The reactions of <i>O</i>
-(4-nitrophenyl) <i>S</i>
-aryl dithiocarbonates with anilines: Effects on the relative nucleofugality
作者:José G. Santos、Marcela Gazitúa
DOI:10.1002/poc.3818
日期:2019.1
studies were investigated for the reactions of S‐phenyl, S‐(4‐chlorophenyl), and S‐(4‐nitrophenyl) O‐(4‐nitrophenyl) dithiocarbonates with anilines. These were performed in the presence of 0.1M borate buffer in 44 wt% aqueous ethanol. For reactions of the 3 substrates, the mechanism is stepwise with 2 tetrahedral intermediates, one zwitterionic (T±), and the other anionic (T−), where the intermediate T−
动力学和高效液相色谱研究调查了S-苯基,S-(4-氯苯基)和S-(4-硝基苯基)O-(4-硝基苯基)二硫代碳酸酯与苯胺的反应。这些在存在于44重量%乙醇水溶液中的0.1M硼酸盐缓冲液中进行。对于3个基板的反应,该机制是阶段性地2种四面体中间体,一种两性离子(T ±),以及其他阴离子(T - ),其中所述中间T,-通过在T质子转移形成±到硼酸盐缓冲液。非离去基团不是被动的,在基团的相对核逸性中起重要作用,这在很大程度上取决于其吸电子能力。尽管它们的碱度不同(3 p K a单位),但来自同一四面体中间体的4-硝基酚酸根离子和4-硝基苯基硫醇盐的核易性相似。在S-(4-硝基苯基)O-(4-硝基苯基)二硫代碳酸酯的反应中,亲核试剂从吡啶(仅4-硝基苯酚离子为核沉子)变为苯胺(2个核苷酸)的亲核试剂的变化表明,胺的性质对基团的相对核易变性。