Microwave-Assisted Organocatalytic Enantioselective Intramolecular aza-Michael Reaction with α,β-Unsaturated Ketones

An organocatalytic enantioselective intramolecular aza-Michael reaction of carbamates bearing conjugated ketones as Michael acceptors is described. By using 9-amino-9-deoxy-epi-hydroquinine as the catalyst and pentafluoropropionic acid as a co-catalyst, a series of piperidines, pyrrolidines, and the corresponding benzo-fused derivatives (indolines, isoindolines, tetrahydroquinolines, and tetrahydroisoquinolines) can be obtained in excellent yields and enantioselectivities. In addition, the use of microwave irradiation at 60 degrees C improves the efficiency of the process giving rise to the final products with comparable yields and enantiomeric excesses. Some mechanistic insights are also considered.