Nucleophile-Initiated Thiol-Michael Reactions: Effect of Organocatalyst, Thiol, and Ene
Nucleophile-Initiated Thiol-Michael Reactions: Effect of Organocatalyst, Thiol, and Ene
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DOI：
10.1021/ma101069c
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发表时间：
2010-08-10
期刊：
影响因子：
5.5
通讯作者：
Bowman, Mark
中科院分区：
文献类型：
--
作者：
Chan, Justin W.;Hoyle, Charles E.;Bowman, Mark
详细评价硫醇迈克尔反应的动力学之间的己烷乙烷和丙烯酸己酯的描述。结果表明，伯胺是比仲胺或叔胺更有效的催化剂，例如，在500 s内实现定量转化，在己胺的情况下，在0.057 mol %的催化剂负载下，表观速率常数为53.4 mol L-1 s（-1）。某些叔膦，特别是三正丙基膦和二甲基苯基膦，显示出甚至在比用于己胺的浓度低2个数量级的浓度下是甚至更有效的物质，并且在溶液中进行，在约10分钟内达到定量转化。100 s，表观速率常数分别为1810和431 mol L-1 s（-1）。硫醇的性质也被证明是一个重要的考虑因素，巯基乙醇酸酯和巯基丙酸酯的反应性明显高于己烷硫醇，反应性反映了硫醇的pK（a）。同样，它表明，活化的烯的结构也是至关重要的活化程度和烯取代模式的重要特征，在确定反应性。在正己基胺催化下，与正己基乙烷的反应顺序为：丙基马来酰亚胺>富马酸二乙酯>马来酸二乙酯>二甲基丙烯酰胺>丙烯腈>巴豆酸乙酯>肉桂酸乙酯>甲基丙烯酸乙酯。
A detailed evaluation of the kinetics of the thiol-Michael reaction between hexanethiol and hexyl acrylate is described. It is shown that primary amines are more effective catalysts than either secondary or tertiary amines with, for example, quantitative conversion being achieved within 500 s in the case of hexylamine with an apparent rate constant of 53.4 mol L-1 s(-1) at a catalyst loading of 0.057 mol %. Certain tertiary phosphines, and especially tri-n-propylphosphine and dimethylphenylphosphine, are shown to be even more effective species even at concentrations 2 orders of magnitude lower than employed for hexylamine and performed in solution with quantitative conversions reached within ca. 100 s for both species and apparent rate constants of 1810 and 431 mol L-1 s(-1), respectively. The nature of the thiol is also demonstrated to be an important consideration with mercaptoglycolate and mercaptopropionate esters being significantly more reactive than hexanethiol with reactivity mirroring the pK(a) of the thiols. Likewise, it is shown that the structure of the activated ene is also crucial with the degree of activation and ene-substitution pattern being important features in determining reactivity. In terms of reaction with hexanethiol in the presence of hexylamine as catalyst, it is shown that propylmaleimide > diethyl fumarate > diethyl maleate > dimethylacrylamide > acrylonitrile > ethyl crotonate > ethyl cinnamate > ethyl methacrylate.