Clara Tortosa Estorach^a, Arantxa Orejón,^a Núria Ruiz,^a Anna M. Masdeu-Bultó^a,* and Gábor Laurenczy^b

.

^aDepartament de Quίmica Fίsica i Inorgànica, Universitat Rovira i Virgili, Marcel.li Domingo s/n 43007 Tarragona, Spain. Fax: +34 977 559563; Tel: +34 977 559575; E-mail: [email protected]

^b Laboratory of Medicinal and Organometallic Chemistry, Institut des Sciences et Ingeniérie Chimiques, Ecole Polytéchnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland, E-mail: [email protected]

Catalytic hydroxycarbonylation of terminal long chain alkenes is an interesting reaction to transform alkenes into carboxylic acids with CO using a palladium complex as catalyst (1).

                                                                                                                                                                                   (1)

The interest of supercritical carbon dioxide (scCO₂), as a substitute solvent for catalytic reactions has quickly increased in the last years because of the advantages it presents compared with organic solvents.[1] Unfortunately, ionic and polar reagents generally exhibit low solubility in scCO₂, and it has limited application of scCO₂ in this catalytic processes.[2] To overcome this limitation modified ligands such as perfluorinated phosphines or/and soluble surfactants, which induces the formation of micelles with high-density fluid phase, have been employed. [3]

In the present work, the hydroxycarbonylation of 1-octene in scCO₂ has been studied using palladium catalytic precursors with fluorinated phoshines. Particular attention has been paid in the effect of perfluorinated surfactants (2) in order to generate microemulsions of water.

                                                                                                                                                                                                                                                                                     (2)

Although this reaction in organic solvent affords high conversions and selectivities, the chemioselectivity in acids is shown to improve in scCO_2. The use of perfluorinated surfactant also enhances the activity and the regioselectivity to the linear acid.

High pressure NMR experiments in toluene-d₆ and scCO₂ showed the formation of Pd(0) species.

[1] Leitner, W., Acc. Chem. Res., 2002, 35, 746.

[2] Jessop, P. G.; Hsiao, Y.; Ikariya, T.; Noyori, R., J. Am. Chem. Soc, 1996, 118, 344.

[3] Johnston, K. P.; Harrison, K. L.; Clarke, M. J.; Howdle, S. M; Heitz, M. P; Bright, F. V.; Carlier,     C.; Randolph, T. W., Science, 1996, 271, 624.

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