seconds) versus that of the typical n, T C * states which is on the order of tenths and hundredths of milliseconds.162 160 Experimental E X P E R I M E N T A L CHAPTER 10 PREPARATION OF SUBSTRATES 10.1. General Procedures Melting Points (MP) The melting points were determined on a Fisher-Johns melting point apparatus and were not corrected. Infrared Spectra (TR) The infrared spectra were taken on a Perkin Elmer 1710 Fourier transform infrared spectrometer. The absorption maxima are given in cm" . Liquid samples were applied neat between two sodium chloride discs, whereas solid samples (2-5 mg) were ground with anhydrous potassium bromide (100-200 mg) and pressed into pellets in an evacuated die (Perkin-Elmer 186-0002) with a laboratory press (Carver, model B) at 15,000 psi. Mass Spectra (MS) A Kratos MS 50 mass spectrometer was used to deterrnine the low and high resolution electron ionization (EI) mass spectra. A Kratos MS 80 spectrometer attached to a Carlo-Erba chromatograph recorded the data for coupled gas chromatography-mass spectral analysis (GC-MS). Electron bombardment at 70 electron volts led to ionization (EI). Fast atom bombardment 161 Experimental (FAB) mass spectra were taken with an A E I MS 9 mass spectrometer. Desorption chemical ionization (DCI) spectra were recorded on a Delsi Nermag RIO-IOC spectrometer with ammonia as the CI gas. Mass to charge ratios (m/e) are given with relative intensities in parentheses. Molecular ions are designated as M + . Nuclear Magnetic Resonance Spectra (NMR) 1II NMR The spectrometers used to record the proton nuclear magnetic resonance spectra ( 1 H-NMR) were: Bruker AC-200 (200 MHz), Varian XL-300 (300 MHz), Bruker WP-400 (400 MHz) and Bruker AMX-500 (500 MHz). The positions of the signals are given as chemical shifts (8) in parts per million (ppm) using tetramethyl silane (TMS) as an internal reference standard. The chemical shifts are reported, followed by the multiplicity of the signals, number of protons, coupling constants (J) in Hz and the molecular assignments. The multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. In some cases HETCOR 13 1 (Heteronuclear Chemical Shift Correlation Spectroscopy, C - H) experiments on the Bruker AMX-500 (500 MHz) spectrometer and N O E (Nuclear Overhauser Effect) experiments on the Bruker WP-400 (400 MHz) spectrometer were conducted to verify structures. " C N M R The spectrometers utilized to record the carbon nuclear magnetic resonance spectra ( 1 3 C N M R ) were: Bruker AC-200 at 50.3 MHz, Varian XL-300 at 75.4 M H z , Bruker WP-400 at 100.6 M H z and Bruker AMX-500 at 125.8 MHz. Chemical shifts ( 8 ) are given in parts per 162 Experimental million under broad band proton decoupling and are followed by the carbon assignment, which was confirmed by the attached proton test (APT) experiment. Ultraviolet Spectra (UV) A Perkin Elmer Lambda-4B UV/VIS spectrometer was used to record the ultraviolet spectra. Given are the wavelength (A) in nanometers (nm) and the extinction coefficient (s (M" 1 cm"1)) of each absorption maximum. Elemental Analysis (Anal) The elemental analyses were carried out by Mr. Peter Borda, Department of Chemistry, University of British Columbia. Chromatography A Hewlett Packard 5890A gas chromatograph fitted with a flame ionization detector and a Hewlett Packard 3392 A integrator was employed for gas liquid chromatography analysis. Samples dissolved in ethyl acetate were injected (2 ul) into one or more of the following columns: 15 m x 0.25 mm DB1 column (J & W Scientific Inc.), 15 m x 0.25 mm DB17 column (J & W Scientific Inc.), 15 m x 0.25 mm DB5 (J & W Scientific Inc.) or 30 m x 0.25 mm HP 5 column (Hewlett Packard) with helium as a carrier gas. Column head pressure was maintained at 15 psi. Gravity column chromatography separations were conducted using silica gel 60, 230-400 mesh gel (E. Merck) with the appropriate solvent systems. 163 Experimental Thin layer chromatography analysis was carried out on pre-coated silica gel plates (type 5554 from E. Merck). Solvents and Reagents A l l solvents and reagents were used as supplied by Fisher Scientific, unless specified. When further purification was necessary, known methods and procedures were followed in each case. Crystallographic Analysis A Rigaku AFC6S 4-circle diffractometer was used to deterrnine the crystal structures by Dr. Bozena Borecka, Tai Y . Fu, and Dr. Gunnar Olovsson under Professor James Trotter's supervision in the University of British Columbia Chemistry Department. Recrystallizations Salts (photochemical substrates) were not recrystallized due to difficulties arising from decomposition. Photoproducts were recrystallized, provided more than 10 mg of the product could be isolated by column chromatography. 164 Experimental 10.2. Preparation of Photochemical Substrates 10.2.1. 9,10[l',2']Benzenoanthracene-l,4-dione Derivatives 4a,9,9a,10-Tetrahydro-9,10[l*,2']benzenoanthracene-l,4-dione(61)75 3 A Diels-Alder reaction was performed by refluxing recrystallized 1,4-benzoquinone (4.3 g, 39 mmoL Eastman Kodak Co.) and anthracene (7.0 g, 39 mmoL Eastman Kodak Co.) in 40 mL of mixed xylenes (o, p and m-isomers) for 2 h according to procedures described by Bartlett et al.15 The rrhxture was cooled in an ice bath and the resulting brown solid was isolated by suction filtration. This was then recrystallized two times from a rnixture of xylenes (isomers) to yield pale yellow crystals of adduct 61 (8.4 g, 29 mmoL 75%). MP : 220-221 °C (lit.75 221-223 °C ). Di (KBr) v m a x : 1674 (C=0), 1611 (C=C) cm"1. MS m/e (relative intensity) : 287 (M+l, 0.4), 286 (M*, 2), 178 (100). Exact mass calculated for C 2 Q H 1 4 0 2 : 286.0994. Found : 286.0991. 165 Experimental *H N M R (200 MHz, CDC13) : 8 7.45-7.00 (m, 8H, aromatic H), 6.30 (s, 2H, vinyl H), 4.85 (s, 2H, bridgehead H 9 & Hi 0), 3.10 (s, 2H, bridgehead H^a & H 9 a ) ppm. 1 3 C N M R (50 MHz, CDCL,): 8 198.34 (C=0), 141.54 (aromatic C), 140.59 (vinyl C-H), 139.69 (aromatic C), 126.73, 126.64, 124.73, 123.88 (aromatic C-H), 49.05 & 48.90 (bridgehead C-H) ppm. 62 Adduct 61 (8.4 g, 29 mmol) was dissolved in 100 mL of boiling acetic acid (Fisher Scientific) and treated with 4 drops of HBr (48%, BDH) as described by Bartlett et al.15 A vigorous evolution of heat resulted and the solution turned orange. After 30 rnin of refluxing, the solution was cooled in an ice bath and a white solid precipitated which was filtered off by suction filtration. The resulting powder (62) was recrystallized from diethyl ether resulting in white needles (6.5 g, 23 mmoL 77%). M P : 338-340°C (lit.75 338-340°C ). HI (KBr) v : 3284 (O-H) cm'. 166 Experimental MS m/e (relative intensity) : 287 (M+1,24), 286 (M",98), 269 (100), 268 (38), 256 (19), 239 (39), 226 (28), 202 (66). Exact mass calculated for C^H, O : 286.0994. Found : 286.1001. 20 14 2 *H NMR (200 MHz, d6-acetone) : 8 7.85 (s, 2H, OH), 7.50-7.35 (m, 4H, aromatic H), 7.05-6.90 (m, 4H, aromatic H), 6.39 (s, 2H, aromatic H), 5.95 (s, 2H, bridgehead H) ppm. 1 3 C NMR (50 MHz, d6-acetone) : 8 146.90, 146.00, 133.47 (aromatic C, aromatic C-OH), 125.48, 124.30 (aromatic C-H), 113.83 (aromatic C-H), 48.18 (bridgehead C-H) ppm. 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63)75 63 Adduct 62 (6.5 g, 23 rnmol) was dissolved in 60 mL of hot acetic acid according to Bartett et al. procedures.75 A solution of KBr0 3 (1.3 g, 7.5 mmoL BDH) in 80 mL of hot water was added. The solution was refluxed for 5 min and 50 mL of hot water was added. The solution was cooled in an ice bath and the orange solid collected. This was then recrystallized from diethyl ether to give bright yellow crystals of 63 (4.5g, 1.6 mmoL 70%). MP : 290-292°C (Ut.75 292-296°C ). 167 Experimental JR (KBr) vm a x : 1660 (C=0), 1581 (C=C) cm'. MS m/e (relative intensity) : 285 (M+l, 24), 284 (M\ 100), 255 (17), 226 (18), 202 (86). Exact mass calculated for C 2 0 H 1 2 O 2 : 284.0837. Found : 284.0837. *H NMR (200 MHz, CDCLJ : 5 7.50-7.35 (m, 4H, aromatic H), 7.10-6.95 (m, 4H, aromatic H), 6.59 (s, 2H, vinyl H), 5.79 (s, 2H, bridgehead H) ppm. 1 3 C NMR (50 MHz, CDCL,) : 5 183.41 (OO), 151.82 (vinyl C), 143.49 (aromatic C), 135.28 (vinyl C-H), 125.47, 124.32 (aromatic C-H), 47.27 (bridgehead C-H) ppm. UV (acetonitrile) : 404 (s 357), 330 (s 993), 251 (s 14,884) nm X-Ray Crystal Data for C 2 0 H 1 2 O 2 : Space group Prima (#62), a = 13.979(2) A , b= 12.608(7) A , c=8.024(2) A , V= 1414.2(7) A 3 , Z = 4, D c a | c d = 1.335 g/cm, R = 0.059. 9,10- Bis(chloromethyl)anthracene (64) 77 CH2C1 CH2C1 64 A solution of 1,4-dioxane (78 mL, Fisher Scientific) and coned HC1 (16 mL, Fisher Scientific) was saturated with HC1 gas (Matheson Gas Products Inc.) according to Miller et al.11 Anthracene (10 g, 56 mmoL Eastman Kodak Co.) and paraformaldehyde (8.4 g, Fisher Scientific) 168 Experimental were added to the flask and the solution was heated until it started to reflux. A fine dispersion of HC1 gas was added over 2 h and the solution stirred an additional 3 h. The solution was allowed to sit for 16 h and the resulting fine yellow solid was removed via suction filtration. The solid was suspended (three times) in 1,4-dioxane, stirred, and filtered. The solid was recrystallized from toluene giving yellow plates of 64 (5.0 g, 18 mmoL 32%). M P : 257-259 °C (lit. 7 7 258-260 °C ). IR (KBr) v m a x : 3087, 3044, 3008 (aromatic C-H), 1248 (CH2C1), 627 (C-Cl) cm _ 1 . M S m/e (relative intensity) : 278 (M+4, 1), 276 (M+2, 8), 275 (M+l, 2), 274 ( M \ 12), 239 (38), 204 (100), 101 (48). Exact mass calculated for C ^ H ^ C L , : 274.0316. Found : 274.0312. *H N M R (200 MHz, CDC13) : 5 8.42-8.31 (m, 4H, aromatic H), 7.75-7.64 (m, 4H, aromatic H), 5.62 (s, 4H,CH 2C1) ppm. 1 3 C N M R (75 MHz, d5-nitrobenzene) : 5 130.93 & 130.27 (aromatic C), 127.39 & 124.90 (aromatic C-H), 39.63 (CH2C1) ppm. 169 Experimental 9,10- Dimethylanthracene (65)76 65 9,10-Bis(chloromethyl)anthracene 64 (2.5g, 9.1 mmol) was extracted (Soxhlet) into dry THF (150 mL) containing lithium aluminum hydride (580 mg, 15 mmol, Aldrich) for 18 h as outlined by Kirby et al.16 The mixture was cooled to room temperature, treated cautiously with water, aqueous NaOH, diluted with ether and filtered. The yellow sohd was recrystallized from benzene giving light yellow needles of 65 (1.7 g, 8.3 mmol, 90%). MP : 181-182 °C (lit.76 180-181 °C ). TR (KBr) v m a x : 3073 (aromatic C-H) cm"1. MS m/e (relative intensity): 207 (M+l, 18), 206 (M+, 100), 191 (43), 178 (8), 101 (25). Exact mass calculated for C 1 6 H 1 4 : 206.1095. Found : 206.1096. *H NMR (200 MHz, CDC13) : 5 8.40-8.23 (m, 4H, aromatic H), 7.59-7.42 (m, 4H, aromatic H), 3.09 (s,6H,CH3) ppm. C NMR (50 MHz, CDCLJ : 5 129.91 & 128.35 (aromatic C), 125.33 & 124.71 (aromatic C-H), 14.09 (CH3) ppm 13 170 Experimental 9,10-Dunethyl-4a,9,9a,10-tetraty^ (67)79 67 A Diels-Alder reaction was performed by refluxing recrystallized 1,4-benzoquinone (415 mg, 3.8 mmol) and 9,10-dimethylanthracene 65 (396 mg, 1.9 mmol) in 2 mL of benzene (1 min), according to procedures developed by Theilacker et al.19 The mixture was cooled in an ice bath and the resulting yellow solid was isolated by suction filtration. This was then recrystallized two times from benzene to yield pale yellow crystals of adduct 67 (574 mg, 1.8 mmoL 95%). M P : 213-215 °C (Ut.79 217 °C (red), 221-222 (melting) °C). BR (KBr) v m a x : 1674 (C=0) cm"1. M S (DCI, N H 3 , relative intensity): 332 (M+18, 13). Exact mass calculated for C 2 2 H 1 9 0 2 : 315.1385. Found : 315.1391 (M+l). *H N M R (200 MHz, CDCl,) : 8 7.46-7.36 (m, 4H, aromatic H), 7.30-7.11 (m, 4H, aromatic H) 6.25 (s, 2H, vinyl H), 2.82 (s, 2H, bridgehead H), 2.02 (s, 6H, CH 2 ) ppm. 1 3 C N M R (50 MHz, CDCLJ : 8 197.75 (C=0), 141.86 (aromatic C), 140.09 (vinyl C-H), 136.53 (aromatic C), 126.71, 126.45, 121.89, 121.19 (aromatic C-H), 56.45 (bridgehead C-H) 44.92 (bridgehead C), 16.25 (CH 3) ppm. 171 Experimental 68 In a round bottomed flask fitted with a condenser, 59 mL of 10% NaOH in methanol was refluxed as described by Theilacker et al.19 Compound 67 (706 mg, 2.2 mmol) was added, and the solution was refluxed for 10 min. The solution was cooled to room temperature and poured into a beaker with 59 mL of 20% aqueous H 2S0 4. This solution was then added to another beaker with 350 mL of water. A light beige powder (68) (565 mg, 1.8 mmol, 80%) was obtained after filtering the solution. MP : > 300 °C (lit.79 332 °C (red), 340 °C ( brown)). IR (KBr) vm a x : 3363 (O-H) cm'. MS m/e (relative intensity) : 315 (M+l, 4), 314(M+, 16), 299 (28), 284 (19). Exact mass calculated for C H, O : 314.1307. Found : 314.1306. 