Synthetic modeling of zinc thiolates: Quantitative assessment of hydrogen bonding in modulating sulfur alkylation rates
Synthetic modeling of zinc thiolates: Quantitative assessment of hydrogen bonding in modulating sulfur alkylation rates
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DOI：
10.1073/pnas.0637221100
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发表时间：
2003-04-01
影响因子：
11.1
通讯作者：
Rheingold, AL
中科院分区：
文献类型：
--
作者：
Chiou, SJ;Riordan, CG;Rheingold, AL
一系列单核硫醇锌配合物已被制备并充分表征。配合物与卤代烷的反应生成卤化锌和相应的硫醚，已通过动力学方法进行了研究。在甲苯中，反应遵循二阶速率定律，显示与锌结合硫醇盐对碳亲电子试剂的 S(N)2 攻击一致的活化参数。酰胺 N-H 与硫醇硫的分子内氢键降低了亲核性，因此在 25℃ 下烷基化速率降低了 30 倍以上。 H 键显示出 0.33 (60°C) 的逆 H/D 同位素效应，归因于两种同位素异构体由于零点能量差异而导致的不同 H 键。这些模型研究提供了氢键对锌硫醇激活蛋白相关反应速率的定量评估。
A series of mononuclear zinc thiolate complexes have been prepared and fully characterized. The reactions of the complexes with alkyl halides, leading to zinc halides and the corresponding thioethers, have been examined by kinetic methods. In toluene, the reactions obey a second-order rate law displaying activation parameters consistent with a S(N)2 attack of the zinc-bound thiolate on the carbon electrophile. Intramolecular hydrogen bonding of an amide N-H to the thiolate sulfur reduces the nucleophilicity and consequently, the rate of alkylation more than 30-fold at 25degreesC. The H-bonding shows an inverse H/D isotope effect of 0.33 (60degreesC) ascribed to differential H-bonding for the two isotopomers due to zero point energy differences. These model studies provide quantitative evaluation of H-bonding on reaction rates relevant to zinc thiol-activating proteins.