Sustainable Catalytic Protocols for the Solvent Free Epoxidation and (anti)-Dihydroxylation of the Alkene Bonds of Biorenewable Terpene Feedstocks Using H2O2 as Oxidant

A tungsten-based polyoxometalate catalyst employing aqueous H2O2 as a benign oxidant has been used for the solvent free catalytic epoxidation of the trisubstituted alkene bonds of a wide range of biorenewable terpene substrates. This epoxidation protocol has been scaled up to produce limonene oxide, 3-carene oxide and alpha-pinene oxide on a multigram scale, with the catalyst being recycled three times to produce 3-carene oxide. Epoxidation of the less reactive disubstituted alkene bonds of terpene substrates could be achieved by carrying out catalytic epoxidation reactions at 50 degrees C. Methods have been developed that enable direct epoxidation of untreated crude sulfate turpentine to afford 3-carene oxide, alpha-pinene oxide and beta-pinene oxide. Treatment of crude epoxide products (no work-up) with a heterogeneous acid catalyst (Amberlyst-15) results in clean epoxide hydrolysis to afford their corresponding terpene-anti-diols in good yields.