GENERATION, REARRANGEMENTS AND SOME SYNTHETIC USES OF BISHOMOALLYLLITHIUMS

A general preparative method for bishomoallyllithiums consists of reductive lithiation by 4,4'-di-teri-butylbiphenylide (LDBB) of bishomoallyl phenyl sulfides, which can be prepared by (1) thioacetalization of gamma,delta-unsaturated ketones followed by replacing one of the phenylthio groups with an alkyl group or a hydrogen or (2) Wittig or Peterson olefination of gamma-(phenylthio)ketones prepared in turn by conjugate addition of phenylthiomethyl cuprates to enones in the presence of chlorotrimethylsilane. Several of the secondary and tertiary bishomoallyllithiums rearrange to primary bishomoallyllithiums via cyclobutylcarbinyllithium intermediates. An oxyanionic group on a carbon atom adjacent to the lithium-bearing carbon atom has a remarkable accelerating effect on the ring closure to a 4-membered ring. Formylation of some bishomoallyllithiums affords the precursors of type-II intramolecular ene reactions, which generate six membered ring compounds when subjected to Lewis acid-catalyzed cyclization.