22 lo 2 *H NMR (200 MHz, CDCy : 5 7.47-7.35 (m, 4H, aromatic H), 7.11-7.00 (m, 4H, aromatic H), 6.17 (s, 2H, aromatic H ), 3.69 (s, 2H, OH), 2.65 (s, 6H, CH2) ppm. 1 3 C NMR (75 MHz, d6-acetone) : 5 150.29, 147.58, 134.99 (aromatic C, aromatic C-OH), 125.21, 121.45 (aromatic C-H), 115.78 (aromatic C-H), 49.68 (bridgehead C), 17.77 (CH3) ppm. 172 Experimental 940-Dmya*o-9,10-dimethy^ 69 Adduct 68 (695 mg, 2.2 mmol) was dissolved in 15 mL of hot acetic acid and refluxed for 5 min. A solution of K B r 0 3 (133 mg, 0.80 mmol BDH) in 15 mL of hot water was added. The solution was refluxed for 3 min and 8 mL of hot water was added. The solution was cooled in an ice bath and the yellow sohd collected (635 mg, 2.0 mmol, 92%). This was then purified by column chromatography (silica geL benzene) and recrystallized from ethyl acetate (444 mg, 1.4 mmoL 64%). M P : > 300°C (lit. 7 8 not reported). IK (KBr) v m a x : 1652 (C=0) cm"1. M S m/e (relative intensity) : 313 (M+l, 16), 312 (M*, 62), 297 (71), 284 (22), 230 (86), 215 (100). Exact mass calculated for C H O : 312.1150. Found : 312.1154. 22 16 2 *H N M R (400 MHz, CDC^) : 8 7.42-7.40 (m, 4H, aromatic H), 7.10-7.08 (m, 4H, aromatic H), 6.40 (s, 2H, vinyl H), 2.58 (s, 6H, CH 2 ) ppm. 173 Experimental 1 3 C NMR (75 MHz, CDC13): 8 185.46 (C=0), 153.70, 147.08 (aromatic C), 135.45 (vinyl C-H), 125.24, 121.64 (aromatic C-H), 50.32 (bridgehead C), 15.18 (CH3) ppm. UV (acetonitrile) Ka* : 399 (s 564), 298 (s 754) nm. 9,10-Bis(methoxymethyl)anthracene (66)77 C H 2 O C H 3 C H 2 O C H 3 66 A suspension of 9, 10 bis(chloromethyl)anthracene 64 (5.5g, 20 mmol) and KOH (5.5g, 98 mmol) in 120 mL of methanol was refluxed for 2.5 h according to procedures described by Miller et al.11 The solution was cooled in an ice bath and a light yellow solid precipitated out. The solid was filtered off and the filtrate was evaporated under reduced pressure. The residue was dissolved in chloroform and washed with excess aqueous HC1 (15%). The organic layer was then washed with aqueous NaCL water and dried over MgS04. After the solvent was evaporated, the resulting solid was combined with the first and recrystallized from 1,4-dioxane to give yellow plates ( 5. lg, 19 mmoL 96%). MP : 182-184 °C (lit.77 183-185 °C ). HI (KBr) v : 3093, 3032, 2987 (aromatic C-H), 2921, 2898 (methyl C-H), 1088 (C-O-C) cm"1. 174 Experimental M S m/e (relative intensity) : 267 (M+l, 19), 266 (Nf, 94), 235 (100), 221 (70), 203 (27), 191 (49), 178 (16). Exact mass calculated for C 1 B H , O : 266.1307. Found : 266.1308. l o l o L *H N M R (200 MHz, C D C y : 8 8.45-8.40 (m, 4H, aromatic H), 7.60-7.55 (m, 4H, aromatic H), 5.45 (s, 4H, CH2OCH3), 3.54 (s, 6H, CHOppm. 1 3 C N M R (50 MHz, C D C y : 8 130.76 & 130.27 (aromatic C), 125.76 & 124.89 (aromatic C-H), 66.72 (CH2OCH3), 58.35 (CH 3)ppm. 9,10-Bis(methoxymethyl)-4a,9,9a,10-tetrahydro-9,10[l',2']benzenoantliracene-l,4-dione (70) 70 A Diels-Alder reaction was performed by refluxing recrystallized 1,4-benzoquinone (823 mg, 7.5 mmol) and 9,10-bis(methoxymethyl)anthracene 66 (1.0 g, 3.8 mmol) in 8 mL of mixed xylenes (0, p and /w-isomers) for 7 h. The mixture was cooled in an ice bath and the resulting yellow sohd was isolated by suction filtration. This was then recrystallized two times from a 175 Experimental mixture of xylenes (o, p and m-isomers) to yield pale yellow crystals of adduct 70 (1.3 g, 3.4 mmol, 90%). MP : 192-194 °C. IR (KBr) vm a x : 1672, 1656 (OO) cm"1. MS (DCI, NKj, relative intensity): 392 (M+18, 10), 375 (M+l, 10). Exact mass calculated for C 2 4 H 2 2 0 4 (M+l) : 375.1596. Found : 375.1585. *H NMR (200 MHz, CDCLJ : 5 7.49-7.42 (m, 4H, aromatic H), 7.20-7.09 (m, 4H, aromatic H) 6.08 (s, 2H, vinyl H), 4.42 (s, 4H, CH2OCH3), 3.65 (s, 6H, CH£), 3.18 (s, 2H, bridgehead H) ppm 1 3 C NMR (50 MHz, CDCLJ : 8 197.60 (OO), 142.10 (aromatic C), 140.31 (vinyl C-H), 139.83 (aromatic C), 128.33, 126.62, 126.33, 122.84 (aromatic C-H), 70.78 (CH2OCH3), 59.08 (CH3), 49.21 (bridgehead C-H) ppm. 9,10-Bis(methoxymethyl)-9,10-dihydro-9,10[l',2,]benzenoanthracene-l,4-diol(71) 71 176 Experimental Compound 70 (95 mg, 0.254 mmol) was added to 10 mL of a refluxing solution of 5% NaOH in methanol followed by refluxing for an additional 10 min. After cooling the reaction rnixture down to room temperature, 10 mL of 10% aqueous H2SO4 was added plus an additional 60 mL of water. A light beige powder (71) (92 mg, 0.246 mmol, 97%) was obtained after filtration. MP : 210-213°C . IR (KBr) v m a x : 3232 (O-H) cm'. MS m/e (relative intensity) : 375 (M+l, 27), 374 (M+, 100), 297 (36), 284 (41), 266 (36). Exact mass calculated for C 2 4 H 2 2 0 4 : 374.1518. Found : 374.1521. *H NMR (200 MHz, CDCLJ : 8 8.75 (s, broad, 2H, OH), 7.60-7.37 (m, 2H, aromatic H), 7.20-6.92 (m, 6H, aromatic H), 6.70 (s, 2H, aromatic H), 5.34-5.20 (m, 2H, CH2OCH3), 4.90-4.75 (m, 2H, CH2OCH3), 3.87 (s, 6H, CH3) ppm. 1 3 C NMR (50 MHz, CDCLJ : 8 145.95, 145.63, 130.74 (aromatic C, aromatic C-OH), 125.27, 125.10, 123.08, 120.49, 118.68 (aromatic C-H), 72.64 (CH2OCH3), 59.35 (CH3), 51.55 (bridgehead C) ppm. 177 Experimental 9,10-Bis(methoxymethyl)-9,10-dmydro-9,10[l*,2']benzenoanthracene-l,4-dione (72) 72 Adduct 71 (738 mg, 1.9 mmol) was mixed with 25 mL of hot acetic acid and refluxed until all of it dissolved. A solution of KBr0 3 (119 mg, 0.713 mmoL BDH) in 10 mL of hot water was added. The solution was refluxed for 3 min and 15 mL of hot water was added. The solution was cooled and the yellow sohd collected (590 mg, 0.157 mmol, 80%). This was then purified by column chromatography (silica geL benzene) and recrystallized from ethyl acetate giving compound 72 (403 mg, 1.1 mmoL 55%). M P : 249-251°C. IR (KBr) vm a x : 1647 ( C O ) cm"1. MS m/e (relative intensity) : 273 (M+l, 10), 272 (NT\ 40), 327 (15), 296 (23), 75 (100). Exact mass calculated for C H O : 372.1361. Found : 372.1354. 24 20 4 *H NMR (200 MHz, CDCL,) : 5 7.72-7.41 (m, 4H, aromatic H), 7.12-7.03 (m, 4H, aromatic H), 6.41 (s, 2H, vinyl H), 5.20 (s, broad, 4H, CH2OCH3), 3.70 (s, 6H, CH3) ppm. 1 3 C NMR (50 MHz, CDCL.) : 8 184.56 (C=0), 154.57, 144.16 (aromatic C), 135.13 (vinyl C-H), 125.22, 124.09 (aromatic C-H), 69.31 (CH2OCH3), 58.91 (CH3), 55.11 (bridgehead C)ppm. 178 Experimental U V (acetonitrile) : 331 (s 1,246), 303 (s 3,544), 248 (s 10,902) nm. Anal, calculated for C 2 4 H 2 0 O 4 : C, 77.40; H , 5.41. Found: C, 77.14; H , 5.36. X-Ray Crystal Data for C 2 4 H 2 Q 0 4 : Space group Cllc (#15), a = 15.772(1) A , b = 8.000(1) A, c = 14.7883(9) A, S = 98.430(6)°, V = 1845.8(3) A 3 , Z = 4, D c a l c d = 1.340 g/cm', R = 0.040. 1-Chloroanthracene (79a)8 1 l-CMoro-9,10-antlrraquinone (1.0 g, 4.1 mmol, Aldrich) and zinc powder (3.2 g, 49 mmol, Aldrich) were added to a round bottomed flask containing pyridine (20 mL) according to procedures specified by Schilling.8 1 The solution was heated under reflux with stirring, while 80 % aqueous acetic acid (8 mL) was added through an addition funnel over 1 h. Upon completion of addition, the reaction rnixture was stirred for an additional 30 min followed by cooling to room temperature. The zinc was filtered off (caution : zinc is pyrophoric, spontaneously ignites with air) and the filtrate was added to ice cold HC1 (80 mL, 3 M). This solution was stirred for 15 ruin until a solid formed, which was filtered and recrystallized from ethanol to give light yellow crystals (720 mg, 3.4 mmol, 82%). a 79a M P : 75-77 °C (lit.8 177-80 °C). 179 Experimental IR (KBr) vm a x : 3022 (C-H), 1110 (C-Cl) cm1. MS m/e (relative intensity) : 214 (M+2, 33), 213 (M+l, 16), 212 (M*, 100), 177 (13), 176 (26), 106 (18). Exact mass calculated for C14H9CI : 212.0393. Found : 212.0391. *H NMR (400 MHz, CDC13) : 8 8.84 (s, lH,aromatic H), 8.42 (s, lFLaromatic H), 8.11-7.95 (m, 2H, aromatic H), 7.91 (d, 1 H, J= 9 Hz, aromatic H), 7.56 (d, 1 H, J= 9 Hz, aromatic H), 7.54 -7.46 (m, 2H, aromatic H), 7.38-7.31 (m, 1 H, aromatic H) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 132.34, 132.16, 131.00, 131.93, 129.02 (aromatic C), 128.68, 127.91, 127.56, 126.89, 126.17, 126.03, 125.32, 124.78, 123.57 (aromatic C-H) ppm. 2-Chloroanthracene (79b)82 A solution of 2-chloro-9,10-anthraquinone (2.0 g, 8.2 mmoL Aldrich) and zinc powder (6.5 g, 99 mmoL Aldrich) in pyridine (40 mL) was refluxed while 80 % aqueous acetic acid (16 mL) was added over a period of 3 h as outlined in procedures by Barnett et al.S2 After cooling the solution to room temperature and filtering off the zinc powder the filtrate was added to ice cold HC1 (65 mL, 3 M) whereupon a light yellow precipitate formed. The solid was filtered off and purified by column chromatography with petroleum ether. After recrystallization with petroleum ether, white shiny plates (585 mg, 2.8 mmoL 33%) were obtained. 79b 180 Experimental MP : 218-220 °C (Ut.82 221-223 °C). IR (KBr) v m a x : 3561(C-H), 1067 (C-Cl) cm1. MS m/e (relative intensity) : 214 (M+2, 33), 213 (M+l, 16), 212 (M*, 100), 177 (13), 176 (31), 106 (22). Exact mass calculated for C14H9CI : 212.0393. Found : 212.0395. *H NMR (400 MHz, CDC13) : 5 8.39 (s, 1H, aromatic H), 8.31 (s, 1H, aromatic H), 7.98 (d, 1 H, J= 5 Hz, aromatic H), 7.96 (s, 2 H, aromatic H), 7.93 (d, 1 H, J = 9 Hz, aromatic H), 7.50-7.44 (m, 2 H, aromatic H), 7.37 (dd, 1 H, J= 9 & 2 Hz, aromatic H) ppm. 5-Chloro-9,10-dihydro-9,10[l',2']benzenoanthracene-l,4-quinone (73) 73 Quinone 73 was synthesized by an initial Diels-Alder reaction between 1-chloroanthracene 79a (279 mg, 1.3 mmol) and recrystallized 1,4-benzoquinone (142 mg, 1.3 mmol) in a mixture of refluxing xylenes (2 mL, o, m, /^ -isomers) over 3.5 h. After filtration the resulting adduct was treated with 5 mL of acetic acid, refluxed and 2 drops of HBr (48%, BDH) were added. Following a refluxing period of 30 min, and cooling the solution, the hydroquinone (49 mg, 0.153 181 Experimental mmol, 12%) was obtained by filtration. This compound was dissolved in acetic acid (5mL), refluxed and K B r 0 3 (9.0 mg, 0.054mmol) dissolved in water (2 mL) was added. After adding an additional amount of water (2 mL) a precipitate formed which was filtered off giving the desired quinone 73 (8.1 mg, 0.025 mmol, 16%). M P : 172-175 °C. JR (KBr) v m a x : 3068 (C-H), 1659 (C=0), 1573 (C=C) cm"1. M S m/e (relative intensity) : 320 (M+2, 36), 319 (M+l, 28), 318 (M+, 100), 285 (42), 284 (35), 283 (46), 255 (80), 236 (79). Exact mass calculated for C 2 o H i i 0 2 C l : 318.0448. Found : 318.0445. *H N M R (400 MHz, CDC13) : 8 7.50-7.40 (m, 2H, aromatic H), 7.29 (d, 1H, J= 8 Hz, aromatic H), 7.15-6.90 (m, 4H, aromatic H), 6.61 (AB-system, 2H, J= 10 Hz, vinyl H), 6.25 & 5.79 (s, 1H each, bridgehead H) ppm. 182 Experimental 6-CMoro-940-dmydro-9,10[l%2']benzenoanthracene-l,4-dione(74) 74 Compound 74 was prepared by a Diels-Alder reaction between recrystallized 1,4-benzoquine (200 mg, 1.8 mmol) and 2-chloroanthracene 79b (391 mg, 1.8 mmol) in refluxing mixed xylenes (3 mL, o, m, /^ -isomers) over 6 h. The reaction rnixture was cooled and the precipitate filtered, washed with a mixture of xylenes and hot water. The resulting product was then refluxed with 4 mL of acetic acid to which a drop of HBr (48 %, BDH) was added. After 30 min of refluxing, the solution was cooled and filtered, resulting in the hydroquinone (327 mg, 1.02 mmol, 55 %). This compound was dissolved in 4 mL of acetic acid and heated until boiling. KBr0 3 (61 mg, 0.365 mmol) dissolved in hot water (4 mL) was added to the reaction mixture which was refluxed an additional 5 rnin. After adding more hot water (3 mL) to the solution, a precipitate formed, which was filtered off after cooling, giving the final product 74 (179 mg, 0.563 mmoL 55 %). Column chromatography with ethyl acetate / petroleum ether (5 : 95) gave a mixture of two compounds (37 mg, 0.116 mmol, 21 %), the desired product plus one or several of the 2 : 1 chloro-anthracene : benzoquinone adducts 77a-d. A chromatotron (Model 8924, Harrison Research) using a 1mm layer plate and 2-4 mL / min rate of solvent ethyl acetate / petroleum ether (15 : 85) gave pure compound 74 (6.1 mg, 0.019 mmoL 2 %) as well as the 2 : 1 adduct(s) 77a-d (25 mg, 0.047 mmoL 10%). 183 Experimental MP : 175-178 °C. IR (KBr) V m a x : 1653 (C=0) cm'. MS m/e (relative intensity) : 320 (M+2, 33), 319 (M+l, 22), 318 (M+,100), 283 (28), 255 (40), 236 (77). Exact mass calculated for C 2 0 H n O 2 C l : 318.0448. Found : 318.0443. *H NMR (400 MHz, CDCL, ) : 8 7.42-7.37 (m, 3H, aromatic H), 7.31 (d, 1H, J= 6 Hz, aromatic H), 7.05-7.01 (m, 2H, aromatic H), 6.98 (AB-system, 1H, J= 8 Hz, aromatic H), 6.60 (s, 2H, vinyl H), 5.74 & 5.73 (s, 1H each, bridgehead H) ppm 184 Experimental Possible 2 : 1 Chloroanthracene: Benzoquinone Adducts 77a-d 77a-d MP : > 300 °C. IR (KBr) vm a x : 3064 (C-H), 1651 (C=0) cm1. MS m/e (relative intensity) : 532 (M+4, 15), 530 (M+2, 67), 529 (M+l, 1), 528 (M\ 100), 494 (10), 493 (7), 472 (17), 437 (17). Exact mass calculated for C34H18O2CI: 528.0684. Found : 528.0691. *H NMR (400 MHz, CDC13) : 5 7.36-7.32 (m, 6H, aromatic H), 7.26-7.23 (m, 2H, aromatic H), 6.92-6.70 (m, 6H, aromatic H), 5.71, 5.70, 5.69, 5.68 (s, 1H each, bridgehead H) ppm 1 3 C NMR (75 MHz, CDC13) : 8 179.50, 179.46 (C=0), 150.97, 150.56 (vinyl C), 145.58, 143.19, 142.85, 142.16 (aromatic C), 131.16 (aromatic C-Cl), 125.78, 125.73, 125.30, 125.09, 124.74, 124.47, 124.35 (aromatic C-H), 47.01, 46.77 (bridgehead C-H) ppm. 185 Experimental 10.2.2. 