Enantioselective para-C(sp 2 )-H Functionalization of Alkyl Benzene Derivatives via Cooperative Catalysis of Gold/Chiral Brønsted Acid.

An asymmetric para-C(sp 2 )-H bond functionalization of alkyl benzene derivatives was successfully developed via cooperative catalysis of gold and chiral phosphoric acid (CPA), leading to synthetically useful chiral 1,1-diaryl motifs. Chiral phosphoric acid, ligand, and molecular sieves were found to be crucial for enantioselectivity control of this transformation. The salient features of this protocol include mild conditions, high efficiency, commercially available starting materials, highly chemo- and site- as well as enantioselective aromatic C-H functionalization, broad substrate scope, and extensive applications of the chiral products. The mechanistic studies suggested that two CPAs might be involved in chiral induction.