Murai Masahito, Okada Ryo, Asako Sobi, Takai Kazuhiko
Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan.
Chemistry. 2017 Aug 10;23(45):10861-10870. doi: 10.1002/chem.201701579. Epub 2017 Jul 21.
Stoichiometric amounts of oxidants are widely used as promoters (hydrogen acceptors) in dehydrogenative silylation of C-H bonds. However, the present study demonstrates that silylative and germylative cyclization with dehydrogenation can proceed efficiently, even without hydrogen acceptors. The combination of [RhCl(cod)] and PPh was effective for both transformations, and allowed a reduction in reaction temperature compared with our previous report. Monitoring of the reactions revealed that both transformations had an induction period for the early stage, and that the rate constant of dehydrogenative germylation was greater than that of dehydrogenative silylation. Competitive reactions in the presence of 3,3-dimethyl-1-butene indicated that the ratio of dehydrogenative metalation and hydrometalation was affected by reaction temperature when a hydrosilane or hydrogermane precursor was used. Further mechanistic insights of oxidant-free dehydrogenative silylation, including the origin of these unique reactivities, were obtained by density functional theory studies.
化学计量的氧化剂在C-H键的脱氢硅基化反应中被广泛用作促进剂（氢受体）。然而，本研究表明，即使没有氢受体，脱氢的硅基化和锗基化环化反应也能高效进行。[RhCl(cod)]和PPh的组合对这两种转化均有效，与我们之前的报告相比，反应温度有所降低。对反应的监测表明，两种转化在早期都有一个诱导期，并且脱氢锗基化的速率常数大于脱氢硅基化的速率常数。在3,3-二甲基-1-丁烯存在下的竞争反应表明，当使用硅烷或锗烷前体时，脱氢金属化和氢金属化的比例受反应温度的影响。通过密度泛函理论研究获得了无氧化剂脱氢硅基化反应的进一步机理见解，包括这些独特反应性的起源。
