Microwave-Assisted Tandem Cross Metathesis Intramolecular Aza-Michael Reaction:  An Easy Entry to Cyclic β-Amino Carbonyl Derivatives

Abstract

Hoveyda−Grubbs catalyst in combination with BF 3 ·OEt 2 efficiently promotes tandem cross metathesis intramolecular aza-Michael reaction between enones and unsaturated carbamates resulting in the creation of β-amino carbonyl units. The use of microwave irradiation dramatically accelerates the process, enhancing the synthetic utility of this methodology for the preparation of these types of derivatives. When enantiomerically enriched α-branched amines were used as starting materials, the process was also very efficient, although with modest selectivity in the newly created stereocenter. The use of microwave irradiation led to an interesting effect, inverting the selectivity in the addition process.