Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Alkynyl and isocyanobiphenyls : new thermotropic liquid crystals Bailey, Austin Lou 1989

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1989_A6_7 B34.pdf [ 3.15MB ]
Metadata
JSON: 831-1.0060432.json
JSON-LD: 831-1.0060432-ld.json
RDF/XML (Pretty): 831-1.0060432-rdf.xml
RDF/JSON: 831-1.0060432-rdf.json
Turtle: 831-1.0060432-turtle.txt
N-Triples: 831-1.0060432-rdf-ntriples.txt
Original Record: 831-1.0060432-source.json
Full Text
831-1.0060432-fulltext.txt
Citation
831-1.0060432.ris

Full Text

A L K Y N Y L A N D I S O C Y A N O B I P H E N Y L S : N E W T H E R M O T R O P I C L I Q U I D C R Y S T A L S by A U S T I N L O U B A I L E Y B . S c , Da lhous ie Un i ve rs i t y , 1986 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F S C I E N C E in T H E F A C U L T Y O F G R A D U A T E S T U D I E S (Depar tment o f C h e m i s t r y ) W e accept this thesis as c o n f o r m i n g to the requ i red standard T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A January 1989 © A u s t i n L o u B a i l e y , 1989 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. Department of CHghil 67HY The University of British Columbia Vancouver, Canada Date HftrfiCtl (Qgy DE-6 (2/88) i i A B S T R A C T T h e p resence o f m e s o m o r p h i s m i n 4 - « - a l k y l - 4 ' - i s o c y a n o b i p h e n y l s 4 and 4 - « - a l k y l - 4 ' - a l k y n y l b i p h e n y l s 5 was invest igated, based on the l i qu id -c rys ta l l i n i t y o f the cyanob ipheny l s 2 (R = « -a lky l ) . C o m p o u n d 4 (R = « -bu ty l ) is n o n - m e s o m o r p h i c , w h e r e a s 4 (R = rc-pentyl) is a v i r t u a l l i q u i d c r y s t a l m e l t i n g at 3 4 - 3 5 ° C and supe rcoo l i ng to a nemat ic phase at 3 0 ° C , and 4 (R = « -hexy I ) is a nemat i c l i q u i d c rys ta l f r o m 9 to 19°C. C o m p o u n d s o f structure 5 (R = « -pen ty l , X = S i (CH3 )3 , H , CH3, C I ) are not l i q u i d c rys ta l s . T h e c o r r e s p o n d i n g b r o m o - and i o d o a l k y n e s (5, R = n-penty l , X = B r , I) are l i q u i d crysta ls w i th m e s o m o r p h i c ranges o f 88 -108°C and 110-119°C, respec t ive ly . 2 i i i T A B L E O F C O N T E N T S page A B S T R A C T i i T A B L E O F C O N T E N T S i i i L I S T O F T A B L E S iv L I S T O F F I G U R E S A N D S Y N T H E T I C S C H E M E S v L I S T O F A B B R E V I A T I O N S v i C O M P O U N D I N D E X v i i A C K N O W L E D G E M E N T S • v i i i I N T R O D U C T I O N 1 Propert ies and C lass i f i ca t i on o f L i q u i d Crys ta ls 1 Re la t i ng C h e m i c a l Structure and M e s o m o r p h i s m 4 4 - A l k y l - 4 ' - c y a n o b i p h e n y l L i q u i d Crys ta ls 7 P r o p o s e d L i q u i d Crys ta ls 9 R E S U L T S A N D D I S C U S S I O N 11 4 - A l k y l - 4 ' - a l k y n y l b i p h e n y l s 11 4 - A l k y l - 4 ' - i s o c y a n o b i p h e n y l s 20 Fu tu re W o r k 32 E X P E R I M E N T A L 33 R E F E R E N C E S 48 S P E C T R A L A P P E N D L X 51 iv L I S T O F T A B L E S page Tab le I M e s o m o r p h i c t ransi t ion temperatures for the 4 - a l k y l - 4 ' - c y a n o b i p h e n y l s 2 8 Tab le II Infrared frequencies o f the a l kyne carbon-carbon stretching s ignal i n compounds 5a-f 17 Tab le III M e l t i n g behav iour o f compounds 5a-f 18 Tab le I V M e l t i n g behav iour o f the i socyanob ipheny ls 4a-c 31 ( L I S T O F F I G U R E S A N D S Y N T H E T I C S C H E M E S page F igu re 1 T w o - d i m e n s i o n a l representat ions o f mo lecu la r organ izat ion in a smect ic and a nemat ic phase 3 F i g u r e 2 E x a m p l e s o f nemat ic l i qu i d crystals 6 F igu re 3 Na tu ra l l y occu r ing isocyanides 21 F i g u r e 4 T h e aromat ic reg ion o f the * H - N M R spectra o f c o m p o u n d 15 i n toluene-ds 28 S C H E M E A Synthes is o f 4 -a lky l-4 ' -a lkynylb iphenyls 5a-f 13 S C H E M E B Synthes is o f i socyan ides v i a acy l az ides 23 S C H E M E C Synthet ic routes to the p r imary amine 12 25 S C H E M E D Synthes is o f i socyan ides f r o m p r imary amines 27 v i L I S T O F A B B R E V I A T I O N S D M S d ime thy l su lph ide E t 3 N t r ie thy lamine G C gas ch romatography I R in f rared l i t l i terature va lue m.p me l t ing point M S mass spect romet ry m/z mass to charge rat io M + parent i on n - B u L i rt-butyllithium P T C phase- t rans fe r ca ta l ys i s T K I c rys ta l - i so t rop ic t rans i t ion temperature T K N c rys ta l -nemat i c t rans i t ion temperature T K S c rys ta l - smec t i c t rans i t ion temperature T N I nemat i c - i so t rop ic t rans i t ion temperature T S N smec t i c -nemat i c t rans i t ion temperature T H F te t rahydrofuran T L C th in - layer ch romatography 5 C B 4 - cyano -4 ' - / i - pen t y l b i pheny l 8 C B 4 -cyano-4 ' - / z -oc ty lb ipheny l * H - N M R proton nuc lear magnet ic resonance 8 chemica l shift i n parts per m i l l i o n s s ing le t d doub le t t t r ip let m mul t ip le t v i i C O M P O U N D I N D E X T h e f o l l o w i n g is a l ist o f compounds prepared and d iscussed in this thesis. T h e number o f each c o m p o u n d is f o l l o w e d by a set o f three numbers : the f irst number refers to the page where the structure o f the c o m p o u n d f i rs t appears ; the second number refers to the page where the preparat ion o f the c o m p o u n d is g i v e n ; the th i rd number refers to the page in the Spect ra l A p p e n d i x where the ^ - N M R and I R spectra o f the c o m p o u n d are p rov ided . N e w compounds are ind icated by aster isks. 4a* (27, 46 , 57) 5f* ( 1 1 , 4 1 , 5 4 ) 4b* (31, 47 , 57) 7 ( 1 3 , 3 5 , - ) 4c* (31, 47 , 58) 8 ( 1 3 , 3 5 , - ) 5a* (11, 37 , 52) 9 ( 1 3 , 3 6 , - ) 5b (11, 37 , 52) 10 (25, 4 2 , 55) 5c* (11, 38 , 53) 11 (25, 4 3 , 55) 5d* (11, 39 , 53) 12 (25, 4 3 , 56) 5e* ( 1 1 , 4 0 , 5 4 ) 15* (27, 4 5 , 56) v i i i A C K N O W L E D G E M E N T S I w o u l d l i k e to express m y s incere grat i tude to m y supe rv i so r , P r o f e s s o r G o r d o n Ba tes , fo r his inva luab le counse l and support ove r the course o f this work . S p e c i a l thanks are a lso extended to P ro fesso r E l l i o t t B u r n e l l f o r p r o v i d i n g the oppor tun i ty to be i n v o l v e d in the invest igat ion o f l i q u i d crysta ls by magnet ic resonance spect roscopy and for h is gu idance toward an unders tanding o f the p h y s i c a l aspects o f these sys tems . T h a n k s a lso go to the magnet ic resonance and mass spectra l support serv ices o f the chemis t ry department, to D r . J i m D e l i k a t n y fo r his humorous spectrometer and c o m p u t e r i ns t r uc t i on sess ions , and to the peop le o f D r . W e i l e r ' s l abo ra to ry f o r p rov id i ng c o m i c re l ie f to the da i ly rout ine. F i n a l l y , I w o u l d l i ke to c o n v e y m y greatest thanks to m y parents, Y v o n n e and P a u l , and to m y f r i end W i l l i a m fo r their immeasurab le support ove r the years. 1 I N T R O D U C T I O N T h e d i scove ry o f room-temperature nemat ic l i q u i d crysta ls i n the ear ly 1970 's was fundamenta l to the advancement o f techno log ica l app l i ca t ions o f l i q u i d c rys ta ls . S i n c e that t ime, the t remendous increase in the use o f these mater ia ls fo r e lec t ron ic d i sp lays has been the mos t obv ious and perhaps the most c o m m e r c i a l l y impor tant resul t o f their d i scove ry . In add i t ion , l i qu i d crysta ls have p roven usefu l as solvents in magnet i c resonance studies, as stat ionary phases i n ch roma tog raphy , as temperature probes i n m e d i c a l appl icat ions, and in opt ica l sw i tch ing d e v i c e s . 1 F r o m a c h e m i c a l pe rspec t i ve , the ef fect o f these deve lopmen ts has been a w i d e - s p r e a d in terest i n the nature o f the l i q u i d - c r y s t a l l i n e p h e n o m e n o n at the mo lecu la r l eve l . Ne i ther the phys i ca l interact ions between l i qu i d c rys ta l mo lecu les nor the s t ruc tura l features o f the m o l e c u l e s respons ib l e f o r those in te rac t ions is w e l l unde rs tood , and w h i l e m a n y l i q u i d c rys ta ls have been s y n t h e s i z e d , the n e e d f o r improvements o f their propert ies st i l l ex is ts . P r o p e r t i e s a n d C l a s s i f i c a t i o n o f L i q u i d C r y s t a l s T h e term " l i q u i d c r y s t a l " refers to a state o f matter in termediate to so l ids and l i q u i d s . In a l i qu id -c rys ta l l i ne phase, o r mesophase , the m o l e c u l e s o f a c o m p o u n d exh ib i t o r ien ta t iona l order w h i c h is absent i n i so t rop ic l i q u i d s , but they a lso en joy some degree o f t ranslat ional f reedom un l i ke crys ta l l ine so l ids . A l t h o u g h they are f l u i d , the an iso t rop ic nature o f l i q u i d crystals lends them some propert ies o f so l ids , such as opt ica l b i ref r ingence. T h e t w o m a i n c lasses o f l i q u i d c rys ta ls are lyotropic a n d thermotropic. L y o t r o p i c l i q u i d c rys ta l s are f o r m e d by the ac t i on o f so l ven ts o n a m p h i p h i l i c c o m p o u n d s . T h e y can be c o n s i d e r e d in te rmed ia tes be tween the s o l i d state and i so t rop i c so l u t i on . T h e mos t c o m m o n e x a m p l e o f this c lass is an aqueous soap Int roduct ion / 2 so lu t ion . L y o t r o p i c l i q u i d crys ta ls w i l l not be d i scussed fur ther i n this thes is . A rev iew o f these systems can be found in reference 1. T h e r m o t r o p i c l i q u i d crys ta ls are compounds fo r w h i c h a t h e r m o d y n a m i c a l l y stable phase exists between the l i q u i d and so l id . A t the me l t i ng po in t , the c o m p o u n d fo rms a tu rb id f l u i d w h i c h at h igher temperatures clears to the iso t rop ic l i q u i d . M o r e than one l i qu i d - c r ys ta l l i ne phase m a y ex is t fo r a g i ven c o m p o u n d ; a character is t ic k n o w n as p o l y m o r p h i s m . S i n c e the d i s c o v e r y o f a l i q u i d - c r y s t a l l i n e phase in c h o l e s t e r y l benzoa te by R e i n i t z e r i n 1 8 8 8 2 and the ea r l y c l a s s i f i c a t i o n w o r k by F r i e d e l , 3 a very large number o f thermotropic l i qu i d crystals have been d i scovered . In 1975, some 5 0 0 0 l i q u i d crys ta ls and their proper t ies were tabu la ted . 4 C o m p o u n d s exh ib i t i ng this behav iour usua l ly have rod - l i ke mo lecu la r shapes. T h e phases o f thermotropic l i qu i d crysta ls , f r o m this po in t referred to s imp l y as l i q u i d c rys ta ls , are c l ass i f i ed acco rd ing to the type o f m o l e c u l a r o rgan iza t ion i n the mesophase . Smectic phases have equid is tant layers o f m o l e c u l e s w h i c h s l i de past one another f ree ly . W i t h i n each layer , the mo lecu les are a l i gned w i t h their l o n g axes p a r a l l e l . S m e c t i c phases are fur ther s u b d i v i d e d a c c o r d i n g to the p o s i t i o n a l and or ien ta t iona l o rde r ing w i t h i n the layers , e.g. p a c k i n g order and tilt o f the mo lecu les w i th in the layers . A t least ten di f ferent types o f smect ic phases are k n o w n , and each type is g i v e n a letter l abe l such as S A , o r " s m e c t i c - A . " A representa t ion o f a smect ic phase is g i ven i n F i g u r e 1 on the f o l l o w i n g page. Nematic phases , w h i c h exh ib i t less order , have a r a n d o m d is t r ibu t ion o f the mo lecu les w i t h a stat is t ica l ly para l le l a l ignment o f their l o n g axes. T h i s arrangement is a lso dep i c ted i n F i g u r e 1. T h e mo lecu les m o v e f ree ly a l ong their l o n g axes and rotate r a p i d l y about t hem. N e m a t i c phases o f some c h i r a l c o m p o u n d s have the d i s t i n g u i s h i n g fea ture o f a h e l i c a l tw i s t i n the o r i e n t a t i o n o f the m o l e c u l e s pe rpend icu la r to the l o n g axes. These are c a l l e d cho les ter ic l i q u i d c rys ta ls after the mater ia ls w h i c h were f irst f ound to exh ib i t this property. Int roduct ion / 3 00 00 000 oooo o k % o | oooooooooooo mhv} 00 00 000 00003 KMM oooooooooo oo o l w ^ y o Figure 1. Two-dimensional representations of molecular organization in a smectic-A phase (left) and a nematic phase (right). In add i t ion to smect ic and nemat ic phases, other l i qu id -c rys ta l l i ne phase types have been mo re recent ly d i scove red i n c l u d i n g d i sco t i c , c u b i c , and b lue p h a s e s . 