Methoxycarbonylation of iodobenzene in ionic liquids. A case of inhibiting effect of imidazolium halides
[ 1 ] Instytut Technologii i Inżynierii Chemicznej, Wydział Technologii Chemicznej, Politechnika Poznańska | [ P ] pracownik
2006
Rocznik: 2006 | Tom: vol. 348 | Numer: iss. 12-13
artykuł naukowy
angielski
- ionic liquids
- methoxycarbonylation
- palladium
- palladium carbenes
EN The palladium(II) complexes, PdCl2(cod) (1), PdCl2[P(OPh)3]2 (2), [bmim]2[PdCl4] (3), and [bmpy]2[PdCl4] (4) (bmim=1-butyl-3-methylimidazolium cation, bmpy=1-butyl-4-methylpyridinium cation), were found to be active catalysts for the methoxycarbonylation of iodobenzene in ionic liquid (IL) media. The best results were obtained in pyridinium salts, [bmpy]X (X=Cl, Br, BF4, PF6) (76–100 % yield). In methoxycarbonylation reactions carried out in imidazolium salts, [bmim]BF4 and [bmim]PF6, the yield of benzoic acid methyl ester was slightly lower (50–78 % yield), whereas in [bmim]X (X=Cl, Br) the reaction was totally retarded. The inhibiting effect was not observed when a Me group was present at C-2 (instead of a proton) on the imidazole ring. A palladium-carbene complex, Pd(bmimy)2Br2 (5), obtained in the reaction of a palladium catalyst precursor with [bmim]Cl, presented much lower activity than precursors 1–4. Its formation may explain the observed inhibition of methoxycarbonylation in a [bmim]Cl medium.
11.08.2006
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