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Asymmetric Heck Silylation of Unactivated Alkenes
Bingcheng Wang1, Jiajin Zhao1, Jiale Ying1
1Department of Chemistry, Zhejiang University, Hangzhou, 310058, China.
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.
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