5 T o c o m p l i c a t e the matter , there are a lso nemat i c phases k n o w n as cybo tac t i c s , w h i c h d i s p l a y shor t - range smec t i c behav iou r . T h e d i scuss i on i n this w o r k is l i m i t e d to nemat i c phases , w i t h par t i cu la r interest i n c o m p o u n d s e x h i b i t i n g l ow- tempera tu re , nemat ic behav iour . T h e var ie ty o f phase types and the poss ib le p o l y m o r p h i c comb ina t ions o f them make an easy sys tem o f ident i f i ca t ion des i rab le . T h e most c o m m o n l y used method to determine the types o f l i qu id -c rys ta l l i ne phases f o r m e d by a mater ia l is to observe its me l t i ng behav iour w i t h a po la r i z i ng m ic roscope equ ipped w i th a heat ing stage. M a n y o f the phase types have d is t inc t textures, and t rans i t ions are m a r k e d by abrupt changes i n tex ture f o r s m a l l changes i n temperature . P h a s e type c a n a l so be de te rm ined by the " m i s c i b i l i t y r u l e " w h i c h is that two phases s h o w i n g comp le te m i s c i b i l i t y be long to a s ingle type. De ta i l s o f the procedure used i n such assignments i Introduct ion / 4 m a y be f ound in references 6 and 7. F o r the s imp le determinat ion o f the presence o f mesomorph ic behav iour , a rout ine mel t ing prof i le is suf f ic ient . N e m a t i c phases have been the most usefu l i n app l icat ions o f l i q u i d crysta ls . In a bu l k sample the average d i rec t ion o f the mo lecu la r l o n g axes, the d i rector , changes c o n t i n u o u s l y f r o m one part o f the sample to another. H o w e v e r , w h e n p l a c e d i n a magnet i c o r e lec t r i c f i e l d , the d i rec tor is or iented by the f i e l d and becomes constant o v e r the ent i re s a m p l e . A l s o , w h e n p l a c e d aga ins t a sur face w h i c h has been un id i rec t iona l l y brushed or e tched, the d i rector at the surface w i l l a l ign accord ing ly . It is these propert ies w h i c h make nemat ic l i qu id crystals usefu l i n e lec t ron ic d isp lays . There is interest i n the deve lopment o f compounds w i t h nemat ic phases hav ing w ide temperature ranges, i dea l l y -40 to + 6 0 ° C fo r app l ica t ions . W h i l e this range has been a c h i e v e d by m i x t u r e s o f e x i s t i n g l i q u i d c r y s t a l s , pu re c o m p o u n d s are advantageous i n p h y s i c a l s tud ies. A l s o , the d i s c o v e r y o f n e w l i q u i d c rys ta l s is impor tant i n ach iev ing an understanding o f mesomorph ic behav iour . R e l a t i n g C h e m i c a l S t r u c t u r e a n d M e s o m o r p h i s m T h e ab i l i t y to relate mo lecu la r structure to l i qu id -c rys ta l l i ne propert ies is k e y in the des ign o f n e w l i q u i d crys ta ls . A number o f rev iews have been wr i t ten on this t o p i c . 5 ' 8 " A s men t i oned p r e v i o u s l y , the c o m m o n feature o f m a n y k n o w n l i q u i d crysta ls is an e longated shape, usua l l y re ferred to as r o d - l i k e o r la the- l i ke . Su f f i c ien t r i g i d i t y to ma in ta i n this shape is a lso impor tant , i.e. c o n f o r m a t i o n s cannot great ly affect the overa l l shape o f the mo lecu le . T h e presence o f po la r func t iona l groups, or at least po la r i zab le structures, seems to p lay some ro le as w e l l . 8 A survey o f nemat ic l i q u i d c rys ta ls d i s cove red p r i o r to 1970 shows that the major i ty are o f the general structure 1, shown on the f o l l o w i n g page. T h e va lues o f m and n and the va r ia t i on o f subst i tuents A , B , and X de te rm ine the ex i s tence and stabi l i ty o f a mesophase. These factors w i l l be br ie f ly d iscussed i n terms o f inc reas ing Int roduct ion / 5 o r dec reas ing ef fects on the nemat i c - i so t rop ic t rans i t ion temperature, T N I , w h i c h is used as a measure o f stabi l i ty . T h e temperature at w h i c h the s o l i d mel ts to a nemat ic phase, T K N » is a lso important , but this property is d i f f i cu l t to correlate w i th mo lecu la r compos i t i on . T h e presence o f p -pheny lene groups p rov ide the requ i red l inear , r i g i d structure as w e l l as be ing po la r i zab le . A n y increase in m o r n great ly enhances the stabi l i ty o f the l i qu id - c r ys ta l l i ne phases. The increase in T N I i s , h o w e v e r , a c c o m p a n i e d by an increase i n m o l e c u l a r we igh t and me l t i ng po in t so that a r o o m temperature nemat ic phase is un l i ke l y . T h e t e rm ina l subst i tuents , A and B, can be a var ie ty o f g roups , eve ry th ing be ing super ior to hyd rogen in p romot ing mesophase stabi l i ty so l o n g as the mo lecu le is not b roadened s ign i f i can t l y . A t yp i ca l r ank i ng fo r the e f fec t iveness o f te rm ina l subst i tuents is C N > O C H 3 > N O 2 > B r > H . W h e n a l k y l cha ins are used , one genera l ly sees a t rend i n T N I w i th the length o f the cha in , longer cha ins usua l ly g i v i n g l o w e r T N I ' S , but occas i ona l l y h igher . B r a n c h i n g o f the a l k y l c h a i n has a negat ive effect, the sever i ty o f w h i c h depends on the d istance o f the b ranch ing centre f r o m the r ings . A n y lateral substituents on the r ings decrease T N I , espec ia l l y i f the structure is af fected by ster ic interact ions between the r i ng systems. T h e l i n k i n g group X often contains mul t ip le bonds to ensure rigidity and prov ide con jugat ion between the rings. A l k y n e , a lkene, i m i n o , azo , and ester l inkages have a l l been used success fu l l y . 1 Int roduct ion / 6 Examples of nematic liquid crystals. p-Methoxybenzy l idene-p -n -bu ty lan i l i ne C 4 H 9 T K N = 2 2 ° C ; T N I = 4 7 ° C 4-Cyano-4 ' -n-penty l - f rans-s t i lbene T K N = 5 5 . 5 ° C ; T N I = 101°C p- r t -Bu ty loxypheny l p-n-penty loxybenzoate T K N = 6 7 ° C ; T N I = 8 2 ° C O C H , p - A z o x y a n i s o l e T K N = 1 1 9 0 C ; T N T = 1 3 5 0 C 4- / i -Hepty l -4 ' -methoxyd ipheny le thyne • C 7 H 7 n 15 T K N = 3 9 ° C ; T n i = 5 4 ° C Int roduct ion / 7 C o m p o u n d s o f general structure 1 wh i ch are nemat ic at r o o m temperature exist and have been used c o m m e r c i a l l y . H o w e v e r , as a result o f the l i n k i n g group X these compounds tend to be chem ica l l y or pho tochemica l l y unstable and are of ten co lou red , w h i c h are undes i rab le traits fo r app l i ca t ions . W i t h these p rob lems i n m i n d , G r a y et a / . 1 0 des igned nemat ic compounds w h i c h d i d not conta in the central l i nkage , but st i l l i ncorpora ted the other factors w h i c h were k n o w n to increase mesophase stabi l i ty . P a r a - s u b s t i t u t e d benzenes do not f o r m l i q u i d - c r y s t a l l i n e phases . W h i l e 4,4 ' -subst i tu ted b i p h e n y l l i q u i d c rys ta ls were k n o w n , they we re a l l h i g h - m e l t i n g mater ia ls . B y reduc ing the mo lecu la r we igh t and us ing subst i tuents w h i c h g i ve the greates t i n c r e a s e s i n T N I , G r a y p r e d i c t e d that the 4 - a l k y l - a n d 4 - a l k o x y -4 ' -cyanob ipheny ls w o u l d have l o w temperature mesomorph ic behav iour . 4 -A lkyI-4 ' -cyanobiphenyI L i q u i d C r y s t a l s G r a y ' s p r e d i c t i o n s l e d to the d i s c o v e r y o f the c o m m e r c i a l l y s u c c e s s f u l a l k y l c y a n o b i p h e n y l s 2. These were the f i rst mesomorphs o f such short m o l e c u l a r length and l o w mo lecu la r weight . T h e y are co lour less , c h e m i c a l l y and thermal ly stable c o m p o u n d s , and they have st rongly pos i t i ve d ie lec t r i c an iso t rop ics , w h i c h makes the nemat i c phases use fu l i n e lec t ron ic d i s p l a y s . T h e t rans i t ion temperatures f o r the series are g iven in Tab le I w h i c h f o l l ows . T h e H-pentyl c o m p o u n d , k n o w n as 5CB, has a reasonab ly w i d e nemat ic range w h i c h i nc ludes r o o m temperature. T h e n - o c t y l 2 In t roduct ion / 8 Table I. Mesomorphic transition temperatures for the 4-alkyl-4'-cyanobiphenyls 2. R T K S o r T K N / 0 C T S N / ° C T N I / ° C / J - C 5 H H 2 2 . 5 - 3 5 rt-C6Hi3 1 3 . 5 - 2 7 n - C 7 H i 5 2 8 . 5 - 4 2 rt-C8Hn 2 1 . 0 3 2 . 5 4 0 /1-C9H19 4 0 . 0 4 4 . 5 4 7 ana logue , 8 C B , is use fu l f o r r o o m temperature smec t i c s tud ies. M i x t u r e s o f the a l ky l cyanob ipheny l s can g ive nemat ic ranges o f - 5 5 to + 5 0 ° C . A n in te res t ing feature o f these c o m p o u n d s , and a l l l i q u i d c rys ta ls bear ing te rm ina l a l k y l cha ins , is the al ternat ion in nemat ic s tabi l i ty w i t h c h a i n length . T h i s e f fec t is seen i n the T N I va lues i n T a b l e I. O d d - n u m b e r e d c h a i n s g i v e h i g h e r t ransi t ions than even -numbered cha ins , each subset f o l l o w i n g a smoo th cu rve w h i c h leve ls o f f as the cha in length increases. S i n c e the d i scove ry o f the a l ky l cyanob ipheny l s , l i t t le w o r k has been pub l i shed o n m o d i f i c a t i o n s to the s imp le b i p h e n y l sys tem i n o rder to f i n d n e w , and p o s s i b l y super ior , l i q u i d crysta ls . G r a y rep laced the cyano group w i th a n i t ro func t ion , but a l l o f the resu l t ing compounds had h igher me l t i ng points and l o w e r mesophase stabi l i ty than their c yano analogues, as w e l l as be ing d is t inc t ly y e l l o w i n c o l o u r . 