Transformations of monoterpenoid ketones in supercritical isopropanol/CO2 in a continuous flow reactor in the presence of alumina. Competitive reduction of olefinic double bond and carbonyl group

•Reactivity of monoterpenoid α,β-unsaturated ketones in sc solvent was studied.•Reactions were performed in a flow reactor in the presence of granular Al2O3.•Competitive reduction of olefinic double bond and carbonyl group was observed.•Monoterpenes 1,5,8-p-mentatriene and verbenene are form from carvone and verbenone.

Reactivity of monoterpenoid α,β-unsaturated ketones (carvone, verbenone and pinocarvone) in binary supercritical solvent isopropanol/CO2 in a flow reactor in the presence of granular Al2O3 was studied. Competitive reduction of olefinic double bond and carbonyl group was observed at the first reaction step. Subsequent transformation of intermediate products – alcohols – enables single step production of polyunsaturated monoterpenes 1,5,8-p-mentatriene and verbenene from carvone and verbenone, respectively, at contact times of several minutes.

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