Remarkable Phosphine-Effect on the Intramolecular Aldol Reactions of Unsaturated 1,5-Diketones: Highly Regioselective Synthesis of Cross-Conjugated Dienones

Abstract

We report a phosphine-mediated intramolecular aldol cyclization of unsaturated diketones that proceeds with extremely high levels of regioselectivity for the cross-conjugated bicyclic dienone products. The sense of regioselectivity observed in this reaction is complementary to that obtained using traditional aldol conditions. Experimental evidence that supports the involvement of a phosphine Michael adduct is described.