Heterogeneous hydrogenation of esters under mild conditions using solid-supported phosphorus-ruthenium catalysts

The catalytic reduction of esters using H₂ offers a more sustainable alternative compared to classic stoichiometric reagents. Nowadays a wide range of highly efficient homogeneous catalysts are known, but these suffer from poor catalyst recoverability. Therefore, most industrial applications are based on heterogeneous catalysts but these processes are generally operated under harsh conditions (>200 °C, >100 bar). Here we describe the first catalytic system which combines the activity of homogeneous catalysts with the recoverability of a heterogeneous catalyst. The presented system is capable of hydrogenating esters under very mild conditions (25 °C, 50 bar) and could easily be recovered. The catalyst is based on phosphorus ligands covalently attached to a polymeric support and could be readily obtained via a facile solid-phase synthetic protocol in high yields with minimal workup.