一系列S-烷基和S-芳基硫代乙酸酯(包括S-乙酰辅酶A )在25°C水溶液中的碱性水解速率(k HO–)与共轭酸的p K a相关(以对数形式)硫醇盐离去基团的β-基团的斜率(βl.g.)为–0.33。与相应的氧酯相比,就给定离去物质的碱性而言,硫酯对氢氧根离子的反应性低1-2个数量级,并且几乎不分散到芳基和烷基离去基团中,这归因于硫羟乙酸盐的较低空间敏感性。酯与氧类似物相比。β的小值l.g.S-的反应性比O-酯低,这是碱性水解的双分子缔合(B Ac 2)机理的证据。所述ë 2路由由缺乏氘掺入到水解的(乙酸盐)的产品中排除。尽管硫醇乙酸盐具有可接受的酸度,但即使在高的非生理pH下,在水溶液中仍形成动力学上无足轻重的酯缀合物碱,因此S-乙酰辅酶A不会通过E 1cB途径水解。
A simple, base-free preparation of S-aryl thioacetates as surrogates for aryl thiols
作者:Adri van den Hoogenband、Jos H.M. Lange、Raymond P.J. Bronger、Axel R. Stoit、Jan Willem Terpstra
DOI:10.1016/j.tetlet.2010.10.125
日期:2010.12
A mild method for the preparation of S-aryl thioacetates by hetero cross-coupling reactions of aryl bromides or aryl triflates with potassium thioacetate is described. The reaction proceeded smoothly in toluene at 110 °C, mediated by catalytic Pd2(dba)3 in combination with CyPF-tBu as the ligand. Neither the presence of a base nor microwave conditions were required. The formed S-aryl thioacetate proved
描述了通过芳基溴化物或芳基三氟甲磺酸酯与硫代乙酸钾酯的杂交联反应制备S-芳基硫代乙酸酯的温和方法。反应在110°C的甲苯中顺利进行,这是由催化性Pd 2(dba)3与CyPF- t Bu作为配体的结合介导的。既不需要存在碱也不需要微波条件。形成的S-芳基硫代乙酸酯证明在快速色谱条件下稳定,在温和的碱性条件下可以快速转化为相应的硫醇。
Newman, Joyce K., Spectrochimica Acta - Part A Molecular Spectroscopy, 1969, vol. 25, # 4, p. 897 - 898