Studying the catalytic activity of zeolites in bromination reactions by mechanochemistry; from small scale to continuous synthesis

Bromination reactions represent one of the most useful transformations in organic chemistry as the reaction delivers products with new C–Br bonds that can be further functionalized. Traditionally, bromination of arenes is conducted in solution using molecular bromine, a corrosive and toxic reagent. In this presentation a solvent-free mechanochemical alternative to carry out the bromination of arenes in a ball mill will be described. Key for the mechanochemical protocol was the use of zeolites as recyclable catalysts which enabled the halogenation to proceed using various solid brominating agents. Posterior transfer of the ball milling approach into a continuous mechanochemical protocol using a twin- screw extruder was also accomplished. This new approach features green chemistry aspects of mechanochemistry, and complements other mechanochemical bromination methodologies.