Catalytic enantioselective synthesis of chiral γ-butyrolactones.

A tandem catalytic asymmetric aldol reaction/cyclization of ß,γ-didehydro-γ-lactones with aldehydes was achieved using chiral tin dibromide as a chiral precatalyst and sodium alkoxide as a base precatalyst. Optically active trans-ß,γ-disubstituted γ-butyrolactones were selectively obtained in moderate to high yields with up to 99% ee from γ-aryl-substituted ß,γ-didehydro-γ-butyrolactones and bulky aliphatic aldehydes.