1 0 A n e x t e n s i v e s tudy b y D a b r o w s k i a n d Z y t y n s k i 1 1 i n 1 9 8 1 i n v o l v e d the rep lacemen t o f the c y a n o group o f 5 C B w i t h a large var ie ty o f subst i tuents, Z i n structure 3. T h e w o r k was not l im i t ed to func t iona l groups w h i c h w o u l d be cons idered »-CK>-z 3 Introduct ion / 9 l i k e l y to g i ve mesomorphs us ing the factors d i scussed above . Ra the r , subst i tuents w i t h l i near , p lanar , and th ree -d imens iona l geomet r ies , r i g i d and f l e x i b l e , po la r and n o n - p o l a r we re a l l t r i ed i n o rder to es tab l i sh w h i c h fac to rs w e r e impor tan t to l i qu id -c rys ta l l i n i t y . N o t surpr is ing ly , the results showed that on l y r i g i d , l inear or p lanar func t iona l groups w o u l d support m e s o m o r p h i s m in 3. A f e w nemat ic c o m p o u n d s were f ound ( Z = C H = N O H , C H = C H C N , C ( C H 3 ) = C H C N ) , but none had m e l t i n g po in ts b e l o w r o o m temperature, and there was no ment ion o f attempts to l o w e r the me l t i ng points by va ry ing the a l k y l cha in length. M i x t u r e s o f the compounds synthes ized in the above w o r k w i t h k n o w n l i q u i d crysta ls were a lso s tudied in an attempt to exp la in the mo lecu la r assoc ia t ion in l i q u i d c rys ta ls . O n e c o m p o u n d o f interest f r o m that study is that w i t h Z = C = C H . W h i l e this c o m p o u n d is not a l i q u i d c rys ta l , i t can increase the nemat ic stabi l i ty o f 5 C B by as m u c h as 2 5 ° C u p o n m i x i n g the two c o m p o u n d s . T h i s obse rva t i on suggests that mod i f i ca t ions to the a l kyne system might produce mesomorph i c compounds . P r o p o s e d L i q u i d C r y s t a l s G i v e n the l i m i t e d p u b l i s h e d w o r k on m o d i f y i n g the structures o f the l i q u i d c rys ta ls 2, w e d e c i d e d that s i m p l e changes to the f u n c t i o n a l g roup w o u l d be an appropr ia te start i n search ing fo r new l i q u i d crysta ls o f that genera l structure. T h e concept o f rep lac ing the cyano group w i th m i n i m a l changes in mo lecu la r geometry led to two types o f target compounds , i socyan ides 4 and a lkynes 5. 4 5 Int roduct ion / 10 T h e subst i tut ion o f the cyan ide func t ion by an i socyan ide w o u l d g i ve the least change to mo lecu la r d imens ions and no change i n mo lecu la r we igh t . In add i t i on , the e f fec t o f r e v e r s i n g the d i r ec t i on o f the s t rong ca rbon -n i t r ogen d i p o l e w i t h i n the m o l e c u l e c o u l d have an in terest ing effect on mesophase s tab i l i ty . W h i l e l i t t le was k n o w n about the chemis t ry o f i socyan ides pr io r to 1 9 7 0 , 1 2 they have been w e l l s tudied ove r the past f i f teen y e a r s . 1 3 M o n o s u b s t i t u t e d a l kynes (5, X = H ) are a lso s im i la r i n geomet ry to the l i qu i d crys ta ls 2 and d i f fer ma in l y i n the absence o f a strong d ipo le . M o d i f y i n g the s ize and po lar i ty o f the substituent X w h i l e ma in ta in ing the rod - l i ke shape o f the m o l e c u l e was ant ic ipa ted to p roduce stable mesophases . F o r this purpose the subst i tuents X = H , C H 3 , S i ( C H 3 ) 3 , C I , B r , and I were chosen. F o r each g roup o f target c o m p o u n d s , the n -pen ty l de r i va t i ves w e r e to be syn thes ized i n order to op t im i ze the effects o f l o w mo lecu la r we igh t and h igh nemat ic s tab i l i t y i n the c o m p o u n d s . T h e d i s c o v e r y o f any m e s o m o r p h i c behav iou r i n these compounds w o u l d warrant the invest igat ion o f analogous compounds w i th other cha in lengths in order to exp lore the var ia t ion in l iqu id -c rys ta l l ine behav iour . 11 R E S U L T S A N D D I S C U S S I O N 4-AlkyI-4'-alkynylbiphenyls T h e f i r s t g r o u p o f c o m p o u n d s i n v e s t i g a t e d w e r e the s u b s t i t u t e d a l k y n y l b i p h e n y l s 5a-f. T h e s ize and polar i ty o f the group X were va r ied to determine under what cond i t ions the a lkyne mo ie ty might support mesomorph i c behav iour . X = S i ( C H 3 ) 3 5 a X = C1 5d H 5b B r 5 e C H 3 5 c I 5 f C l a s s i c a l methods for the synthesis o f a lkynes genera l l y i n v o l v e e l im ina t i on react ions, espec ia l l y dehydroha logenat ions o f 1,2-dihaloalkanes o r h a l o a l k e n e s . 1 4 -CHX—CHX —CH=CX— C=C— Subs t i t u t i on reac t ions o f a l kynes o n l y became p o s s i b l e w i t h the d e v e l o p m e n t o f o rganometa l l i c chemis t ry . A c e t y l i d e s o f a l ka l i meta ls , a l u m i n i u m , copper , bo ron , and m a g n e s i u m have a l l been u s e d . 1 4 T h e Stephens-Cas t ro c o u p l i n g r e a c t i o n 1 5 between a ry l iod ides and cuprous acety l ides has ach ieved w ide app l i ca t ion . A r l + R C = C C u A r C = C R Resu l ts and D i s c u s s i o n / 12 T h i s r e a c t i o n r e q u i r e s the p r e p a r a t i o n o f the c u p r o u s a c e t y l i d e f r o m the o rganomagnes ium o r l i t h i um reagent and prohib i ts the presence o f sensi t ive func t iona l g roups . A n i m p r o v e d c o u p l i n g procedure , deve loped by Sonogash i ra et a / . 1 6 i n v o l v e s ca ta lys is by a pa l lad ium(O) species generated in situ f r o m ( P P h 3 ) 2 P d C l 2 by reduct ion w i t h t r ie thy lamine, us ing cuprous iod ide as a co-cata lys t . pjO A r l + HC=CR + E13N - ~ A r C = C R + E t 3 N + H r T h e procedure is s imp le and the react ion proceeds at r o o m temperature. T h i s use o f pa l l ad ium(O) cata lys ts has been recen t l y r e v i e w e d . 1 7 T h e mechan i s t i c ro le o f the cuprous i od ide is uncer ta in , but its presence is necessary fo r the c o u p l i n g reac t ion to p roceed at r o o m temperature. In order to use this c o u p l i n g react ion fo r the synthesis o f te rmina l a lkynes , such as 5b, a p ro tec t ing group must be used to prevent d isubst i tu t ion . T a k a h a s h i et a / . 1 8 r ecogn i zed that the t r ime thy l s i l y l group was an idea l protect ing group fo r syn thes iz ing te rmina l a r y l a l kynes , s ince the C - S i bond in a ry le thyny ls i l anes is read i l y c l e a v e d by di lute a l k a l i . 1 9 A r C = C - S i ( C H 3 ) 3 A r C = C H C o m p o u n d 5a was chosen as the in i t i a l target m o l e c u l e s ince the r e m a i n i n g c o m p o u n d s 5b-f can be m a d e by appropr ia te subs t i tu t ions . T h e syn thes is is s u m m a r i z e d i n S c h e m e A o n the f o l l o w i n g p a g e . T h e s tar t ing m a t e r i a l was pract ica l -grade 4 -bromobipheny l 6, conta in ing about 10% b i pheny l . Pu r i f i ca t i on o f this Resu l ts and D i s c u s s i o n / 13 ~00 -*-(K) y > = / X = / n - C 5 H „ B r • 7 B r 2 , F e B r 3 9 8 HC£CSi (CH 3 )3 PdCl 2 (PPh 3 ) 2 Cul , E t 3 N SCHEME A. Synthesis of 4-alkyl-4'-alkynylbiphenyls 5a-f. Resu l ts and D i s c u s s i o n / 14 mater ia l on the requ i red scale p roved d i f f i cu l t , so separat ion was left fo r a latter stage in the synthes is . T h e preparat ion o f 4- rc-penty lb ipheny l 7 was ach ieved b y a copper( I ) c o u p l i n g o f the G r i g n a r d reagent o f 6 and 1-bromopentane. T h e react ion g ives a h igh y i e l d o f the des i red c r o s s - c o u p l e d produc t w i thou t any a l k y l - a r y l exchange o f the G r i g n a r d reagent to p roduce homo-coup led d imers . A d i scuss ion o f the m e c h a n i s m and k inet ics o f this react ion may be found in reference 20 . C o m p o u n d 7 was subsequent ly b romina ted i n ca rbon te t rach lor ide, a few i ron f i l i ngs p r o v i d i n g the necessary catalyst . A n excess o f b rom ine was used s ince the b ipheny l impur i t y reacts to g ive 4 ,4 ' -d ib romob ipheny l w h i c h is read i l y separated f r om the des i red mater ia l . P o l y b r o m i n a t i o n o f 7 is avo ided by us ing a short reac t ion t ime. T h e bromide 8 was pur i f i ed by recrys ta l l i za t ion f r om methano l . A n a l te rna te rou te to c o m p o u n d 8 b y F r i e d e l - C r a f t s a c y l a t i o n o f 4 - b r o m o b i p h e n y l 6 f o l l o w e d by reduct ion has been u s e d , 1 0 but the m e t h o d descr ibed above is p rocedura l l y s imp ler w i th an overa l l y i e l d o f 6 6 % compared to 3 0 - 5 0 % . Transha logenat ion o f the b romide 8 to the iod ide 9 was a c c o m p l i s h e d us ing the h a l o g e n — m e t a l in te rconvers ion r e a c t i o n 2 1 w i th / j -buty l l i th ium. T h e resu l t ing i od ide 9 w a s c o u p l e d w i t h e t h y n y l t r i m e t h y l s i l a n e to g i v e the target c o m p o u n d 5a. T h e fo rma t ion o f the pa l lad ium(O) cata lyst was ev i denced by a v i s c o u s , b lack e m u l s i o n . T h i n - l a y e r ch romatograph ic ana lys is i nd ica ted that the reac t ion at r o o m temperature was v i r t ua l l y instantaneous. C o m p o u n d 5a was i so la ted w i t h an o v e r a l l y i e l d f r o m 4 -b romob ipheny l (6) o f 4 3 % . T h e r e m o v a l o f the t r ime thy l s i l y l g roup to g i v e 5b was a c h i e v e d w i t h I M p o t a s s i u m h y d r o x i d e in m e t h a n o l . T h e reac t ion p roceeds q u i c k l y a n d essen t ia l l y quant i ta t ive ly at r o o m temperature. Subst i tu t ion o f the te rmina l a l kyne 5b can be ach ieved by tak ing advantage o f the re la t ive ac id i t y o f the a lkyne . T h e proton is read i l y abstracted by n - b u t y l l i t h i u m . Resu l ts and D i s c u s s i o n / 15 A d d i t i o n o f an e lec t roph i le g ives the appropr ia te ly subst i tuted a l kyne . C o m p o u n d 5c was m a d e by the a d d i t i o n o f m e t h y l benzenesu lphona te to a s o l u t i o n o f the a l k y n y l l i t h i u m reagent o f 5b at - 8 0 ° C . T h e reac t ion p roceeds as the so lu t ion is a l l o w e d to w a r m , as i n d i c a t e d by the appearance o f a p rec ip i t a te o f l i t h i u m benzenesu lphona te . F o r the p repara t ion o f the h a l o a l k y n e s 5d-f a n u m b e r o f reac t ions were cons idered . H a l o a l k y n e s have p rev ious ly been prepared f r o m g e w - d i h a l o a l k e n e s 2 2 by e l im ina t i on react ions s im i l a r to those ment ioned ear l ier . F o r ou r purposes this route w o u l d requ i re the separate p repa ra t i on o f each o f the d i h a l o a l k e n e s a n d the deve lopmen t o f e l im ina t i on cond i t ions for each one. A n attract ive a l ternat ive is the subst i tu t ion o f the te rm ina l hyd rogen in the a l k y n e 5b w i t h each o f the requ i red ha logens . B r o m o e t h y n y l b e n z e n e has been success fu l l y prepared f r o m the co r respond ing a l k y n e i n a two-phase reac t ion w i t h h y p o b r o m i t e . 2 3 A t tempts at a s i m i l a r reac t ion w i t h 5b us ing phase- t ransfer ca ta lys is gave o n l y a ve ry s m a l l amount o f b romina ted product . T h e me thod by w h i c h a l l o f the ha loa lkynes were f i na l l y p repared was by the deprotonat ion o f 5b by rt-butyllithium and subsequent react ion w i t h an e lec t ropos i t i ve h a l o g e n . In the case o f c h l o r i n e , such a r e a c t i o n h a d been r e p o r t e d w i t h p h e n y l e t h y n y l l i t h i u m u s i n g 7V-ch lo rosucc in imide as a source o f C l + . 2 4 A var ie ty o f cond i t i ons had been at tempted and y ie lds o f ch lo roe thyny lbenzene f r o m 55 to 7 0 % were repor ted . In each case s ign i f i can t s tar t ing ma te r i a l was r e c o v e r e d , and the f o l l o w i n g react ion equ i l i b r i um was p roposed to ra t iona l ize this observat ion . O o A x — C = C — L i + O o Resu l ts and D i s c u s s i o n / 16 U s i n g reac t ion cond i t i ons s i m i l a r to those repor ted i n the ear l ie r s tudy , the ch lo ro c o m p o u n d 5d was prepared and isolated in 8 5 % y i e l d w i th 12% start ing mater ia l r ecove red . R e p o r t e d a t t e m p t s at b r o m i n a t i o n o f a r y l e t h y n y l l i t h i u m w i t h i V - b r o m o s u c c i n i m i d e to p r o d u c e b r o m o e t h y n y l a r e n e s f a i l e d . 