Oxidation of monoterpenes with hydrogen peroxide catalysed by Keggin-type tungstoborates

The Keggin-type anions [Mn III(H 2O)BW 11O 39] 6− and [BW 12O 40] 5− were used for the first time as catalyst in oxidative studies of monoterpenes by hydrogen peroxide in acetonitrile. Oxidations of geraniol 1, nerol 2, (+)-3-carene 3, thymol 4 and carvacrol 5 in the presence of catalytic amounts of...

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Bibliographic Details
Published in:	Journal of molecular catalysis. A, Chemical Vol. 195; no. 1; pp. 253 - 262
Main Authors:	Santos, I.C.M.S, Simões, M.M.Q, Pereira, M.M.M.S, Martins, R.R.L, Neves, M.G.P.M.S, Cavaleiro, J.A.S, Cavaleiro, A.M.V
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 18-03-2003 Elsevier
Subjects:	Catalysis Catalytic reactions Chemistry Exact sciences and technology General and physical chemistry Hydrogen peroxide Keggin polyoxotungstates Manganese Oxidation Terpenes Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry Tungstoborates Keggin polyoxotungstates Hydrogen peroxide Tungstoborates Oxidation Catalysis Terpenes Manganese Heteropolysalt Boron compound Terpenoid Catalytic reaction Manganese compound Carene Transition metal Complexes Experimental study Hydrogen Peroxides Heterogeneous catalysis Tungsten complex Epoxidation Monoterpene Geraniol
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Summary:	The Keggin-type anions [Mn III(H 2O)BW 11O 39] 6− and [BW 12O 40] 5− were used for the first time as catalyst in oxidative studies of monoterpenes by hydrogen peroxide in acetonitrile. Oxidations of geraniol 1, nerol 2, (+)-3-carene 3, thymol 4 and carvacrol 5 in the presence of catalytic amounts of the polyoxoanions were examined. The Keggin-type anions [Mn III(H 2O)BW 11O 39] 6− and [BW 12O 40] 5− were used for the first time as catalysts in studies of oxidation of monoterpenes by hydrogen peroxide. The oxidation of geraniol 1, nerol 2, (+)-3-carene 3, thymol 4 and carvacrol 5 was examined. The reactions were carried out in acetonitrile, at room temperature (for 1 and 2) or at reflux (for 3, 4 and 5). Compounds 1 and 2 were preferentially epoxidised at the C 2–C 3 double bond, whereas 3, under controlled reaction conditions, could afford only the α-epoxide. The oxidation of 4 and 5 yielded a mixture of benzoquinones. For tetrabutylammonium salts, the Mn III substituted anion was found to be a more efficient catalyst than [BW 12O 40] 5−. The infrared spectra of the recovered solids at the end of reaction showed that the Keggin anions were still present, but the electronic spectra of the manganese residues indicate that oxidation of Mn III had taken place.
ISSN:	1381-1169 1873-314X
DOI:	10.1016/S1381-1169(02)00582-4