Enantioselective Synthesis of Triarylmethanes via Intermolecular C–H Functionalization of Cyclohexadienes with Diaryldiazomethanes

Rhodium-catalyzed C–H functionalization of cyclohexadiene derivatives with diaryldiazomethanes followed by oxidation with DDQ provides ready access to triarylmethanes. Two chiral dirhodium tetracarboxylates, Rh₂(S-PTAD)₄ and Rh₂(S-TPPTTL)₄, were found to be the optimum chiral catalysts for these transformations. This method showcases the ability of diaryldiazomethanes to perform intermolecular C–H insertion with high enantioselectivity and good yields. The method has a broad substrate scope, leading to triarylmethane products with a variety of aryl and heteroaryl substituents, including benzofuran and pyridine heterocycles.