Phosphotungstic heteropoly acid as efficient heterogeneous catalyst for solvent-free isomerization of α-pinene and longifolene

Silica-supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an efficient, environmentally friendly heterogeneous catalyst for the liquid-phase isomerization of α-pinene and longifolene into their more valuable isomers – camphene and isolongifolene, respectively, which are intermediates in the synthesis of expensive fragrances. The reactions occur under solvent-free conditions in the temperature range of 80–100 °C, with low catalyst loadings (0.15–5 wt%) and high turnover numbers (up to 6000 per proton). The catalyst can be easily recovered and reused. No PW leaching is observed in the reaction system.

Graphical abstractSilica-supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an efficient, environmentally friendly solid catalyst for the liquid-phase isomerization of α-pinene (1) and longifolene (2) to respectively camphene (3) and isolongifolene (4), which are intermediates in the synthesis of expensive fragrances.Figure optionsDownload full-size imageDownload as PowerPoint slide