A fundamental understanding of biomass-based transformation of furfural (1a) to 2-furamide (4a) is highly desirable for the extension of amide chemistry. In this research, direct amidation of 1a with hydroxylamine to 4a was investigated by using a Cu-doped Co 3 O 4 (Cu/Co 3 O 4 ) catalyst with 2-furancarboxaldehyde oxime (2a) and 2furonitrile (3a) as detectable intermediates. Mechanism research has demonstrated the presence of two competitive, independent, and parallel reaction pathways: (i) direct 2a-to-4a rearrangement (the Williams mechanism), and (ii) 2a-to-3a dehydration followed by 3a-to-4a rehydration (the classic mechanism) with the rehydration as the ratedetermining step. Subsequent kinetic analysis by "concentration−time" integrals revealed that the Williams mechanism was always the predominant reaction pathway, with the reaction rate constant being almost 22 times greater than that of the classic mechanism. The catalytic performance of Cu/Co 3 O 4 was correlated to its surface concentration of oxygen vacancy and surface acidity. The insights thus highlight a kinetic understanding of a complex consecutive/ parallel transformation of biomass-based aldehyde for amide product.

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.

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