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

Abstract

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 FeCl 2 .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.

Air-Stable Coordinatively Unsaturated Ruthenium(II) Complex for Ligand Binding and Catalytic Transfer Hydrogenation of Ketones from Ethanol

“…As a consequence, the transfer hydrogenation of acetophenone with iPrOH was calculated to be only +4.4 kJ/mol uphill at 40 °C, while the equilibrium with EtOH is much more unfavorable (Δ G = +24.4 kJ/mol) . In addition, side-products from aldol condensation often constitute undesired side products under the basic reaction conditions. − Nonetheless, Grützmacher and co-workers demonstrated in 2005 the suitability of EtOH in the transfer hydrogenation of ketones and activated olefins with rhodium­(I) amide catalysts, even at high substrate/catalyst ratio (S/C = 10,000). , Even though the use of EtOH as hydrogen source has remained scarce, − transfer hydrogenation from EtOH has expanded gradually to, for example, asymmetric versions, − base-free nickel(0)-catalyzed hydrogenation, and to diverse substrates including aldehydes, esters, unactivated alkenes, and the semihydrogenation of alkynes . Moreover, successful transfer hydrogenation with MeOH as hydrogen sources was recently reported. − …”

Copper(i)-catalyzed click chemistry in deep eutectic solvent for the syntheses of β-d-glucopyranosyltriazoles

“…84 However, coordination of that NNS ligand with CuI resulted in insoluble solid and we could not reveal its identity. Similar tridentate NNO ligand system 111,112 might also be effective to develop copper(I) catalyst with high efficiency. Therefore, we have selected a NNO ligand L 1 and facile coordination of ligand L 1 with CuI resulted in the formation of a dinuclear copper(I) complex 1 (Scheme 2).…”

“…In past, several research groups (including us) utilized this toolkit to determine the green and sustainable aspects of various catalytic transformations. 111,[121][122][123][124][125] Herein, we examined the optimized CuAAC reaction protocols by utilizing zero pass and rst pass of CHEM21 green metrics toolkit. This toolkit also has second and third pass, but these are considered as industrial toolkits and outside the scope of the present study.…”

Base metal iron catalyzed sustainable oxidation of vanillyl alcohol to vanillic acid in deep eutectic solvents and implementation of vanillic acid for fine-chemical synthesis

“…Therefore, phosphine-free (and carbene-free) ligand synthesis is important for the development of air-stable complexes and gaining serious attention in homogeneous catalysis. [85][86][87][88][89] Particularly, air-sensitive metal complexes are of no use in the eld of oxidation of alcohols. Therefore, we wanted to use a tridentate NNN pincer ligand which is expected to give good stability of the resulting metal complex by tridentate coordination and might give an air-stable metal complex.…”