TEBABr_3对苯胺类的溴代反应

Bromination of Anilines by TEBABr_3

作者在三乙基苄基氯化铵和溴酸钠的水溶液中加入氢溴酸,以高产率制得 PhCH2Et3N+·Br3-（TEBABr3,1）。1为橙色固体,m.p.73～74℃,能在 CH3OH-CH2Cl2介质中于 NaH-

We report herein the bromination of anilines(2)by the new brominating agent triethylbenzylammonium tribromide(TEBABr_3,1),which was prepared by the reaction of triethylbenzylammonium chloride with sodium bromate and hydrobromic acid in aqueous solution.A variety of twelve anilines was brominated in a CH_2Cl_2-CH_3OH medium in the presence of NaHCO_3,yielding the corresponding polybrominated products in excellent yields(Tab 1).It is noticeable that the presence of methanol has proved essential to the initiation of the reaction.The bromination of anilines described above was characterized by the ease and quicknessof the reactions,simplicity and mildness of the reaction conditions,and excellent yields.Itis expected that this procedure would turn out to be a highly useful method for the bromi-nation of anilines. General procedure:To a solution of 0.01mol of p-O_2NC_6H_4NH_2 and 0.02mol of TEBABr_3 in 25mL CH_2Cl_2and 10mL CH_3OH was added 0.02mol NaHCO_3.The mixture was stirred at room temperatureuntil the orange color of the solution was decolorized.The precipatate was filtered out and reerystallized from ethyl alcohol,yielding 2.80g of 2,6-dibromo-4-nitroaniline(94.6%),m.p.207～208℃.