2 2 T h e authors r a t i ona l i zed this resu l t by a s s u m i n g that the above e q u i l i b r i u m l ies far to the left . H o w e v e r , use o f N - b r o m o s u c c i n i m i d e under iden t i ca l reac t ion cond i t i ons as fo r the preparat ion o f the ch l o ro c o m p o u n d 5d p r o v i d e d the des i red b r o m o c o m p o u n d 5e in 6 8 % y i e l d a long w i th 8% recovered starting mater ia l . T h e i odoa l kyne 5f was prepared by add ing iod ine crysta ls to the a l k y n y l l i t h i u m preparat ion, aga in let t ing the mix tu re w a r m f r o m - 8 0 ° C to r o o m temperature. U n l i k e c o m p o u n d s 5d and 5e, however , 5f c o u l d not be separated f r o m start ing mater ia l by c o l u m n chromatography . Pu r i f i ca t i on was ach ieved by rec rys ta l l i za t ion f r o m hexane, g i v ing a y i e l d o f 5 5 % . T h e 3 0 0 M H z ^ - N M R and I R spectra f o r c o m p o u n d s 5a-f are shown in the Spect ra l A p p e n d i x . A s expected, ve ry l i t t le var ia t ion occurs i n the c h e m i c a l shif ts o f co r respond ing hydrogens in the series o f compounds . T h e s ignals f o r the protons on the a lkyne-subs t i tu ted r i n g o c c u r e i ther as a sharp s ing le t o r as an A A ' X X ' pat tern. T h e most interest ing feature o f the IR spectra is the var ia t ion in in tensi ty o f the a lkyne carbon-carbon stretching s igna l . T h e s igna l fo r the t r ime thy ls i l y l c o m p o u n d 5a is very s t rong re la t i ve to that o f the t e rm ina l a l k y n e 5b. W i t h the m e t h y l subst i tu ted c o m p o u n d 5c th is s igna l i s not obse rved , p resumab l y as a resul t o f the l a c k o f a s ign i f i can t d ipo le . W i t h the ha loa lkynes , the ch lo r ide 5d g ives a stronger s igna l than the b rom ide 5e. T h e iod ide again g ives no observab le s i gna l , p robab l y as a resul t o f the increased a tomic we ight and decreased induc t ive effect o f i od ine . T h e compounds w h i c h d o g i ve observab le a l k yne s t re tch ing s igna ls are eas i l y d i s t i ngu i shed by the f requency o f that s igna l wh i ch ranges f r o m 2221 to 2108 c n r 1 . Resu l ts and D i s c u s s i o n / 17 Table II. Infrared frequencies of the alkyne carbon-carbon stretching signal in compounds 5a-f. n - C 5 H „ - / W/ u C E C - X compound X C = C stretch / c m " 1 5 a 5b 5 c 5d 5 e 5 f S i ( C H 3 ) 3 H C H 3 ci B r I 2155 2108 no s igna l 2221 2199 no s igna l T h e m e l t i n g behav iou rs o f c o m p o u n d s 5a - f were o b s e r v e d u s i n g a s i m p l e cap i l l a ry me l t i ng po in t apparatus. T h e results are g i ven in T a b l e I I I w h i c h appears on the f o l l o w i n g page . C o m p o u n d s 5a -c have n a r r o w m e l t i n g ranges , i.e. c r y s t a l -i so t rop ic t ransi t ions, i nd ica t ing the absence o f mesomorph i c behav iour . The re is a lso v e r y l i t t le va r i a t i on a m o n g these three c o m p o u n d s , a s l igh t inc rease i n T K I be i ng observed w i th inc reas ing mo lecu la r we ight and the bu lk iness o f the substi tuent. C o m p o u n d 5 d a lso has a nar row me l t i ng range, but the iso t rop ic l i q u i d q u i c k l y y e l l o w s . T h e m e l t i n g range is not no t i ceab ly a f fec ted w i t h the appearance o f the y e l l o w co lou r as the reso l id i f i ed mater ia l g ives the same T K I - T h i s p r o b l e m o f thermal s tabi l i ty i n the ha loa l kyne systems is addressed be low . Resul ts and D i s c u s s i o n / 18 Table III. Melting behaviour of compounds Sa-f. compound X me l t ing range / °C 5a - S i ( C H 3 ) 3 8 5 - 8 6 5b H 7 9 - 8 0 5c C H 3 8 2 - 8 3 5d C I 1 1 5 - 1 1 6 5e B r 8 8 - 1 0 8 * 5f I 1 1 0 - 1 1 9 * * mesomorphic compound C o m p o u n d s 5e and 5f d o not exh ib i t sharp T K I ' S . C r y s t a l s o f the b r o m o c o m p o u n d mel ts at 88°C to a t ranslucent, v i scous phase w h i c h c lears to an iso t rop ic l i q u i d at 108°C. T h e i o d o ana logue has s i m i l a r behav iou r , m e l t i n g at 110°C and c lea r ing at 119°C. In each case a ye l l ow-o range c o l o u r beg ins to deve lop before the fo rmat ion o f the isot rop ic phase, ind ica t ing thermal instabi l i ty . In add i t ion to the d isco lo ra t ion o f the ha loa lkynes near thei r me l t i ng po in ts , a s i m i l a r y e l l o w i n g was obse rved at r o o m temperature ove r l onge r per iods . T h e i odo c o m p o u n d 5f d i s co lou rs at r o o m temperature i n a matter o f d a y s , w h i l e the same process occu rs o v e r weeks w i t h the c h l o r o c o m p o u n d 5d. T h e reac t ive nature o f h a l o a l k y n e s has been d o c u m e n t e d , 2 5 and examp les o f n u c l e o p h i l i c at tack at the ha logen and both the a and B a l k y n y l carbons have been d e m o n s t r a t e d . 2 6 T h e exact nature o f the process occur r ing i n compounds 5d-f was not invest igated. Resul ts and D i s c u s s i o n / 19 W h i l e the r e a c t i v i t y o f h a l o a l k y n e s l i k e l y renders t h e m i m p r a c t i c a l as c o m m e r c i a l l y use fu l l i q u i d c rys ta ls , the i r apparent ab i l i t y to suppor t m e s o m o r p h i c behav iour is o f substant ia l interest. W e have seen that the subst i tut ion o f the a l k y n y l hyd rogen o f c o m p o u n d 5b w i th iod ine and b rom ine* g ives c o m p o u n d s w i t h l i q u i d -c rys ta l l ine phases, wh i l e the smal le r , more e lectronegat ive ch lo r ine does not. + P r e l i m i n a r y studies o f the ana logous n -hexy l series o f c o m p o u n d s ind ica te that the b r o m o e t h y n y l der i va t i ve has a w i d e temperature range o f m e s o m o r p h i c behav iou r , me l t i ng at 7 5 ° C and c lear ing at 104°C. Resul ts and D i s c u s s i o n / 20 4-AIkyI-4'-isocyanobiphenyIs T h e second c lass o f c o m p o u n d s studied were the i s o c y a n o b i p h e n y l s 4. W e were interested i n see ing what ef fect reve rs ing the d i rec t ion o f the carbon-n i t rogen d ipo le w i t h i n the m o l e c u l e re la t ive to 5CB w o u l d have on the ex is tence o f a l i q u i d -c r ys ta l l i ne phase . T h e geomet r i ca l change is c l ea r l y m i n i m a l , but the e lec t ron ic i n f l uence o f the i s o c y a n o subst i tuent on the r i ng sys tem and on the i n te rmo lecu la r in teract ions was unpred ic tab le . ^ ^ ^ ^ — N = C R = n -a l ky l Isocyanides are isoe lec t ron ic w i th carbon monox ide and may be v i e w e d as ' ca rbeno id ' i n cha rac te r . O f the t w o c o m m o n d e p i c t i o n s o f the e l e c t r o n i c s t ruc tu re , R - N = C : " R - N = C : the structure on the r ight most accura te ly descr ibes the b o n d i n g o f i socyan ides but g ives an incor rec t i m p r e s s i o n o f the actua l charge d i s t r i bu t i on . M o l e c u l a r o rb i ta l ca lcu la t ions ind icate that the e lect ron densi ty i n the bond ing orbi ta ls is greater a round the n i t rogen atom, g i v i ng a net d ipo le moment f r o m the carbon to the n i t rogen. A few natura l ly occur r ing compounds conta in ing the i socyano group have been iso la ted and character ized. T w o examples are g i ven in F i g u r e 3 on the next page. Resu l ts and D i s c u s s i o n / 21 Figure 3. Naturally occurring isocyanides. ( ± ) - A x i s o n i t r i l e - l * r HO—17 v—CH=C—c-cn—^ ^ N N - O H Xan thoc i l l i n C C T h e preparat ion o f i socyan ides is most c o m m o n l y ach ieved by the dehydrat ion o f N-monosubs t i tu ted fo rmamides . R - N H - C H O R - N = C A range o f dehyd ra t i ng agents have p r o v e n success fu l f o r this purpose i n c l u d i n g p h o s g e n e , 2 7 d i p h o s g e n e , 2 8 and phospho roy l c h l o r i d e , 2 9 usua l l y i n comb ina t i on w i th t r i e thy lamine . H i g h e r y i e l ds have genera l l y been a c h i e v e d w i t h phosgene , but the ext reme tox ic i t y and cumbersome hand l ing o f the gas m a k e it an undes i rab le reagent. In 1985 , U g i et a / . 3 0 i m p r o v e d the p h o s p h o r o y l c h l o r i d e p r o c e d u r e b y u s i n g d i i s o p r o p y l a m i n e as the base. Y i e l d s were comparab le to those o f the phosgene method , but the react ion proceeds under m i l d e r cond i t i ons and g ives h igher product pur i ty . Resu l ts and D i s c u s s i o n / 22 Ano the r method fo r prepar ing isocyan ides is the H o f m a n n ca rby lam ine react ion i n v o l v i n g the addi t ion o f d ich lorocarbene to p r imary amines. : C C 1 2 + R N H 2 " R N C + 2 H C 1 Reasonab le y ie lds have been ach ieved by this me thod us ing phase- t ransfer ca ta lys is to generate the c a r b e n e . 3 * A mo re recen t l y d e v e l o p e d route to i s o c y a n i d e s i n v o l v e s the reduc t i on o f i socyanates w i t h t r i ch lo ros i lane and t r ie thy lamine . H i g h y ie lds o f a ry l i socyan ides have been ach ieved by this m e t h o d . 3 2 It was by this method that we o r i g ina l l y chose to prepare the b ipheny l i socyan ides 4, s ince the isocyanates were access ib le via the a c y l az ides by the Cur t ius rearrangement. T h e azides c o u l d be prepared in g o o d y i e l d f r o m the appropr iate b romob ipheny l s , such as c o m p o u n d 8. T h i s route is dep ic ted in Scheme B shown on the next page. T h i s reac t i on sequence was c a r r i e d out on 4 - b r o m o - 4 ' - n - p e n t y l b i p h e n y l , g i v i n g the isocyanate i n about 8 0 % overa l l y i e l d . T h e reduct ion step appeared to wo rk w e l l on a sma l l scale (0 .5mmol ) ; the I R spect rum c lear l y ind ica ted the presence o f an i socyan ide in the crude product . H o w e v e r , i so la t ion o f the produc t p roved d i f f i cu l t . W h i l e the i socyan ide appeared to be stable i n the produc t m ix tu re , ch romatograph ic separat ion resul ted in the fo rmat ion o f a b rown tar. A t tempts to repeat the react ion on a larger scale fa i l ed , g i v i n g no desi red product . G i v e n the d i f f i cu l t i es o f i so la t i ng the i socyan ides f r o m the reduc t ion o f the isocyanate , the alternate route chosen fo r their preparat ion was the dehydra t ion o f the c o r r e s p o n d i n g f o r m a m i d e . T h i s p l a n i n v o l v e d the N - f o r m y l a t i o n o f the p r i m a r y aromat ic amine f o l l o w e d by treatment w i t h phospho roy l c h l o r i d e — d i i s o p r o p y l a m i n e . A s before, the in i t i a l effort was d i rected at the n-penty l c o m p o u n d 4a. Resu l ts and D i s c u s s i o n / 23 -OO . ) M 8 . T H P > _ ^ ^ 2) C0 2 (s) \ / \ / 3) H + 1) S O C l 2 2) NaN3, PTC f ~ W \ - N = c = o C - N , Cl 3 SiH E t 3 N N = C 4 a R = / i - C 5 H n 4 b R = / z - C 4 H 9 4 c R = n - C 6 H 1 3 SCHEME B. Synthesis of isocyanides via acyl azides. Resu l ts and D i s c u s s i o n / 24 Severa l p laus ib le routes to the requ i red amine are shown in Scheme C on page 25 . D i rec t aminat ion o f the aromat ic r i ng v i a the a ry l l i t h ium der ivat ive o f c o m p o u n d 8 m a y be ach ieved w i t h an imat ing reagents such as m e t h o x y a m i n e - m e t h y l l i t h i u m 3 3 or 0 - ( d i p h e n y l p h o s p h i n y l ) h y d r o x y l a m i n e . 