Enantioselective aldol reactions catalyzed by chiral phosphine oxides

Abstract

The development of enantioselective aldol reactions catalyzed by chiral phosphine oxides is described. The aldol reactions presented herein do not require the prior preparation of the masked enol ethers from carbonyl compounds as aldol donors. The reactions proceed through a trichlorosilyl enol ether intermediate, formed in situ from carbonyl compounds, which then acts as the aldol donor. Phosphine oxides activate the trichlorosilyl enol ethers to afford the aldol adducts with high stereoselectivities. This procedure was used to realize a directed cross-aldol reaction between ketones and two types of double aldol reactions (a reaction at one/two α position(s) of a carbonyl group) with high diastereo- and enantioselectivities.

Keywords: aldol reaction; diastereoselectivity; enantioselectivity; organocatalysis; phosphine oxides.