Selective hydroformylation of unsaturated esters using a Rh/PPh3-supported ionic liquid-phase catalyst, followed by a novel route to pyrazolin-5-ones

Methyl acrylates were hydroformylated with high regioselectivity and excellent yield to the corresponding branched aldehydes using Rh/PPh3-supported ionic liquid-phase (SILP) catalyst in water as a reaction medium. The effect of various reaction variables like temperature, pressure, P/Rh ratio, substrate/Rh ratio, and phosphorous ligands on chemoselectivity and regioselectivity for hydroformylation reaction were optimized. The optimized reaction conditions were then applied for hydroformylation of various unsaturated esters. The methyl acrylate hydroformylation products were further reacted with phenyl hydrazine to obtain, 4-methyl-substituted pyrazolin-5-ones with high yield.

Various unsaturated esters were hydroformylated to the corresponding branched aldehydes with essentially perfect regioselectivity and excellent yield using a conventional Rh/PPh3 catalyst in ionic liquid film supported on silica (Rh/PPh3/SILPC) in water as reaction medium. The high selectivity towards α-formylation obtained is then used to synthesize 4-methyl-substituted pyrazolin-5-ones using phenyl hydrazine under mild reaction conditions.Figure optionsDownload as PowerPoint slide