2-(l-Cyclopentenyl)cyclopentanones and 2-(l-Cyclohexenyl)cyclohexanones 2-Cyclopentylidenecyclopentanone (119) 119 Cyclopentanone (52 g, 619 mmol Aldrich) dissolved in ethanol (100 mL) and NaOH (2.5 g, 63 mmol) in water (45 mL) were stirred at room temperature for 24 h following procedures developed by Varech et al.125 Ethanol was then rotary evaporated and the aqueous layer extracted with diethyl ether (three times). The combined organic layers were washed with water and brine, dried over MgSCu and evaporated to dryness giving a red oil (38 g, 253 mmol, 83%). The oil was then vacuum distilled resulting in a colorless oil of 119 (29 g, 193 mmoL 62%). BP : 103-105 °C (10 mm) (lit.125 117-119 °C (13mm)). JR (NaCl) v m a x : 2959 ( C - H ) , 1708 (C=0), 1641 (C=C), 1253 (C-O) cm1. MS m/e (relative intensity) : 151 (M+l, 12), 150 (M+, 100), 149 (35), 135 (12), 122 (23), 121 (29), 107 (31). Exact mass calculated for C i o H 1 4 0 : 150.1045. Found : 150.1044. *H NMR (200 MHz, CDC13): 5 2.79-2.64 (m, 2H, CFLJ, 2.55-2.40 (m, 2H, CFb), 2.29-2.15 (m, 4H, CHa), 1.94-1.74 (m, 2H, CH2), 1.72-1.52 (m, 4H, CH2) ppm. 186 Experimental 1 3 C NMR (50 MHz, CDC13) : 8 207.00 (C=0), 158.27, 127.77 (vinyl C), 39.63, 34.14, 32.38, 29.40, 26.83, 25.14, 19.98 (CH2). Ethyl l-(l-cyclopenten-l-yl)-2-oxocyclopentaneacetate (120) 120 Sodium methylsiufinylmethide was synthesized by the method of Ide and Iwai124b by adding anhydrous DMSO (57 mL) to sodium hydride (1.7g, 44 mmol, 60% in oil, Aldrich) in a round bottomed flask with stirring under nitrogen, followed by heating the solution to 80 °C for 30 min. To the cooled solution, compound 119 (5.7 g, 38 mmol) in DMSO (45 mL) was added dropwise and the solution was stirred for 1 h at room temperature, following the experimental procedure of Givens et al.124a While cooling the solution in an ice bath, ethyl bromoacetate (7.4 g, 44 mmol, 98%, Aldrich) in DMSO (35 mL) was added dropwise and the solution was stirred for 30 min at room temperature. The reaction mixture was then quenched with a saturated aqueous solution of ammonium chloride (100 mL, Fisher Scientific) and extracted with «-pentane (three times). The organic layer was dried over MgS0 4 and the solvent evaporated leaving a golden oil (7.7 g, 33 mmoL 86%). After vacuum distillation a colorless oil (120) was obtained (5.1 g, 22 mmol, 57%). BP : 150-153 °C (20 mm) (fit. 2 4 aBPnot reported). 187 Experimental JR (NaCl) v m a x : 2958 (C-H), 1734 (C=0) cm'1. MS m/e (relative intensity): 237 (M+l, 16), 236 (M+, 100), 191 (75), 190 (78), 173 (36), 163 (54), 162 (54), 149 (61). Exact mass calculated for C14H20O3: 236.1412. Found : 236.1411. *H NMR (200 MHz, CDC13) : 8 5.36-5.34 (m, IH, vinyl H), 3.93 (q, 2H, J = 8 Hz, CH 2C02CH2CH 3), 2.53 (AB-system, 2H, J= 16 Hz, CH2CO2CH2CH3), 2.30-1.86 (m, 8H, CH2), 1.85-1.50 (m, 4H, CILJ, 1.09 (t, 3H, J= 8 Hz, CH 2C0 2 CH 2 CH3) ppm. 1 3 C NMR (50 MHz, CDC1 3) : 8 218.20 (pentanone C=0), 171.23 (ester C=0), 141.69 (vinyl C), 127.54 (vinyl C-H), 60.29 (CH 2C0 2CH 2CH3), 52.81 (CH 2C0 2CH 2CH3), 39.61, 37.01, 32.91, 32.39, 31.59, 23.23, 19.00 (CH2, C), 14.09 (CH 2C0 2 CH 2 CH 3 ) ppm. l-(l-Cyclopenten-l-yl)-2-oxocyclopentaneacetic acid (121)124a 121 Ester 120 (4. lg, 17 mmol) and KOH (2.9g, 52 mmol) were refluxed in methanol (100 mL) overnight as described by Givens et al.124a The solvent was evaporated and the solid was dissolved in diethyl ether and washed with water. The aqueous layer was acidified with HC1 (15%) and extracted with diethyl ether three times. The organic layer was dried over MgSC>4, filtered and evaporated giving a white solid (3.3 g, 16 mmol 90%). After column chromatography on silica 188 Experimental gel with ethyl acetate / petroleum ether (3 : 7) and recrystallization from diethyl ether / petroleum ether (1:1), white crystals of 121 were obtained (2.3 g, 11 mmol 64%). MP : 93-94 °C (lit.124a 93-94 °C). TR (KBr) vm a x : 3400-2960 (OH), 2957 (C-H), 1742 (C=0), 1703 (C=0) cm1. MS m/e (relative intensity): 209 (M+l, 10), 208 (M*, 69), 191 (13), 190 (72), 173 (16), 163 (21), 162 (42), 152 (21), 149 (37), 148 (27), 144 (14), 135 (21), 134 (28), 131 (32), 121 (31), 107 (100). Exact mass calculated for C i 2 H i 6 0 3 : 208.1099. Found : 208.1098. *H NMR (200 MHz, CDC13) : 5 11.00 (s, 1H, broad, OH), 5.50-5.48 (m, 1H, vinyl H), 2.65 (AB-system, 2H, J= 17 Hz, CH2CO2H), 2.38-1.70 (m, 12H, CH2) ppm 1 3 C NMR (50 MHz, CDC13): 5 217.22 (pentanone C-O), 176.71 (acid ester C=0), 141.13 (vinyl C), 128.27 (vinyl C-H), 52.79 (CH2C02H), 39.54, 36.95, 33.06, 32.49, 31.58, 23.24, 19.04 (CH2, C)ppm. 3 UV (methanol) : 296 (e 222), 208 (e 2,200) nm 189 Experimental Methyl l-(l-cyclopenten-l-yl)-2-oxocyclopentaneacetate (121a)124a 121a Methyl ester 121a was prepared by treating the corresponding acid 121 with an ethereal solution of diazomethane. The reaction was complete when the initially yellow solution remained yellow. Evaporation of the solvent resulted in total conversion to an oil corresponding to ester 121a. IR (NaCl) vm a x : 2954 (C-H), 1738 (C=0) cm'1. MS m/e (relative intensity) : 223 (M+l, 10), 222 (M+, 74), 191 (41), 190 (60), 173 (36), 163 (42), 162 (38), 150 (37), 149 (66), 107 (96), 91(100). Exact mass calculated for C i 3 H i 8 0 3 : 222.1256. Found : 222.1252. J H NMR (400 MHz, CDC13) : 5 5.41-5.39 (m, IH, vinyl H), 3.52 (s, 3H, CH 2C0 2CH 3), 2.58 (AB-system, 2H, J= 16 Hz, CH2C02CH3), 2.26-1.66 (m, 12H, CH^ppm. 1 3 C NMR (50 MHz, CDC13) : 8 217.80 (ketone C=0), 171.67 (ester C=0), 141.62 (vinyl C), 127.59 (vinyl C-H), 52.74 (CH 2C0 2CH 3), 51.38 (CH 2C0 2CH 3), 39.31, 36.95, 32.84, 32.37, 31.57, 23.21, 18.98 (CH2, C)ppm UV (acetonitrile) A™*: 297 (s 234), 204 (s 2,980) nm. 190 Experimental 2-(l-Cyclohexenyl)cyclohexanone (123a)126 123a As outlined by Gault et al.,126 H2SO4 (9 mL, 60%, Fisher Scientific) was added to a round bottomed flask fitted with a condenser and stirring bar. While stirring the solution at room temperature, cyclohexanone (15 g, 157 mmol, Aldrich) was added dropwise. The solution was stirred for 2 h at room temperature resulting in an increase of the temperature of the reaction rnixture to 30 °C. The stirring was stopped and the solution was then left in the fumehood for 24 h. The reaction mixture was treated with water and diethyl ether and the layers were separated. The ether layer was washed three times with a saturated aqueous N a 2 S 0 4 solution and water. After drying the organic layer over M g S 0 4 , the solution was filtered and rotary evaporated. An orange oil was obtained (15 g, 81 mmol, 52%). Following distillation of the crude product (2.08g, 12 mmol), a clear oil of 123a was obtained (1.2 g, 6.7 mmol, 60%). B P : 130 °C (6 mm), (lit. 1 2 6 150 °C(18-20 mm)). IR (NaCl) v m a x : 2931 (C-H), 1713 (C=0) cm' 1 . M S m/e (relative intensity) : 179 (M+l, 9), 178 (M+, 59), 150 (16), 149 (100), 135 (36), 121 (19), 107 (22), 98 (16), 93 (32), 92 (22), 91 (37). Exact mass calculated for C i 2 H i 8 0 : 178.1358. Found : 178.1360. 191 Experimental *H NMR (200 MHz, CDC13) : 5 5.09-5.07 (m, 1H, vinyl H), 2.65-2.45 (m, 1H, CH), 2.10-1.93 (m, 4H, CHa), 1.80-1.15 (m, 12H, CH2)ppm. 1 3 C NMR (50 MHz, CDC13): 8 211.50 (C=0), 135.75 (vinyl C), 123.44 (vinyl C-H), 58.60 (CH2), 41.98, 31.75, 27.56, 27.14, 25.40, 25.35, 22.74, 22.31 (CH2, Qpprn. Ethyl l-(l-cyclohexen-l-yl)-2-oxocyclohexaneacetetate (124) 124 FoUowing the procedure used to make keto-ester 120, dry DMSO (25 mL) was added to a round bottomed flask containing sodium hydride (539 mg, 13 rnmoL 60% in oil, Aldrich) under nitrogen. The mixture was then heated in an oU bath to 75 °C for 30 min. FoUowing cooling of the flask in a water bath to 30 °C, cyclohexenylcyclohexanone 123a (2.08 g, 12 mmol) in DMSO (20 mL) was added dropwise to the solution and stirred for 1 h. Ethyl bromoacetate (2.3 g, 14 mmol, Aldrich) dissolved in DMSO (15 mL) was then added dropwise to the flask. The solution was stirred for 30 min. After quenching the reaction mixture with a saturated aqueous solution of ammonium chloride, an extraction with «-pentane was performed. After drying the solution over MgS04, filtration and rotary evaporation, a hght yeUow oU was obtained (2.1 g, 7.9 mmol, 68%). After column chromatography with sihca gel eluting the compound with ethyl acetate / petroleum ether (3 : 97), a colorless oU of 124 (1.1 g, 4.1 mmol, 35%) resulted. 192 Experimental IR (KBr) vm a x : 2934 (C-H), 1710 (C=0) cm"1. MS m/e (relative intensity): 265 (M+l, 8), 264 (M 4 , 38), 235 (46), 219 (32), 218 (37), 190 (22), 177 (100), 91 (70). Exact mass calculated for CieHwOs : 264.1725. Found : 264.1732. J H NMR (200 MHz, CDC13) : 5 5.51-5.49 (m, IH, vinyl H), 3.99 (q, 2H, J = 7 Hz, CO2CH2CH3), 2.45 (AB-sysem, 2H, J= 14 Hz, CH2CO2CH2CH3), 2.25-2.12 (m, 2H, CH2), 2.07-1.64 (m, 6H, CfJa), 1.63-1.43 (m, 8H, CH2), 1.15 (t, 3H, J= 8 Hz, C0 2CH 2CIJ3) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 212.12 (ketone C=0), 171.87 (ester C=0), 135.02 (vinyl C), 125.13 (vinyl C-H), 59.90 (C0 2 CH 2 CH 3 ) , 57.07 ( C H 2 C 0 2 C H 2 C H 3 ) , 41.21, 39.80, 34.11, 27.46, 25.56, 25.07, 22.98, 22.03, 21.57 (CH 2 , C), 14.20 (C0 2 CH 2 CH 3 ) ppm. l-(l-Cyclohexen-l-yl)-2-oxocyclohexaneacetic acid (125) 125 To a solution of ester 124 (143 mg, 0.542 mmol) in methanol (4 mL), KOH (91 mg, 1.62 mmol) was added and the mixture was refluxed overnight. The methanol was evaporated and the rermining solid was dissolved in diethyl ether and washed with water. The aqueous layer was acidified with 15% HCL extracted with diethyl ether (three times) and the organic layer was dried 193 Experimental over MgS04, filtered and rotary evaporated. After column chromatography on silica gel with diethyl ether / petroleum ether (3 : 7), followed by recrystallization from the same solvent system, white crystals of 125 (70 mg, 0.297 mmoL 55%) were obtained. MP : 101-102 °C. JR (KBr) vm a x : 3400-2960 (OH), 2941(C-H), 1708 (C=0) cm"1. MS m/e (relative intensity) : 237 (M+l, 7), 236 ( M \ 42), 207 (90), 177 (100), 149 (25), 148 (28), 133 (26). Exact mass calculated for C14H20O3: 236.1412. Found : 236.1412. *H NMR (200 MHz, CDC13) : 5 10.95-10.38 (s, 1H, broad, OH), 5.36-5.34 (m, 1H, vinyl H), 2.50 (AB-system, 2H, J= 14 Hz, CHaC02H), 2.34-2.20 (m, 2H, CH2), 2.10-1.70 (m, 6H, CH2), 1.65-1.38 (m, 8H, CH2) ppm 1 3 C NMR (50 MHz, CDC13) : 5 215.55 (ketone C=0), 175.43 (ester C=0), 135.13 (vinyl C), 126.56 (vinyl C-H), 57.56 (CH2C02H), 42.30, 39.74, 34.86, 27.41, 25.63, 24.68, 22.88, 21.94, 21.57 (CH2, C) ppm. UV (methanol) A^ ax : 290 (e 120), 204 (e 2,978) nm. Anal, calculated for Ci4H 2 0 O 3 : C, 71.14; H, 8.54. Found : C, 71.14; H, 8.53. X-Ray Crystal Data for Ci4H 2 0 O 3 : Space group C2/c (# 15), a = 26.516(2) A, b = 6.9831(3) A, c = 18.503(2) A, P = 131.394(4)°, V = 2570.2(4) A3,.Z = 8, D c ai c d= 1.22 g/cm3, R = 0.056. 194 Experimental /)-(Tiimethylaminomethyl)benzonitrile (127)127 C S N CH2 I N Hsc/ CH3 127 A solution of a-bromo-/?-toluonitrile (1.0 g, 5.1 mmoL Aldrich) in anhydrous diethyl ether / benzene (8 mL / 2 mL) was chilled to -78 °C in a dry ice / acetone bath as described by Norman et al.127 Dimethyl amine gas (230 mg, 5.1 mmol, Aldrich) was bubbled through the solution for 10 min, the flask was sealed and was allowed to warm up to room temperature over a period of 48 h. After cooling the solution to -10 °C in a salt / ice bath, the flask was opened and the solvent rotary evaporated. The rermining solid was dissolved in a minimum amount of water, extracted with diethyl ether, the ether layer dried over MgS04, filtered and evaporated to give a pale yellow oil of 127 (543 mg, 3.4 mmol, 66%). m (NaCl) v m a x : 2942 (C-H), 2361 (C=N), 1018 (C-N) cm1. MS m/e (relative intensity) : 161 (M+l, 3), 160 (M*, 28), 116 (29), 102 (2), 58 (100). Exact mass calculated for Ci 0 Hi 2 N 2 : 160.1000. Found : 160.0996. *H NMR (200 MHz, CDC13) : 5 7.42 (m, 2H, aromatic H), 7.28 (m, 2H, aromatic H), 3.32 (s, 2H, CIL), 2.10 (s, 6H, CH3) ppm. 195 Experimental 1 3 C NMR (50 MHz, CDC13) : 8 144.81 (aromatic C), 131.94, 129.39 (aromatic C-H), 118.90 (CN), 110.71 (aromatic C), 63.65 (CH2), 45.31 (CH3)ppm. j»-Acetyl-7V^V-dimethylbenzylamine (128) O CH 2 I N CH3 128 Following the procedure of Norman et al., compound 127 (685 mg, 4.3 mmol) dissolved in toluene (5 mL) was added to a solution of MeMgl (1.6 mL, 12 mmol, Aldrich) in toluene (10 mL) and refluxed for 48 h. The reaction rnixture was poured onto crushed ice and HC1 (6 M) was added until the precipitate dissolved. The solution was heated in an oil bath (100 °C) for 2 h, cooled, extracted with diethyl ether and washed with water and brine. The organic layer was dried over MgS04, filtered and evaporated, resulting in a pale yellow oil of 128 (585 mg, 3.3 mmoL 77%). HI (NaCl) vm a x : 2975 (C-H), 1685 (C=0), 1017 (C-N) cm"1. MS m/e (relative intensity): 178 (M+l, 8), 177 (M\ 67), 133 (21), 105 (12), 58 (100). Exact mass calculated for CnH 1 5NO : 177.1154. Found : 177.1154. 