UBC Theses and Dissertations
(Z)-4-(Trimethylstannyl)-1,3-Butadienes : preparation and uses in organic synthesis Tillyer, Richard D.
This thesis is divided into three parts. Part 1 describes the chemistry of dilithium (trimethylstannyl)(2-thienyl)(cyano) cuprate (61). This higher order cuprate reagent efficiently transfers the trimethylstannyl group, in a conjugate sense, to a variety of α,β-unsaturated carbonyl compounds. Also, it reacts with α,β-acetylenic esters 43 to give, stereoselectively, (Z)-β-trimethylstannyl α,β-unsaturated esters 46. Part 2 describes the stereoselective preparation of (Z)-β-trimethylstannyl α,β-unsaturated aldehydes/ketones 151 via the Pd(0)-catalyzed reactions of α,β-acetylenic aldehydes and ketones 115 with hexamethylditin. Compounds 151 were converted into stannyldienes 166 via Wittig olefinations. The aldehydes 151 (R¹=H) undergo Wittig-Horner olefination. For example, reaction of 154 with the sodio-phosphonate reagent prepared from diisopropyl rm-butylphosponoacetate 179, afforded 180. The stannyldienes 166 are synthetic equivalents of the diene donor synthon 183. For example, transmetallation of 169 with methyllithium, followed by alkylation of the resulting alkenylithium species with ethylene oxide, provided 187. The third section describes the synthesis of 6-endo-(1-alkenyl)bicyclo[3.1.0]hexan-2-ones 237 (R¹=H) from stannyldienes 250. The stannyldienes 250 were converted into the corresponding iodo dienes 249, which undergo Pd(0)-catalyzed cross coupling with the reagent 246 to give the diene esters 241. Compounds 241 were converted into diene diazoketones 240 which, upon reaction with an appropriate transition metal catalyst, provided, stereospecifically, the ketones 237 (R¹=H). The ketones 237 (R¹=H) are excellent precursors to functionalized, substituted 6-endo-(1-alkenyl)bicyclo[3.1.0]hex-2-enes 215 (R¹=H). The cis divinylcyclopropanes 215 undergo facile, clean and efficient Cope rearrangement to the bicyclo[3.2.1]octa-2,6-dienes 216 (R¹=H). The rates of a number of these Cope rearrangements were measured at 43'C using ¹H nmr spectroscopy. The effects of different substituents on the rate of Cope rearrangement were rationalized in terms of steric and/or electronic factors.
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