Uniformly microporous diatomite supported Ni0/2+ catalyzed controllable selective reductive amination of benzaldehydes to primary amines, secondary imines and secondary amines

Abstract

The controllable highly selective reductive amination of carbonyl compound to primary amines, secondary imines and secondary amines is one of the challenging problems in organic synthesis. However, there are still many problems, such as difficulty in selective regulation, cumbersome and costly preparation of catalysts, and insufficient green solvents. In this work, commercial diatomite, activated carbon, Al2O3, TiO2 and CeO2 were employed to support nickel through a simple impregnation method. With H2O as the green solvent, Ni/diatomite-400 can achieve controllable selective reductive amination of benzaldehyde to benzylamine, N-benzylidenebenzylamine and dibenzylamine only by regulating H2 pressure and ammonia concentration. Accompanying spectroscopic characterizations and detailed mechanistic experiments illustrate that the synergistic effect of the appropriate proportion of Ni0/Ni2+ is the key to the successful modulation of selectivity, and this catalytic reaction mechanism was proposed. Moreover, the unique uniformly microporous structure of diatomite may facilitate the mass transfer and diffusion process of reactants, intermediates and products, leading to high catalytic efficiency. In addition, the catalyst also has excellent reuse performance and substrate universality. This work provides a new economical and efficient way for the reductive amination of carbonyl compounds in industry.