POLITAG-Pd(0) catalyzed continuous flow hydrogenation of lignin-derived phenolic compounds using sodium formate as a safe H-source

Phenols are aromatic biobased compounds and as they are accessible from lignin depolymerization, they can be a useful platform chemicals to produce value-added products. Herein we report our recent investigations on the definition of an approach to the efficient continuous flow selective hydrogenation of phenols in water. Our protocol is based on the use of sodium formate as a clean and safe hydrogen source in combination with our newly defined heterogeneous POLITAG-Pd(0) catalytic system. POLITAG is a polymeric heterogeneous support decorated with pincer-type ionic ligands proven to be highly efficient for the stabilization of Pd(0) nanoparticles. The results obtained are remarkable in comparison with other protocols that employ sodium formate as H-source. Indeed, our investigation has been extended to a variety of differently substituted phenolic compounds that have been hydrogenated with excellent to good selectivity in continuous flow conditions. Durability of the catalyst has been also tested with a representative continuous processing of over 100 mmol that showed no loss in efficiency and minimal metal leaching.