Synergetic catalysis of Se and Cu allowing diethoxylation of halomethylene ketones using O₂as the mild oxidant

PhSe(O)OH/Cu(OAc)2-Catalyzed diethoxylation of halomethylene ketones for the construction of useful α-keto acetals was developed. Synergetic catalysis of Se and Cu allowed the utilization of molecular oxygen as a safe oxidant instead of explosive hydrogen peroxide. The easily accessible bromo-containing substrates could release HBr during the reaction, which promoted the key enol intermediate to avoid the use of acidic additives and allow the reaction to occur under mild conditions.