One-pot redox cascade paired electrosynthesis of gamma-butyrolactone from furoic acid.

The catalytic valorisation of biomass to afford synthetically useful small molecules is essential for sustainable biorefinery processes. Herein, we present a mild cascaded electrochemical protocol for converting furoic acid, a common biomass-derived feedstock, into a versatile platform chemical, gamma-butyrolactone. In the platinum(+)|nickel(-) electrode paired undivided cell, furoic acid is electrochemically oxidised with 84.2% selectivity to 2(5H)-furanone, the olefin of which is then hydrogenated to yield gamma-butyrolactone with 98.5% selectivity. The final gamma-butyrolactone yield is 69.1% with 38.3% Faradaic efficiency and 80.1% carbon balance when the reaction is performed with 100 mM furoic acid at 80 °C at +2.0 V. Mechanistic investigation revealed the critical temperature and electrolyte pH conditions that maximise the production and protection of the key intermediate, furan radical, promoting its transition to 2(5H)-furanone rather than self-polymerising. The reaction is scalable, as 2.1 g of 98.1% pure gamma-butyrolactone is isolated through a simple solvent extraction.