A New Synthesis and Stereocontrolled Functionalization of Substituted Silacyclopent-3-enes

C2-Substituted silacyclopent-3-enes have been prepared in good yields in two steps starting from commercially available diallylsilane 9. Coupling between carbanion of 9 and aldehydes or epoxides followed by ring-closing metathesis of the corresponding substituted diallylsilanes led to various silacyclopent-3-enes having a beta- or a gamma-hydroxysilane moiety. Dihydroxylation and epoxidation of the sila-cycle then led stereoselectively to polyhydroxylated silacyclopentanes. These processes were shown to occur with opposite topicity, offering a complementary and stereocontrolled access to diastereomeric polyols having up to five contiguous stereogenic centers.