196 Experimental *H NMR (200 MHz, CDC13) : 6 7.75 (m, 2H, aromatic H), 7.25 (m, 2H, aromatic H), 3.25 (s, 2H, CH2), 2.40 (s, 3H, COCH3), 2.08 (s, 6H, NCH3) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 197. 50 (C=0), 144.69, 135.95 (aromatic C), 129.05, 128.25 (aromatic C-H), 63.77 (CH2), 45.27 (NCH3), 26.40 (COCH3) ppm. 197 Experimental 10.2.3. 9,10-Dihydro-9,10-ethenoanthracene Derivatives Ethyl 9,10-Dihydro-9,10-ethenoanthracene-ll-carboxylate (130) 130 Anthracene (5.0 g, 28 mmol) and ethyl propiolate (3.3 g, 34 mmoL Aldrich) were placed in a Carius tube which was then sealed and heated to 180 °C for 6 h, a reaction initially carried out by Vaughan and Milton in refluxing mixed xylenes.128 After column chromatography (1% ethyl acetate in petroleum ether) over silica gel and recrystallization from petroleum ether, white crystals of the ester 130 were obtained (15 g, 55 mmol 61%). MP : 103-105 °C (Ut.128111.5-112.5 °C). IR (KBr) vm a x : 1700 (C=0), 1611 (C=C), 1218 (C-O) cm 1 . MS m/e (relative intensity): 277 (M+l, 7), 276 (M+, 35), 203 (100), 178 (12). Exact mass calculated for C i 9 H i 6 0 2 : 276.1150. Found : 276.1158. *H NMR (200 MHz, CDC13) : 5 7.88 (dd, IH, J= 2 Hz & 7 Hz, vinyl C-H), 7.41-7.31. (m, 4H, aromatic H), 6.95-7.05 (m, 4H, aromatic H), 5.70 (d, IH, J= 2 Hz, bridgehead H), 5.25 (d, IH, J = 7 Hz, bridgehead H), 4.19 (q, 2H, J= 7 Hz, CO2CH2CH3), 1.27 (t, 3H, J= 7 Hz, C02CH2CH3_) ppm. 198 Experimental 1 3 C NMR (50 MHz, CDC13): 5 164.78 (C=0), 149.25 (vinyl C-H), 145.38 (aromatic C), 144.75 (vinyl C), 144.48 (aromatic C), 125.06, 124.88, 123.75, 123.52 (aromatic C-H), 60.70 (C0 2CH 2CH 3), 51.61, 50.40 (bridgehead C-H), 14.29 (C0 2CH 2CH 3) ppm. ll-Hydroxymethyl-9,10-dihydro-9,10-ethenoanthracene (131)129 131 Ethyl ester 130 (3.2 g, 12 mmol) dissolved in 38 mL of anhydrous ether was added dropwise over a period of 30 rnin to a solution of 1.2 g (12 mmol) of aluminum trichloride (caution) and 1.0 g (26 mmol) of hthium aluminum hydride in 150 mL of anhydrous ether while stirring at room temperature. The reaction mixture was then stirred for 2 h at room temperature and quenched with a saturated solution of aqueous Na2S04. The precipitate was filtered through a Celite filter and washed with ethyl acetate. Following an extraction with ethyl acetate, the organic layer was washed with water and brine and dried over MgSCu. The solvent was rotary evaporated and the oil redissolved in ethanol. After evaporation of the solvent in an evaporating dish and recrystalhzation from ethanol, 2.2 g (9.2 mmol, 80%) of white crystals of the alcohol 131 were obtained. MP : 121-123 °C (lit.129 126-127 °C). 199 Experimental JR (KBr) v m a x : 3200 (O-H), 2980 (C-H) cm \ MS m/e (relative intensity) : 235 (M+l, 9), 234 (M+, 45), 203 (100), 178 (67). Exact mass calculated for C17H14O: 234.1045. Found : 234.1043. *H NMR (200 MHz, CDC13) : 8 7.35-7.20 (m, 4H, aromatic H), 7.04-6.90 (m, 4H, aromatic H), 6.75 (dd, IH, J= 2 & 7 Hz, vinyl H), 5.11 (d, IH, J= 7 Hz, bridgehead H), 5.05 (d, IH, J= 2 Hz, bridgehead H), 4.28 (s, 2H, CH2OH), 1.43 (s, broad, IH, OH) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 152.59 (vinyl C), 146.44, 145.80 (aromatic C), 133.58 (vinyl C-H), 124.65, 124.53, 123.07, 122.91 (aromatic C-H), 63.32 (CH2OH), 52.51 & 50.72 (bridgehead C-H) ppm. UV (acetonitrile) 7^ : 280 (s 5,870), 272 (e 3,893), 253 (e 2,696) nm. 13-(ll-Methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132) CH 2 OCOCH 2 CH 2 CDOH 132 To a round bottomed flask fitted with a condenser, alcohol 131 (452 mg, 1.9 mmol) and succinic anhydride (396 mg, 4.0 mmoL Eastman Kodak Co.), as well as 20 mL of dry pyridine were refluxed overnight, adapting procedures described by Aries130 and applying them to the above system. After cooling the solution to room temperature, water was added and the solution was acidified with coned HC1. The reaction rnixture was then extracted three times with ethyl 200 Experimental acetate. The organic layer was washed with warm water and aqueous 5% Na 2C03 (three times). The basic layer was then acidified with aqueous HC1 (15%). The acidic aqueous layer was extracted with ethyl acetate (three times) and the organic layer was washed with water and brine and dried over MgS04. Evaporation of the solvent resulted in a yellow oil which was column chromatographed on silica gel ( 3 : 7 : 1 , ethyl acetate: petroleum ether: ethanol) giving a colorless oil (132), which sohdified in the freezer (524 mg, 1.5 mmol 81%). M P : 90-93 °C. IR (KBr) v m a x : 3210 (O-H), 2971 (C-H), 1737 (C=0), 1713 (C=0) cm 1 . M S m/e (relative intensity): 335 (M+l, 1), 334 ( M + , 4), 233 (13), 216 (100). Exact mass calculated for C 2 i H i 8 0 4 : 334.1205. Found : 334.1197. *H N M R (200 MHz, CDC13) : 8 10.55 (s, broad, 1H, OH), 7.40-7.25(m, 4H, aromatic H), 6.97-6.89 (m, 4H, aromatic H), 6.86 (m, 1H, vinyl H), 5.21 (d, 1H, J = 6 Hz, bridgehead H), 5.15 (d, 1H, J= 2 Hz, bridgehead H), 4.78 (d, 2H, J= 1 Hz, CH2O), 2.57 (s, broad, 4H, COC&CIlaCO) ppm. 1 3 C N M R (75 MHz), CDC13) : 8 178.17, 171.84 (C=0), 147.42 (vinyl C), 145.87, 145.42 (aromatic C), 136.82 (vinyl C-H), 124.67, 124.56, 123.00, 123.00 (aromatic C-H), 64.45 (CH 2 0), 52.68 & 50.76 (bridgehead C-H), 28.75 (COCH 2 CH 2 CO) ppm U V (acetonitrile) : 279 (s 3,305), 272 (s 2,170), 212 (s 22,309) nm. 201 Experimental Methyl 13-(ll-methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132a) CH2OCOCH2CH2COOCH3 To carboxyhc acid 132 (431 mg, 1.3 mmol) dissolved in diethyl ether, an ethereal solution of diazomethane was added until the solution remained yellow. The flask was left in the fumehood to evaporate the excess diazomethane and the solvent was rotary evaporated giving a yellow oil which was column chromatographed on silica gel (1 : 9, ethyl acetate : petroleum ether) resulting in a colorless oil (132a) which sohdified upon standing in the freezer overnight (346 mg, 0.994 mmoL 77%). MP : 85-86 °C. IR (KBr) vm a x : 2944 (C-H), 1727 (C=0) cm \ MS m/e (relative intensity) : 349 (M+l, 3), 348 (M+, 12), 233 (14), 217 (39), 216 (100), 203 (27). Exact mass calculated for C22H20O4 : 348.1362. Found : 348.1356. *H NMR (400 MHz, CDC13): 8 7.31-7.25 (m, 4H, aromatic H), 6.98- 6.93 (m, 4H, aromatic H), 6.85-6.83 (m, IH, vinyl H), 5.09 (d, IH, J = 6 Hz, bridgehead H), 5.02 (d, 1H, J = 2 Hz, bridgehead H), 4.79 (d, 2H, J = 1 Hz, CH2O), 3.68 (s, 3H, OCH2), 2.62 (s, broad, 4H, COCH2CH2CO)ppm. 132a 202 Experimental 1 3 C NMR (50 MHz), CDC13) : 8 172.67, 172.00 (C=0), 147.59 (vinyl C), 145.96, 145.50 (aromatic C), 136.70 (vinyl C-H), 124.72, 124.60, 123.07, 123.03 (aromatic C-H), 64.39 (CH20), 52.74, 50.84 (bridgehead C-H), 51.87 (OCH3), 29.09, 28.86 (COCH 2CH 2CO) ppm. UV (acetonitrile) : 279 (e 3,180), 272 (e 2,067), 252 (s 1,337) run. Anal, calculated for C 2 2 H 2 0 O 4 : C, 75.84; H, 5.79. Found C, 75.93; H, 5.79. 13-(ll-Methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetic Acid (133) CH2OCH2CXX)H In a round bottomed two-neck flask fitted with a condenser, alcohol 131 (500 mg, 2.1 mmol) and bromoacetic acid (297 mg, 2.1 mmol, Aldrich) were dissolved in 25 mL of dry THF under nitrogen adapting procedures described by Brady and Giang131 and applying them to the above system. While cooling the flask in an ice bath, sodium hydride (256 mg, 6.4 mmol, 60% in oil) was added and the solution was stirred for 20 min at room temperature. The solution was then refluxed for 2 h. After quenching the reaction with a mixture of ethyl acetate and water, the solution was acidified with aqueous 15% HC1 and an extraction with ethyl acetate was performed, followed by a wash with brine. The organic layer was dried over MgSCu, filtered and rotary evaporated. The resulting carboxylic acid 133 was purified by an aqueous 10 % KOH wash, followed by an acidification of the aqueous layer with 15% HC1. The acidic aqueous layer was 133 203 Experimental extracted with ethyl acetate (three times) and washed with water and brine. After drying the organic layer over M g S 0 4 , filtration and evaporation of the solvent, acid 133 (487g, 1.7 mmol, 78%) was obtained. M P : 55-57 °C. IR (KBr) v m a x : 3067(O-H), 2906 (C-H), 1724 (C=0) cm "\ M S m/e (relative intensity) : 293 (M+l, 2), 292 (M*, 10), 216 (54), 215 (42), 202 (62), 178 (100). Exact mass calculated for C i 9 H i 6 0 3 : 292.1099. Found : 292.1094. *H N M R (200 MHz, CDC13) : 8 11.6 (s, broad, IH, OH), 7.26-7.12 (m, 4H, aromatic H), 6.93-6.80 (m, 4H, aromatic H), 6.75 (d, IH, J= 6 Hz, vinyl H), 5.06 (s, IH, bridgehead H), 5.01 (d, IH, J= 6 Hz, bridgehead H), 4.19 (s, 2H, CFbO), 3.65 (s, 2H, CH2CO2H) ppm. 1 3 C N M R (50 MHz, CDC13) : 8 178.00 (C=0), 148.59 (vinyl C), 146.04, 145.55 (aromatic C), 137.73 (vinyl C-H), 124.72, 124.65, 123.14, 123.00 (aromatic C-H), 70.85, 65.70 (CH 2), 52.36 & 50.93 (bridgehead C-H) ppm. U V (acetonitrile) A™*: 279 (s 3,853), 272 (s 2,564), 210 (e 22,331) nm. 204 Experimental Methyl 13-(ll-methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetate (133a) ch 2och 2cooch 3 The carboxyhc acid 133 (635 mg, 2.1 mmol) was dissolved in diethyl ether and treated with an ethereal solution of diazomethane until the solution remained yellow. The reaction flask was left in the fumehood until the yellow color disappeared and the rermining ether was rotary evaporated leaving a yellow oil which was purified by column chromatography (silica geL 1 : 9, ethyl acetate: petroleum ether) resulting in a colorless oil. This oil (133a) sohdified upon standing overnight in the freezer (513 mg, 1.7 mmol 78%). M P : 71-73 °C. TR (KBr) v m a x : 2952 (C-H), 1753 (C=0) cm \ M S m/e (relative intensity) : 307 (M+l, 8), 306 (M*, 38), 217 (43), 216 (100), 215 (43), 204 (16), 203 (77), 202 (34), 178 (48). Exact mass calculated for C 2 o H 1 8 0 3 : 306.1255. Found : 306.1250. *H N M R (400 MHz, CDC13) : 8 7.40-7.25 (m, 4H, aromatic H), 7.03-6.92 (m, 4H, aromatic H), 6.84 (d, 1H, J= 6Hz, vinyl H), 5.19 (s, 1H, bridgehead H), 5.11 (d, 1H, J= 6 Hz, bridgehead H), 4.29 (s, 2H, CHbO), 3.77 (s, 2H, CH2C0 2 CH 3 ) , 3.71 (s, 3H, OCH 3 ) ppm. 133a 205 Experimental 1 3 C NMR (75MHz, CDC13) : 8 170.62 (C=0), 148.81 (vinyl C), 146.00, 145.53 (aromatic C), 137.15 (vinyl C-H), 124.54, 124.45, 123.05, 122.83 (aromatic C-H), 70.64, 66.05 (CH 2), 52.20 (bridgehead C-H), 51.69(OCH3), 50.79 (bridgehead C-H) ppm. U V (acetonitrile) A™* : 279 (s 3,711), 272 (s 2,376), 211 (s 20,246) nm. Anal, calculated for C 2 oHi 8 0 3 : C, 78.41; H , 5.92. Found C, 78.28; H , 5.78. 206 Experimental 10.3. Salt Formation of Photochemical Substrates 10.3.1. Sensitizer Salts Formed with 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 3-(Dimethylamino)propiophenone Salt of Acid 121 (138) 3-(Dimemylarnino)propiophenone hydrochloride (76 mg, 0.355 mmol, Aldrich) was dissolved in ethanol (5 mL), and KOH (20 mg, 0.355 mmol) in ethanol (2 mL) was added. The solution was centrifuged and the hquid pipetted off and added to a solution of acid 121 (74 mg, 0.355 mmol) in ethanol. Some of the solvent was evaporated and ethyl acetate added. After a week fine white needles (138) had formed (19 mg, 0.050 mmol 14%). M P : 117-118 °C. m (KBr) vm a x : 3422 (N-H), 2954 (C-H), 1736 (pentanone C=0), 1680 (C=0) cm 1 , 1579 (COO asym.), 1409 (COO" sym.) cm"1. MS FAB (matrix : Thioglycerol) : 386 (M+l). Exact mass calculated for C23H31NO4 (Thioglycerol +M+1): 386.2331. Found : 386.2313. 138 207 Experimental *H NMR (400 MHz, dg-DMSO) : 8 8.70 (s, broad, 1H, N-H), 8.05-7.85 (m, 2H, aromatic H), 7.63-7.04 (m, 3H, aromatic H), 5.38 (t, 1H, J= 2 Hz, vinyl H), 3.54 & 3.30 (s, broad, 2H each, CEbCHa), 2.62 (AB-system, 2H, J= 16 Hz, CH2COO), 2.31-1.52 (m, 12H, C£b), 2.30 (s, 6H, CH3) ppm. /?-Acetylpyridine Salt of Acid 121 (140) 140 Acid 121 (100 mg, 0.481 mmol) was dissolved in ethanol (3 mL) and ^ -acetylpyridine (60 mg, 0.481 mmol, Aldrich) in ethanol (1 mL) was added dropwise to the solution. After evaporation of some of the solvent and addition of diethyl ether (3 mL) colorless plates of 140 formed (131 mg, 0.399 mmoL 83%). MP : 68-70 °C. IR (KBr) vm a x : 3059 (N-H), 2962 (C-H), 1734 (pentanone C=0), 1692 (C=0), 1606 (COO" asym.), 1405 (COO" sym.) cm"1. MS FAB (matrix : 3-Nitrobenzyl alcohol) : 330 (M+l). 208 Experimental Exact mass calculated for C19H23NO4 (Thioglycerol + CHC13,M+1) : 330.1705. Found : 330.1695. *H NMR (200 MHz, CDC13) : 8 10.40 (s, broad, IH, N-H), 8.68 (s, broad, 2H, aromatic H), 7.70-7.52 (m, 2H, aromatic H), 5.36-5.34 (m, 1H, vinyl H), 2.63 (AB-system, 2H, J = 17 Hz, CH2COO"), 2.48 (s, 3H, CH3), 2.25-1.55 (m, 12H, CILJppm. 