Asymmetric synthesis of 4H-1,3-oxazines: enantioselective reductive cyclization of N-acylated beta-amino enones with trichlorosilane catalyzed by chiral Lewis bases.

N-Acylated beta-amino enones reductively cyclize by treatment with trichlorosilane and a chiral Lewis base catalyst to afford optically active 4H-1,3-oxazines, which can be transformed to other chiral compounds without racemization.