Recent advances in enantioselective direct CH addition to carbonyls and michael acceptors#

Abstract

Enantioselective C-H addition is one of the most straightforward and efficient approaches towards the synthesis of optically active molecules from readily available arenes. The most significant feature of these reactions is that the nucleophilic aryl metal species is generated catalytically in situ via CH bond activation. These reactions typically proceed without requirement of either strongly basic or acidic conditions, thus with good functional group compatibility. In this review, recent progress on transition-metal-catalyzed enantioselective direct C-H addition to polar unsaturated bonds is summarized. The intramolecular C-H additions to carbonyls enabled by Ir(I) or Rh(III) catalyst provided an access to chiral alcohol scaffolds with high efficiency. Planar chiral 1,2-substituted ferrocenes were afforded by C-H addition of ferrocenes to acrylates by an Ir/chiral diene catalyst. In addition, the asymmetric hydroarylation reactions of Michael acceptors including acrylates, α, β-unsaturated esters and nitroolefins were also described. Moreover, the enantioselective conjugate additions of aromatic and benzylic C-H bonds to α, β-unsaturated ketones catalyzed by Cp*M(III)/chiral acid hybrid catalyst (M = Rh, Co) were presented. These enantioselective C-H additions provided a straightforward access to structurally diverse and valuable chiral fragments. Meanwhile, the reaction mechanisms are also introduced.