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 degrees 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 degrees C. Deuterium labelling of C-H functions in the furanic alcohols was also investigated in the presence of ethanol-d(6). Finally, proposed catalytic resting species derived from the interactions between one of the catalysts and furanic reagents/product as well as the solvent during the transfer hydrogenation (TH) reaction were analysed.

Automated summary

In this study, the base-free transfer hydrogenation of biomass derived furanic aldehydes using bio-alcohols as the hydrogen source was investigated using ruthenium and iridium pincer complexes as catalysts. The furanic substrates were successfully converted to the desired alcohols under mild conditions, and the methodology could be extended to different temperatures and deuterium labeling of C-H functions in furanic alcohols was also explored.