Beyond H2: Exploiting H-Transfer Reaction as a Tool for the Catalytic Reduction of Biomass

The hydrogenation of biomass-derived molecules is a key reaction in the upgrading of these compounds into chemicals and fuels. For reduction processes, catalytic hydrogenation using molecular H2 is still the main technique in use today. Nevertheless, the use of H2 is neither economic nor entirely green; therefore, a catalytic transfer hydrogenation process for the reduction of carbonyl groups, which employs alcohols as hydrogen sources, offers an alternative approach that avoids the use of both H2 pressure and precious metal catalysts. This reaction is a well-known process, which involves hydrogen transfer from an alcohol to the carbonyl moiety of an aldehyde or a ketone; recently it has attracted significant interest. This review reports some significant examples in this research area, while the considerable attention to this field makes it possible for us to envisage that some new processes based on the H-transfer reaction will be developed in coming years for the efficient production of chemicals and fuels from renewable raw materials.