Copper‐Catalyzed Asymmetric Synthesis of Silicon‐Stereogenic Benzoxasiloles
Wan‐Er Gan, Yong‐Shun Wu, Bin Wu, Chun‐Yuan Fang, Jian Cao, Zheng Xu, Li‐Wen Xu
Abstract
A Cu-catalyzed asymmetric synthesis of silicon-stereogenic benzoxasiloles has been realized via intramolecular Si-O coupling of [2-(hydroxymethyl)phenyl]silanes. Cu(I)/difluorphos is found to be an efficient catalytic system for enantioselective Si-C bond cleavage and Si-O bond formation. In addition, kinetic resolution of racemic substituted [2-(hydroxymethyl)phenyl]silanes using Cu(I)/ PyrOx (pyridine-oxazoline ligands) as the catalytic system is developed to afford carbon- and silicon-stereogenic benzoxasiloles. Ring-opening reactions of chiral benzoxasiloles with organolithiums and Grignard reagents yield various enantioenriched functionalized tetraorganosilanes.