Brønsted Acid-Catalyzed Regioselective Coupling between Azoles and Arylcyclobutenes.

Herein, we describe a protocol for Brønsted acid-catalyzed regioselective coupling of azoles such as pyrazoles, 1,2,3-triazole, 1,3,4-triazole, benzotriazole, indazole and tetrazole, to cyclobutenes. These azoles could be directly coupled with various arylcyclobutenes with high site-selectivity, offering a distinct entry to more functionalized cyclobutanes. The usage of inexpensive TsOH•H2O catalyst, broad substrate scope, and open-air conditions make this protocol practically viable. This study not only contributes a feasible tool for selective functionalization of cyclobutenes, but also provides a strategy to introduce cyclobutane moieties into complex molecules.