Ethanol-mediated N-formylation of amines with CO2/H2 over cobalt catalysts

Abstract

The CO₂-involved synthesis of chemicals is of great significance from a green and sustainable point of view. Herein, we present an efficient Co-based catalytic system composed of a commercially available Co salt, the tetradentate phosphine ligand P-(CH₂CH₂PPh₂)₃, and a base, denoted as [Co]/PP₃/base, for the synthesis of formamides via the formylation of amines with CO₂/H₂. It was indicated that the selectivity of products (i.e., formamide or methylamine) could be tuned to some extent via changing the solvent and the base. Using ethanol as the solvent, the Co(ClO₄)₂·6H₂O/PP₃/K₂CO₃ system showed high activity for the production of formamides, affording product yields of 82–95%, together with its broad substrate scope. Exploration of the reaction mechanism indicated that formamide was formed with HCOOH as the intermediate, while the methylamine byproduct was produced with HCHO as the intermediate via the hydrogenolysis of dialkylaminomethane.