在铝粉催化下,以对甲苯磺酰胺(TsNH2)和N-溴代丁二酰亚胺(NBS)为氮源和卤素源,二氯甲烷作溶剂,建立了肉桂酸酯双键上的高度区域选择和立体选择性氨卤加成反应新体系.该法在室温下,无需惰性气体保护可高产率的给出邻位氨基、卤素的加成产物,最高收率可达97%.实验证明,当肉桂酸酯中与双键直接相连苯环上对位具有强给电子基团时(如CH3O),该反应的产率高,同时得到唯一的α-溴β-氨基肉桂酸酯加成产物;当肉桂酸酯中与双键直接相连苯环对位不具有强给电子基团(如CH30)时,该反应的产率较低,同时得到唯一的α-氨基-β-溴的肉桂酸酯加成产物.这一实验结果证明了肉桂酸酯衍生物(缺电子烯键)的氨溴加成反应是一个亲电加成反应.共考察了20种不同结构的肉桂酸酯的氨溴加成反应情况,其产物结构经核磁共振氢谱、碳谱、质谱及元素分析方法进行了确证,并对该反应的机理进行了探讨.
A new system for the high regio- and stereoselective amlnohalogenatlon ot clnnamlc esters wlm NBS and p-toluenesulfonamide (TsNH2) as bromine/nitrogen sources catalyzed by A1 powder in CH2C12 has been developed. This method offered vicinal haloamine products in high yield (up to 97%) at room tem- perature without inert gases protection. The cinnamic esters bearing a strong electron-donating group (e.g., OCH3) on the 4-position of the benzene ring afforded the trans isomer as the sole products of α -bromine and β-amine adductive products up to nearly quantitative yields. However, the cinnamic esters without the strong electron-donating group (e.g., OCH3) or bearing a poor electron-withdrawing group (Br) on the 4-position of the benzene ring, the yield of reaction was decreased and the a-amine and r-bromine adductive products as sole product were afforded. These results of experiment indicated that the aminohalogenation to cinnamic esters catalyzed by Al-powder is an electrophilic addition reaction. In this paper, a series of the aminohalogenation of cinnamic esters (20 samples) has been investigated. All products structure were characterized by elemental analysis, 1H NMR and 13C NMR and the possible reaction pathway have been proposed.