3 4 S ince 8 had been prepared p rev ious l y as an i n te rmed ia te i n ou r a l k y n y l b i p h e n y l syn thes i s , th is m e t h o d c o u l d have been a conven ien t route. H o w e v e r , g i ven the l o w y ie lds o f the amina t ion react ions and the lack o f ava i lab i l i t y o f the reagents, more convent iona l routes to 12 were cons idered . T h e c lass i ca l me thod o f prepar ing p r imary aromat ic amines is a ry l n i t rat ion in a mix ture o f n i t r ic and su lphur ic acids f o l l owed by reduct ion o f the ni t ro group by z i nc or i r on i n the presence o f a c i d . T h e c h i e f cons ide ra t ion in a p p l y i n g th is p rocess to b ipheny l was that on l y mononi t ra t ion in the para pos i t ion o f a s ing le r i ng was des i red. W h i l e the deact iva t ing nature o f the ni t ro group genera l ly prec ludes d isubst i tu t ion o f a s ingle aromat ic r i ng under m i l d cond i t ions , the b ipheny l sys tem has an obv ious p i t fa l l . A s dep ic ted i n Scheme C , ni t rat ion o f c o m p o u n d 7 was attempted w i t h the hope that ster ic in teract ions o f the a l k y l cha in m igh t over r ide the ac t i va t ing nature o f the a l k y l subst i tuent and d i rect the n i t rat ion to the para pos i t i on o f the monosubs t i tu ted r i ng . Un fo r tuna te ly , the resul t was a mix ture o f products w h i c h conta ined very l i t t le o f the des i red 4 ,4 ' -d isubst i tu ted c o m p o u n d . C o l u m n ch roma tog raphy w i t h 2 0 % e thy l acetate i n hexanes gave two ma jo r products w h i c h were de te rm ined by ! H - N M R to be c o m p o u n d s 13 and 14 shown o n page 26 . T h e ac t iva t ion by the a l k y l subst i tuent, d i rec t ing the n i t ra t ion ortho, is ev iden t l y the p redominant factor . Consequen t l y , the presence o f an a l k y l cha in dur ing the ni t rat ion step was p rec luded . Resu l ts and D i s c u s s i o n / 25 SCHEME C. Synthetic routes to the primary amine 12. Resul ts and D i s c u s s i o n / 26 7 R = n - C 5 H n N i t ra t i on o f b ipheny l a lso gave mix tures o f m o n o - and d isubst i tu ted, ortho and para p roduc ts . T h e so lu t ion to these p rob lems was to f i rst deact iva te one r i n g by F r i e d e l - C r a f t s a c y l a t i o n to g i v e c o m p o u n d 10.35 T h e r e was no e v i d e n c e o f d isubst i tu t ion, and the desi red ary l ketone was read i ly iso la ted. T h e ma jo r impur i t y i n the p roduc t was unreacted b i p h e n y l , w h i c h was r e m o v e d by rec rys ta l l i za t i on f r o m me thano l . Subsequent n i t ra t ion o f ke tone 10 gave 11 as the ma jo r p roduc t w i t h some ortho impur i ty . Recrys ta l l i za t ion o f 11 f r o m methanol gave the des i red c o m p o u n d in an overa l l y i e l d f r o m b ipheny l o f 3 9 % . S i m u l t a n e o u s r e d u c t i o n o f the n i t r o g r o u p to the p r i m a r y a m i n e and deoxygena t ion o f the ketone was accomp l i shed by the H u a n g - M i n i o n mod i f i ca t i on o f the W o l f f - K i s h n e r reduc t ion . T h e impur i t ies f r o m the reduc t ion are br igh t ly co lou red and are p robab ly a resul t o f incomple te reduct ion o f coup led azo species. Th i s p rob lem was ove rcome by the use o f excess hydraz ine and longer react ion times. T h e product was pur i f i ed by c o l u m n chromatography and sub l imat ion to g ive 12 i n a 5 6 % y ie ld . T h e next step i n the preparat ion o f i socyan ide 4 a was the iV - fo rmy la t i on o f the am ine 12 as s h o w n in S c h e m e D on the f o l l o w i n g page. A c y l a t i o n s o f amines are genera l ly car r ied out w i t h ac id anhydr ides , but, s ince f o r m i c anhydr ide is not a stable c o m p o u n d , a m i x e d anhydr ide must be used . A c e t i c f o r m i c anhydr ide is c o m m o n l y used fo r this purpose, and is eas i l y prepared f r o m f o rm i c a c i d and acet ic a n h y d r i d e . 3 6 W h e n this react ion was attempted w i th 12 at 0 ° C , a mix tu re o f the f o r m a m i d e 15 and Resul ts and D i s c u s s i o n / 27 SCHEME D. Synthesis of isocyanides from primary amines. the co r respond ing acetamide were f o rmed i n an 80 :20 rat io . T h e two products p roved d i f f i cu l t to separate by chromatography, and a h igh l y pure product was des i red fo r the f o l l o w i n g step o f the synthesis. In order to imp rove the se lect iv i ty o f the f o rmy la t i on , w e dec ided to use f o rm ic p i va l i c anhydr ide. T h i s reagent had been p rev ious ly shown to be a h igh l y e f f ic ient and se lect ive N - f o r m y l a t i n g agent fo r p r imary a m i n e s . 3 7 It is conven ien t l y prepared f r o m sod ium formate and the a c i d ch lor ide o f t r imethlyacet ic ac id (p i va loy l ch lo r ide) . R e a c t i o n o f 12 w i t h this m i x e d anhyd r i de gave the f o r m a m i d e 15 as the e x c l u s i v e p roduc t w i t h no ev idence o f the p i v a l a m i d e . T h e ! H - N M R spectra o f 15 (see Spec t ra l A p p e n d i x and F i g u r e 4 o n page 28) seemed to ind ica te a m ix tu re o f p roduc ts , but this ev idence was in con t rad ic t ion w i t h the sharp me l t i ng po in t o f the reac t i on p roduc t . T h e p roduc t is i n fact a m i x t u r e o f ro ta t iona l i s o m e r s . T h i s phenomenon is a c o m m o n proper ty o f N - a r y l a m i d e s . 3 8 T h e carbon-n i t rogen bond o f Resul ts and D i s c u s s i o n / 28 Figure 4. The aromatic region of the ]H-NMR spectra of compound 15 in toluene-ds. O H Y , C - H a , C = 0 A r — N , " A r — N \ \ H p H§ s-cis s-trans (a) 2 5 ° C a toluene I LLl (b) 80°C toluene I I [ I I I I I I I I I I I I I I I I I I l I i i i i I M I I I I I I i I I I I I I I I ! : I I I ! i i I 8 7 6 8 7 6 Resul ts and D i s c u s s i o n / 29 the amide group has suf f ic ient doub le bond character that free rotat ion about that bond does not occu r at r o o m temperature. N e a r l y equa l amounts o f each i somer are apparent i n the ! H - N M R spect rum o f 15 s h o w n i n F i g u r e 4(a) . Separate s igna ls appear fo r the p ro tons at tached to the c a r b o n y l carbon ( H a , H Y ) and to the ni t rogen (Hp , H5) fo r each isomer . T h e structure w i th the hydrogens trans g ives the s ignals at 6.4 and 7 .2ppm w i th a sp in -sp in coup l i ng constant o f 1 2 H z . T h e s-cis i somer g ives the same s ignals at 5.7 and 7 .7ppm w i th no c o u p l i n g . A t 80°C the same sample g ives a spect rum i n w h i c h these fou r s ignals have co l l apsed , and the aromat ic pattern has s imp l i f i ed (F igure 4(b)). W h i l e l i te ra ture p recedents i m p l y that the i s o l a t i o n o f e i the r i s o m e r o f N - a r y l a m i d e s 15 m igh t be ach ieved by rec rys ta l l i za t i on i n d i f ferent so lven ts , th is process was unnecessary p r io r to the f i na l step in the synthes is . D e h y d r a t i o n o f the am ide was pe r f o rmed w i t h p h o s p h o r o y l ch lo r i de and d i i s o p r o p y l a m i n e as d i scussed ear l ier . T h e react ion was car r ied out i n d ich lo romethane at 0 ° C and was comp le te i n f i ve minutes. T h e I R spec t rum o f the crude product c lea r l y i nd ica ted that conve rs i on to the i s o c y a n i d e 4 a had occu r red . T h e co lou r less p roduc t was separated f r o m the c rude , orange mix tu re by c o l u m n chromatography w i th d ich lo romethane on a lum ina . Ro ta ry evapora t ion o f the f rac t ions con ta i n i ng the i socyan ide gave a tu rb id f l u i d w i t h the v i s u a l cha rac te r i s t i c s o f a nema t i c l i q u i d c r y s t a l ; s w i r l i n g the f l a s k gave the appearance o f a th read- l i ke texture, t ouch ing the f lask l i gh t l y gave textural changes caused by temperature gradients, and the f l u i d c leared when w a r m e d in the p a l m o f the hand . T h e apparent ex is tence o f a room- tempera tu re , nemat ic l i q u i d c r ys ta l o f the structure 4 a was very encourag ing , but it was soon apparent that the react ive nature o f the i s o c y a n i d e group was p rob lemat i c . U p o n s tand ing , the tu rb id f l u i d became b lue-green i n co lou r , and upon exposure to a i r gave a b r o w n tar. In the absence o f a i r , Resu l ts and D i s c u s s i o n / 30 the b lue-green co lou r s t i l l fo rms. T h i s co lou r has a lso been noted in pheny l i socyan ide and has been attr ibuted to the format ion o f the tetramer 1 6 . 3 9 I I H H 16 W i t h th is apparent r eac t i v i t y o f the i s o c y a n i d e 4 a , i s o l a t i o n o f the pure c o m p o u n d and p re l im ina ry study o f its mesomorph i c behav iour had to be car r ied out q u i c k l y a n d i n the absence o f a i r . T h e c o m p o u n d i s , h o w e v e r , s tab le i n d i ch l o rome thane so lu t i on fo r l o n g pe r iods . A f t e r r e m o v i n g the so lven t b y ro tary evapora t ion , a sample was t ransferred to a h i g h - v a c u u m system and c o o l e d to - 78 °C . A whi te , c rys ta l l ine so l i d f o rmed w i t h a fan- l i ke texture on the sides o f the f lask . T h e f lask was charged w i t h d ry n i t rogen and a l l o w e d to w a r m to r o o m temperature. N o d isco loura t ion o f the wh i te so l i d occur red . S l o w w a r m i n g o f the f lask i n a water bath g ives a t rans i t ion to an i so t rop ic l i q u i d at 34°C . A s the samp le o f 4 a is a l l o w e d to c o o l , turb id i ty deve lops at about 30 °C and the f l u i d appears to rema in nemat ic at r o o m temperature . T h i s s u p e r c o o l i n g b e h a v i o u r is c o m m o n i n nema t i c l i q u i d c rys ta ls . Rec rys ta l l i za t i on occur red w i th in a f ew hours by w h i c h time the b lue-green co lou r had begun to appear. G i v e n the ex is tence o f mesomorph i c behav iour i n the i socyan ide 4 a , ana logous c o m p o u n d s w i t h d i f ferent cha in lengths were a lso inves t iga ted . P rocedu res fo r the Resul ts and D i s c u s s i o n / 31 syntheses o f these c o m p o u n d s f r o m b i p h e n y l were i d e n t i c a l to that f o r 4a. T h e react ions were sca led to produce rough ly lOOmg o f the target compounds w i th m i n i m a l p u r i f i c a t i o n a n d c h a r a c t e r i z a t i o n o f i n t e r m e d i a t e s . E a c h o f the r e s u l t i n g i s o c y a n o b i p h e n y l s was aga in a i r - sens i t i ve and t he rma l l y uns tab le . T h e m e l t i n g b e h a v i o u r s we re s tud ied u s i n g the p rocedu re d e s c r i b e d a b o v e . T h e resu l ts are summar i zed in Tab le I V . T h e n-buty l c o m p o u n d 4b does not exhib i t l i qu id -c rys ta l l ine behav iour , g i v i ng a s imp le so l id - iso t rop ic transi t ion at 36°C w i th no ev idence o f supercoo l ing to a nemat ic phase. T h e / i - hexy l analogue 4c, however , exh ib i ts def in i te m e s o m o r p h i c behav iour . Tex tu ra l changes are obse rved as the wh i te , c rys ta l l i ne s o l i d is s l o w l y w a r m e d . A turb id f l u i d fo rms at 9 ° C and does not c lear unt i l the temperature reaches 19°C. The reverse process is observed upon c o o l i n g . A s w i t h 4a, a b lue -g reen c o l o u r s l o w l y deve lops in the l i q u i d phase. Table TV. Melting behaviour of the isocyanobiphenyls 4a-c. R compound M e l t i n g range / °C rt-C4H9 4b 3 6 - 3 7 "-C5H11 4a 3 4 - 3 5 t 4c 9 - 1 9 * ^supercools to nematic at room temperature and clears with warming, T N I = 3 0 ° C mesomorphic compound Results and Discussion / 32 Liquid-crystalline behaviour in isocyanobiphenyls is an interesting discovery. The geometry of the structure is very close to that of the cyanobiphenyls, but the effect of the functional group to the chemistry of the system is very different. The implication is that the presence of an appropriate functional group is more important than its orientation within the molecule in determining the existence of mesomorphism in these simple biphenyl systems. Future Work The presence of liquid-crystalline behaviour in both the alkynylbiphenyl and the isocyanobiphenyl systems warrants further investigation into these classes of compounds. The respective thermal instability and reactivity of these systems are the main considerations for future work. We have shown that by varying the substituent X in the alkynylbiphenyl 5, it is possible to produce mesomorphic compounds. To what extent the factors of substituent size and induced polarity of the alkyne system contribute to liquid-crystalline behaviour is difficult to deduce from the few compounds synthesized. Further studies with substituents of low molecular weight with various polarities giving stable alkynes are required. The previous observation that the terminal alkyne 5 b greatly extends the nematic temperature range of 5CB suggests that similar studies with these compounds would be useful. In addition, compounds analogous to the mesomorphs 5e and 5f with other alkyl chain lengths should be investigated. The isocyanobiphenyls 4, while reactive, also warrant further investigation as liquid crystals. The three compounds synthesized indicate that this family of compounds may well parallel the cyanobiphenyls in mesomorphic behaviour. Investigations into the reactive nature of arylisocyanides could lead to the synthesis of stable liquid crystals bearing this functional group. If this reactivity is due to activation of the ring positions ortho to the isocyano group as the limited literature seems to indicate, then blocking these positions may allow the preparation of stable liquid crystals. 