Search

No Abstract

An asymmetric allylmetalation followed by a silicon-stereodirected cycloaddition gives enantiomerically pure bicyclic compounds. The synthesis of enantiopure 1 (see scheme) in a yield of 65–74 %, 93 % ee, and >98 % de provides an illustration of the efficacy of the method. The preferential formation of 1 rather than its diastereoisomer (32:1), during the cycloaddition step, matches the result predicted by RHF and density functional theory studies.

A highly selective cis-fusionis observed for the reaction of the chiral 1,3-dipole equivalent 1with cyclic enone 2to form the bicyclic cyclopentenone 3. This multistep method, which does not require isolation of intermediates, is conceptually analogous to the Robinson annulation and should find wide applicability.

No Abstract