Pd/C-Catalyzed Selective N-Monomethylation by Transfer Hydrogenation of Urea Derivatives using Methanol as H2 and C1 Sources

A highly selective commercially available carbon supported palladium (Pd/C)-catalyzed N-monomethylation of Urea derivatives is achieved using Methanol as both a hydrogen (H₂) and methyl (C1) Source. This one-pot synthetic methodology presents an alternative route for the synthesis of mono-methylated amines from urea derivatives via transfer hydrogenation.

N-monomethyl amines are useful intermediates in drugs, natural products, paints. Yet their synthesis is a tremendous challenge due to their high reactivity, typically leading to overmethylation. In this contribution, a highly selective catalytic N-methylation methodology is reported, converting urea derivatives to monomethylated amines, using a commercially available heterogeneous Pd/C catalyst and methanol as unique reagent. Methanol provides a sustainable alternative protocol for the selective preparation of mono-methylated derivatives as it acts as both H₂ and C1 sources. In addition, several control experiments were performed to provide a proposal for the mechanism, namely dehydrogenation of methanol and subsequent hydrogenation of urea derivatives, followed by reduction of the in situ formed methyl imine. Importantly, the approach is simple, highly productive and enables novel synthetic procedures for the preparation of monomethylamines from urea derivatives.