Selective preparation of campholenic aldehyde over heterogenized methyltrioxorhenium

Abstract

The presented report focuses on the isomerization of α-pinene oxide over methyltrioxorhenium (MTO) immobilized on a range of mesoporous materials with different SiO2/Al2O3 ratios, namely mesoporous alumina (m-Al2O3), aluminosilicates type Siral (with Al content 60–80 %), silica and MCM-41 or in its homogeneous form. Optimization of MTO immobilization has been studied and published previously. α-Pinene oxide, an oxygenated derivative of α-pinene, isomerizes rapidly into various valuable substances useful as flavors, fragrances and pharmaceutical compounds. Campholenic aldehyde is the one of the most desired products of α-pinene oxide isomerization, being a valuable intermediate for the production of sandalwood-like fragrances. The prepared catalytic systems were successfully used for selective preparation of campholenic aldehyde. Homogeneous and heterogenized MTO showed very high activity in α-pinene oxide isomerization (100 % conversion within a few minutes) and very high selectivity to campholenic aldehyde, amounting to over 80 %. Furthermore, the possibility of catalyst regeneration was proven.