Hydrogen Peroxide → 4-Hydroxy-α,α,4-trimethyl-2-cyclohexene-1-methanol

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Reaction Conditions

Reaction Steps

131 mg methyl trioxorhenium was dissolved in 30% aqueous hydrogen peroxide (23.6 ml) and cooled to 0° C. internal in a 21, 3-necked flask. A solution was separately prepared from 1,3-dioxolane (100 ml), (+)-2-carene (13.6 g, 0.1 mol), and pyridine (12 ml). This was also cooled to 0° C. internal. While stirring the cold aqueous solution vigorously, the cold dioxolane solution was added over 70 minutes, keeping the exothermic reaction at 0-5° C. After three hours (when TLC indicated disappearance of (+)-2-carene), the mixture was poured in to a separating funnel and the layers were separated. Saturated NaCl solution (20 ml) was added to the aqueous layer and more separation occurred. The layers were separated again. The aqueous layer was extracted once more with dioxolane (10 ml). The organics were combined. Aqueous pH 5.8 buffer solution (304 ml) was added and stirred vigorously at room temperature until (+)-2-carene epoxide had disappeared by TLC and HPLC (4 hours). The reaction was transferred to a separating funnel and washed once with heptane (75 ml). NaCl (45 g) was added to the aqueous layer and this was extracted with ethyl acetate (3×125 ml, 1×100 ml). The ethyl acetate extracts were combined, dried over Na2SO4, and concentrated in vacuo to ˜150 ml. 200 ml heptane was added and the solution was concentrated to ˜150 ml. 5-10 ml of EtOAc was added to dissolve the solid. It was allowed to cool with stirring and then cooled to 0° C. The solid was collected by vacuum filtration and washed twice with cold 5% EtOAc/heptane. After drying under vacuum, 11.857 g of (+)-p-menth-2-ene-1,8-diol (69.8% yield from (+)-2-carene) was obtained. NMR showed some residual heptane. Elemental Analysis: 70.6% C, 10.6% H.

Provenance & Evidence