Asymmetric synthesis of octahydroindoles via a domino robinson annulation/5-endo intramolecular aza-michael reaction

摘要

A straightforward two-step asymmetric synthesis of octahydroindoles has been developed based on two complimentary strategies: (i) an organocatalyzed Michael reaction followed by a tandem Robinson-aza-Michael double cyclization catalyzed by PS-BEMP; (ii) a diastereoselective cyclization, which formally constitutes a remote 1,6 asymmetric induction mediated by PS-BEMP. This allowed the construction of complex octahydroindoles with up to 4 stereocenters, excellent enantioselectivities (up to 95% ee) and complete diastereoselective control in a single pot operation. DFT calculations were performed to understand the origin of this effect.