Copper(I) tert-Butoxide-Promoted 1,4 Csp2-to-O Silyl Migration: Stereospecific Allylation of (Z)-γ-Trimethylsilyl Allylic Alcohols

[reaction--see text] The cyclic silyl ethers, 2,2-dimethyl-1-oxa-2-sila-3-cyclopentenes, were produced by the treatment of (Z)-gamma-trimethylsilyl allylic alcohols with a catalytic or stoichiometric amount of lithium tert-butoxide. On the other hand, successive treatment of the alcohols with copper(I) tert-butoxide and allylic halides followed by the tetrabutylammmonium fluoride assisted hydrolysis produced the allylation products, 2,5-alkadien-1-ols, with complete retention of configuration of the double bond.