Nickel-catalyzed sustainable synthesis of N-heterocycles through dehydrogenative coupling of alcohols

Abstract

The synthesis of N-heterocycles is considered to be an emerging field in synthetic chemistry owing to their application in the pharmaceutical as well as bulk and fine chemical industries. The disadvantages associated with the classical methods for the synthesis of these N-heterocycles involves multiple synthetic steps, scarcity of the starting materials and stoichiometric waste generation. Acceptorless dehydrogenative coupling and borrowing hydrogen methodology provide an alternative protocol to synthesize the N-heterocycles in a sustainable and environmentally benign way. This protocol is atom economical and produces hydrogen (or H2O2) and water as byproducts. In this regard, earth-abundant metal catalysts have shown promising activity. In particular, enormous progress has been observed lately with nickel catalysts which exhibited good catalytic efficacy. The focus of this review is to account for the recent progress of the nickel-catalyzed dehydrogenative coupling of alcohols to synthesize the N-heterocycles, their substrate scope and a brief discussion of the mechanism.