Chiral Base-Catalyzed Reductive Aldol Reaction with Trichlorosilane

Significance

In the presence of chiral Lewis base catalysts [(S)-BINAPO or (R,R)-DIOPO] and tri­chlorosilane as the reducing agent, α,β-unsaturated ketones undergo 1,4-reduction and subsequent aldol reaction with aldehydes smoothly and with excellent stereoselectivity (dr up to 99:1 and er up to 99:1). Because 1,2- and 1,4-reductions of α,β-unsaturated aldehydes scarcely happen under these conditions, enals are well tolerated as aldol partners keeping the C=C bond intact.