33 E X P E R I M E N T A L A l l a i r -sens i t i ve man ipu la t i ons were ca r r i ed out under an atmosphere o f dry n i t rogen . F o r reac t ions requ i r i ng anhydrous c o n d i t i o n s , g lassware was o v e n - d r i e d ove rn igh t . S t i r r i n g was a c h i e v e d by T e f l o n - c o a t e d magne t i c s t i r r i ng bars. C o l d temperature baths used were as f o l l o w s : - 2 4 ° C , ca rbon tet rachlor ide / d ry i ce ; - 7 8 ° C , acetone / d ry i ce . A n h y d r o u s te t rahydro fu ran was ob ta ined by d i s t i l l a t i o n f r o m s o d i u m and benzophenone . M e t h a n o l fo r rec rys ta l l i za t ions was d r ied ove r L i n d e 3A m o l e c u l a r s ieves . D i c h l o r o m e t h a n e was d r i ed by passage through a c o l u m n o f a l um ina . A l l r e a c t i o n and ex t rac t i on so lven ts were d i s t i l l e d p r i o r to use . T h e l o w - b o i l i n g ( 35 -60°C) f rac t i on o f pe t ro leum ether was used . P rac t i ca l - g rade 4 - b r o m o b i p h e n y l (90%) was pu rchased f r o m A l d r i c h C h e m i c a l C o m p a n y , Inc. , and was not p u r i f i e d before use. E thyny l t r ime thy l s i l ane was p rev ious l y prepared in ou r laboratory b y the method o f W e s t m i j z e and V e r m e e r . 4 0 C o p p e r b romide d ime thy l su lph ide c o m p l e x was p repa red a c c o r d i n g to H o u s e et alA1 H e x a n e so lu t i ons o f w - b u t y l l i t h i u m w e r e purchased f r o m A l d r i c h C h e m i c a l C o m p a n y , Inc. , and were s tandard ized b y t i t rat ion against d ipheny lace t ic ac id . P i v a l o y l ch lo r ide , phosphoroy l ch lo r ide , d i i sop ropy lam ine , and the st ra ight-chain ac id ch lor ides were a l l d i s t i l l ed p r io r to use. H y d r a z i n e hydrate and cuprous iod ide were purchased f r o m Ma theson , C o l e m a n & B e l l . T h i o n y l ch lo r ide , f o r m i c a c i d , anhydrous a l u m i n i u m c h l o r i d e , ana ly t i ca l -g rade p o t a s s i u m ni t rate, and spectra l -grade c h l o r o f o r m were a l l pu rchased f r o m B D H C h e m i c a l s . O t h e r reagents were purchased f r o m A l d r i c h C h e m i c a l C o m p a n y , Inc., and were used w i thou t further pur i f icat ion. Expe r imen ta l / 34 M e l t i n g po in ts (m.p.) were de te rmined w i t h a G a l l e n k a m p c a p i l l a r y me l t i ng p o i n t appara tus a n d are u n c o r r e c t e d . A p p a r e n t m e s o m o r p h i c t rans i t i ons are expressed as w i d e me l t i ng ranges. In f rared ( IR) spectra were recorded as solut ions in spectra l -grade c h l o r o f o r m , u n l e s s o t h e r w i s e s p e c i f i e d , u s i n g a P e r k i n - E l m e r 1 7 1 0 F o u r i e r t r a n s f o r m spectrophotometer. P rominen t s ignals are repor ted w i th units o f c m - 1 . P r o t o n magne t i c resonance ( ' H - N M R ) spect ra were r eco rded o n a V a r i a n X L - 3 0 0 spec t rometer . U n l e s s o the rw i se s p e c i f i e d , samp les we re d i s s o l v e d i n d e u t e r i o c h l o r o f o r m , a n d c h e m i c a l sh i f ts we re d e t e r m i n e d r e l a t i v e to i n t e r n a l te t ramethy ls i lane. T h e s ignals are repor ted as c h e m i c a l shifts (8) i n parts per m i l l i o n , f o l l o w e d by mu l t i p l i c i t y , re la t ive peak integrat ion and sp in -sp in c o u p l i n g constants i n parentheses: s=singlet, d=doublet , t=triplet, m=mul t ip le t . L o w a n d h i g h - r e s o l u t i o n e l e c t r o n i m p a c t m a s s spec t r a l a n a l y s e s w e r e pe r fo rmed on a K ra tos M S - 5 0 mass spectrometer. T h e mass to charge ra t io (m/z) o f the m o l e c u l a r i o n s ( M + ) a n d the base peaks are repo r ted w i t h the i r r e l a t i ve intensi t ies. T h e measured exact masses are a lso compa red to ca l cu la ted va lues . T h i n - l a y e r chromatography ( T L C ) was pe r fo rmed o n M e r c k s i l i c a ge l 60 F254 p r e - c o a t e d a l u m i n i u m sheets. V i s u a l i z a t i o n w a s a c h i e v e d b y i r r a d i a t i o n w i t h u l t rav io le t l ight at 2 5 4 n m . C o l u m n chromatography was ca r r i ed out on M e r c k f lash s i l i c a , 2 3 0 - 4 0 0 m e s h , un less o the rw i se s p e c i f i e d . G a s c h r o m a t o g r a p h i c ( G C ) a n a l y s i s w a s p e r f o r m e d o n a H e w l e t t - P a c k a r d 5 8 3 0 A c h r o m a t o g r a p h w i t h a 1.8m x 3 m m c o l u m n packed w i th 3 % O V - 1 7 . Expe r imen ta l / 35 4-7t-Pentylbiphenyl (7) « - C s H i A m ix tu re o f 4 - b r o m o b i p h e n y l 6 (3 .5g , 1 5 m m o l ) a n d m a g n e s i u m turn ings (0 .36g , 15mmo l ) i n 2 0 m l o f te t rahydrofuran was re f l uxed fo r 9 0 minutes to g ive the G r i g n a r d reagent, as ind ica ted by a go lden co lou r and the d isappearance o f the meta l . Cup rous b romide d imethy lsu lph ide c o m p l e x (0.3g, 1.5mmol) was added at 0 ° C to g ive a br ight y e l l o w - g r e e n m ix tu re . A d d i t i o n o f n -b romopen tane ( 2 . 0 m l , 1 6 m m o l ) and heat ing to re f lux p roduced a dark green so lu t ion w h i c h s l o w l y turned turb id . R e f l u x i n g was con t inued fo r 2 0 hours resu l t ing in a grey and purp le mix tu re . T h e so lvent was r e m o v e d by rotary evapora t ion and 100ml o f pe t ro leum ether was used to extract the hyd roca rbon . T h e mix tu re was f i l te red through a short p l u g o f s i l i c a ge l w h i c h was then w a s h e d w i t h a fur ther 1 0 0 m l o f pe t ro leum ether. R e m o v a l o f the so lvent and c o l u m n c h r o m a t o g r a p h y u s i n g p e t r o l e u m ether as e luant y i e l d e d 3 .2g (95%) o f c o l o u r l e s s , l i q u i d p roduc t . G C ana lys is s h o w e d the presence o f the o r i g i n a l 1 0 % b ipheny l impur i t y . N o pur i f i ca t ion o r fur ther analys is was car r ied out before the next step in the synthes is . 4 -B romo -4 ' - n -pen ty Ib ipheny l (8) 4 - / z - P e n t y l b i p h e n y l 7 (9 .0g , 4 0 m m o l ) , 0 .2g o f i r o n f i l i n g s , and 5 0 m l o f 1 M b r o m i n e so lu t i on i n c a r b o n te t rachlor ide were s t i r red f o r 1.5 hours . Concen t ra ted aqueous NaHSC»3 was added to quench the excess b r o m i n e , and the m ix tu re was f i l t e red . T h e o r g a n i c phase was w a s h e d w i t h 2 x 5 0 m l o f wa te r and d r i e d o v e r Expe r imen ta l / 36 anhydrous MgSC»4. T h e solvent was r e m o v e d under reduced pressure to y i e l d 12.3g o f a crude y e l l o w product . Recrys ta l l i za t ion f r o m 100ml o f methano l gave 8.4g (69%) o f wh i te c rys ta ls : m.p. 94 -95°C (lit. 9 5 ° C 1 1 ) ; i H - N M R 8 7.54 (d, 2 H , 8 H z ) , 7.47 (d, 2 H , 8 H z ) , 7.43 (d, 2 H , 8 H z ) , 7.24 (d, 2 H , 8 H z ) , 2.64 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.36 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3012, 2 9 3 1 , 1 4 8 4 c m - 1 . 4- Iodo-4 ' - / i-pentylbiphenyl (9) T o a so lu t i on o f 4 - b r o m o - 4 ' - n - p e n t y l b i p h e n y l 8 (3 .0g , l O m m o l ) i n 5 0 m l o f te t rahydrofuran at - 7 8 ° C was added n -bu ty l l i t h ium (6 .6ml 1 . 5 M i n hexane , l O m m o l ) g i v i n g a pa le y e l l o w so lu t i on , w h i c h turned tu rb id af ter a f e w m inu tes . A f t e r 3 0 minutes o f s t i r r ing, i od ine crystals (2 .54g, l O m m o l ) were added , and the m ix tu re was lef t , s l o w l y w a r m i n g overn igh t . T h e so lven t was r e m o v e d f r o m the c l e a r y e l l o w so lu t ion by rotary evapora t ion , and the res idue was extracted w i th 5 0 m l o f pe t ro leum ether and f i l te red. W a s h i n g w i th 5 0 m l o f water , d r y i ng ove r anhydrous MgSC>4, and r e m o v a l o f the so lvent gave 3.9g o f a c rude, o f f -whi te product . Rec rys ta l l i za t i on f r o m methano l y i e l ded 2.8g (80%) o f whi te crysta ls : m.p. 111-112°C (lit. 1 1 2 0 C n ) ; ^ - N M R 8 7.75 (d, 2 H , 8 H z ) , 7.47 (d, 2 H , 8 H z ) , 7 .32 (d, 2 H , 8 H z ) , 7.24 (d, 2 H , 8 H z ) , 2.64 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.36 (m , 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3 0 1 2 , 2 9 3 1 , 1 4 8 4 c m - 1 . Expe r imen ta l / 37 4-n-Pentyl-4'-(trimethylsilylethynyI)biphenyl (5a) C = c — S i ( C H 3 > 3 4 - I odo -4 ' - r t - pen t y l b i pheny l 9 ( l . O g , 2 . 8 5 m m o l ) , e t h y n y l t r i m e t h y l s i l a n e 4 0 ( 4 .0m l 0 . 8 5 M i n te t rahydro fu ran , 3 . 4 m m o l ) , t r i pheny lphosph ine (0 .16g , 0 . 6 m m o l ) , pa l l ad ium d ich lo r ide (0.05g, 0 .3mmo l ) , t r ie thy lamine (3ml) , and cuprous iod ide (0 .03g, 0 . 1 5 m m o l ) were c o m b i n e d and st i r red at r o o m temperature. A f t e r f i ve m inu tes , a b lack mix ture f o rmed , and st i r r ing was cont inued for a further 15 minutes. R e m o v a l o f the vo la t i les f o l l o w e d by ext ract ion w i th 5 0 m l o f pe t ro leum ether, f i l t e r ing , w a s h i n g w i t h 5 0 m l o f water , d r y i n g ove r anhydrous MgSC»4, and r e m o v a l o f the so lvent gave 1.02g o f a l igh t b r o w n produc t . C o l u m n ch romatog raphy w i t h pe t ro leum ether as eluant y i e l ded 0.74g (81%) o f whi te crysta ls : m.p. 85 -86°C ; ! H - N M R 8 7.53 (s, 4 H ) , 7.49 (d, 2 H , 8 H z ) , 7.24 (d, 2 H , 8 H z ) , 2.63 (t, 2 H , 7 H z ) , 1.65 (m , 2 H ) , 1.35 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) , 0.25 (s, 9 H ) ; I R 3 0 1 1 , 2960 , 2 9 3 1 , 2155 (strong, sharp), 1 4 9 4 c m - l ; M S m /z 320 (89.5, M + ) , 305 (100, M + - C H 3 ) , exact mass measured 320 .1962 , exact mass ca lcu la ted 320.1960. 4-Ethynyl-4'-/i-pentyIbiphenyl (5b) A so lu t ion o f 4 - / i -pen ty l -4 ' - ( t r ime thy l s i l y le thyny l )b ipheny l 5a ( l . O g , 3 .1mmo l ) and p o t a s s i u m h y d r o x i d e ( 1 0 m l I N i n methano l ) i n 2 0 m l o f d i ch l o rome thane was Expe r imen ta l / 38 st i r red fo r 45 minutes . T h e solvents were r e m o v e d under reduced pressure, and the res idue was ext rac ted w i t h 5 0 m l o f pe t ro leum ether, w a s h e d w i t h 5 0 m l o f aqueous 0 . 