Catalytic Enantioselective Synthesis of Quaternary 3,3′-Indolyloxindoles by Combination of Rh(II) Complexes and Chiral Phosphines.

Rh(II)/chiral phosphine combined catalysis has been developed for a highly efficient sequential C–H functionalization/asymmetric allylation or Michael addition reaction of indoles and 3-diazooxindoles with allenoates or vinyl ketones to afford a diverse range of quaternary 3,3′-indolyloxindole derivatives. Moreover, a significantly positive effect of LiCl in the sequential C–H functionalization/allylation reaction was observed, which led to an unusual ternary activation mechanism in the allylation step.