Environmentally-Benign and Rapid Bromination of Industrially-Important Aromatics Using an Aqueous CaBr2−Br2System as an Instant and Renewable Brominating Reagent

Abstract

Selective bromination of various industrially and pharmaceutically important substituted aromatics using an aqueous CaBr2−Br2 system as an instant and renewable brominating reagent is disclosed. The direct bromination of anilines and phenols with molecular bromine in solution often results in polybromination, and when brominated in the presence of oxidants, they also get oxidized rather than undergoing substitution and, in some cases, require protection of the amino (−NH2) group. We report instantaneous, facile, and regiospecific bromination of industrially important substituted anilines, phenols, aldehydes, and anilides in excellent yields and purity under ambient conditions. The byproduct HBr waste has been utilized effectively, and the brominating reagent has been rejuvenated and reused in the subsequent brominations without any significant loss of reactivity.