Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, USA.
J Am Chem Soc. 2012 Aug 22;134(33):13804-17. doi: 10.1021/ja305441d. Epub 2012 Aug 8.
The influence of alkene functionality on the energetics and kinetics of radical initiated thiol-ene click chemistry has been studied computationally at the CBS-QB3 level. Relative energetics (ΔH°, ΔH(++), ΔG°, ΔG(++)) have been determined for all stationary points along the step-growth mechanism of thiol-ene reactions between methyl mercaptan and a series of 12 alkenes: propene, methyl vinyl ether, methyl allyl ether, norbornene, acrylonitrile, methyl acrylate, butadiene, methyl(vinyl)silanediamine, methyl crotonate, dimethyl fumarate, styrene, and maleimide. Electronic structure calculations reveal the underlying factors that control activation barriers for propagation and chain-transfer processes of the step-growth mechanism. Results are further extended to predict rate constants for forward and reverse propagation and chain-transfer steps (k(P), k(-P), k(CT), k(-CT)) and used to model overall reaction kinetics. A relationship between alkene structure and reactivity in thiol-ene reactions is derived from the results of kinetic modeling and can be directly related to the relative energetics of stationary points obtained from electronic structure calculations. The results predict the order of reactivity of alkenes and have broad implications for the use and applications of thiol-ene click chemistry.
采用 CBS-QB3 方法计算研究了烯键官能团对自由基引发的巯基-烯点击化学的能量学和动力学的影响。对巯基-烯反应的逐步增长机制中所有驻点的相对能量（ΔH°、ΔH(++)、ΔG°、ΔG(++））进行了确定，其中涉及甲基硫醇与一系列 12 种烯烃（丙烯、甲基乙烯基醚、甲基烯丙基醚、降冰片烯、丙烯腈、甲基丙烯酸甲酯、丁二烯、甲基（乙烯基）硅烷二胺、甲基巴豆酸酯、富马酸二甲酯、苯乙烯和马来酰亚胺）之间的反应。电子结构计算揭示了控制逐步增长机制中增长和链转移过程的活化势垒的潜在因素。结果进一步扩展到预测正向和反向增长及链转移步骤的速率常数（k(P)、k(-P)、k(CT)、k(-CT）），并用于模拟整体反应动力学。根据动力学建模的结果得出了巯基-烯反应中烯烃结构和反应性之间的关系，并可以直接与电子结构计算得到的驻点相对能量相关联。研究结果预测了烯烃的反应活性顺序，对巯基-烯点击化学的应用具有广泛的意义。
