Nickel‐Catalyzed Asymmetric Hydrovinylation Using Lewis Acid Activation

Abstract

AbstractA broad range of commercially available Lewis acids were investigated for their ability to activate and regulate nickel catalysts for asymmetric hydrovinylation processes using styrene as model substrate and ligand (Ra,SC,SC)‐5 as benchmark system. The colour change during the activation step associated with the halide abstraction furnishes helpful indications to adapt the activation conditions to the pre‐catalyst/Lewis acid system. In general, metal halide Lewis acids led to higher activities and enantioselectivities than the corresponding triflates. In particular, the use of InI3 as co‐catalyst resulted in the same chemo‐ and enantioselectivity and even higher activity than the benchmark system based onNaBArF. Moreover, InI3 is safe to handle and cheap, thus providing a simple and practical protocol for an efficient hydrovinylation reaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)