1 3 C NMR (75 MHz, CDC13): 8 219.00 (cyclopentanone C=0), 197.06 (C=0), 175.18 (COO), 150.22 (aromatic C-H), 143.13 (aromatic C), 141.37 (vinyl C), 127.97 (vinyl C-H), 52.80 (CH2), 39.70, 37.05, 33.03, 32.46, 31.59, 23.22, 19.07 (CH 2, C), 26.64 (CH3)ppm. /j-Acetyl-iV^V-dimethylbenzylamine Salt of Acid 121 (139) 139 To a solution of acid 121 (127 mg, 0.611 mmol) in acetone (5 mL), p-acetyl-JV^-dimethylbenzylamine (128, 325 mg, 1.8 mmol) in 5 mL of acetone was added. Upon addition of diethyl ether (10 mL) no salt formation was observed. The rnixture was chromatographed on silica gel 60 (1:1, methanol : ethyl acetate) and a white solid formed after evaporation of the solvent, which proved to be the salt 139 (85 mg, 0.221 mmoL 36%). MP : 165-167 °C. 209 Experimental IR (KBr) vm a x : 3415 (N-H), 2961 (C-H), 1728 (pentanone C=0), 1668 (C=0), 1570 (COO asym.), 1423 (COO" sym.) cm'1. MS FAB (matrix : Thioglycerol) : 386 (M+l). a H NMR (400 MHz, d6-DMSO) : 5 7.95-7.82 (m, 2H, aromatic H), 7.50-7.33 (m, 2H, aromatic H), 5.336-5.34 (m, IH, vinyl H), 3.44 (s, broad, 3H, CH2N & NH), 2.54 (s, broad, 5H, CH2COO & COCH3), 2.36-1.57 (m, 12H, CH2), 2.14 (s, 6H, NCH3) ppm. 10.3.2. Alkali Metal Salts Formed with 9,10-Dihydro-9,10-ethenoanthracene Derivatives 10.3.2.1. Alkali Metal Salts Formed with Succinate Derivative 132 Sodium Salt of Succinate Derivative 132 (153) 153 Succinate derivative 132 (102 mg, 0.306 mmol) was dissolved in a mixture of acetone (lmL) and diethyl ether (2 mL). A solution of NaHC0 3 (26 mg, 0.306 mmol) in water (0.5 mL) was added dropwise to the ice-cooled solution. The solution was then stirred until a white precipitate formed. After centrifuging the solution, salt 153 was obtained as a white powder (48 mg, 0.135 mmoL 44%). 210 Experimental M P : 205-207 °C. IR (KBr) v m a x : 3421 (O-H), 2969 (C-H), 1730 (C=0), 1580 (COO - asym), 1420 (COO" sym) M S FAB (matrix : 3-Nitrobenzyl alcohol) : 357(M+1). Exact mass calculated for C 2 i H i 7 0 4 N a (3-Nitrobenzyl alcohol, M+l ) : 357.1103. Found: 357.1100. *H N M R (200 MHz,CDCl 3 ) : 8 7.23-7.09 (m, 4H, aromatic H), 6.94-6.76 (m, 4H, aromatic H), 6.65-6.53 (m, 1H, vinyl H), 4.92 (d, 1H, J = 6 Hz, bridgehead H), 4.88 (d, 1H, J = 2 Hz, bridgehead H), 4.52 (s, 2H, CHgO), 2.45-2.03 (m, 4H, COCHaCHaCOO") ppm. Anal, calculated for C 2 i H i 7 0 4 Na . 2 H 2 0 : C, 64.28; H , 5.39. Found : C, 64.31; H , 5.31. Potassium Salt of Succinate Derivative 132 (154) CH 2OCX)CH 2CH 2COO" K + After dissolving succinate derivative 132 (78 mg, 0.234 mmol) in a niixture of acetone (1 mL) and diethyl ether (2 mL), K H C O 3 (23 mg, 0.234 mmol) dissolved in water (0.5 mL) was added dropwise to the ice-cooled solution. The mixture was stirred until a white precipitate formed. A white powder resulted which was filtered off, giving salt 154 (31 mg, 0.084 mmol, 36%). cm -1 154 211 Experimental M P : 244-246 °C. IR (KBr) v m a x : 3426 ( 0 - H ) , 2968 (C-H), 1728 (C=0), 1577 (COO" asym), 1402 (COO" sym) cm"1. M S FAB (matrix : Thioglycerol + C H C 1 3 ) : 373 (M+l). Exact mass calculated for C 2 i H 1 7 0 4 K (Thioglycerol + C H C 1 3 , M+l) : 373.0842. Found : 373.0841. * H NMR (200 MHz ,CDCl 3 ) : 8 7.23-7.09 (rn, 4 H , aromatic H ) , 7.00-6.75 (m, 4 H , aromatic H ) , 6.70-6.55 (m, 1 H , vinyl H ) , 4.95 (d, 1 H , J = 6 H z , bridgehead H ) , 4 .90 (d, 1 H , J = 2 H z , bridgehead H ) , 4.58 (s, 2 H , CH2O), 2.45-2.05 (m, 4 H , C O C H a C H a C O O " ) ppm Anal, calculated for C 2 i H 1 7 0 4 K. H 2 0 : C, 64 .60; H , 4.90. Found : C, 64 .24; H , 4.45. 212 Experimental 10.3.2.2. Alkali Metal Salts Formed with Acetic Acid Derivative 133 Lithium Salt of Acid 133 (158) 158 Dissolved acid 133 (286 mg, 0.979mmol) in ethanol (3 mL) and Li(OH).H20 (41 mg, 0.979 mmol) in H 2 0 (0.5 mL) were combined and stirred. Diethyl ether was added and the solution was placed in the freezer. A beige powder (158) resulted (240 mg, 0.805 mmol, 82%). MP : 262-264 °C. m (KBr) vm a x : 3400 (OH), 2967(C-H), 1609 (COO" asym.), 1423 (COO" sym) cm"1. MS FAB (matrix : Thioglycerol + MeOH) : 299 (M+l). Exact mass calculated for C i 9 H i 5 0 3 L i (Thioglycerol + MeOH, M+l) : 299.1259. Found : 299.1248. *H NMR (400 MHz,CD3OD) : 8 7.29-7.22 (m, 4H, aromatic H), 6.91-6.89 (m, 4H, aromatic H), 6.79 (m, IH, vinyl H), 5.14 (d, IH, J= 1 Hz, bridgehead H), 5.08 (d, IH, J= 6 Hz, bridgehead H), 4.21 (s, 2H, CH 20), 3.57 (s, 2H, CH2COO") ppm UV (methanol) X m a x : 279 (e 3,550), 272 (s 2,515), 213 (8 14,937) nm Anal, calculated for C 1 9 H 1 5 0 3 L i . H 2 0 : C, 72.15; H, 5.42. Found : C, 72.40; H, 5.33. 213 Experimental Sodium Salt of Acid 133 (159) 159 Acid 133 (183 mg, 0.627 mmol) in ethanol (2 mL) and a solution of NaOH (31 mg, 0.627 mmol) in H 2 0 (0.5mL) were combined. Diethyl ether (2 mL) was added and the solution was left in the freezer overnight. A white powder of 159 was obtained (153 mg, 0.487 mg, 78%). MP : 260 °C (decomp). IR (KBr) vm a x : 3400 (O-H), 3065 (C-H), 1610 (COO" asym.), 1426 (COO" sym.) cm"1. MS FAB (matrix : Thioglycerol + MeOH): 315 (M+l). Exact mass calculated for Ci 9 H 1 5 0 3 Na (Thioglycerol + MeOH, M+l) : 315.0997. Found : 315.1004. *H NMR (400 MHz,CD 3OD): 8 7.29-7.22 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.78 (m, 1H, vinyl H), 5.14 (d, 1H, J=2 Hz, bridgehead H), 5.08 (d, 1H, J = 6 Hz, bridgehead H), 4.20 (d, 2H, J = 1 Hz, CffcO), 3.55 (s, 2H, CH2COO") ppm UV (methanol) ^  : 279 (s 3,895), 272 (s 2,566), 211 (s 25,845) nm Anal, calculated for C i 9 H 1 5 0 3 Na .H 2 0 : C, 68.67; H, 5.16. Found : C, 68.82; H, 5.00. 214 Experimental Potassium Salt of Acid 133 (160) CH2OCH2COO" K + 160 To a solution of acid 133 (185 mg, 0.634 mmol) in ethanol (3 mL) KOH (44 mg, 0.634 mmol) dissolved in H 2 0 (0.5 mL) was added. The solution was stirred and diethyl ether was added (3 mL). Small white crystals formed after 2 h in the freezer, which turned into a fine powder of 160 (177 mg, 0.476 mmoL 75 %), which was collected by filtration. MP : 242-244 °C. TR (KBr) vm a x : 3387 (O-H), 2908 (C-H), 1602 (COO- asym.), 1413 (COO" sym.) cm1. MS FAB (matrix : Thioglycerol + MeOH): 331 (M+l). Exact mass calculated for C19H15O3K (Thioglycerol + MeOH, M+l) : 331.0736. Found : 331.0727. *H NMR (400 MHz,CD 3OD): 5 7.29-7.22 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.78 (m, 1H, vinyl H), 5.14 (d, 1H, J= 2 Hz, bridgehead H), 5.08 (d, 1H, J= 6 Hz, bridgehead H), 4.20 (d, 2H, J= 1 Hz, CH20), 3.55 (s, 2H, CHzCOO) ppm. UV (methanol) : 279 (s 4,903), 272 (s 3,170), 213 (s 15,981) nm. Anal, calculated for C i 9 H 1 5 0 3 K . H 2 0 : C, 65.49; H, 4.92. Found : C, 65.77; H, 4.81. 215 Experimental Rubidium Salt of Acid 133 (161) CH 2 OCH 2 COO"Rb + 161 To a solution of acid 133 (265 mg, 0.908 mmol) in ethanol (3 mL) an aqueous solution of Rb(OH) (186mg, 0.912 mmol, 50% w/w) was added. The solution was stirred and diethyl ether was added (3 mL). After letting the solution sit in the freezer overnight, off-white needles corresponding to salt 161 were formed (190 mg, 0.505 mmol, 56%). M P : 190-192 ° C . IR (KBr) vm a x : 3398 (O-H), 3005 (C -H) , 1597 (COO" asym.), 1420 (COO" sym.) cm"1. MS FAB (matrix : Thioglycerol + MeOH) : 377 (M+l). Exact mass calculated for C i 9 H i 5 0 3 R b (Thioglycerol + MeOH, M+l): 377.0217. Found: 377.0214. *H NMR (400 MHz,CD3OD) : 8 7.29-7.22 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.78 (m, IH, vinyl H), 5.14 (d, IH, J= 2 Hz, bridgehead H), 5.08 (d, IH, J = 6 H z , bridgehead H), 4.20 (d, 2H, J= 1 Hz, CH2O), 3.55 (s, 2H, CH2COO") ppm. UV (methanol) : 279 (s 3,653), 272 (s 2,602), 213 (s 14,294) nm Anal, calculated for C 1 9 H i 5 0 3 Rb . 1/2 [Rb(OH). H20] : C, 52.22; H, 3.81. Found : C, 52.33; H, 3.69. 216 Experimental Cesium Salt of Acid 133 (162) 162 Acid 133 (209 mg, 0.717 mmol) was dissolved in ethanol (5 mL) and an aqueous solution of Cs(OH) (215mg, 0.717 mmoL 50% w/w) was added. The solution was stirred and diethyl ether was added (5 mL). Off-white crystals (162) formed overnight in the freezer (181 mg, 0.427 mmol, 60 %). MP : 40-42 °C. IR (KBr) v m a x : 3525 (O-H), 2906 (C-H), 1593 (COO" asym.), 1417 (COO" sym.) cm"1. MS FAB (matrix : Thioglycerol + MeOH): 425 (M+l). Exact mass calculated for Ci 9 H 1 5 0 3 Cs (Thioglycerol + MeOH, M+l) : 425.0154. Found : 425.0142. *H NMR (400 MHz,CD3OD) : 5 7.29-7.22 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.78 (m, IH, vinyl H), 5.14 (d, IH, J= 2 Hz, bridgehead H), 5.08 (d, IH, J= 6 Hz, bridgehead H), 4.20 (d, 2H, J= 1 Hz, 3.55 (s, 2H, CHjCOO) ppm. UV (methanol) A™* : 279 (e 3,285), 272 (s 2,110), 213 (s 12,817) nm. Anal, calculated for Ci 9 Hi 5 0 3 Cs . H 2 0 : C, 51.60; H, 3.87. Found : C, 51.81; H, 3.84. 217 Experimental 10.3.3. Sensitizer Salts Formed with Acetic Acid Derivative 133 3-(Dimethylamino)propiophenone Salt of 133 (164) 164 To a solution of acid 133 (157 mg, 0.538 mmol) in ethyl acetate (7 mL) 3-(dimethylamino)propiophenone was added (95 mg, 0.538 mmoL Aldrich) dissolved in ethanol (1 mL). The solution was stirred for 5 min and left in the fumehood. After two days colorless plates of the salt 164 (186 mg, 0*397 mmoL 74 %) had formed which were filtered off. MP : 65-66 °C. m (KBr) vm a x : 3385 (N-H), 2974 (C-H), 1681 (C=0), 1598 (COO- asym.), 1401 (COO- sym.) cm "\ MS FAB (matrix : 3-Nitrobenzyl alcohol) : 470 (M+l), 178 (arnine + 1). Exact mass calculated for C30H31NO4 (3-Nitrobenzyl alcohol, M+l) : 470.2331. Found : 470.2337. *H NMR (400 MHz, CDCI3) : 8 11.74 (s, IH, broad, N-H), 7.94 (d, 2H, J= 7 Hz, aromatic H), 7.58-7.54 (m, IH, aromatic H), 7.46-7.42 (m, 2H, aromatic H), 7.26-7.21 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.74 (m, IH, vinyl H), 5.14 (d, IH, J= 1 Hz, bridgehead H), 5.03 218 Experimental (d, 1H, J= 6 Hz, bridgehead H), 4.24 (d, 2H, J= 1Hz, CHzO), 3.63 (s, 2H, CHaC02"), 3.41, 3.18 (t, 4H, J= 7 Hz, CHaCHz), 2.55 (s, 6H, CH3) ppm. 1 3 C NMR (75 MHz, CDC13) : 8 197.04 (COPh), 175.69 (COO), 149.76 (vinyl C), 146.32, 145.84 (acid aromatic C), 136.10 (amine aromatic C), 135.90 (vinyl C-H), 133.67 (amine aromatic C-H), 128.78, 128.16 (amine aromatic C-H), 124.48, 124.40, 123.09, 122.78 (acid aromatic C-H), 70.42, 68.16 (CH2), 52.54 (CH2N), 52.27, 50.86 (bridgehead C-H), 43.45 (CH3), 34.46 (CH2CO) ppm UV (acetonitrile) ^  : 279 (s 4,593), 272 (s 3,406), 238 (s 14,307) nm Anal, calculated for C30H31NO4 : C, 76.72; H, 6.66; N, 2.98. Found C, 76.43; H, 6.90; N, 2.99. X-Ray Crystal Data for C30H31NO4 : Space group Cllc (#15), a = 37.712(3) A, b = 8.977(1) A, c = 15.922(1) A, B = 92.055(6) °, V = 5387.0(7) A 3 , Z = 8, D c a l c d = 1.16 g/cm 3 , R=0.045. 219 Experimental /j-Acetylpyridine Complex with 133 (165) 2:1 ratio o II CH2OCH2CO —H N 2 165 To a solution of acid 133 (204 mg, 0.699 mmol) in ethyl acetate (1 mL) was added p-acetylpyridine (85 mg, 0.699 mmol, Aldrich) dissolved in ethanol (5 mL). The solution was stirred for 5 min and left in the fiunehood. After one day colorless needles of the complex 165 (130 mg, 0.185 mmol, 53%) had formed which were filtered off. M P : 112-114 °C. IR (KBr) v m a x : 3018 (N-H), 2977 (C-H), 1698 (C=0), 1605 (COO" asym), 1414 (COO" sym.) MS FAB (matrix : Thioglycerol + CHC13) : 293 (acid + 1), 123 (amine + 1), 584 (2 acids). Exact mass calculated for Csgl^Oe (Thioglycerol + CHC13, 2 acids) : 584.2199. Found : 584.2176. *H NMR (400 MHz, CDC13) : 5 10.27 (s, 1H, broad, N-H), 8.82 (s, broad, 2H, aromatic H), 7.78 (d, 2H, J= 6 Hz, aromatic H), 7.30-7.25 (m, 8H, aromatic H), 6.97-6.91 (m, 8H, aromatic H), 6.83 (dd, 2H, J = 1 & 6Hz, vinyl H), 5.14 (d, 2H, J= 1 Hz, bridgehead H), 5.09 (d, 2H, J = 6 Hz, bridgehead H), 4.29 (d, 4 H, J - 1 Hz, CH2O), 3.78 (s, 4H, CH 2C0 2"), 2.63 (s, 3H, COCH3) ppm -1 cm 220 Experimental 1 3 C NMR (75MHz, CDC13) : 5 196.84 (C0CH3), 174.07 (COO), 149.61 (pyridine aromatic C-H), 148.62 (vinyl C), 145.96,. 145.47 (acid aromatic C), 143.51 (pyridine aromatic C), 137.40 (vinyl C-H), 124.60, 124.52, 123.04, 122.89 (acid aromatic C-H), 70.70, 65.89 (CH2), 52.24, 50.80 (bridgehead C-H), 26.63 (CH3) ppm UV (acetonitrile) ?w : 279 (s 6,005), 272 (s 4,404), 252 (s 2,288), 218 (s 19,829), 213 (s 20,066), 208 (8 19,694) nm Anal, calculated for C 4 5 H 3 8 N0 7 : C, 76.69; H, 5.43; N, 1.99. Found C, 76.80; H, 5.33; N, 2.05. X-Ray Crystal Data for C45H39N07: Space Group PI (#2), a = 12.344(1) A, b = 18.439(3) A, c = 8.2721(7) A, a = 101.789(9)°, B = 94.525(8)°, y = 95.05(1)°, V = 1826.8(4) A 3 , Z = 2, D c a i c d = 1.283 g/cm3R = 0.051. 