Potassium Carbonate → HCID 57316274, compound

Participants

Reaction Conditions

Reaction Steps

A solution of (1R, 3R, 4S)-p-menth-3-yl (1R, 2S)-2-methyl-4,6- dioxocyclohexanecarboxylate (2, 24.0 g, 77.8 mmol, 1 equiv) in methanol (300 mL) was treated with camphorsulfonic acid (ca. 800 mg, 3.9 mmol, 0.05 equiv) and the resulting solution was stirred at 23° C. for 12 h. The reaction mixture was neutralized by the addition of solid potassium carbonate (1.08 g, 7.78 mmol, 0.10 equiv) and the resulting suspension was filtered and the filtrate was concentrated. The residue was concentrated from toluene (2×15 mL) and then was purified by flash column chromatography (20% ethyl acetate-hexanes) to afford (1R, 3R, 4S)-p-menth-3-yl (1R, 6S)-4-methoxy-6-methyl-2-oxo-3-cyclohexene-1-carboxylate (4) as a white solid (mp 78°-80° C., 17.9 g, 71%). The regioisomeric enone, (1R, 3R, 4S)-p-menth-3-yl (1R, 6S)-2-methoxy-6-methyl-4-oxo-2-cyclohexene-1-carboxylate (5) was isolated in separate fractions and was resubjected to the reaction conditions to establish the equilibrium mixture of enones, in which the desired product 4 is strongly favored.

Provenance & Evidence