Selective <i>N</i>,<i>N-</i>Dibenzylation of Primary Aliphatic Amines with Dibenzyl Carbonate in the Presence of Phosphonium Salts
作者:Alessandro Loris、Alvise Perosa、Maurizio Selva、Pietro Tundo
DOI:10.1021/jo049840c
日期:2004.5.1
promotes high selectivity toward the benzylated amine and an increase of the reaction rate as well. However, in a single case explored for an amino acidic compound, namely 4-(aminomethyl)benzoic acid [4-(NH2CH2)C6H4CO2H], both N,N-dibenzylation and esterification of the acid group were observed. Analysis of the IR vibrational modes of benzylamine in the presence of tetrabutylphosphonium bromide supports
在催化量的四烷基phosph盐存在下且在无溶剂条件下,脂肪族伯胺(RNH 2:R = PhCH 2,Ph(CH 2)2,正癸基和1-萘甲基)有效地被N-苄基化为相应的RN(CH 2 Ph)2,使用碳酸二苄酯作为苄化剂。与不加盐的反应相比,氨基苯甲酸苄酯的竞争性形成是有利的,salt盐促进了对苄基胺的高选择性并提高了反应速率。然而,在一个单一的案例中研究了一种氨基酸化合物,即4-(氨基甲基)苯甲酸[4-(NH2 CH 2)C 6 H 4 CO 2 H],同时观察到N,N-二苄基化和酸基的酯化。在存在溴化四丁基phosph的情况下对苄胺的红外振动模式进行分析,支持以下假设:这种增强的选择性可能是由于盐与胺之间的酸碱相互作用所致,这增加了胺的空间体积,有利于胺的进攻。碳酸二苄酯的受阻较少的烷基末端上的亲核试剂。