G. Papadogianakis, L. Maat, R. Sheldon
Sep 1, 1997
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0
Influential Citations
47
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Journal
Journal of Chemical Technology & Biotechnology
Abstract
1-(4-Isobutylphenyl)ethanol (IBPE) was carbonylated to 2-(4-isobutylphenyl)propionic acid (ibuprofen) in an aqueous/organic two phase system using the water-soluble Pd(tppts) 3 catalyst [tppts = P(C 6 H 4 -m-SO 3 Na) 3 ] in the presence of p-CH 3 C 6 H 4 SO 3 H at 363 K, 15 MPa CO pressure and a palladium concentration of 150 ppm without addition of organic solvents. Under these conditions the conversion of IBPE was 83% and the selectivity to ibuprofen 82% with no decomposition of the Pd(tppts) 3 catalyst. Both the activity and selectivity were strongly influenced by the tppts/Pd molar ratio and the nature of the added Bronsted acid. Maximum efficiency was observed for P/Pd = 10. Acids of weakly or non-coordinating anions, such as p-CH 3 C 6 H 4 SO 3 H, CF 3 COOH or HPF 6 afforded carbonylation. No catalytic activity was observed in the presence of acids of strongly coordinating anions, such as HI. The water-soluble Pd/dppps catalyst [dppps = Ar 2-n Ph n P-(CH 2 ) 3 -PP h Ar 2-h ; Ar = C 6 H 4 -m-SO 3 Na; n = n = 0: 86% and n = 0, n = 1: 14%] exhibited low catalytic activity and the major product obtained was the linear isomer of ibuprofen, 3-(4-isobutylphenyl) propionic acid (3-IPPA) with selectivities up to 78%. Replacement of tppts by a ligand containing less -SO 3 Na groups such as monosulphonated triphenylphosphine (tppms) gives rise to a dramatic drop in the catalytic activity and selectivity to ibuprofen. No catalytic activity was observed using palladium catalysts modified with 2-pyridyldiphenylphosphine (PyPPh 2 )and tris(2-pyridyl) phosphine (PPy 3 ) which are both water soluble in their protonated form. A catalytic cycle is proposed to explain the observed results.