Acetic Acid → N-cyclohexyloxy-4-oxo-2,2,6,6-tetramethylpiperidine

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A mixture of 0.115 g (1.37 mmol) of sodium bicarbonate and 0.275 g (0.834 mmol) of sodium tungstate dihydrate in 2 mol of water is added to a mixture of 10.00 g (64.4 mmol) of 2,2,6,6-tetramethylpiperidin-4-one and 9 ml of acetonitrile at 300 C. A solution of 11.83 g (174 mmol) of 50% aqueous hydrogen peroxide is added dropwise to the reaction mixture over 4.25 hours while the reaction temperature is maintained at 30-35° C. Approximately 3.25 hours after the peroxide addition is begun, a mixture of 0.056 g of sodium bicarbonate and 0.134 g of sodium tungstate dihydrate in 1 ml of water is added to the reaction mixture. After a total reaction time of 6.5 hours, the reaction mixture is diluted with cyclohexane. The aqueous layer is extracted twice with a mixture of 2:1 cyclohexane-acetonitrile. The total amount of cyclohexane used is 60 ml. Acetonitrile (60 ml) is added to the combined organic layers. The reaction mixture is heated to 45° C. and a solution of 0.334 g (1.24 mmol) of ferrous chloride tetrahydrate and 0.312 g (5.20 mmol) of glacial acetic acid in 5 ml of water is added. A solution of 14.95 g (220 mmol) of 50% aqueous hydrogen peroxide is added dropwise to the reaction mixture over 4.25 hours as the reaction mixture is maintained at the reflux temperature of 60° C. The reaction mixture is cooled, and 10% aqueous sulfite solution is added to decompose excess peroxide. The aqueous layer is extracted with a 2:1 mixture of acetonitrile-cyclohexane and then with ethyl acetate. The combined organic layers are concentrated, and the concentrate is purified by flash chromatography with 100:7.5 heptane-ethyl acetate to afford 9.65 g (59% yield) of the title compound, a white solid, mp 33-37. GC assay is 99%.

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