4'-Piperazinoacetophenone Salt of 133 (166) 166 To a solution of acid 133 (183 mg, 0.627 mmol) in ethyl acetate (15 mL) was added 4'-piperazinoacetophenone (128 mg, 0.627 mmoL Aldrich) dissolved in ethanol (15 mL). The solution was stirred for 5 min and left in the fumehood. After two days yellow crystals of the salt 166 (157 mg, 0.317 mmoL 50 %) had formed which were filtered off. 221 Experimental M P : 143-145 °C. JR (KBr) vm a x : 3043 (N-H), 2883(C-H), 1663 (C=0), 1597 (C=0) cm"1. MS FAB (matrix : 3-Nitrobenzyl alcohol) : 497 (M+l), 205 (amine + 1). Exact mass calculated for C31H32O4N2 (3-Nitrobenzyl alcohol, M+l): 497.2440. Found : 497.2436. *H NMR (400 MHz, CDC13): 8 7.89 (d, 2H, J= 9 Hz, aromatic H), 7.24-7.19 (m, 4H, aromatic H), 6.92-6.87 (m, 4H, aromatic H), 6.77 (d, 2H, J= 9 Hz, aromatic H), 6.69 (dd, 1H, J= 1 & 6 Hz, vinyl H), 6.60-6.30 (s, broad, 2H, NH2), 5.03 (d, 1H, J= 1 Hz, bridgehead H), 4.99 (d, 1H, J = 6 Hz, bridgehead H), 4.16 (s, 2H, CH2O), 3.71 (s, 2H, CH2CO2), 3.28 (m, 4H, piperazine H), 2.94 (m, 4H, piperazine H), 2.53 (s, 3H, COCH3) ppm 1 3 C NMR (75MHz, CDC13) : 8 196.54 (COCH3), 176.32 (COO), 153.25 (piperazine aromatic C), 149.58 (vinyl C), 146.11, 145.59 (acid aromatic C), 135.84 (vinyl C-H), 130.31 (piperazine aromatic C-H), 128.80 (piperazine aromatic C), 124.59, 124.45, 123.06, 122.88 (acid aromatic C-H), 114.21 (piperazine aromatic C-H), 70.64, 69.32 (CH2), 52.47, 50.70 (bridgehead C-H), 45.31, 42.70 (piperazine CH2), 26.21 (CH3) ppm. UV (methanol) A ^ : 325 (s 20,712), 280 (s 8,278), 274 (e 5,116), 231 (s 11,971), 215 (s 26,342) nm Anal, calculated for C 3 i H 3 2 N 2 0 4 • Vi H 2 0 : C, 73.64; H, 6.58; N, 5.54. Found C, 73.68; H, 6.53; N, 5.56. X-Ray Crystal Data for C31H32O4N2: Space Group PI (#2), a = 9.760(1) A, b = 16.254(2) A, c = 9.114(1) A, a = 99.47(1)°, R = 109.17(1)°, y = 88.101(1)°, V = 1346.7(3) A3, Z = 2, D c a l c d = 1.25 g/cm3, R = 0.044. 222 Experimental CHAPTER 11 PHOTOCHEMICAL STUDIES OF SUBSTRATES 11.1. General Procedures Irradiation Sources Photolysis experiments were conducted either with a 450 W Hanovia medium pressure mercury lamp at room temperature through various glass filters, namely Pyrex (A > 290 nm), quartz (A, > 200 nm), Vycor (A- > 240 nm) and uranium (A- > 330 nm), or with a Rayonet Photochemical Chamber Reactor (Model RPR-100). This light source was equipped with up to 16 lamps at 3000 A (21 watts), 2537 A (35 watts) or 3300 A (24 watts) and operated at a temperature of 35 °C. Solution State Irradiation Solution state irradiation studies were carried out by dissolving the samples (10"2M) in spectral grade solvents (Fisher). Prior to analytical runs, the samples were degassed by three freeze-pump-thaw cycles and sealed under nitrogen. In the case of preparative scale photolyses, oxygen was purged by bubbling nitrogen through the solution 30 min before and during the irradiation period, while stirring it. The photoreactions were monitored by gas chromatographic analysis. Following irradiation, the solvent was removed in vacuo and the photoproducts isolated by column chromatography. 223 Experimental Solid State Irradiation Solid state photolysis studies were carried out by crushing the crystals and distributing them evenly between two Pyrex or quartz glass plates. The samples were then placed in a polyethylene bag, which was sealed under nitrogen with a heat-sealing device. After irradiation, the samples were dissolved prior to gas chromatographic analysis and chromatographic isolation. Acid derivatives were treated with an ethereal solution of diazomethane to esterify the starting materials and photoproducts prior to GC injection and isolation. The salts were acidified with aqueous 15 % HC1 (Fisher), and the resulting acids were extracted with ethyl acetate and treated with diazomethane. 224 Experimental 11.2 Photolysis of Substrates 11.2.1. Photolysis of 9,10[l',2']Benzenoanthracene-l,4-dione Derivatives in Solution Photolysis of 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63) in Acetonitrile A solution of compound 63 (250 mg, 0.880 mmol) in anhydrous acetonitrile (400 mL) was irradiated under nitrogen with a 450 W Hanovia medium pressure lamp through a Pyrex glass filter for 4 h. The solvent was removed and the rerriaining oil purified by column chromatography with ethyl acetate / petroleum ether (3 : 7) resulting in a light yellow crystalline photoproduct 80 (195 mg, 0.687 mmol, 78%). Compound 80 was characterized as 4b,8b,8c,8d-tetrahydrodibenzo [aj] cyclopropa [c</]pentalene-8d,8c-benzeno-l %4'-dione. 80 MP : 167-169 °C (recryst from diethyl ether). TR (KBr) v ^ : 1677 (C=0), 1596 (C=C) cm'. MS m/e (relative intensity) : 285 (M+l, 22), 284 (M+, 100), 202 (12). Exact mass calculated for C 2 0 H 1 2 O 2 : 284.0837. Found : 284.0838. 225 Experimental lIi NMR (200 MHz, CDCf, ) : 8 8.05-7.97 (m, IH, aromatic H), 7.35-7.03 (m, 7H, aromatic H), 6.63 (s, 2H, vinyl H), 5.13 & 4.37 (s, IH each, pentalene H) ppm. 1 3 C NMR (50 MHz, CDC13 ) : 8 191.99 (CO), 191.07 (C=0), 150.34, 149.03 (aromatic C), 138.46, 138.09 (vinyl C-H), 133.40, 131.41 (aromatic C), 128.72, 128.16, 127.10, 127.10 126.14, 125.51, 121.82, 121.55 (aromatic C-H), 77.28 & 58.86 (pentalene C), 58.53 & 51.43 (pentalene C-H) ppm. UV (acetonitrile)A.max : 378 (s 791), 277 (s 3,366) nm. Anal, calculated for C 2 0 H 1 2 O 2 : C, 84.48; H, 4.26. Found: C, 84.26 H, 4.30. Photolysis of 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63) in Air-Saturated Acetone Compound 63 (275 mg, 0.968 mmol) dissolved in dry acetone (500 mL) was photolysed for 16 h with a Rayonet Photoreactor (11 bulbs at 3000 A ) while saturating the solution with air. Evaporation of the solvent, followed by column chromatography (ethyl acetate / petroleum ether, 3 : 7), gave the yellow crystalline triketone 81 (52 mg, 0.173 mmoL 18%). 81 226 Experimental MP : 171-174 °C (recryst from petroleum ether / ethyl acetate). IR (KBr) : 1709 (C=0), 1760 (C=0) cm"1. MS (DCI, N H 3 , relative intensity): 318 (M+18, 100), 301 (M+l, 10), 215 (5), 189 (15), 178 (100). Exact mass calculated for C 2 0 H 1 2 O 3 (M+l) : 301.0864. Found : 301.0872. *H NMR (400 MHz, CDC13 ) : 8 7.50-7.40 (m, 2H, aromatic H), 7.38 (s, 2H, vinyl H) 7.37-7.23 (m, 6H, aromatic H), 4.98 & 4.47 (s, IH each, bridgehead H) ppm 1 3 C NMR (75 MHz, CDCL,) : 8 196.75 (C=0), 194.46 (C=0), 151.02 (vinyl C-H), 138.68, 135.65 (aromatic C),127.53, 127.49, 125.78, 125.20 (aromatic C-H), 62.78 (bridgehead C), 61.89 & 49.61 (bridgehead C-H) ppm X-Ray Crystal Data for C 2 0 H 1 2 O 3 : Space group Pna2v a = 12.273(3) A, b = 7.957(3) A, c = 15.444(3) A, V= 1508(1) A 3 , Z = 4, Dcaicd = 1.322 g/cm3, R = 0.037. Photolysis of 9,10-Dihydro-9,10[l',2']benzenoanthracene-l,4-dione (63) in Chloroform Irradiation of compound 63 (257 mg, 0.905 mmol) in dry chloroform (150 mL) was conducted for 6 h with the Rayonet Photoreactor (16 lamps at 3000 A). After evaporation of the solvent and column chromatography with chloroform / petroleum ether (2 : 3) two monochlorinated photoproducts, 75 (64 mg, 0.201 mmoL 25%) and 74 (62 mg, 0.195 mmol, 24%) and one dichlorinated photoproduct 76 ( 1 mg, 0.003 mmol, 1%) were isolated. 227 Experimental 2-Choro-9,10-dihydro-9,10[l',2']benzenoanthracene-l,4-dione (75) 75 MP : 275-279 °C (recryst from diethyl ether / ethyl acetate). JR (KBr) : 1671 (C=0), 1650 (C=0) cm'. MS m/e (relative intensity) : 320 (M+2, 24), 319 (M+l, 17), 318 (M^l ) , 255 (32), 226 (27), 202 (100). Exact mass calculated for C 2 0 H n O 2 C l : 318.0448. Found : 318.0449. m NMR (400 MHz, CDClj ) : 87.48-7.36 (m, 4H, aromatic H), 7.10-6.94 (m, 4H, aromatic H), 6.79 (s, 1H, vinyl H), 5.82 & 5.75 (s, 1H each, bridgehead H) ppm 1 3 C NMR (75 MHz, CDC13 ) : 8 181.23 (C=0), 167.99 (C-Cl), 152.76, 151.98 (vinyl C) 143.24, 143.12 (aromatic C), 132.17 (vinyl C-H), 125.73, 124.47 (aromatic C-H), 47.95 & 47.43 (bridgehead C-H) ppm. 228 Experimental 6-Chloro-9,10-dihydro-9,10[1 ',2'] benzenoanthracene-1,4-dione (74) 74 MP : 175-178 °C (recryst from diethyl ether / ethyl acetate). IR (KBr) : 1653 (C=0) cm'. MS m/e (relative intensity) : 320 (M+2, 33), 319 (M+l, 22), 318 (M+,100), 283 (28), 255 (40), 236 (77). Exact mass calculated for C 2 0 H n O 2 C l : 318.0448. Found : 318.0443. 1 H NMR (400 MHz, CDCL, ) : 5 7.42-7.37 (m, 3H, aromatic H), 7.31 (d, IH, J= 6 Hz, aromatic H), 7.05-7.01 (m, 2H, aromatic H), 6.98 (AB-system, IH, J = 8 Hz, aromatic H), 6.60 (s, 2H, vinyl H), 5.74 & 5.73 (s, IH each, bridgehead H) ppm. The spectral data of photoproduct 74 was compared to the authentic sample of the quinone proving that the compounds were identical. 229 Experimental 3,6-DicUoro-9,10-diQiydro-9,10[l',2']benzenoanthracene-l,4-dione (76a) 2,6-Dichloro-9,10-dihydro-9,10[l',2']benzenoanthracene-l,4-dione (76b) 76 a R i = H , R 2 = Cl 76 b R i = CL R 2 = H M P : 125-128 °C. IR (CHC13) v ^ : 2927 (C-H), 1673 (C=0) 1581 (C=C) cm"1. MS m/e (relative intensity): 356 (M+4, 3), 354 (M+2, 14), 353 (M+l, 5), 352 (Nf, 21), 317 (8), 289 (12), 236 (25), 40 (100). Exact mass calculated for C 2 0 H 1 0 O 2 C l 2 : 352.0058. Found : 352.0068. *H NMR (400 MHz, CDCI3 ) : 8 7.50-7.38 (m, 3H, aromatic H), 7.35-7.29 (m, 1H, aromatic H), 7.14-6.98 (m, 3H, aromatic H), 6.82 (s, 1H, vinyl H), 5.87-5.68 (m, 2H, bridgehead H) ppm 230 Experimental Photolysis of 9,10-Dmydro-940-dimethyl-9,10[l',2']benzenoanthracene-l,4-dione (69) in Acetonitrile A solution of compound 69 (106 mg, 0.340 mmol) in dry acetonitrile (600 mL) was irradiated under a nitrogen atmosphere with the Rayonet Photoreactor (16 bulbs at 3000 A) for 4.5 h. Following solvent removal and purification by column chromatography with ethyl acetate / petroleum ether (2 : 98), the yellow photoproduct 102 (31 mg, 0.099 mmoL 29%) and the midnight blue photoproduct 103 (24 mg, 0.077 mmol, 23%) as well as starting material 69 (8 mg, 0.026 mmol, 7%) were isolated. Irradiation of compound 69 (105 mg, 0.336 mmol) in dry methanol (600 mL) for 1 h under the same conditions led to the isolation of 102 (65 mg, 0.208 mmol, 63%), 103 (8 mg, 0.026 mmol, 7%) and starting material (1 mg, 0.003 mmol, 11%). 4b,8b-Dimethyl-4b,8b,8c,8d-tetrahydrodibenzo [aj\ cyclopropa [cd\ pentalene-8d,8c-benzeno-l',4'-dione (102) 102 MP : 130-132 °C (recryst from diethyl ether). IR (KBr) vm a x : 2927 (C-H), 1668 (C=0) cm"1. 231 Experimental MS m/e (relative intensity): 313 (M+l, 22), 312 (M+, 94), 284 (18), 269(44), 242(31), 239 (32), 215 (100). Exact mass calculated for C 2 2Hi 602: 312.1150. Found : 312.1152. *H NMR (400 MHz, CDC13) : 5 7.80 (d, IH, J= 7 Hz, aromatic H), 7.20-7.02 (m, 7H, aromatic H), 6.74 (AB-system, 2H, J= 10 Hz, vinyl H), 2.13 & 1.98 (s, 3H each, CH 3) ppm. 1 3 C NMR (75 MHz), CDC13) : 6 193.00, 191.87 (C=0), 153.07, 152.69, 137.45, 132.95 (aromatic C), 142.67, 140.38 (vinyl C-H), 128.66, 127.71, 127.15, 126.85, 125.01, 124.51, 119.06, 118.97 (aromatic C-H), 73.06, 61.03, 60.48, 59.08 (pentalene C), 14.96 & 13.99 (CH3) ppm. Anal, calculated for C 2 2 H 1 6 0 2 : C, 84.59; H, 5.16. Found C, 84.19; H, 5.13. Norcaradiene Derivative 103 103 MP : 172-173 °C (recryst from petroleum ether / ethyl acetate). IR (KBr) v m a x : 2922 (C-H), 1664, 1645 (C=0), 1252 (C-O) cm1. MS m/e (relative intensity): 313 (M+l, 8), 312 (M+, 32), 297 (100), 284 (6), 269 (27), 241 (23), 239 (27), 215 (44). Exact mass calculated for C 2 2 Hi 6 0 2 : 312.1150. Found : 312.1157. 232 Experimental *H NMR (200 MHz, CDC13) : 8 7.78-7.69 (m, IH, aromatic H), 7.40-7.30 (m, 1H, aromatic H), 7.28-7.19 (m, 2H, aromatic H), 6.98 (d, IH, J= 6 Hz, vinyl H), 6.65 (AB-system, 2H, J= 10 Hz, quinone vinyl H), 6.31 (dd, 1H, J = 9 & 6 Hz, vinyl H), 6.03 (dd, IH, J = 9 & 5 Hz, vinyl H), 2.55 (d, IH, J= 5 Hz, cyclopropylH), 1.50 & 1.06 (s, 3H each, CH2) ppm. 1 3 C NMR (100 MHz), CDC13) : 8 186.11, 185.87 (C=0), 149.51, 148.17, 146.45, 141.89 (aromatic C), 137.87, 136.19 (vinyl C-H), 134.89 (vinyl C), 128.01, 127.14, 126.74, 124.97 (aromatic C-H), 126.65, 126.32, 121.84 (vinyl C-H), 61.01, 56.88 (cyclopentyl C), 37.82 (cyclopropyl C-H), 23.88 (CH3), 21.99 (cyclopropyl C), 10.77 (cyclopropyl CH 3) ppm. UV (acetonitrile) Ka* : 569 (s 2,066), 316 (s 3,577), 232 (s 9,756) nm. UV (chloroform) ?w : 594 (s 2,423), 324 (s 4,157), 256 (s 8,889) nm. Anal, calculated for C 2 2 H 1 6 0 2 : C, 84.59; H, 5.16. Found : C, 84.40; H, 5.14. X-Ray Crystal Data for C 2 2 Hi 6 0 2 : Space group Pljn (#14), a = 8.114(3) A, b = 11.966 (3) A, c = 16.694(3) A, B = 95.53(2)°, V = 1613.3(7) A 3 , Z = 4, D c a i c d = 1.29 g/cm3, R = 0.037. Photolysis of 9,10-Bis(methoxymethyl)-9,10[l',2']benzenoanthracene-l,4-dione (72) in Acetonitrile A solution of compound 72 (220 mg, 0.591 mmol) in dry acetonitrile (500 mL) was irradiated in a Rayonet Photoreactor (8 bulbs at 3000 A) for 1 h while under nitrogen. Evaporation of the solvent and column chromatography with ethyl acetate / petroleum ether (3 : 7) resulted in three photoproducts. The isolated products were identified as the blue norcaradiene derivative 110 (7 mg, 0.019 mmoL, 3%), the white dihydrofuran derivative 111 (42 mg, 0.113 233 Experimental mmol, 19%) and red benz[a]aceanthrylene derivative 112 (39 mg, 0.105 mmol, 18%). Upon photolysis of compound 72 (41 mg, 0.110 mmol) in benzene (100 mL) for 45 min under the above conditions, followed by the same isolation procedures, dihydrofuran 111 (4.0 mg, 0.011 mmoL 10%) and benz[a]aceanthrylene 112 (14 mg, 0.038 mmol, 33%) were isolated. Norcaradiene Derivative (110) 110 MP : 125-128 °C. HI (KBr) vm a x : 2926 (C-H), 1665 (C=0), 1646 (C=0) cm1. MS m/e (relative intensity) : 373 (M+l, 27), 372 (M+, 100), 343 (16), 327 (11), 311 (10), 297 (15). Exact mass calculated for C24H20O4 : 372.1362. Found : 372.1364. *H NMR (400 MHz, CDC13) : 8 7.66 (d, 1H, J = 7 Hz, aromatic H), 7.58 (d, 1H, J = 7 Hz, aromatic H), 7.28-7.19 (m, 2H, aromatic H), 6.90 (d, 1H, J = 6 Hz, vinyl H), 6.64 (AB-system, 2H, J= 8 Hz, quinone vinyl H), 6.31 (dd, 1H, J= 9 & 6 Hz, vinyl H), 6.16 (dd, 1H, J= 9 & 5 Hz, vinyl H), 4.05 (d, 1H, J= 9 Hz, CH2), 3.30 (d, 1H, J= 9 Hz, CH2), 3.28 (AB-system, 2H,J = 9 Hz, CH2), 3.21 & 3.17 (s, 3H each, CH3), 2.85 (d, 1H, J= 5 Hz, cyclopropyl H) ppm 234 Experimental Dihydrofuran Derivative 111 111 MP : 252-254 °C (recryst from benzene). HI (KBr) vm a x : 3270 (O-H), 2922 (C-H) cm"1. MS m/e (relative intensity) : 373 (M+l, 27), 372 (M+, 100), 310 (13), 281 (11), 258(18). Exact mass calculated for C24H20O4 : 372.1362. Found : 372.1365. *H NMR (500 MHz, CDCI3) : 8 8.28 (s, 1H, OH), 8.16-8.12 (m, 1H, aromatic H), 7.40 (d, 1H, J = 7 Hz, aromatic H), 7.22-7.17 (m, 2H, aromatic H), 7.08-6.97 (m, 4H, aromatic H), 6.87 (s, 1H, acetal methine H), 6.48 (AB-system, 2H, J = 8 Hz, aromatic H), 4.96 (s, 2H, CH2OCH3), 3.98 & 3.91 (s, 3H each, OCH2) ppm 1 3 C NMR (125 MHz, CDC13) : 8 146.17, 146.15, 145.96, 145.62, 145.36, 145.03, 138.24, 126.00 (aromatic C), 125.16, 124.97, 124.82, 124.59, 124.81, 121.82, 121.31, 120.48, 116.61 (aromatic C-H), 112.06 (acetal C-H), 107.83 (aromatic C-H), 71.43 (CH2OCH3), 59.60 (CH2OCH3), 58.22 (OCH3), 57.60 & 53.91 (bridgehead C) ppm Anal, calculated for C24H20O4: C, 77.40; H, 5.41. Found C, 77.28; H, 5.25. 