Stereoselective Oxidative Mannich Reaction of Ketones with Dihydrodibenzo-Oxazepines via a Merger of Photoredox-/Electro-Catalysis with Organocatalysis

Abstract

An enantio- and diastereoselective sp3-sp3 coupling of acyclic/cyclic ketones with dihydrodibenzo-oxazepines has been developed by merging visible light photo-redox- or electro-catalysis with organocatalysis. This approach parallelly utilizes Eosin Y or graphite electrodes for the co-catalyst-free oxidative conversion of dihydrodibenzo-oxazepines to oxazepines, followed by L-Proline catalyzed direct Mannich-type reaction with ketones. A series of enantioenriched dihydrodibenzo-oxazepines have been prepared in high yields and enantioselectivity. This method shows substantial advantages over the existing protocols by using potentially safer starting materials and cheap commercially available catalysts.