Mechanochemical Bromination of Naphthalene Catalyzed by Zeolites: From Small Scale to Continuous Synthesis

Catalyzed reactions of organic substrates that operate continuously by extrusion techniques are rare. In this study, we developed a mechanochemical bromination of unactivated naphthalene (1) with 1,3-dibromo-5,5-dimethylhydantoin (DBDMH), catalyzed by zeolites in a ball mill. The use of DBDMH enabled the atom economy of the reaction to be superior compared to the other brominating agents evaluated. Among the zeolites tested, a FAU-type zeolite demonstrated high catalytic activity and recyclability. The success of the bromination route on a small scale enabled the development of a continuous catalyzed bromination of 1 by twin-screw extrusion.