Catalytic base-free transfer hydrogenation of biomass derived furanic aldehydes with bioalcohols and PNP pincer complexes

The base-free transfer hydrogenation of biomass derived furanic aldehydes with ruthenium and iridium pincer complexes was studied using bio-alcohols as the hydrogen source. The furanic substrates, such as 5-hydroxymethyl furfural (HMF) and thiophene-2-carboxaldehyde (TC), were reduced under mild conditions (35-80 °C) affording the desired alcohols with excellent conversions and yields. It was also possible to extend this methodology for the transfer hydrogenation of 5-formylfurfural (DFF) at 130 °C. Deuterium labelling of C-H functions in the furanic alcohols was also investigated in the presence of ethanol-d₆ . Finally, proposed catalytic resting species derived from the interactions between one of the catalysts and furanic reagent/product as well as the solvent during the transfer hydrogenation (TH) reaction were analysed.