Oxidation-Deformylation Cascade Catalyzed By a Mononuclear Copper Complex.

In this study, two copper complexes were synthesized using N3 (arising from two pyridines and one amide group) containing ligands N-(2-picolyl)picolinamide (LH) and bis(2-pyridylcarbonyl)amine (LH), forming [(L)Cu(OH)(NO)] (1) and (L)Cu(OH) (2). The reaction of complex 1 with hydrogen peroxide in alcoholic solvents yielded a formate-bound complex. Studies with isotopically labeled C ethanol indicated that formate originates from the C1 of ethanol after C-C bond cleavage. Complex 1 was found to catalytically convert primary alcohols into formic acid probably following a two-step process: (i) alcohol oxidation to aldehyde and (ii) aldehyde deformylation. Further experiments with 2-phenylpropionaldehyde (2-PPA) confirm the ability of complex 1 to catalyze aldehyde deformylation. Both steps of the reaction are associated with significant kinetic deuterium isotope effects (KDIE), suggesting that hydrogen atom abstractions (HAA) occur during the rate-determining steps of both conversions. Overall, this system proposes a clean catalytic process for alcohol-to-formic acid conversion, operating under mild conditions, and offering potential synthetic applications.