Catalytic Transfer Hydrogenation of Lignocellulosic Biomass Model Compounds Furfural and Vanillin with Ethanol by an Air-stable Iron(II) Complex

The chemical transformation of lignocellulosic biomass into various fine chemicals is the necessity for sustainable developments. A significant research interest has been devoted to develop catalysts for the reduction of cellulose and lignin model compounds furfural and vanillin, respectively. An iron(II) complex (1) was readily synthesized by facile coordination of NNO pincer ligand with FeCl2.4H(2)O. The air-stable complex 1 was efficiently utilized for the catalytic transfer hydrogenation of furfural and vanillin using ecologically benign but challenging primary alcohol ethanol. Secondary alcohol isopropanol was also utilized. Various other biomass model compounds and structurally related aldehydes were also effectively reduced. Kinetic studies suggested first order kinetics in catalyst and zeroth order in substrate. Based on the experimental evidences and published reports, a catalytic cycle is proposed which proceed via iron(II)-dialkoxides and alkoxide-hydride intermediates. Finally, CHEM21 green metrics toolkit was utilized to evaluate the sustainable and green credentials of the catalytic protocols.