Dual-Organocatalyst-Promoted Asymmetric Cascade Reaction: Highly Efficient Construction of Enantiopure Fully Substituted Tetrahydro-1,2-oxazines

A four-component asymmetric alpha-aminoxylation/aza-Michael/Mannich cascade reaction for the construction of fully substituted chiral tetrahydro-1,2-oxazine derivatives was accomplished in high yields with excellent enantio- and diastereoselectivities under mild conditions. The 1,2-oxazine derivative could be transformed to the corresponding multifunctional chiral amino alcohol by N-O cleavage and fused-tricyclic 4-amino-substituted tetrahydroquinolines in good yields with excellent stereoselectivities followed by a Friedel-Crafts reaction. Also a 4-alkoxy-substituted tetrahydroquinoline was achieved by C-4 inversion of a 4-amino-substituted tetrahydroquinoline.