Asymmetric, catalytic, vinylogous aldol reactions using pyrrole-based dienoxy silanes. Enantioselective synthesis of α,β-unsaturated γ-butyrolactam synthons

A practical, catalytic and enantioselective vinylogous Mukaiyama aldol reaction between 2-silyloxypyrrole donors and aromatic or heteroaromatic aldehyde acceptors is described. Using an enantiopure bisphosphoramide catalyst in conjunction with SiCl(4), a variety of alpha,beta-unsaturated-delta-hydroxylated gamma-butyrolactam compounds were synthesized in high yields and with good to excellent levels of site-, diastereo- and enantioselectivity. (C) 2009 Elsevier Ltd. All rights reserved.