Direct and selective hydrogenolysis of arenols and aryl methyl ethers

Abstract

For valorization of biomass, the conversion of lignin to deoxygenated bulk aromatic compounds is an emerging subject of interest. Because aromatic rings are susceptible to metal-catalysed hydrogenation, the selective hydrogenolysis of carbon-oxygen bonds still remains a great challenge. Herein we report direct and selective hydrogenolysis of sp2 C-OH bonds in substituted phenols and naphthols catalysed by hydroxycyclopentadienyl iridium complexes. The corresponding arenes were obtained in up to 99% yields, indicating the possible production of arenes from lignin-derived bio-oils. Furthermore, the same catalysts were applied to the unprecedented selective hydrogenolysis of the sp3 C-O bonds in aryl methyl ethers. Thus, the hydrodeoxygenation of vanillylacetone, a lignin model compound, afforded alkylbenzenes as the major products via triple deoxygenation.