Cu(triNHC)-Catalyzed N-Methylation and N-Formylation of Amines Using CO2

To address carbon emissions and promote sustainable chemical use, the development of carbon-utilizing protocols is essential. In this context, leveraging CO₂ as a methyl group precursor holds significant potential for broadening its scope in organic reactions. Aiming to reduce the carbon footprint in organic synthesis, we introduce an efficient and selective Cu(triNHC) (triNHC = tri-N-Heterocyclic Carbene) catalyst designed for the reduction of CO₂ and subsequent N-methylation and N-formylation of amines. The triNHC ligand's tridentate chelation is crucial for modulating Cu(triNHC)’s reactivity. This configuration enables direct N-methylation of amines, bypassing the typical N-formylation and subsequent reduction pathway. As a result, N-methylation proceeds faster than in reactions catalyzed by copper catalysts with simpler NHC ligand coordination. Our mechanistic investigations provide support for the proposed reaction pathway, involving CO₂ reduction to a methyl precursor followed by its reaction with amines.