Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore.
Division of Science and Math, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore.
J Am Chem Soc. 2020 Nov 11;142(45):19065-19070. doi: 10.1021/jacs.0c00183. Epub 2020 Oct 29.
Silicon hydrides, alkynylsilanes, and alkoxylsilanes were activated by fluoride in the presence of bisguanidinium catalyst to form hypervalent silicate ion pairs. These activated silicates undergo 1,4-additions with chromones, coumarins, and α-cyanocinnamic esters generating enolsilicate intermediates, for a consequent stereoselective alkylation reaction. The reduction-alkylation reaction proceeded under mild conditions using polymethylhydrosiloxane, a cheap and environmentally friendly hydride source. The addition-alkylation reactions with alkynylsilanes and alkoxylsilanes resulted in the construction of two vicinal chiral carbon centers with excellent enantioselectivities and diastereoselectivities (up to 99% ee, >99:1 dr). Density functional theory calculations and experimental NMR studies revealed that penta-coordinated silicates are crucial intermediates.
硅氢化物、炔基硅烷和烷氧基硅烷在双胍催化剂存在下被氟离子激活，形成高价硅酸盐离子对。这些激活的硅酸盐与色酮、香豆素和α-氰基肉桂酸酯发生 1,4-加成反应，生成烯醇硅酸盐中间体，从而进行立体选择性的烷基化反应。在温和条件下，使用廉价且环保的氢化物源——聚甲基氢硅氧烷进行还原-烷基化反应。与炔基硅烷和烷氧基硅烷的加成-烷基化反应导致构建了两个具有优异对映选择性和非对映选择性的相邻手性碳原子中心（高达 99%ee，＞99:1dr）。密度泛函理论计算和实验 NMR 研究表明，五配位硅酸盐是关键中间体。