235 Experimental Benz(a|aceanthrylene Derivative 112 OH 112 MP : 236-238 °C (recryst from benzene). Di (KBr) vm a x : 3332 (O-H), 1643 (C=0) cm1. MS m/e (relative intensity):297 (M+l, 23), 296 (M+, 100), 279 (17), 268 (54), 267 (30), 240 (21), 239 (71), 238 (23), 237 (44). Exact mass calculated for C 2 iHi 2 0 2 : 296.0837. Found : 296.0840. *H NMR (500 MHz, dg-acetone) : 5 11.55 (s, IH, CHO), 10.20 (s, IH, OH), 9.28 (d, IH, J= 9 Hz, aromatic H), 9.02 (d, IH, J= 8.5 Hz, aromatic H), 8.85 (d, IH, J = 9 Hz, aromatic H), 8.62 (dd, IH, J= 6 & 7 Hz, aromatic H), 8.26 (dd, IH, J= 7 & 6 Hz, aromatic H), 7.84-7.80 (m, IH, aromatic H), 7.73-7.70 (m, IH, aromatic H), 7.55-7.46 (m, 3H, aromatic H) ppm. 1 3 C NMR (125 MHz, d6-acetone) : 6 193.26 (CHO), 154.34, 140.10, 138.03, 136.36, 133.21, 132.48, 130.01, 129.12 (aromatic C), 128.83, 128.47, 128.32, 127.90, 127.31, 126.47, 125.99, 125.68, 125.35, 125.12 (aromatic C-H), 126.07 (aromatic C), 117.12 (aromatic C)ppm. UV (acetonitrile) X™« : 484 (s 14,393), 456 (s 14,306), 390 (s 14,891) nm. 236 Experimental 11.2.2. Photolysis of 2-(l-Cyclopentenyl)cyclopentanone Derivative 121 in Solution Photolysis of l-(l-Cyclopenten-l-yl)-2-oxocyclopentaneacetic Acid (121) in Hexane124a Compound 121 (150 mg, 0.721 mmol) was dissolved in dry hexane (300 mL) and irradiated with a Hanovia medium pressure mercury lamp (Pyrex glass filter, X > 290 nm) for 6 h while bubbling nitrogen through the solution. After evaporation of the solvent and treatment with diazomethane, the reaction mixture was purified by column chromatography with ethyl acetate / petroleum ether (15 : 85). The isolated products, which have been characterized by Givens et al.,12** were the singlet product 135a, an oil (44 mg, 0.198 mmol, 28%), starting material 121 (51 mg, 0.230 mmoL 32%) and a trace of triplet product 134a, an oil (1.0 mg, 0.005 mmoL 0.6%). Methyl l,2,3,5,6,7,8,8a-octahydro-8-oxo-4-azuleneacetate (135a) 135a m (NaCl) vm a x : 2952 (C-H), 1736 (C=0), 1710 (C=0) cm1. MS m/e (relative intensity) : 223 (M+l, 16), 222 (M*, 100), 190 (62), 149 (63), 107 (73), 91 (91). Exact mass calculated for C i 3 H i 8 0 3 : 222.1256. Found : 222.1255. 237 Experimental NMR (400 MHz, CDC13) : 8 3.99-3.98 (m, IH, CH2), 3.67 (s, 3H, CO2CH3), 3.02 (AB-system, 2H, J= 15 Hz, CH2CO2CH3), 2.63-2.11 (m, 9H, CHg), 1.86-1.55 (m, 3H, CH2) ppm. 1 3 C NMR (50 MHz, CDC13): 5 208.46 (ketone C=0), 171.90 (ester C O ) , 137.93, 125.29 (vinyl C), 52.80, 51.76 (C0 2CH 3 , CH), 43.70, 41.37, 34.41, 32.43, 27.49, 24.70, 22.24 (CH 2C0 2CH 3 , CH2) ppm. Photolysis of l-(l-Cyclopenten-l-yl)-2-oxocyclopentaneacetic Acid (121) in Acetone124" Irradiation of compound 121 (146 mg, 0.702 mmol) dissolved in dry acetone (300 mL) was carried out with a Hanovia medium pressure mercury lamp (k > 290 nm) for 45 min under nitrogen. Following removal of the solvent, methylation with diazomethane and column chromatography with ethyl acetate / petroleum ether (15 : 85) the main photoproduct was 134a (98 mg, 0.441 mmoL 61%). Small amounts of the singlet product 135a (7 mg, 0.032 mmol, 4%) and starting material 121 (13 mg, 0.058 mmoL 8%) were also isolated. Methyl octahydro-7-oxo-3b//-cyclopenta[1,3]cyclopropa[1,2] benzene-3b-acetate (134a) o 134a 238 Experimental IR (NaCl) vm a x : 1739 (C=0), 1675 (C=0) cm1. MS m/e (relative intensity) : 223 (M+l, 6), 222 (M+, 39), 190 (24), 163 (47), 149 (100). Exact mass calculated for C i 3 H i 80 3 : 222.1256. Found : 222.1256. *H NMR (400 MHz, CDC13) : 8 3.72 (s, 3H, C0 2 CH 3 ) , 2.95-2.86 (m, 1H, CHz), 2.49 (s, 2H, CH2C0 2 CH 3 ) , 2.41 (d, 1H, J = 6 Hz, CH?), 2.37-2.20 (m, 2H, CHg), 2.15-1.40 (m, 9H, CH2) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 209.00 (ketone C=0), 172.35 (ester C=0), 51.71 (C02CH3), 50.31 (CH 2C0 2 CH 3 ), 37.11, 36.70 (CH), 35.70 (CH2), 34.12 (C), 29.24, 27.19, 16.21, 24.71, 17.86 (CH2) ppm 11.2.3. Photolysis of 9,10-Dihydro-9,10-ethenoanthracene Derivatives in Solution Photolysis of 11-Hydroxymethyl -9,10-dihydro-9,10-ethenoanthracene (131) in Acetonitrile A solution of compound 131 (204 mg, 0.872 mmol) in 100 mL of acetonitrile in a quartz vessel was irradiated for 2 h under nitrogen with the Rayonet Photoreactor (16 bulbs at 254 nm). Gas chromatographic analysis (HP5, 30m) led to the determination of a 89:11 product ratio corresponding to cyclooctatetraene derivative 143 and starting material 131. Removal of the solvent gave a yellow oil which was purified by column chromatography with ethyl acetate / 239 Experimental petroleum ether (2 : 8). The resulting clear oil was identified as cyclooctatetraene derivative 143 (140 mg, 0.598 mmoL 69%); starting material 131 (27 mg, 0.115 mmoL 13%) was also isolated. Dibenzo [a,e\ cyclooctene-5-methanol (143) IR (KBr) vm a x : 3320 (O-H), 3007 (C-H) cm"1. MS m/e (relative intensity) : 235 (M+l, 6), 234 (M+, 38), 216 (28), 203(100), 202 (83), 178 (18). Exact mass calculated for C17H14O : 234.1045. Found : 234.1043. J H NMR (400 MHz, CDC13): 5 7.19-7.05 (m, 8H, aromatic H), 6.86 (s, IH, vinyl H), 6.79 (AB-system, 2H, J= 12 Hz, vinyl H), 4.42 (AB-system, 2H, J= 14 Hz, CFbOH), 2.10 (s, broad, IH, OH) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 144.05 (vinyl C-H), 137.88, 137.73, 137.27, 137.27, 137.04 (aromatic C, vinyl C), 133.47, 132.69 (vinyl C-H), 128.67, 128.67, 127.83, 127.75, 127.13, 127.03, 126.84, 126.60 (aromatic C-H), 67.66 (CH2OH) ppm. UV (acetonitrile) A^x : 229 (s 29,250), 204 (s 27,426), 202 (s 26,661) nm. C H 2 O H 143 240 Experimental Photolysis of 11-Hydroxymethyl -9,10-dihydro-9,10-ethenoanthracene (131) in Acetone Irradiation of compound 131 (231 mg, 0.987 mmol) was carried out in dry acetone with a Hanovia medium pressure mercury lamp for 5 h while maintaining a positive pressure of nitrogen in the reaction vessel. The reaction was tested by gas chromatography (HP 5, 30 m) resulting in 55% of semibullvalene derivative 144, 34% of regioisomer 145 and 11% of aldehyde 146. Evaporation of the solvent and column chromatography with ethyl acetate / petroleum ether (2 : 8) gave white crystalline semibullvalene derivative 144 (88 mg, 0.376 mmol 38%) and the regioisomeric semibullvalene 145 (56 mg, 0.239 mmol 24%) as well as the aldehyde derivative 146 (15 mg, 0065 mmol, 6%). 4b,8b,8c,8d-tetrahydrodibenzo [aj\ cyclopropa [cd\ pentalene-8c-methanol (144) 6 5 4 144 MP : 132-135 °C (recryst from petroleum ether / diethyl ether). TR (KBr) vm a x : 3304 (O-H), 3017 (C-H) cm \ MS m/e (relative intensity) : 235 (M+l, 6), 234 (M", 29), 216 (18), 203 (100), 202 (56). Exact mass calculated for C 1 7 H 1 4 O : 234.1045. Found : 234.1044. 241 Experimental *H NMR (400 MHz, CDC13) : 5 7.24-7.19 (m, 2H, aromatic H), 7.14-7.00 (m, 6H, aromatic H), 4.50 (s, IH, pentalene H,b), 3.96 (s, 2H, CHgOH), 3.08 (s, 2H, pentalene H 8 b > d ) , 1.56 (s, broad, IH, OH) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 150.46, 138.10 (aromatic C), 126.52, 126.32, 124.78, 121.31 (aromatic C-H), 64.77 (CH2OH), 64.07 (pentalene C), 56.08 (pentalene C-EUb), 41.32 (pentalene C-H8b,d) ppm. Anal, calculated for C 1 7 H i 4 0 : C, 87.14; H, 6.03. Found C, 87.28; H, 5.94. 4b,8b,8c,8d-tetrahydrodibenzo[al/]cyclopropa[crf|pentalene-8d-methanol (145) xCH2OH M P : 135-137 °C (recryst from petroleum ether / diethyl ether). HI (KBr) vm a x : 3230 (O-H), 2917 (C-H) cm"1. MS m/e (relative intensity) : 235 (M+l, 10), 234 (M*, 48), 233 (10), 217 (18), 216 (33), 215 (31), 205 (22), 204 (35), 203 (100), 202 (47). Exact mass calculated for C17H14O : 234.1045. Found : 234.1051. *H N M R (400 MHz, CDC13) : 5 7.37-7.35 (m, IH, aromatic H), 7.24-6.98 (m, 7H, aromatic H), 4.49 (d, IH, J = 6 Hz, pentalene H 4 b ) , 4.12 (AB-system, 2H, J = 12 Hz, CH2OH) , 3.58 (t, IH, J = 6 Hz, pentalene Hsc), 3.12 (d, IH, J= 6 Hz, pentalene Hgb), 1.60 (s, broad, IH, OH) ppm. 145 242 Experimental 1 3 C NMR (50 MHz, CDC13) : 8 151.39, 138.08 (aromatic C), 126.72, 126.59, 126.36, 126.26, 124.91, 124.05, 121.17, 121.17 (aromatic C-H), 91.95 (pentalene C 8 d), 65.26 (CH2OH), 53.97, 52.90 (pentalene C-Hg^b), 42.28 (pentalene C-Hgb) ppm UV (acetonitrile) ^  : 222 (s 21,587), 273 (s 2,534) nm Anal, calculated for C 1 7 H 1 4 0: C, 87.14; H, 6.03. Found C, 86.76; H, 6.03. 4b,8b,8c,8d-Tetrahydrodibenzo [aj\ cyclopropa [cd\ pentalene-8c-aldehyde (146) CHO MP : 179-181 °C (recryst petroleum ether / diethyl ether). HI (KBr) v m a x : 2960 (C-H), 2831 (C-H), 1686 (CHO) cm"1. MS m/e (relative intensity) : 233 (M+l, 1), 232 (M+, 6), 203 (100), 202 (51). Exact mass calculated for d 7 Hi 2 0: 232.0888. Found : 232.0885. *H NMR (200 MHz, CDCI3): 8 9.24 (s, 1H, CHO), 7.25-6.95 (m, 8H, aromatic H), 4.96 (s, 1H, pentalene lUb), 3.83 (s, 2H, pentalene Hgb,d) ppm 1 3 C NMR (50 MHz, CDCI3) : 8 195.86 (CHO), 150.15, 134.51 (aromatic C), 127.41, 126.77, 124.93, 121.61(aromatic C-H), 72.52 (pentalene C 8 c), 50.91 (pentalene C-Htb), 46.46 (pentalene C-H8b,8d) ppm Anal, calculated for Ci 7 H 1 2 0: C, 87.90; H, 5.21. Found : C, 87.51; H, 5.11. 146 243 Experimental Photolysis of Methyl 13 -(ll-methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132a) in Acetonitrile Irradiation of compound 132a (134 mg, 0.385 mmol) dissolved in dry acetonitrile (300 mL) in a quartz vessel was carried out in a Rayonet Photoreactor (15 bulbs at 254 nm) for 3.5 h under nitrogen. Gas chromatographic analysis (HP 5, 30 m) showed the presence of cyclooctatetraene derivative 150 (83%), semibullvalene derivative 151 (14%) and starting material 132a (3%). After removal of solvent, the oil was purified on a silica gel column with ethyl acetate / petroleum ether (5 : 95) resulting in the isolation of the cyclooctatetraene derivative 150 (88 mg, 0.247 mmoL 66%, oil), the semibullvalene derivative 151 (14 mg, 0.040 mmol, 11%, oil) and starting material 132a (3 mg, 0.009 mmol, 2%). Methyl 13-(5-methyldibenzo[a,e]cyclooctenyl)succinate (150) m (KBr) v m a x : 2952 (C-H), 1734 (C=0), 1155 (C-O) cm1. MS m/e (relative intensity): 349 (M+l, 3), 348 (M+, 9), 217 (37), 216 (100), 203 (15), 202 (16). Exact mass calculated for C 2 2 H 2 0 O 4 : 348.1359. Found : 348.1362. CH2OX>CH2CH2CDCCH3 150 244 Experimental *H NMR (400 MHz, CDC13) : 8 7.20-7.00 (m, 8H, aromatic H), 6.83 (s, broad, IH, vinyl H), 6.78 (AB-system, 2H, J= 12 Hz, vinyl H), 4.88 (d, 2H, J= 1 Hz, CILO), 3.66 (s, 3H, s, CH3), 2.67-2.57 (m, 4H, COCIJ2CH2CO2CH3) ppm 1 3 CNMR(50 MHz, CDC13) : 8 172.64, 171.80 (C=0), 138.78, 137.75, 137.11, 137.02, 136.70 (aromatic C, vinyl C), 133.22, 132.58, 130.61 (vinyl C-H), 128.62, 128.50, 128.50, 127.83, 127.21, 126.96, 126.79, 126.79 (aromatic C-H), 68.58 (CH20), 51.86 (CH3), 129.21 & 28.86 (COCH 2CH 2C0 2CH 3) ppm Photolysis of Methyl 13 -(ll-methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132a) in Acetone A solution of compound 132a (142 mg, 0.408 mmol) in dry acetone (400 mL) was irradiated with a Hanovia medium pressure mercury lamp for 2 h under nitrogen through a Pyrex glass filter. Gas chromatographic analysis showed the following photoproduct distribution: 151 (75%), 152 (11%), 132a (5%). The solvent was removed and the oil purified by column chromatography with ethyl acetate / petroleum ether (5 : 95). The isolated photoproducts were the white crystalline dibenzosemibuhvalenes 151 (83 mg, 0.238 mmol 58%) and 152 (17 mg, 0.049 mmoL 12%) as well as starting material 132a (6 mg, 0.017 mmol 4%). 