Efficient Hydroformylation in Dense Carbon Dioxide using Phosphorus Ligands without Perfluoroalkyl Substituents

Rhodium catalysts modified with triphenylphosphine, triphenyl phosphite, and tris(2,4-di-tert-butylphenyl) phosphite have been evaluated for their performance in the hydroformylation of 1-octene using carbon dioxide as the solvent. It is demonstrated that these catalysts are very efficient for the hydroformylation in carbon dioxide, although they are not designed for use in this medium. In particular, the catalyst prepared in situ from dicarbonyl(2,4-pentanedione)rhodium(I) and tris(2,4-di-tert-butyl-phenyl) phosphite gave rise to an initial turnover frequency in excess of 3×104 molaldehyde molRh h-1. Such a reaction rate is unprecedented for hydroformylation in supercritical carbon dioxide-rich reaction mixtures