Rhodium(III)-Catalyzed Asymmetric Addition of Inert Arene C-H Bond to Aldehydes To Afford Enantioenriched Phthalides.

An asymmetric rhodium(III)-catalyzed Grignard-type addition of inert arene C-H bond to aldehydes is reported. It provides a new strategy for the synthesis of chiral 3-substituted phthalides in good yields (up to 87%) with high enantiomeric purity (up to 99% ee). Interestingly, a chiral-matching effect between substrate and catalyst was observed, which is crucial to accomplish satisfied reaction outcomes. Mechanistically, the reaction is assumed to proceed via consecutive C(sp2)-H activation of benzamide, addition to aldehyde, and lactonization.