Organocatalytic and Regiodivergent Mannich Reaction of Ketones with Benzoxazinones

Abstract

In this study, we have developed solvent-controlled regioselective Mannich reaction of cyclicimines (benzoxazinones) with various ketones by using &-proline as catalyst to afford Mannich products in high yields with excellent enantio- and diastereoselectivity. The unsymmetrical ketones produced the linear isomer as the major product in chloroform solvent. On contrary, using the DMSO solvent favoured the formation of branch isomer product with excellent enantio- and diastereoselectivity. The aromatic auxiliary was successfully removed and afforded N-protected chiral amino acid derivative.