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, Rh-2(S-PTAD)(4) and Rh-2(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. [GRAPHICS]