Bifunctional organometallic reagents: Preparation and use in annulation sequences

he use of bifunctional organometallic reagents (182, 35, and 271) to afford novel annulation products, such as the trans-fused bicyclo (3.3.0) octane (236) and bicyclo (4.3.0) nonane (83) systems and highly functionalized cyclopentene (273) systems, was investigated.;The bifunctional reagent 132, was obtained in three steps from the bromo alcohol 134 via the alcohol 133 and the tosylate 158. The novel functionalized allylcopper(I) reagents, 162 and 182, were prepared from the corresponding allylstannanes 132 and 183 by treatment with methyllithium followed by ;A general annulation method for the preparation of trans-fused bicyclo (3.3.0) octane and bicyclo (4.3.0) nonane systems from a cyclopentanone system 61 was also developed. A palladium(0) catalyzed methoxycarbonylation of the alkenyl triflate 67, obtained from the keto ketal 61, provided the ;A copper(I) chloride-mediated intramolecular coupling reaction of alkenyltrimethylstannane moieties was used to provide highly substituted cyclopentene systems (273). Addition of 271, generated from 183 by treatment with methyllithium, to...