Efficient and selective approach to biomass-based amine by reductive amination of furfural using Ru catalyst

Reductive amination of furfural (1a) to furfurylamine (2a) was developed as a powerful and practical approach to biomass-based amine. Herein, Ru catalyst (Ru/BNC) supported on boron/nitrogen co-doped carbon (BNC) was reported for the reductive amination with hydrous hydrazine (N2H4·H2O) as a nitrogen source and hydrazone as intermediate. Our mechanism investigation suggested rich Frustrated Lewis acid−base pairs (FLPs) on the BNC surface synergistically enhanced the activity of Ru catalyst. Moreover, quick formation rate of hydrazone intermediate and its moderate reactivity significantly improved 2a selectivity. Under optimal conditions, Ru/BNC catalyst can highly efficiently and selectively promote 1a/N2H4-to-2a transformation with 2a yield exceeding 99%. Moreover, the role of nitrogen sources such as N2H4, NH3 and hydroxylamine on the 2a selectivity was systematically investigated. Additionally, the developed Ru/BNC−N2H4 system was applicable to a wide range of aldehydes to give the desired primary amines in excellent to good yields (85–99%) in the reductive amination reaction.