Nickel‐Catalyzed Branch‐Selective C−H Alkylation of Indoles and Azoles with Alkenes: An Additive‐ and Solvent‐Free Approach

Abstract

AbstractThe development of sustainable protocols for the synthesis of alkylated heteroarenes is crucial owing to their widespread existence in medicinally relevant and bioactive natural products. Herein, we describe an efficient, additive‐ and solvent‐free approach for the regioselective C−H alkylation of indoles and azoles with alkenes using a nickel catalyst, which proceeds through a chelation‐assistance strategy. The reaction exclusively provided branched alkylated products with the compatibility of alkyl, alkoxy, fluoro, trifluoromethyl, alkene, cyano, ester, and carbonyl groups. This protocol is applicable to other heteroarenes, such as imidazoles and benzimidazoles, providing the desired alkylated products with exclusive Markovnikov selectivity. The synthetic utility and scale‐up of the reaction are demonstrated, and the protocol is in concord with the principles of green chemistry. Alkylation proceeds through facile and reversible C−H nickelation and alkene insertion processes, presumably involving rate‐limiting reductive elimination.