Rhodium(II)-Catalyzed Enantioselective C-H Functionalization of Indoles

A catalytic, enantioselective method for the C-H functionalization of indoles by diazo compounds has been achieved. With catalytic amounts of Rh-2(S-NTTL)(4), the putative Rh-carbene intermediates from alpha-alkyl-alpha-diazoesters react with indoles at C(3) to provide alpha-alkyl-alpha-indolylacetates in high yield and enantioselectivity. From DFT calculations, a mechanism is proposed that involves a Rh-ylide intermediate with oxocarbenium character.