Asymmetric Heck Silylation of Unactivated Alkenes
Bingcheng Wang, Jiajin Zhao, Jiale Ying, Biao Cheng, Zhan Lu
Abstract
Heck silylation of unactivated alkenes is an efficient strategy for the synthesis of useful organosilicon compounds. However, extensive efforts have been dedicated to only achieving achiral molecules. Herein, a highly regio- and enantioselective cobalt-catalyzed Heck silylation of unactivated alkenes with hydrosilanes is reported for the first time, providing access to axially chiral alkenes in good to excellent yields with 87-98 % ee. Aryl and alkyl groups as well as quaternary carbon centers at the 4-position of vinylcyclohexane could be well tolerated, featuring good functional group tolerance. The gram-scale reaction proceeds smoothly under mild conditions even with 0.5 mol % catalyst loading. A possible mechanism has been proposed, in which enantioselectivity is controlled by alkene insertion. A templating strategy that enhances weak bond interaction is employed to control regioselectivity by modifying the substituents on the ligand and silane.