Catalytic aerobic production of imines en route to mild, green, and concise derivatizations of amines

Abstract

The development of a general, mild, and chemoselective catalytic aerobic oxidation of amines to imines is described. The combination of a less sterically demanding and electron-deficient new N-oxyl radical (ketoABNO: 5) and copper(I) salt is key for the high catalytic activity and allows for the use of molecular oxygen as the stoichiometric oxidant producing H₂O as the sole side-product. The novel method is extendable to a direct α-derivatization of secondary amines via sequential aerobic oxidation of amines to imines followed by C–C bond-formation to the resulting imines, including the novel catalytic asymmetric aerobic cross-dehydrogenative coupling reaction. Mechanistic insight into the novel catalytic system is also discussed.