Chromium catalyzed acceptorless dehydrogenative (cross)coupling of primary amines to secondary imines

We present here acceptorless dehydrogenative coupling of primary amines to form secondary aldimines catalyzed by a complex of Earth-abundant chromium. The reaction is promoted by Cr(DAFO)(CO)4 (DAFO = 4,5-diazafluorene-9-one) without using any additives, base or oxidant generating NH3 and H2 as sole by-products. Dehydrogenative cross-coupling of primary amines with aniline derivatives to unsymmetrical secondary imines was also achieved with good to excellent yields. A probable mechanism is proposed based on the stoichiometric investigation and computational studies.