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UBC Theses and Dissertations

Synthesis and reactions of a 2-cyclopenten-1-one d³ synthon Nadarajah, Sivakumar


This thesis describes the preparation of 3-trimethylstannyl-2-cyclo-penten-1-one 14 via the higher order stannylcuprate 78, a new reagent prepared to convert 3-iodo-2-cyclopenten-1-one 75 to the desired product. The observations made from this chemistry led to the development of "one-pot" cuprate formation which was demonstrated to be a viable and practically convenient way to generate such species compared with traditional methods. This thesis also describes the preparation of 3-tert-butyldimethyl-siloxy-1-trimethylstannylcyclopentene 83, its conversion into the corresponding lithio species, and reaction of the latter reagent with electrophiles. Thus, transmetalation of 83 with methyllithium produced 1—lithio— 3-tert-butyldimethylsiloxycyclopentene 84, which reacted smoothly at -78°C in tetrahydrofuran with alkyI halides, aldehydes, and ketones, providing the corresponding products in good yield. Treatment of the vinyllithium reagent 84 with 1 equiv. of phenylthiocopper or cuprous cyanide at -78° C for 1 h gave solutions of the corresponding cuprate reagents 103 and 104, respectively. Similarly the corresponding Grignard reagent 105 was made by addition of 1 equiv. of magnesium bromide to the solution of 84 at -78°C. The reagents thus produced reacted in a conjugate sense, the latter catalyzed by copper (I) bromide-dimethylsulphide complex, to enones such as 2-cyclopenten-1-one and 2-cyclohexen-l-one, affording the corresponding products 106 and 107 in excellent yields. β-lodo enones such as 3-iodo-2-cyclopenten-1-one 75 and 3-iodo-2-cyclohexen-1-one 7 also reacted with the cuprate 103 in a conjugate sense to give the corresponding products 108 and 109 in excellent yields. The cyanocuprate 104 prepared by a "one-pot" process also reacted with 3-iodo-2-cyclopenten-1-one 75 to give the enone 108 in good yield. [See Thesis For Diagrams]

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