Selective para-bromination of phenyl acetate . under the control of zeolites, bases, acetic anhydride or metal acetates in the liquid phase

Abstract

HBr formed during the bromination of phenyl acetate has a major influence on the selectivity of the reaction. Sodium forms of zeolites X and Y increase the selectivity markedly by a process of cation exchange that removes this HBr. Removal of the HBr prevents formation of phenol and allows the bromination of PA to give almost exclusively the para isomer in quantitative yield. Bases, acetic anhydride and some metal acetates also improve the selectivity. These findings offer a variety of strategies for clean synthesis of para-bromophenyl acetate.