Heterogeneous catalytic hydrogenation of N-benzyl nicotinamide: a comparative study with nicotinamide adenine dinucleotide

Abstract

In this study, we report the hydrogenation of N-benzyl nicotinamide (BNA⁺), a structural mimic of the coenzyme nicotinamide adenine dinucleotide (NAD⁺) required for enzymatic reactions, to 1,4-dihydro-N-benzyl nicotinamide (1,4-BNAH) using a Pt/SiO₂ catalyst. This reaction was performed under mild conditions (20 °C, 1 atm H₂), with a view to future applications in enzymatic reactions. A production rate of 1,4-BNAH reaching 170 mmol-1,4-BNAH g-Pt⁻¹ h⁻¹ or 81 mmol-1,4-BNAH mmol-Pt per surface sites per h was achieved, which was approximately 6.8 times higher than that of 1,4-NADH (26 mmol-1,4-NADH g-Pt⁻¹ h⁻¹ or 12 mmol-1,4-NADH mmol-Pt per surface sites per h). Kinetic analysis revealed that both BNA⁺ and NAD⁺ hydrogenation were first-order in H₂ pressure; however, the reaction order with respect to NAD⁺ concentration was 0.14, indicating strong adsorption on the Pt/SiO₂ catalyst surface, whereas that for BNA⁺ was 0.56, suggesting weaker adsorption that contributes to the enhanced 1,4-BNAH production rate. Moreover, the Pt/SiO₂ catalyst exhibited excellent recyclability, retaining its activity over five consecutive cycles without deactivation. This stability is attributed to the weaker adsorption of BNA⁺, mitigating catalyst fouling. Consequently, hydrogenation of BNA⁺ emerges as a promising strategy for cofactor regeneration in biocatalytic processes.