Epoxidation of DL-limonene using an indenyl molybdenum(II) tricarbonyl complex as catalyst precursor

The complex IndMo(CO)3Me (Ind = η5-C9H7) is an effective catalyst precursor for the epoxidation of DL-limonene using the following oxidant solutions: (i) commercial tert-butylhydroperoxide in decane (TBHPdec), (ii) commercial aqueous TBHP (TBHPaq) pre-mixed with limonene (TBHP_lim), or (iii) TBHPaq pre-mixed with 1,2-dichloroethane (TBHPdce); simple pre-drying treatments of the reaction solutions were applied prior to feeding the catalyst precursor to the batch reactor. The best results were found for the efficiently pre-dried reaction system (iii), which gave higher 1,2-epoxy-p-meth-8-ene yield at 35 min/55 °C than (i) (82% and 73% yield, respectively). This approach avoids the undesirable partial oxidation of decane, which would imply costly work-up procedures to remove high boiling point impurities from the epoxides. These results together with studies on the reactivity of different olefins indicate fairly high regioselectivity toward the epoxidation of the internal double bonds.

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► First report of an indenyl molybdenum carbonyl used in catalytic olefin epoxidation.
► Promising performance for the epoxidation of DL-limonene.
► Under dry conditions the reaction rate and selectivity to epoxides are high.
► Three consecutive runs indicate fairly high catalyst stability.