1 M H C I , 5 0 m l o f water, and dr ied over anhydrous MgSC»4. R e m o v a l o f the solvent gave 0.76g o f a l ight y e l l o w product . C o l u m n chromatography w i th pe t ro leum ether as eluant gave 0 .72g (94%) o f whi te crysta ls : m.p. 79 -80°C (lit. S0°Cn); 1H-NMR 8 7.55 (s, 4 H ) , 7.50 (d, 2 H , 8 H z ) , 7.25 (d, 2 H , 8 H z ) , 3.13 (s, 1H) , 2.64 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3303 , 3015 , 2932 , 2108 (med. , sharp), 1 4 9 3 c m " 1 ; M S m /z 248 (53.2, M + ) , 191 (100, M + - C 4 H 9 ) , exact mass measured 248 .1563 , exact mass ca lcu la ted 248 .1565 . 4-/i-PentyI-4'-(propyn-l-yl)biphenyl (5c) / i -Bu t y l l i t h i um (1 .5ml 1 .5M in hexane, 2 .25mmol ) was added s l o w l y by syr inge to a so l u t i on o f 4 -e thyny l -4'-H -pen ty lb ipheny l 5b ( 0 . 5 g , 2 . 0 m m o l ) i n 2 5 m l o f tet rahydrofuran at - 7 8 ° C to g i ve a y e l l o w so lu t ion w h i c h became opaque after a f e w m i n u t e s . T h e m i x t u r e w a s s t i r r ed f o r 3 0 m i n u t e s at - 7 8 ° C a n d m e t h y l benzenesu lphonate ( 0 . 3 4 m l , 2 . 5mmo l ) was added ca re fu l l y . T h e m i x t u r e was then a l l o w e d to w a r m s l o w l y , and a wh i te prec ip i ta te f o r m e d w h i c h r ed i sso l ved as r o o m temperature was reached. T h e so lvent was r e m o v e d by rotary evapora t i on , and the s o l i d res idue was ext racted w i th 5 0 m l o f pe t ro leum ether. W a s h i n g w i t h 2 x 5 0 m l o f water , d r y i ng ove r anhydrous MgSC>4, and r e m o v a l o f the so lvent y i e l d e d 0.65g o f a Expe r imen ta l / 39 c rude y e l l o w product . C o l u m n chromatography w i th pe t ro leum ether as e luant gave 0 .43g (81%) o f whi te crysta ls : m.p. 82 -83°C ; i H - N M R 8 7.6-7.4 (m, 6 H ) , 7.24 (d, 2 H , 8 H z ) , 2.63 (t, 2 H , 7 H z ) , 2 .06 (s, 3 H ) , 1.65 (m, 2 H ) , 1.35 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3011 , 2 9 3 1 , 1 4 9 6 c m - * ; M S m / z 262 (51.5, M + ) , 205 (100, M + - C 4 H 9 ) , exact mass measured 262 .1719 , exact mass ca lcu la ted 262 .1721 . 4 - C h l o r o e t h y n y l - 4 ' -n-pent y l b i pheny l (5d) A so lu t ion o f 4 -e thyny l - 4 ' - n -pen t y l b i pheny l 5b (0 .50g , 2 . 0 m m o l ) i n 1 5 m l o f te t rahydro fu ran was c o o l e d to - 7 8 ° C , and n - b u t y l l i t h i u m ( 1 . 5 m l 1 . 5 M i n h e x a n e , 2 . 2 5 m m o l ) was added s l o w l y to g i v e a pa le y e l l o w s o l u t i o n . T h e so lu t i on was w a r m e d to - 2 5 ° C , and A ^ - c h l o r o s u c c i n i m i d e ( 0 . 29g , 2 . 2 m m o l ) was added to g i ve in i t i a l l y a l i m e green, then y e l l o w mix tu re . A f t e r 2 hours o f s t i r r ing, the m ix tu re was a l l o w e d to c o m e to r o o m temperature and was poured in to 5 0 m l o f aqueous 2 M H C l and 5 0 m l o f d ie thy l ether. T h e organ ic phase was separated and washed w i th 5 0 m l o f aqueous 2 M N a O H and 5 0 m l o f aqueous saturated N a C l , then d r i ed o v e r anhydrous MgSC»4 and f i l tered. T h e solvent was removed to g ive 0 .69g o f a crude y e l l o w product . C o l u m n ch roma tog raphy w i th pe t ro l eum ether as the e luant gave 5 9 m g (12%) o f start ing mater ia l and 0.49g (85%) o f des i red product as wh i te needles: m.p. 115-116°C; Expe r imen ta l / 40 1 H - N M R 8 7.6-7.4 (m, 6 H ) , 7.24 (d, 2 H , 8 H z ) , 2.64 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3012 , 2 9 3 1 , 2221 (med. , sharp), 1 4 9 6 c m ' 1 ; M S m / z 282 (48.0, M + ) , 225 (100, M + - C 4 H 9 ) , exact mass measured 282 .1175 , exact mass ca lcu la ted 282 .1175 . 4-Bromoethynyl-4'-rt-pentylbiphenyl (5e) T h e procedure f o l l o w e d was as above fo r 5d, but N - b r o m o s u c c i n i m i d e (0 .45g , 2 .5mmoI) was used i n p lace o f A^ -ch lo rosucc in im ide . T h e amounts o f other reagents and so lvent were as g i v e n above. T h e crude product , 1.06g o f a f l a k y , b r o w n s o l i d , was c h r o m a t o g r a p h e d u s i n g pe t ro l eum ether as the e luant to g i v e 4 0 m g (8%) o f start ing mater ia l and 0 .45g (68%) o f des i red product as wh i te needles: m.p. range 88 -108°C w i th an orange co lou r deve lop ing at 104°C; i H - N M R 8 7.6-7.4 (m, 6 H ) , 7.24 (d, 2 H , 8 H z ) , 2.64 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m, 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3012 , 2 9 3 1 , 2199 (weak, sharp), 1 4 9 5 c m - 1 ; M S m /z 326 (81.2, M + ) , 269 (100, M + - C 4 H 9 ) , exac t mass measured 326 .0672 , exact mass ca lcu la ted 326 .0671 . Expe r imen ta l / 41 4-Iodoethynyl-4'-n-pentylbiphenyl (5f) T o a so lu t ion o f 4 -e thyny l -4 ' -n -pen ty lb ipheny l 5b (0 .43g, 1.7mmol) i n 2 0 m l o f tetrahydrofuran at - 78°C was added n-bu ty l l i th ium (1 .15ml 1 . 5 M in hexane, 1.7mmol) . A f t e r 30 minu tes o f s t i r r ing , i od ine crys ta ls (0 .44g , 1 .7mmol ) we re added . A s the m ix tu re was a l l o w e d to s l o w l y w a r m to r o o m temperature, the dark b r o w n c o l o u r d i sappeared resu l t i ng i n a y e l l o w so lu t i on . S t i r r i ng was con t i nued overn igh t . T h e so lvent was r e m o v e d by rotary evapora t ion , and the res idue was extracted w i th 5 0 m l o f hexane. F i l t r a t i on through s i l i ca ge l and par t ia l r e m o v a l o f the so lvent resu l ted in the p rec ip i t a t i on o f the p roduc t as co lou r l ess need les . T h e s tar t ing mate r ia l and p r o d u c t w e r e i n d i s t i n g u i s h a b l e b y T L C , and the p r o d u c t was uns tab le to G C c o n d i t i o n s . A n a l y s i s b y * H - N M R s h o w e d less than 1% s tar t ing m a t e r i a l . T h e product y e l l o w s q u i c k l y at r o o m temperature: m.p. range 110-119°C; ! H - N M R 8 7.6-7.4 (m , 6 H ) , 7.25 (d, 2 H , 8 H z ) , 2.63 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m, 4 H ) , 0 .90 (t, 3 H , 7 H z ) ; I R 3013 , 2 9 3 2 , 1 4 9 4 c m " 1 ; M S m /z 374 (70.6, M+) , 317 (100, M + - C 4 H 9 ) , exact mass measured 374 .0533 , exact mass ca lcu la ted 374 .0533 . Expe r imen ta l / 42 l-(Biphenyl-4-yl)-l-pentanone (10) T o a so lu t ion o f b ipheny l (5.0g, 32mmo l ) i n 2 0 m l o f carbon tetrachlor ide at 0 °C was added anhydrous a l u m i n i u m ch lor ide (5.3g, 4 0 m m o l ) i n one por t ion . Immedia te ly , the s l ow addi t ion o f a so lu t ion o f pentanoy l ch lo r ide (4 .0ml , 33mo l ) i n 2 0 m l o f carbon te t rach lor ide f r o m a p ressu re -equa l i z i ng d r o p p i n g f unne l was begun and con t i nued over 15 minutes. A further 10ml o f carbon tetrachlor ide was used to r inse the contents o f the d r o p p i n g f unne l in to the reac t ion m ix tu re . T h e resu l t i ng b lue so lu t i on was st i r red overn ight at r o o m temperature and then re f l uxed for two hours . A f t e r c o o l i n g , the mix tu re was poured onto 50g o f ice and 2 0 m l o f aqueous concentrated H C l to g ive a y e l l o w m ix tu re w h i c h was f i l te red in to a separatory funne l . T h e o rgan ic layer was w a s h e d w i t h 3 x 5 0 m l o f water and d r ied ove r anhydrous MgSC>4. Ro ta r y evaporat ion o f the so lvent gave a c rude , b r o w n product w h i c h by G C ana lys is con ta ined a sma l l amoun t o f b i p h e n y l . R e c r y s t a l l i z a t i o n f r o m m e t h a n o l y i e l d e d 5 .1g (68%) o f a co lour less c rys ta l l ine product : m.p. 79 -80°C (lit. 79°C35); ! H - N M R 8 8.03 (d , 2 H , 8 H z ) , 7.67 (d, 2 H , 8 H z ) , 7.62 (d, 2 H , 8 H z ) , 7.2-7.5 (m , 3 H ) , 2.99 (t, 2 H , 7 H z ) , 1.74 (m, 2 H ) , 1.43 (m, 2 H ) , 0.97 (t, 3 H , 7 H z ) ; I R 3017 , 2 9 6 1 , 1678 (strong), 1 6 0 5 c m " 1 ; M S m / z 238 (15.3, M + ) , 181 (100, M + - C 4 H 9 ) , exac t mass measured 238 .1349 , exact mass ca lcu la ted 238.1358. Exper imen ta l / 43 l-(4'-Nitrobiphenyl-4-yI)-l-pentanone (11) T o a st i r red so lu t ion o f l - ( b i p h e n y l - 4 - y l ) - l - p e n t a n o n e 10 ( l . O g , 4 . 1 m m o l ) in 5 m l o f concentrated H2SO4 at 0 ° C was added po tass ium nitrate (0 .45g, 4 . 5 m m o l ) over f i ve minutes . A f t e r one hour the br ight red so lu t ion was pou red onto 50g o f i ce w i th v i go rous m i x i n g . T h e mix tu re was a l l o w e d to c o m e to r o o m temperature, and the c r e a m c o l o u r e d s o l i d was f i l te red and w a s h e d w i t h 3 x 5 0 m l o f water . T h i n - l a y e r ch roma tog raphy w i t h d i ch lo rome thane as e luant s h o w e d o n l y one produc t w i t h no s tar t ing m a t e r i a l . H o w e v e r , G C i n d i c a t e d the p resence o f a s e c o n d p roduc t . R e c r y s t a l l i z a t i o n o f the crude mater ia l f r o m methano l y i e l ded 0 .66g (57%) o f 11 as l o n g , y e l l o w needles: m.p. 122-123°C (lit. 123°C35) ; 1 H - N M R 8 8.33 (d, 2 H , 8 H z ) , 8.09 (d, 2 H , 8 H z ) , 7.78 (d, 2 H , 8 H z ) , 7.72 (d, 2 H , 8 H z ) , 3.01 (t, 2 H , 7 H z ) , 1.75 (m, 2 H ) , 1.43 (m , 2 H ) , 0.97 (t, 3 H , 7 H z ) ; I R 3018 , 2962 , 1683, 1521 and 1347cm-* (strong); M S m / z 283 (10.6, M+) , 226 (100, M + - C 4 H 9 ) , exact mass measured 283 .1201 , exact mass ca lcu la ted 283 .1208 . 4-Amino-4'-n-pentyIbiphenyl (12) l - ( 4 ' - N i t r o b i p h e n y l - 4 - y l ) - l - p e n t a n o n e 11 ( l g , 3 . 5 m m o l ) , h y d r a z i n e hydrate ( l m l , 2 1 m m o l ) , and 5 m l o f d ie thy lene g l y c o l were re f l uxed (180°C) fo r two hours. A Expe r imen ta l / 44 st ream o f d ry n i t rogen enter ing through a C l a i s e n adapter was used to r emove water f r o m the reac t ion . T o the c o o l e d so lu t ion was added p o w d e r e d po tass ium hyd rox ide (1 .2g, 2 1 m m o l ) , and the mix tu re was re f l uxed overn ight . T h e resu l t ing b r o w n so lu t ion was poured in to 5 0 m l o f aqueous 1 0 % N a O H w h i c h was then extracted w i th 2 x 4 0 m l o f benzene. T h e br ight red organ ic so lu t ion was washed w i t h 5 0 m l o f water , d r ied ove r anhydrous M g S C * 4 and f i l tered. R e m o v a l o f the so lvent by rotary evaporat ion y i e l ded 0 .82g o f c rude orange product . T h i n - l a y e r chromatography us ing d ich lo romethane as the e luant i n d i c a t e d three p roduc ts , the c o l o u r l e s s c o m p o u n d w i t h in te rmed ia te retent ion p r o v i n g to be the des i red amine . C o l u m n ch romatography gave 0 .53g o f a y e l l o w p o w d e r w h i c h was fur ther p u r i f i e d by sub l ima t i on to g i ve 0 .46g (56%) o f co lou r less need les : m.p. 71 -72°C (lit. 7 2 ° C 3 5 ) ; ! H - N M R 8 7.44 (d, 2 H , 8 H z ) , 7.39 (d, 2 H , 8 H z ) , 7 .20 (d, 2 H , 8 H z ) , 6.72 (d, 2 H , 8 H z ) , 3.57 (broad, exchanges w i th D 2 0 , 2 H ) , 2.62 (t, 2 H , 7 H z ) , 1.64 (m, 2 H ) , 1.34 (m , 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3400 (broad), 3022 , 2932 , 1 5 0 0 c m - 1 ; M S m / z 239 (66.4, M + ) , 182 (100, M + - C 4 H 9 ) , exact mass measured 239 .1672 , exact mass ca lcu la ted 239 .1674. F o r m i c p i v a l i c a n h y d r i d e 3 7 O O II II H — C — O — C — C ( C H 3 ) 3 P i v a l o y l ch l o r i de ( 4 . 9 5 m l , 4 0 m m o l ) , o v e n - d r i e d , p o w d e r e d s o d i u m fo rmate (3 .3g , 4 8 m m o l ) and 18 -c rown-6 (0 .5g , 2 m m o l ) we re st i r red r ap i d l y at 0 ° C fo r fou r hours . T h e d isappearance o f the a c i d c h l o r i d e was p e r i o d i c a l l y m o n i t o r e d b y I R Expe r imen ta l / 45 spec t roscopy . T h e m ix tu re was d i s t i l l ed at 0 ° C under h igh v a c u u m in to a trap at - 78°C . T h e co lour less l i q u i d product was stored at - 5 °C : 1 H - N M R 8 9.10 (s, 1H ) , 1.32 (s, 9 H ) ; I R 2 9 8 1 , 1787 and 1762 (strong), 1483, 1 0 4 5 c m " 1 (strong, broad). A / - ( 4 ' - n - p e n t y l b i p h e n y l - 4 - y l ) f o r m a m i d e (15) T o a so lu t ion o f 4 -amino-4 ' -« -pen ty lb ipheny l 12 (0 .55g, 2 .3mmo l ) d i s s o l v e d in 5 m l o f dry d ich loromethane at 0 ° C was added fo rm ic p i va l i c anhydr ide (0 .4ml , approx. 