Synthesis of formamides containing unsaturated groups by N-formylation of amines using CO2 with H2

Abstract

Formamides have wide applications in the industry and have been synthesized using CO₂ as a carbon source and H₂ as a reducing agent. However, previous systems required a noble catalyst and high temperature to achieve high efficiency, and the substrate scope was mostly limited to saturated amines. The selective N-formylation of amines containing unsaturated groups using CO₂ and H₂ is challenging because the efficient catalysts for the N-formylation are usually very active for hydrogenation of the unsaturated groups. Herein, we achieved for the first time a selective and efficient N-formylation of amines containing unsaturated groups using CO₂ and H₂ with a Cu(OAc)₂–4-dimethylaminopyridine (DMAP) catalytic system. The substrates were converted to the desired formamides, while the unsaturated groups, such as the carbonyl group, the CC bond, CN bond and the ester group remained. The main reason for the excellent selectivity of the Cu(OAc)₂–DMAP catalytic system was that it was very active for the N-formylation reaction, but was not active for the hydrogenation of the unsaturated groups.