Rhodium catalyst immobilization in trialkylamine-functionalized ionic liquids as a new efficient way to promote biphasic reductive hydroformylation of methyl 10-undecenoate

Abstract

In this work, trialkylamine-functionalized ionic liquids were assessed for their dual role as solvents and ligands in the biphasic reductive hydroformylation of methyl 10-undecenoate (MU), a renewable substrate derived from castor oil. Systematic tuning of the aminated ionic liquids through cation and anion variation identified 1-(2-piperid-1-yl-ethyl)-3-ethanolimidazolium hexafluorophosphate, [PEEtOHim][PF₆] combined with dodecane as the most effective biphasic couple, enabling efficient rhodium reductive hydroformylation with a turnover frequency in alcohols of 33 h⁻¹ while limiting rhodium leaching in the apolar phase to as little as 1.5% of its initial loading. Under optimized conditions, the system was recycled for at least nine consecutive runs with constant selectivity in alcohols, highlighting the robustness of the catalytically active species stabilized within the ionic liquid phase. A cumulative total turnover number in alcohols of 1282 was achieved through this atom-economical tandem process, further demonstrating the potential of aminated ionic liquids in biphasic catalytic systems. This work underscores the relevance of ionic liquid-based strategies for sustainable catalysis and the valorization of renewable feedstocks, bridging high-performance chemistry with the principles of green chemistry.