Enantioselective Copper(II)-Catalyzed Conjugate Addition of Indoles to β-Substituted Unsaturated Acyl Phosphonates

The first copper-catalyzed enantioselective conjugate addition of indoles to β-substituted unsaturated acyl phosphonates was successfully realized by using a heteroarylidene-tethered bis(oxazoline) ligand. The reaction features high efficiency, cheap catalyst and broad generality. In the case of either β-alkyl- or β-aryl-substituted unsaturated acyl phosphonates, the 3-indolyl adducts were achieved in high yields with good to excellent enantioselectivities (up to 97% ee). The 3-indolyl adducts can serve as important intermediates in the synthesis of indole alkaloids.