Catalytic Reductive Alkylation of Amines in Batch and Microflow Conditions Using a Silicon-Wafer-Based Palladium Nanocatalyst.

We describe the development of the catalytic reductive alkylation of amines with aldehydes under the atmospheric pressure of H using a brush-like silicon-nanostructure-supported palladium nanoparticle composite (SiNS-Pd) as a silicon-wafer-based reusable heterogeneous catalyst. The present reaction of primary and secondary amines with various aliphatic and aromatic aldehydes in the presence of the catalyst (0.02-0.05 mol % Pd) gave the corresponding secondary and tertiary amines including Lomerizine and Aticaprant in a 68% quantitative yield without overalkylation. We also designed and fabricated a flow device equipped with SiNS-Pd for microflow reactions, which was applied to the gas-liquid-solid triphasic reaction system (i.e., H gas, a substrate solution, and a solid catalyst). A multigram-scale reaction of aniline and benzaldehyde was demonstrated to obtain -benzylaniline (ca. 4 g/day), in which the internal volume of the flow channel was 43 μL, the residence time was approximately 1 s, and the turnover number (TON) reached 4.0 × 10 in a continuous 24 h run (1.7 × 10 h; 0.50 s).