α-Silicon effect assisted Curtin-Hammett allylation using allylcopper reagents derived from 1,3-dienylsilanes.

Cu-catalyzed stereoselective synthesis of ()-δ-silyl--homoallylic alcohols from 1,3-dienylsilane was developed. Mechanistic studies revealed that the borocupration of dienylsilane proceeded through a 1,2-addition pathway to give an allylcopper intermediate with Cu distal to the silyl group. However, the subsequent aldehyde allylation proceeded Curtin-Hammett control to give ()-δ-silyl--homoallylic alcohols with high diastereoselectivities. This method was applied to the synthesis of the C fragment of a polyketide natural product, mycinolide IV.