Isomerization of α-pinene oxide in the presence of methyltrioxorhenium(VII)

The catalytic performance of methyltrioxorhenium(VII) (MTO) has been investigated for the first time in the isomerization of α-pinene oxide (PinOx) into campholenic aldehyde (CPA). The high isomerization activity of MTO is coupled with high selectivity to CPA: CPA yield of up to 87% (100% conversion) was obtained by using α,α,α-trifluorotoluene as solvent at 15 °C. Catalyst recycling is possible in a relatively simple fashion by using MTO coupled to an appropriate ionic liquid. The catalytic application of MTO in the isomerization of PinOx versus the integrated epoxidation–isomerization process of the conversion of α-pinene into CPA is discussed.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► First report of methyltrioxorhenium used in catalytic isomerization of α-pinene oxide ► Catalyst recycling was successful using an MTO/ionic liquid mixture. ► Four consecutive batch runs indicate a fairly high catalyst stability. ► Synthesis of CPA from α-pinene by an integrated epoxidation–isomerization was also studied.