Selective Construction of a Biomass-Based Secondary Amine by Hydrogenative Homocoupling of Nitrile Using an Iridium Complex in a Metal–Organic Framework

Reductive amination of furfural was recently investigated as a straightforward method for the construction of biomass-based primary amine (furfurylamine) and tertiary amine [tris(2-furanylmethyl)amine] with, however, secondary amine [bis(2-furanylmethyl)amine] as a problem due to a selectivity issue. In this research, we demonstrated a highly selective and efficient strategy for the construction of bis(2-furanylmethyl)amine in 99% yield by Ir-catalyzed hydrogenative homocoupling of biomass-based 2-furanacarbonitrile in one pot. The Ir catalyst was prepared by immobilization of the [Cp*Ir(bpy)Cl]Cl complex in a 2,2′-bipyridine-functionalized UiO-67. Both furfurylamine and furfurylamine-derived secondary imine were successively detected as intermediates. Detailed kinetic analysis suggested the secondary imine hydrogenation as the rate-determining step instead of 2-furanacarbonitrile hydrogenation. A variety of symmetry secondary amines (18 examples) were selectively prepared in excellent to moderate yields from the corresponding nitriles with the Ir catalyst. This research thus built a bridge between a well-defined single-site catalyst with a metal–organic framework as ligand/support and its homogeneous counterpart to understand kinetic details in the biomass-based amine formation.