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A remarkable effect of the solvent nature on the acid catalyzed transformation of ␣-pinene oxide allowed direction of the reaction to either trans-carveol or trans-sobrerol. Each of these highly valuable compounds was obtained in nearly 70% yield using an appropriate polar solvent, whose basicity affected strongly the product distribution. In acetone, a weakly basic solvent, the reaction over heterogeneous sol-gel Sn/SiO 2 or Ce/SiO 2 catalysts gave mainly trans-sobrerol. No leaching of active components occurs under the reaction conditions and the catalysts can be recovered and reused. On the other hand, in more basic solvent, i.e., dimethylacetamide, the reaction was essentially directed to trans-carveol. Due to the leaching problems with Sn/SiO 2 and Ce/SiO 2 materials, the synthesis of trans-carveol was performed under homogeneous conditions using CeCl 3 or SnCl 2 as catalysts with a catalyst turnover number up to ca. 1200. The method represents one of the few examples of the synthesis of isomers from ␣-pinene oxide, other than campholenic aldehyde, with a sufficient for practical usage selectivity.

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Cobalt-containing MCM-41 was used as a heterogeneous catalyst for the liquid-phase aerobic oxidation of isolongifolene, one of the most available sesquiterpenes. The material was prepared by direct incorporation of cobalt into the framework through the hydrothermal method, and was characterized by ICP-AES, N 2 adsorption-desorption, TEM, XRD, SAXS, XPS, and H 2-TPR techniques. Characterizations suggest that cobalt introduced into MCM-41 exists mainly in a single-site Co 2+ state, whereas the amounts of the extraframework Co 3 O 4 are relatively low. The oxidation of isolongifolene under mild solvent-free conditions results mainly (90% selectivity) in isolongifolen-9-one, a compound which occupies a vintage place in modern perfume industry. The total concentration of oxygenated products in the final mixtures reaches 90 wt%. The catalyst undergoes no metal leaching, and can be easily recovered and re-used. A silica-included cobalt catalyst prepared through a conventional sol-gel method shows a catalytic activity comparable with that of Co-MCM-41; however, selectivity is much lower.

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Heterogeneous catalysts based on Sm-doped ceria were employed for the first time in the liquid-phase oxidation of α-bisabolol. Nanometer-sized catalysts were obtained by microwave-hydrothermal synthesis and were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), Raman spectroscopy and N 2-physisorption. The influence of Sm doping, temperature and the solvent used on the catalytic behavior was investigated. Conversions up to 84% and a combined selectivity for the products up to 77% were obtained for Ce 0.9 Sm 0.15 O 1.85−δ catalysts. The reactions were highly selective for the epoxidation products (only bisabolol oxides A and B were obtained) and shown to be strongly dependent on the temperature and solvent employed. Best results were achieved for higher Sm concentrations, which indicate that changes in the textural properties due to doping produced a significantly more active catalyst.