Cu(ii)- or Co(ii)-Catalyzed C(SP3)-H oxidation of N,N-dimethylaminoethanol: facile synthesis of methylene-bridged biindoles and 3-formylindoles selectively

Methylene-bridged biindoles and 3-formylindoles were selectively synthesized using a new carbon donor N,N-dimethylethanolamine, catalyzed by CuCl2 and CoCl2 respectively. A high conversion rate and good regioselectivity were achieved. Oxygen atmosphere promoted the reaction toward the conversion of 3-formylindoles.