Lewis Base-Catalyzed Dynamic Kinetic Asymmetric Transformation of Racemic Chlorosilanes <i>en</i> Route to <i>Si</i>-Stereogenic Silylethers
Tianbao Hu, Yan Zhang, Wanshu Wang, Qin Li, Liying Huang, Jiahui Gao, Yuzhong Kuang, Zhao Chen, Song Zhou, Lu Gao, Zhishan Su, Zhenlei Song
Abstract
Enantiopure Si -stereogenic organosilanes are highly valued in the fields of organic synthesis, development of advanced materials, and drug discovery. However, they are not naturally occurring, and their synthesis has been largely confined to resolution of racemic silanes or desymmetrization of symmetric silanes. In contrast, the dynamic kinetic asymmetric transformation (DYKAT) of racemic organosilanes offers a mechanistically distinct approach and would broaden the accessibility of Si -stereogenic silanes in an enantioconvergent manner. In this study, we report a Lewis base-catalyzed DYKAT of racemic chlorosilanes. The chiral isothiourea catalyst, ( S )-benzotetramisole, facilitates silyletherification with phenols, yielding ( R )-silylethers in good yields with high enantioselectivity (27 examples, up to 86% yield, up to 98:2 er ). Kinetic analysis, control experiments, and DFT calculations suggest that a two-catalyst-bound pentacoordinate silicate is responsible for the Si -configurational epimerization of the ion-paired tetracoordinated silicon intermediates.