Asymmetric Conjugate\nAddition of Vinyl Arene-Derived\nChiral Benzylcopper Nucleophiles

We report the copper-catalyzed asymmetric conjugate addition\nof\nvinyl arene-derived nucleophiles to α,β-unsaturated diesters.\nDue to the high electrophilicity of α,β-unsaturated diesters\ntoward nucleophilic copper catalysts, inclusion of vinyl arenes as\npronucleophiles is challenging due to chemoselectivity issues in a\nmulticomponent reaction compared with those of other successful examples\nof dienes, allenes, and enynes. In this method, chemoselective <i>in situ</i> generation of a chiral benzylic copper intermediate\nand its stereoselective addition to α,β-unsaturated diesters\nprovided organoboron adducts with contiguous stereogenic centers with\ngood levels of diastereoselectivity and enantioselectivity (≤85:15\ndiastereomeric ratio and 99% enantiomeric excess, respectively).