Hf4+-exchanged montmorillonite-boosted Pd-catalyzed reductive aminolysis of aryl ethers to efficiently synthesize cyclohexylamines

The construction of N-substituted amines from biomass-derived aryl ethers via reductive aminolysis is an emerging and highly attractive strategy for biomass valorization. However, realizing this transformation remains a great challenge over heterogeneous catalysts at a low H-2 pressure. Herein, we designed Hf-exchanged montmorillonite supported Pd nanoparticles (Pd/Hf-MMT) as a functional heterogeneous catalyst. Very interestingly, the fabricated Pd/Hf-MMT was highly efficient for the direct reductive aminolysis of aryl ethers with amines to synthesize various N-cyclohexyl-substituted amines at a low H-2 pressure of 0.3 MPa without using any homogeneous acidic additives. Systematic investigations revealed that the strong acidity of Hf-MMT and the lower electron density of metallic Pd synergistically resulted in the excellent activity of Pd/Hf-MMT. Notably, the Pd/Hf-MMT catalyst has great potential for practical applications because of some obvious advantages, such as low H-2 pressure, the heterogeneous nature, high efficiency, and broad substrate scope.

Automated summary

The construction of N-substituted amines from biomass-derived aryl ethers via reductive aminolysis is a promising strategy for biomass valorization. However, realizing this transformation over heterogeneous catalysts at a low H-2 pressure has been a challenge. In this study, a Hf-exchanged montmorillonite supported Pd nanoparticles catalyst (Pd/Hf-MMT) was designed and found to be highly efficient for the direct reductive aminolysis of aryl ethers with amines, without the need for homogeneous acidic additives, at a low H-2 pressure of 0.3 MPa. The excellent activity of Pd/Hf-MMT was attributed to the strong acidity of Hf-MMT and the lower electron density of metallic Pd. The Pd/Hf-MMT catalyst also showed great potential for practical applications due to its advantages such as low H-2 pressure, heterogeneous nature, high efficiency, and broad substrate scope.