Copper-catalyzed dehydrogenative cross-coupling reaction between unactivated ethers and simple ketones mediated by pyrrolidine

A copper-catalyzed dehydrogenative cross-coupling reaction between unactivated ethers and simple ketones mediated by pyrrolidine has been developed. Under the catalysis of CuBr2 and in the presence of pyrrolidine, either tetrahydrofuran 2a or tetrahydropyran 2b can react smoothly with a series of methyl aryl ketones 1a-m to give desired coupling products 3aa-mb using TBHP as an oxidant. The advantages of the dehydrogenative cross-coupling reaction are adoption of unmodified ethers as substrates, good tolerance of many functional groups and use of cheap copper salt as a catalyst. A plausible radical mechanism through enamine attack is proposed.