Aminolysis of <i>O</i>-Aryl Thionobenzoates: Amine Basicity Combines with Modulation of the Nature of Substituents in the Leaving Group and Thionobenzoate Moiety to Control the Reaction Mechanism
作者:Ik-Hwan Um、So-Jeong Hwang、Sora Yoon、Sang-Eun Jeon、Sun-Kun Bae
DOI:10.1021/jo801539w
日期:2008.10.3
nucleophile and nucleofuge, that is, the reaction proceeds through T(+/-) when the leaving aryloxide is less basic than the attacking amine, but through T(+/-) and T(-) when the leaving group is more basic than the amine. However, the reaction mechanism is not influenced by the electronic nature of the substituent X in the nonleaving group. The Hammett plot for the reactions of 2a-f with benzylamine is
动力学研究表明,OY取代的苯基硫代苯甲酸酯(1a-f)和O-4-硝基苯基X取代的硫代苯甲酸酯(2a-f)在80 mol%H2O / 20 mol%DMSO中在25.0 +/- 0.1度下氨解C.通过亲核试剂和亲核试剂之间的碱性差异,通过一种或两种中间体(即两性离子四面体中间体T(+/-)及其去质子化形式T(-))进行反应,即反应通过当离去的芳基氧化物比攻击性胺的碱性差时,T(+/-),但当离去的基团比胺的碱性更高时,则通过T(+/-)和T(-)。然而,反应机理不受非离去基团中取代基X的电子性质的影响。2a-f与苄胺反应的哈米特图由两条相交的直线组成,可以将其解释为速率确定步骤(RDS)中的更改。然而,相同反应的汤川-日野图表现出极好的线性相关性,表明非线性哈米特图不是由于RDS的变化,而是由于电子之间的共振相互作用而使基质的基态稳定而引起的。 -供体取代基X和硫代羰基部分。