Wang Zheng, Zhou Yu, Marder Todd B, Lin Zhenyang
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, P. R. China.
Org Biomol Chem. 2017 Aug 23;15(33):7019-7027. doi: 10.1039/c7ob01475a.
Boroles can react with CO to give Lewis acid-base adduct 1AD, tricyclic boracycle 1TB or ketene derivative 1KD depending on the substituents on the borole. DFT calculations at the M06-2X level of theory were performed to study systematically the influence of borole substituents on these reactions. It was found that the Lewis acid-base adduct 1AD is a kinetic product, which can further transform to the tricyclic boracycle 1TB or ketene derivative 1KD. The computational results show that strong electron-withdrawing perfluorophenyl substituents significantly stabilise the Lewis acid-base adduct 1AD, allowing its successful isolation. In most cases, the tricyclic boracycle 1TB is both kinetically and thermodynamically more favourable than the ketene derivative 1KD. However, a -B(CF) substituent at the 4-position and a silyl substituent at the 5-position together are able to lower the barrier leading to the formation of the ketene derivative 1KD.
硼杂环戊二烯能够与一氧化碳反应，根据硼杂环戊二烯上的取代基不同，生成路易斯酸碱加合物1AD、三环硼杂环化合物1TB或乙烯酮衍生物1KD。在M06 - 2X理论水平上进行了密度泛函理论计算，以系统研究硼杂环戊二烯取代基对这些反应的影响。研究发现，路易斯酸碱加合物1AD是动力学产物，它能够进一步转化为三环硼杂环化合物1TB或乙烯酮衍生物1KD。计算结果表明，强吸电子的全氟苯基取代基能显著稳定路易斯酸碱加合物1AD，使其得以成功分离。在大多数情况下，三环硼杂环化合物1TB在动力学和热力学上都比乙烯酮衍生物1KD更有利。然而，4位的 -B(CF) 取代基和5位的硅基取代基共同作用能够降低生成乙烯酮衍生物1KD的势垒。
