External Base-Free Approach for Copper-Catalyzed N-Arylation of Indoles and Pyrroles in Green Reaction Medium

Abstract

N-Arylated heterocyclic molecules are extensively found as key components in numerous pharmaceutical and agrochemical compounds. Herein, inexpensive 1,10-phenanthroline-assisted copper-catalyzed sustainable greener methodology has been developed for N-arylation of indoles and pyrrole under commercial base and additive-free conditions. Waste biomass–derived water extract of banana peel ash (WEB) has been used as safe reaction medium and base instead of hazardous solvents, and hence, the current green protocol has achieved an environmentally benign profile. Reaction of pyrrole with aryl iodides and electronically diverse indoles with aryl iodides/aryl bromides in the presence of CuI as catalyst, 1,10-phenanthroline as ligand, and WEB as a base and solvent at 100°C has furnished N-arylated product within 12 h. Reaction of indoles with aryl iodides furnished up to 93% yields while aryl bromides resulted in up to 54% yield of the desired product. The utilization of waste biomass derivative for organic transformation reaction is the key step of this protocol, which is in consistence with the goals of green chemistry.