3 m m o l ) . A f t e r f i v e m i n u t e s o f s t i r r i n g , t h i n - l a y e r c h r o m a t o g r a p h y u s i n g d i ch lo romethane as the e luant i nd ica ted that no start ing mate r ia l r ema ined . Ro ta r y evapo ra t i on f o l l o w e d b y v a c u u m p u m p i n g to r e m o v e so lven t t races a n d vo la t i l e products gave .a wh i te so l i d . Rec rys ta l l i za t i on f r o m methano l gave 0 .58g (96%) o f a mix ture o f s-cis and s-trans isomers o f the desi red amide ; m.p. 170-171°C; i H - N M R 8 8.74 (d, 0 . 5 H , 11Hz ) , 8.40 (s, 0 .5H) , 7.83 (d, 0 . 5 H , 1 1 H z ) , 7 .7-7.0 (m, 8 .5H) , 2.65 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m , 4 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3424 (sharp), 3014, 2 9 3 1 , 1695 (strong), 1 5 0 5 c m " 1 ; M S m /z 267 (72.2, M + ) , 210 (100, M + - C 4 H 9 ) , exac t mass measured 267 .1623 , exact mass ca lcu la ted 267 .1623 . O II Expe r imen ta l / 46 4 - I s o c y a n iO-4'-/t-pentyIbiphenyl (4a) N = C 7 V - ( 4 ' - « - P e n t y l b i p h e n y l - 4 - y l ) f o r m a m i d e 1 3 ( 0 . 4 0 g , 1 . 5 m m o l ) a n d d i i sop ropy lam ine (0 .42ml , 3mmo l ) were d i sso l ved i n 6 m l o f d i ch lo romethane , and the so lu t i on was c o o l e d to 0 ° C . P h o s p h o r o y l ch l o r i de (150p. l , 1 .6mmol ) was added d r o p w i s e . A f t e r f i ve minu tes o f s t i r r ing at 0 ° C , th in - laye r ch roma tog raphy u s i n g d ich lo romethane as the eluant ind icated a s ingle product and no start ing mater ia l . Ten mi l l i l i t res o f aqueous 2 0 % N a 2 C 0 3 was added s l o w l y , and the two-phase mix tu re was s t i r red at r o o m temperature f o r f i v e m inu tes be fore b e i n g p o u r e d i n to 4 0 m l o f d i ch lo romethane and 4 0 m l o f water . T h e o rgan ic l aye r was separated and w a s h e d w i t h another 4 0 m l o f water , d r ied ove r anhydrous Na2SC«4 and f i l te red to g ive a pa le y e l l o w so lu t i on . C o l u m n ch romatography o n a l u m i n a u s i n g d i ch lo romethane as the eluant gave a co lour less l i q u i d product w h i c h was q u i c k l y t ransferred to a v a c u u m l ine and so l i d i f i ed by c o o l i n g . F a i l u r e to remove the res idua l so lvent i n the absence o f a i r leads to the fo rmat ion o f b r o w n , tarry mater ia l . U n d e r a dry n i t rogen atmosphere the resu l t ing wh i te , c rys ta l l ine so l i d 0 .32g (87%) melts at 34°C. T h e iso t rop ic mel t coo ls to g ive a nemat ic l i q u i d at approx imate ly 30°C , w h i c h remains at r o o m temperature but reso l id i f i es w i th in a f e w hours . A b lue-green c o l o u r s l o w l y deve lops i n the nemat ic l i q u i d . T h e t rans i t i on temperatures w e r e d e t e r m i n e d b y s u b m e r g i n g the f l a sk con ta in ing the mater ia l under n i t rogen in a water bath w h i c h was s l o w l y wa rmed . 1 H - N M R 8 7.59 (d, 2 H , 8 H z ) , 7.47 (d, 2 H , 8 H z ) , 7.42 (d, 2 H , 8 H z ) , 7.27 (d , 2 H , 8 H z ) , 2.65 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m , 4 H ) , 0 .90 (t, 3 H , 7 H z ) ; I R 3 0 1 1 , 2932 , 2130 (strong, sharp) and 1496 c m " 1 ; Exper imen ta l / 47 M S m/z 249 (20.6, M + ) , 192 (100, M + - C 4 H 9 ) , exact mass measured 283 .1201 , exact mass ca lcu la ted 283 .1208 . T h e preparat ions o f compounds 4 b and 4 c were car r ied out us ing the procedures g iven above fo r c o m p o u n d 4 a . T h e preparat ions were sca led to p r o v i d e app rox ima te l y lOOmg o f the f ina l products. 4 - I s o c y a n o - 4 ' - n - b u t y l b i p h e n y l (4b) m.p. 36 -37°C ; ! H - N M R 8 7.59 (d, 2 H , 8 H z ) , 7.47 (d, 2 H , 8 H z ) , 7.42 (d, 2 H , 8 H z ) , 7.27 (d, 2 H , 8 H z ) , 2.65 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m , 2 H ) , 0.90 (t, 3 H , 7 H z ) ; I R 3011 , 2932 , 2 1 3 0 (strong, sharp) and 1495 c m " 1 ; M S m/z 235(20.9 , M + ) , 192 (100, M + - C 3 H 7 ) . 4 - I s o c y a n o - 4 ' - w - h e x y l b i p h e n y l (4c) m.p. range 9 -19°C ; ! H - N M R 8 7.59 (d, 2 H , 8 H z ) , 7.47 (d, 2 H , 8 H z ) , 7 .42 (d , 2 H , 8 H z ) , 7.27 (d, 2 H , 8 H z ) , 2.65 (t, 2 H , 7 H z ) , 1.65 (m, 2 H ) , 1.35 (m , 6 H ) , 0 .90 (t, 3 H , 7 H z ) ; I R (neat) 3 0 1 1 , 2932 , 2130 (strong, sharp) and 1496 c m - 1 ; M S m/z 263 (32.8, M + ) , 192 (100, M+-C 5 Hn). 48 R E F E R E N C E S 1. Gene ra l references for l i q u i d crysta ls : a) L i q u i d Crys ta ls - T h e Fou r th State o f  M a t t e r : S a e v a , F . D . , E d . ; M a r c e l D e k k e r : N e w Y o r k , 1974. b) de Jeu , W . H . , Physical Properties of Liquid Crystalline Materials; L i q u i d C r y s t a l  M o n o g r a p h s . V o l . 1; G r a y , G . W . , E d . ; G o r d o n and B r e a c h S c i e n c e : N e w Y o r k , 1980. c) Chandrasekhar , S . , L i q u i d C r y s t a l s : C a m b r i d g e U n i v e r s i t y P r e s s : C a m b r i d g e , 1977. d) A d v a n c e s in L i q u i d Crys ta l s . V o l . 1-6; B r o w n , G . H . , E d . ; A c a d e m i c P r e s s : N e w Y o r k , 1975 -1983 . e) L i q u i d C r y s t a l s and P l a s t i c  C r y s t a l s : G r a y , G . W . and W i n s o r , P . E . , E d s . ; John W i l e y & S o n s : N e w Y o r k , 1974. 2. Re in i t ze r , F . , Monatsh. Chem., 9, 421 (1888), as quoted i n reference 5. 3. F r i e d e l , C , Ann. Phys., 18, 273 (1922), as quoted in reference l a ) . 4. D e m u s , D . , D e m u s , H . , and Z a s c h k e , H . , F l u s s i g e - K r i s t a l l e n i n T a b e l l e n ; D e u t s c h e r V e r l a g f u r G r u n d s t o f f i n d u s t r i e : L e i p z i g , 1 9 7 4 , as q u o t e d in reference 5. ^ 5. G r a y , G . W . , Molecular Geometry and the Properties of Nonamphiphilic Liquid Crystals; A d v a n c e s i n L i q u i d C r y s t a l s . V o l . 2 ; A c a d e m i c P ress : N e w Y o r k , 1976 6. S a c k m a n , H . , and D e m u s , D . , Mol. Cryst. Liq. Cryst., 21, 39 (1973). 7. S a c k m a n , H . , Pure Appl. Chem., 38, 503 (1974). 8. D e w a r , M . J . S . , and R i d d l e , R . M . , / . Amer. Chem. Soc, 97, 6658 (1975) 9. G r a y , G . W . , Relationship Between Chemical Structure and Properties for Low Molecular Weight Liquid Crystals; P o l y m e r i c L i q u i d C r y s t a l s ; C i f f e r i , A . , K r i g b a u m , W . R . , and M e y e r , R . B . , E d s . ; A c a d e m i c P r e s s : L o n d o n , 1982; pp . 1-33. 10. G r a y , G . W . , Ha r r i son , K . J . , N a s h , J . A . , Constant , J . , H u l m e , D . S . , K i r t o n , J . , and R a y n e s , E . P . , Liq. Cryst. Ord. Fluids, 2, 617 (1974). 11. D a b r o w s k i , R . and Z y t y n s k i , E . , Mol. Cryst. Liq. Cryst., 87, 109 (1982). 12. H o f f m a n , P . , M a r q u a r d i n g , D . , K l i i m a n n , H . , and U g i , I., Isonitriles; C h e m i s t r y  o f the C y a n o G r o u p : R a p p o p o r t , Z . , E d . ; I n te rsc ience : N e w Y o r k , 1970 ; pp . 853 -883 . 13. W a l b o r s k y , H . M . , a n d P e r i a s a m y , M . P . , Recent Advances in Isocyanide Chemistry; T h e C h e m i s t r y o f Func t i ona l G r o u p s . Supp lement C ; Pa ta i , S . , and Rappopor t , Z . , E d s . ; John W i l e y & Sons : N e w Y o r k , 1983; pp . 835-887 . References / 49 14. B e n - E f r a i m , D . A . , The Preparation of Acetylenes and their Protection: T h e  C h e m i s t r y o f the C a r b o n - C a r b o n T r i p l e B o n d : Pa ta i , S . , E d . ; John W i l e y & S o n s : N e w Y o r k , 1978; pp. 755-812 . 15. Cas t ro , C . E . , and Stephens, R . D . , J. Org. Chem., 2 8 , 2163 (1963). 16. Sonogash i ra , K . , T o h d a , Y . , Hag iha ra , N . , Tetrahedron Lett., 4467 (1975). 17. H e g e d u s , L . S . , Angew. Chem. Int. Ed. Engl., 2 7 , 1113 (1988). 18. T a k a h a s h i , S . , K u r o y a m a , Y . , Sonogash i ra , K . , H a g i h a r a , N . , Synthesis, 627 (1980 ) . 19. E a r b o r n , C , and W a l t o n , D . R . M . , / . Organomet. Chem., 4 , 217 (1965). 20 . T a m u r a , M . , and K o c h i , J . K . , J. Organomet. Chem., 4 2 , 2 0 5 (1972). 2 1 . Jones, R . G . , and G i l m a n , H . , Organic Reactions, 6, 339 (1952). 22 . a) V i l l i e r a s , J . , P e r r i o t , P . , and N o r m a n t , J . F . , Synthesis, 4 5 8 (1975 ) ; b) B e s t m a n n , G . H . , and F r e y , H . , Liebigs. Ann. Chem., 2061 (1980) ; c) L i , P . , and A l p e r , H . , / . Org. Chem., 51,4354 (1986). 23 . M i l l e r , S. I . , Z i eg le r , G . R . , and W i e l e s e c k , R. , O r g a n i c Syntheses . C o l l . V o l . V ; Baumgar ten , H . E . , E d . ; John W i l e y & Sons : N e w Y o r k , 1973; pp . 921 -923 . 24. M u r r a y , R . E . , Synth. Commun., 10, 345 (1980). 25 . D i c k s t e i n , J . I . , and M i l l e r , S . I . , Nucleophilic Attacks on Acetylenes; T h e  C h e m i s t r y o f the C a r b o n - C a r b o n T r i p l e B o n d : Pa ta i , S . , E d . ; John W i l e y & Sons : N e w Y o r k , 1978; pp . 813-955 . 26. T a n a k a , R. , Rodge rs , M . , S imona t i s , R. , and M i l l e r , S.I. , Tetrahedron, 27, 2651 (1971 ) . 27 . U g i , I., Fe tze r , U . , E h o l z e r , U . , K n u p f e r , H . , and O f f e r m a n n , K . , Angew. Chem. Int. Ed. Engl., 4 , 474 (1965). 28 . Sko rna , G . , and U g i , I., Angew. Chem. Int. Ed. Engl, 16, 259 (1977). 29 . N u n a m i , K . , S u z u k i , M . , and Y o n e d a , N . , Synthesis, 840 (1978) . 30 . Obrech t , R. , R u d o l f , H . , and U g i , I., Synthesis, 400 (1985). 3 1 . W e b e r , W . P . , and G o k e l , G . W . , Tetrahedron Lett., 1637 (1972). 32 . B a l d w i n , J . E . , Bo t ta ro , J . C . , R i o r d a n , P . D . , and D e r o m e , A . E . , J. Chem. Soc, Chem- Commun., 943 (1982). References / 50 33 . B e a k , P . , and K o k k o , B . , / . Org. Chem., 47,2822 (1982). 34. a) B o c h e , G . , B e r n h e i m , M . , and Schro t t , W . , Tetrahedron Lett., 23, 5 3 9 9 (1982) ; b) C o l v i n , E . W . , K i r b y , G . W . , and W i l s o n , A . C , Tetrahedron Lett., 23, 3835 (1982) . 35. P a v l y u c h e n k o , A . I . , S m i r n o v a , N . I . , K o v s h e v , E . I . , T i t i v , V . V . , a n d Purvanetskas , G . V . , / . Org. Chem. U.S.SJR., 12, 1066 (1976). 36. V l i e s t r a , E . J . , No l t e , R . J . M . , Z w i k k e r , J . W . , D ren th , W . , and Jansen, R . H . A . M . , Recueil, J. Roy. Netherlands Chem. Soc, 101, 183 (1982). 37. V l i e s t r a , E . J . , N o l t e , R . J . M . , Z w i k k e r , J . W . , and D r e n t h , W . , Recueil, J. Roy. Netherlands Chem. Soc, 101, 460 (1982). 38. a) Car ter , R . E . , Acta Chem. Scand., 22, 2643 (1968) ; b) S i d d a l l , T . H . , Stewart , W . E . , and M a r t s o n , A . L . , J. Phys. Chem., 72, 2135 (1968) ; c ) N i w a , J . , Bull. Chem. Soc Japan, 42,1926 (1969). 39. G r u n d m a n n , C , Chem. Ber., 91,1380 (1958). 40 . W e s t m i j z e , H . , V e r m e e r , P . , Synthesis, 390 (1979) . 4 1 . H o u s e , H . O . , C h u , C . - Y . , W i l k i n s , J . M . , and U m e n , M . J . , J. Org. Chem., 40, 1460 (1975) . 51 S P E C T R A L A P P E N D I X 52 Spect ra l A p p e n d i x / 53 Spect ra l A p p e n d i x / 54 Spect ra l A p p e n d i x / 55 Spect ra l A p p e n d i x / 56 Spect ra l A p p e n d i x / 57 Spect ra l A p p e n d i x / 58 i i 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0060432/manifest

Comment

Related Items