CO₂ Valorization toward Selective <i>N</i>-Formylation of Nitroarenes and Aminoarenes under Homogeneous Titanium Catalysis

Achieving selective and versatile access to formamides from nitroarenes remains a challenge in modern synthetic chemistry. These formamides have broad applications in nucleic acid research and cryopreservation as well as in the production of pesticides, fungicides, polymers, and pharmaceuticals; additionally, they are used as effective solvents. We herein present a versatile and straightforward method for the direct synthesis of these compounds through selective N-formylation of nitroarenes and/or anilines, employing renewable CO2 as a C1 source and ammonia borane as the hydrogen donor, using Cp2TiCl2 as the potential catalyst. A broad range of structurally diverse nitroarenes and anilines was efficiently converted to their corresponding formamides as sole products in good to excellent yields. The coordination between the titanium center and the oxygen atom of the CO2 molecule, along with the formation of a key titanocene intermediate and a stable Cp2TiO complex, played a crucial role in preventing overreduction and driving the reaction in a desired path with improved efficiency and selectivity.