Hydroformylation Catalyst Recycle with Gas-Expanded Liquids

Tunable solvents such as gas-expanded liquids offer unique opportunities as benign and economic reaction media. We have improved the turnover frequency of a water-soluble catalyst system by a factor of 85 for the hydroformylation of 1-octene by using a tunable solvent system, which also increases substrate solubility. In our approach, the reaction is run homogeneously in a miscible water−organic solution, and after reaction, CO2 is used as a “miscibility switch” for efficient product and catalyst recovery. Two water-soluble ligands, TPPTS (tris(3-sulfophenyl)phosphine) and TPPMS ((3-sulfophenyl)diphenylphosphine), were compared to triphenylphosphine for hydroformylation activity of their rhodium complexes. The catalyst was recycled three times with no loss of activity.