Methyl 9(10)‐formylstearate by selective hydroformylation of oleic oils

A highly selective catalyst system has been discovered for the hydroformylation of methyl oleate into methyl 9(10)‐formylstearate in high yields. A rhodium catalyst in the presence of triphenylphosphine is used with oleic esters, acids or triglycerides. Hydroformylation proceeds smoothly at 95‐110C with a 1:1 mixture of H 2 and CO at 500 to 2000 psi with or without a solvent, such as toluene. The formylstearate obtained in 90% to 99% conversion from oleate can be either hydrogenated (Raney Ni) or reduced (NaBH 4 ) to hydroxymethylstearate or oxidized (KMnO 4 ) to carboxystearate. According to TLC and mass spectrometry, the methylated carboxystearate consists of about equal proportions of the 9 and 10 isomers. Addition of triphenylphosphine inhibits isomerization of the double bond and leads to the formation of a rhodium carbonyl triphenylphosphine complex, which is apparently the active catalyst. Other known methods for hydroformylation (cobalt carbonyl) and carboxylation (Koch’s method) of oleate give a wide distribution of isomers.