理论研究“受阻路易斯酸碱对”催化的烯醇硅醚氢化反应机理  

Mechanism of Silyl Enol Ethers Hydrogenation Catalysed by Frustrated Lewis Pairs: A Theoretical Study

作　　者：王英辉 魏思敏 段金伟[1] 王康[1] Yinghui Wang;Simin Wei;Jinwei Duan;Kang Wang(College of Science,Chang’an University,Xi’an 710064,China;Co-construction Collaborative Innovation Center for Chinese Medicine Resources Industrialization by Shaanxi&Education Ministry,Shaanxi University of Chinese Medicine,Xianyang 712083,China)

机构地区：[1]长安大学理学院,西安710064 [2]陕西中医药大学陕西中药资源产业化省部共建协同创新中心,咸阳712083

出　　处：《化学学报》2021年第9期1164-1172,共9页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.21705029,21804066);陕西省高校科协青年人才托举计划(No.20190307);陕西省自然科学基金(No.2021JQ-221);长安大学中央高校基本科研业务费专项资金(No.300102120303);陕西省教育厅自然科学研究项目(No.19JK0233)资助。

摘　　要："受阻路易斯酸碱对"(FLPs)催化的烯醇硅醚氢化反应是一类重要的直接合成醇类化合物的方法,然而目前其反应机理仍不明确.基于此,以乙基取代的全氟苯基硼作为路易斯酸(Et-B(C_(6)F_(5))_(2)),三叔丁基膦(t-Bu_(3)P)作为路易斯碱,烯醇硅醚化的苯乙酮(Me-TMS)作为底物建立了模型反应,并使用密度泛函理论系统研究了其催化氢化反应机理.结果显示:FLPs催化的烯醇硅醚氢化反应从Et-B(C_(6)F_(5))_(2)和t-Bu_(3)P形成B-P-FLPs开始,随后会依次经过H2裂解, H^(+)和H^(-)转移等过程,其中H^(+)转移为决速步, H^(-)转移无势垒, B-P-FLPs生成及H^(+)转移是吸热反应.升高温度不利于氢化反应发生,但是增大压力可促进反应进行.底物取代基效应会影响H^(-)转移过程,可能使反应不发生.Silyl enol ethers have attracted enormous attention as they could serve as a test bed for the development of novel frustrated Lewis pairs(FLPs) catalytic systems. However, the reaction mechanism of hydrogenation catalysed by metal-free FLPs for these compounds to the corresponding secondary alcohols remains elusive to a large extent in previous studies. We thus performed a thorough investigation on the reaction mechanism by density functional theory(DFT). To illustrate the reaction mechanism of FLPs-catalysed hydrogenation for silyl enol ethers, trimethyl((1-phenylvinyl)oxy)silane(Me-TMS) was chosen as the prototype substrate and toluene as the solvent, where the FLPs were generated by ethylbis(perfluorophenyl)-borane(Et-B(C_(6)F_(5))_(2)) and tri-tert-butylphosphine(t-Bu_(3)P). The M06-2 X functional in connection with 6-31+G(d) basis set was used to optimize the structures of related species including in the Gibbs free energy profiles, and the energies were obtained at M06-2 X/6-311++G(d,p) level of theory, where the solvent effect was simulated with the integral equation formalism, polarized continuum mode(IEF-PCM) in both calculations. Our results suggest that the FLPs-catalysed hydrogenation of silyl enol ethers in toluene begins with the formation of B-P-FLPs followed by hydrogen activation, proton transfer and hydride transfer to complete the process. It is obvious from the Gibbs free energy profile that the proton transfer is rate-determining step, the formation of B-P-FLPs and proton transfer are endothermal and the hydride transfer is no barrier. This indicates that the amount of H2 and prototype substrate have significant influence on the FLPs-catalysed hydrogenation of silyl enol ethers. A higher temperature(328.15 K) is disadvantageous to hydrogenation reaction catalysed by FLPs but the reaction could be accelerated under higher pressure(4040 k Pa). The Gibbs free energy profile calculations for trimethyl((1-phenylprop-1-en-1-yl)oxy)silane(Et-TMS) and tert-butyldimethyl((1-phenylvinyl)oxy)silane(Me-T

关 键 词：受阻路易斯酸碱对 烯醇硅醚 氢化反应 密度泛函理论 

分 类 号：O621.251[理学—有机化学]