245 Experimental Methyl 9-(8c-methyl-4b,8b,8c,8d-tetrahydrodibenzo [aj] cyclopropa [cd] pentalenyl) succinate (151) MP : 101-102 °C (recryst from petroleum ether / diethyl ether). IR (KBr) vm a x : 2958 (C-H), 1729 (C=0) cm1. MS m/e (relative intensity): 349 (M+l, 1), 348 (M\ 4), 234 (6), 216 (100), 215 (34), 203 (34), 202 (27). Exact mass calculated for C22H20O4 : 348.1362. Found : 348.1368. J H NMR (400 MHz, CDC1 3 ) : 8 7.22-7.20 (m, 2H, aromatic H), 7.12-7.10 (m, 2H, aromatic H), 7.04-6.99 (m, 4 H , aromatic H), 4.49 (s, 2H, CH2O), 4.47 (s, 1H, pentalene HU), 3.61 (s, 3 H , CH3), 3.13 (s, 2H, pentalene H 8 b , 8 d ) , 2.54 (m, 4 H , COCHaCKbCOjCHs) ppm. 1 3 C NMR (50 MHz, CDC1 3 ) : 8 172.62, 172.47 (C=0), 150.26, 137.08 (aromatic C), 126.52, 126.39, 124.82, 121.23 (aromatic C-H), 66.51 (CH 20), 60.41 (pentalene C), 56.45, 56.45, (pentalene C-H), 51.80 (CH3), 41.84 (pentalene C-H), 29.09, 28.90 (COCH 2 CH 2 C02CH 3 ) ppm. Anal, calculated for C22H20O4: C, 75.84; H, 5.79. Found : C, 75.72; H, 5.88. CH2OCOCH2CH2COOCH3 151 246 Experimental Methyl 9-(8d-methyl-4b,8b,8c,8d-tetrahydrodibenzo [aJ] cyclopropa [cd] pentalenyl) succinate (152) MP : 88-90 °C (recryst from petroleum ether / diethyl ether). JR (KBr) vm a x : 2968 (C-H), 1726 (C=0) cm"1. MS m/e (relative intensity) : 349 (M+1,0.3 ), 348 (M+, 1), 217 (32), 216 (100), 215 (37), 202 (16). Exact mass calculated for C22H20O4 : 348.1362. Found : 348.1371. *H NMR (400 MHz, CDC13) : 8 7.28-7.23 (m, 2H, aromatic H), 7.10-6.99 (m, 6H, aromatic H), 4.60 (AB-system, 2H, J= 12 Hz, CH2O), 4.49 (d, IH, J= 6 Hz, cycopentyl H,b), 3.64 (s, 3H, CH3), 3.60 (t, IH, J= 6 Hz, pentalene Hsc), 3.18 (d, 2H, J=. 6 Hz, pentalene Hgb), 2.70-2.60 (m, 4H, COCHaCHaCOjC^) ppm. 1 3 C NMR (50 MHz, CDC13) : 8 172.67, 172.45 (C=0), 151.27, 150.97, 137.60, 137.57 (aromatic C), 126.70, 126.53, 126.37, 126.37, 125.10, 124.11, 121.09, 121.02 (aromatic C-H), 66.93 (CH20), 53.90, 53.17 (pentalene C-H), 51.87 (CH3),46.52 (pentalene C), 42.83 (pentalene C-H), 29.17, 28.90 (COCH 2CH 2C0 2CH 3) ppm Anal, calculated for C22H20O4 : C, 75.84; H, 5.79. Found : C, 75.51; H, 5.83. C H 2 0aXH2CH 2 C X X X H 3 152 247 Experimental Photolysis of 13-(ll-Methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetic Acid (133) in Acetonitrile Compound 133 (189 mg, 0.647 mmol) was dissolved in dry acetonitrile (400 mL), saturated with nitrogen and photolysed with a Rayonet Photoreactor (16 bulbs at 254 nm) for 4 h. A yellow oil resulted (179 mg, 0.585 mmol, 90%) after solvent evaporation and esterification with diazomethane. This was purified on silica gel with ethyl acetate / petroleum ether (1 : 9). The photoproducts isolated were an oil identified as cyclooctatetraene derivative 155 (71 mg, 0.232 mmol, 40%), and the white crystalline semibullvalene analogue 156 (17 mg, 0.056 mmol, 10%). Gas chromatographic analysis showed the presence of 77% of 155, 23% of 156. Methyl 13-(5-methyleneoxydibenzo[a,e]cyclooctenyl)acetate (155) IR (KBr) vm a x : 3013, 2952 (C-H), 1755 (C=0), 1213 (C-O) cm1. MS m/e (relative intensity) : 307 (M+l, 1), 306 ( M \ 5), 217 (52), 216(100), 203(37), 202 (41). Exact mass calculated for C2oHi803: 306.1256. Found : 306.1250. *H NMR (200 MHz, CDC1 3 ) : 8 7.15-6.90 (m, 8 H , aromatic H), 6.78 (s, 1H, vinyl H), 6.72 (s, 2H, vinyl H), 4.35 (AB-system, 2H, J= 13 Hz, CH2O), 4.11 (d, 2H, J= 2 Hz, CH2C0 2 CH 3 ) , 3.66 (s, 3 H , CH3) ppm CH 2 OCH 2 COOCH 3 155 248 Experimental 1 3 C NMR (50 MHz, CDC13) : 8 170.79 (C=0), 139.85, 137.60, 137.08, 137.08, 137.01 (aromatic C, vinyl C), 133.50, 132.64, 130.83 (vinyl C-H), 128.61, 128.55, 128.52, 127.82, 127.09, 126.98, 126.79, 126.70 (aromatic C-H), 75.97 (CH 2C0 2CH 3), 66.93 (CH20), 51.83 (CH3) ppm. Photolysis of 13-(ll-Methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetic Acid (133) in Acetone A solution was made up containing compound 133 (197 mg, 0.675 mmol) in acetone (400 mL). Irradiation with a Hanovia medium pressure mercury lamp for 1 h under nitrogen, followed by removal of the solvent and treatment with diazomethane, resulted in a yellow oil (174 mg, 0.569 mmol, 88%). After column chromatography with ethyl acetate / petroleum ether (5 : 95) two esterified dibenzosemibullvalene derivatives were isolated : compound 156 (80 mg, 0.261 mmol, 46%) and 157 (26 mg, 0.085 mmol, 15%). Gas chromatographic analysis (HP 5, 30 m) showed the presence of compounds 156 and 157 in a ratio of 72 : 28. 249 Experimental Methyl 9-(8c-methyleneoxy-4b,8b,8c,8d-tetrahydrodibenzo [aJ] cyclopropa [cd] pentalenyl) acetate (156) MP : 94-96 °C (recryst petroleum ether / ethyl acetate). IR (KBr) vm a x : 2951 (C-H), 1750 (C=0), 1212 (C-O) cm1. MS m/e (relative intensity): 307 (M+l, 3), 306 (M+, 14), 217 (33), 216(100), 215 (50), 203 (98), 202 (65). Exact mass calculated for C 2 oH 1 8 0 3 : 306.1256. Found : 306.1253. *H NMR (200 MHz, CDC13) : 8 7.25-6.85 (m, 8H, aromatic H), 4.48 (s, IH, pentalene ILb), 3.99 (s, 2H, CH2C02CH3), 3.90 (s, 2H, CHgO), 3.63 (s, 3H, CHj), 3.02 (s, 2H, pentalene H 8 b, 8 d) ppm. 1 3 C NMR (50 MHz, CDC13) : 5 170.88 (C=0), 150.37, 137.21 (aromatic C), 126.48, 126.35, 124.88, 121.36 (aromatic C-H), 73.11 (CH 2C0 2CH 3), 67.62 (CH20), 61.11 (pentalene C), 56.17, 56.17 (pentalene C-H), 51.75 (CH3), 41.53 (pentalene C-H) ppm. Anal, calculated for C 2 0 H 1 8 O 3 : C, 78.41; H, 5.92. Found : C, 78.08; H, 5.96. CH 2 CXH 2 CXXXH 3 156 250 Experimental Methyl 9-(8d-methyleneoxy-4b,8b,8c,8d-tetrahydrodibenzo [aj\ cyclopropa [c</|pentalenyl)acetate (157) CH 2 OCH 2 COOCH 3 157 MP : 74-76 °C (recryst from petroleum ether / ethyl acetate). IR (KBr) vm a x : 3039, 2952 (C-H), 1752 (C=0), 1212 (C-O) cm"1. MS m/e (relative intensity) : 307 (M+l, 1), 306 (M1", 3), 217 (37), 216(100), 215 (64), 203 (54), 202 (51). Exact mass calculated for C 2 oHi 8 0 3 : 306.1256. Found : 306.1262. *H NMR (200 MHz, CDC1 3 ) : 8 7.43-7.33 (m, 1H, aromatic H), 7.25-7.11 (m, 1H, aromatic H), 7.10-6.85 (m, 6 H , aromatic H), 4.42 (d, 1H, J= 6 Hz, pentalene HUb), 4.15 (s, 2H, CH2C0 2 CH 3 ) , 3.99 (AB-system, 2H, J= 11 Hz, CH2O), 3.70 (s, 3 H , CH3), 3.50 (t, 1H, J= 6 Hz, pentalene H 8 c), 3.14 (d, 1H, J= 6 Hz, pentalene Hsb) ppm. 1 3 C NMR (50 MHz, CDC1 3 ) : 8 170.91 (C=0), 151.35, 150.93, 138.13, 137.89 (aromatic C), 126.54, 126.49, 126.26, 126.19, 125.03, 124.53, 121.03, 120.83 (aromatic C-H), 74.08 (CH 2 C0 2 CH 3 ) , 67.89 (CH 20), 53.86, 52.88 (pentalene C-H), 51.78 (CH3), 47.18 (pentalene C), 42.70 (pentalene C-H) ppm Anal, calculated for C 2 0 H i 8 O 3 : C, 78.41; H, 5.92. Found : C, 78.39; H, 5.82. 251 Experimental 11.2.4. Photolysis 9,10-Dihydo-9,10-ethenoanthracene Derivatives in the Solid State Photolysis of ll-Hydroxymethyl-9,10-dihydro-9,10-ethenoanthracene (131), 13-(11-Methyl-9,10-dihydro-9,10-ethenoanthracenyl)succinate (132) and Methyl 13-(ll-methyleneoxy-9,10-dihydro-9,10-ethenoanthracenyl)acetate (133a) in the Solid State Alcohol 131 was irradiated in the solid state as a powder with a Hanovia medium pressure mercury lamp through a quartz filter (A, > 200 nm). The product ratios were deterrnined by dissolving the sample in ethyl acetate prior to gas chromatographic analysis (HP 5, 30m). The results are represented in Table XX. Crystals of acid 132 and ester 133a crushed between two quartz plates were photolyzed with a Hanovia medium pressure mercury lamp through a Vycor filter (A. > 240 nm). After methylation of 132 with diazomethane, the product ratios were detennined by GC (HP 5, 30 m) and are shown in Table XX. Table XX Photoproduct Mixture Composition of Derivatives 131,132 and 133a Dibenzobarrelene Rxn time (h) Photoproduct ratio8 SMb: S: TI : T2 131 7 92: 8: 0 : 0 132 8 87: 6: 7 : 0 133a 2 93: 6: 1 : 0 (a) Estimated error in GC analysis is ± 2%.(b) Dibenzobarrelene 132 was identified as the methyl ester derivative. T = triplet derived product, S = singlet derived product. 252 Experimental S SM, S, TI, T2 131, 143,144,145 R = OH 132, 150,151,152 R=CH2OCOCH2CH2C02H 133a, 155,156,157 R = CH2OCH2CO2CH3 11.3. Photochemical Studies of Salts 11.3.1. Photolysis of Sensitizer Salts Formed with 2-(l-Cyclopentenyl)cycIopentanone Derivative 121 Photolysis of Sensitizer Salts 138, 139 and 140 Salts 138, 139 and 140 were irradiated through a uranium glass filter (A. > 330 nm) in solution and the solid state with a Hanovia medium pressure mercury lamp (450 W). Following photolysis, the solvent was removed, the remaining oil dissolved in diethyl ether, washed with 15% aqueous HC1 and dried over MgS04. After filtering off the drying agent, the acids were esterified with an ethereal solution of diazomethane to produce the corresponding methyl esters. Gas chromatography (DB 5, 15 m) was used to determine the product ratios. The results are summarized in Table XXI. 253 Experimental Table XXI Photoproduct Mixture Composition of Salts 138,139 and 140 a Salt (acid 121 and sensitizer Medium Concentration Photoproduct moieties): IIISIIII lime ratio (10 121 b :T:S 138 (3-dimethylamino propiophenone) Sohd State 21 72 : 28 : 0 Methanol 1 x IO"2 24 99 : 1:0 140 (p-acetylpyridine) Sohd State 24 No Reaction Methanol 1 x IO"2 24 No Reaction 139 (/?-acetyl-iV ,^-dimethylbenzylamine) Sohd State 50 83 : 17 : 0 Methanol 1 x 10'2 24 99 : Trace : 0 (a) Estimated error in GC analysis is ± 2%.(b) Acid 121 was identified as the methyl ester derivative. T = triplet derived product, S = singlet derived product. 121 134a 254 Experimental 11.3.2. Photolysis of Alkali Metal Salts Formed with 9,10-Dihydo-9,10-ethenoanthracene Derivatives Photolysis of Salts Formed with Succinate Derivative 132 Photolysis of Alkali Metal Salts 153 and 154 Salts 153 and 154 were photolyzed in solution and the solid state through a Vycor glass filter (A- > 240 nm) with a Hanovia medium pressure mercury lamp (450 W). The reaction mixture was then acidified and methylated as described before. Product ratios were determined by GC analysis with a HP 5 column (30 m). Table XXII Photoproduct Mixture Composition of Salts 153 and 154 Salt (acid 132 and alkali moiety) Medium Concentration (M) Rxn time <h) Photoproduct ratio3 S : TI : T2 153 (sodium) Solid State 7 23 : 63 : 14 Ethanol 1.0 x 10"3 1.5 84: 15 : Trace 154 (potassium) Solid State 8 0: 94 : 6 Methanol 4.5 x IO"4 2 87: 7 : 6 (a) Crystal photolyses were conducted on powders to conversions of 53-57%, whereas solution photolyses were carried out to 100% conversion. Estimated error in GC analysis is ± 2%. 255 Experimental S TI T2 150 151 152 R = CH2OCOCH2CH2CO2CH3 Photolysis of Alkali Metal Salts Formed with Acetic Acid Derivative 133 Photolysis of Alkali Metal Salts 158,159,160,161, and 162 The salts 158 to 162 were irradiated in the solid state and solution through a Vycor glass filter (A, > 240 nm) with a Hanovia medium pressure mercury lamp. The samples were derivatized as described previously and the product ratios were determined by GC (HP 5, 30 m). 256 Experimental Table X X U I Photoproduct Mixture Composition of Salts 158 to 162 Salt (acid 133 and alkali moiety) Medium Concentration Photoproduct ratio S: T l : T2 158 (hthium) Sohd State 2 33: 50 : 17 Methanol 5.6 x IO"4 5 87: 12 : 1 159 (sodium) Sohd State 2 62: 38 : 0 Methanol 5.3 x IO"4 3 89: 11 : 0 160 (potassium) Sohd State 2 27: 73 : 0 Methanol 5.1 x lO" 4 3 89: 9 : 1 161 (rubidium) Sohd State 2 25: 63 : 12 Methanol 4.4 x IO"4 1 91: 9 : 0 162 (cesium) Sohd State 2 75: 25 : 0 Methanol 4.0 x 10"4 5 84: 14 : 2 (a) Crystal photolyses were conducted on powders to < 16% conversion. Solution photolyses were carried out to conversions of 80-95%. Estimated error in GC analysis is ± 2%. 257 Experimental 11.3.3. Photolysis of Sensitizer Salts Formed with Acetic Acid Derivative 133 Photolysis of Sensitizer Salts 164,166 and Complex 165 Salts 164, 166 and complex 165 were irradiated through an uranium glass filter (X > 330 nm) in solution and the solid state with a Hanovia medium pressure mercury lamp. Following derivatization to the corresponding methyl ester, the reaction mixture was injected into the GC (HP 5, 30 m) to determine the product ratios. Table XXIV Photoproduct Mixture Composition of Salts 164,166 and Complex 165 Salt or Complex (acid 133 with sensitizer moiety) iiillillB Concentration Rxn time <h) Product ratio8 SM : S: TI : T2 164 (3-dimethylamino propiophenone) Solid State 9 93 : 0: 6 : 1 Methanol 1.0 x IO"2 1.0 x 10"3 6 6 96 : 0: 3 : 1 98 : 0: 1 : 1 165 (4-acetylpyridine) Solid State 9 94 : 0: 5 : 1 Methanol 1.0 x IO"2 1.0 x 10-3 6 6 98 : 0: 1 : 1 98 : 0: 1 : 0 166 (4'-piperazino-acetophenone) Solid State 8 81 : 0: 15 : 4 Methanol 1.0 x IO"2 1.0 x IO"3 6 6 98 : 0: 1: 1 98 : 0: 1 : 0 (a) Estimated error in GC analysis is ± 2%. 258 Experimental 259 References R E F E R E N C E S 1. Ciamician, G. Science 1912, 36, 385. 2. Emmelius, M.; Pawlowski, G ; Volmann, H.W. Angew. Chem., Int. Ed. Engl. 1989, 28, 1445. 3. CRC Handbook of Organic Photochemistry; Scaiano, J.C, Ed.; CRC Press: Boca Raton, Fl., 1987, Vol. 2. 4. Kopecky, J. In Organic Photochemistry: A Visual Approach; VCH Publishers: New York, 1992, p 256. 5. 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