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 CaBr 2 -Br 2 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 (-NH 2 ) 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.

Recent Update on Transition Metal‐Free C(sp2)−H Bond Halogenation in (Hetero) Arenes

“…Kumar et al in 2011 developed a methodology in an aqueous CaBr 2 -Br 2 system [24][25] to efficiently brominate various organic systems (21) like aromatic aldehydes, anilides, anilines and phenols. Anilines and phenols with electron withdrawing substituents (e. g. COOH, NO 2 ) also produced brominated products with high yields and purity.…”

“…Bromide-bomate couple [63] H 2 O 2 , alkali metal halide [49] Bareluenga Reagent [41] (IPy 2 BF 4 ) DMSO /HBr [32] Phosphine sulfide /NXS [103] (X=Cl/Br/I) NH 4 Br Oxone [30] CaBr 2 -Br 2 system [24,25] DBH [66] TBABr [64] Ts 2 O (tosic anhydride)…”

Bromination of Phthalate-Containing Systems Obtained From Industrial Waste

“…Экспериментальные исследования посвящены изысканию и обоснованию оптимальных условий бромирования сложноэфирного пластификатора, полученного из отходов производства бутанола, а также оценке влияния природы среды на его эффективность. Большинство бромсодержащих соединений в настоящее время получают в различных средах [8][9][10][11][12][13][14][15] с использованием бромирующих агентов [16][17][18][19][20][21][22]. Однако применение растворителей оказывает отрицательное воздействие на качественные характеристики получаемой продукции, экономические показатели производства и налагает определенные требования на технологические параметры: температуру, скорость введения брома и т.д.…”

Bromination of Aromatic Amines

“…Kumar L. et al have reported [51,52] about the selective bromination of various substituted aromatic compounds of industrial and pharmacological significance with the use of an aqueous solution of CaBr2Br2. The derivatives of anilines and phenols with such strong electron-acceptor groups as carbonyl, nitro showed the good reactivity with the brominating reagent, and in a short reaction time were brominated with good yield (92-98%) and purity (>99%).…”