Regioselective one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles over Ag–Zn-based nanoheterostructured catalysts

Abstract

Reported herein is the first viable copper-free bimetallic catalyst for one pot multicomponent synthesis of 1,4-disubstituted 1,2,3-triazoles. A simple thermal procedure followed by two separate solution-phase synthesis methods have been designed to develop a series of Ag-based NPs (namely Ag and Ag₂O) supported on the nanorod architecture of ZnO. Utilizing the as-synthesized NPs as the catalyst, we present the first one-step synthesis of 1,4-disubstituted 1,2,3-triazoles at room temperature, in which both benzyl bromides and aryl amines afford their respective benzyl azides and phenyl azides in situ under mild reaction conditions. The catalytic role of the as-synthesized nanoheterostructures was compared with their individual counterparts, revealing that the distinct structural features and oxidation state of Ag in Ag–ZnO and Ag₂O–ZnO NPs play a crucial role in the unprecedented catalytic behaviour. Among all, Ag₂O–ZnO emerges as the dominant catalyst for the regioselective AAC reaction. Our catalytic protocol eliminates the usage of any external additives, harsh reaction conditions and time-consuming catalyst synthesis. High recoverability of the catalyst (for at least eight catalytic cycles) made the process more useful. The 100% regioselectivity is strongly validated by a single crystal X-ray structure of one of the desired products. It also covers a broad substrate range with extensibility to some medicinally important drug molecules. Because of its gram-level scalability, the protocol can also be designed for industrial use.