Hydrogen Peroxide → 1-Cyclohexyloxy-2,2,6,6-tetramethyl-piperidin-4-ol

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A solution of 0.234 g (0.842 mmol) of ferrous sulfate heptahydrate, 3 ml of water, and 0.293 g (3.05 mmol) of methanesulfonic acid is added to a mixture of 5.00 g (29.0 mmol) of 1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol, 45 ml of acetonitrile, and 32 ml of cyclohexane, which has been heated to 62° C. A solution of 8.07 g (119 mmol) of 50% aqueous hydrogen peroxide is added dropwise over 2.25 hours to the reaction mixture while the temperature is maintained at reflux. A solution of 0.069 g of ferrous sulfate heptahydrate and 0.188 g of methanesulfonic acid in 2 ml of water is added to the reaction mixture 2 hours after the peroxide addition is started. A solution of 0.065 g of ferrous sulfate heptahydrate and 0.108 g of methanesulfonic acid in 1 ml of water is added to the reaction mixture 3.5 hours after the peroxide addition is started. After a total reaction time of 4.5 hours at reflux, the reaction mixture is allowed to cool. Excess peroxide is quenched with aqueous sodium sulfite solution. The aqueous layer is extracted with a 2:1 mixture of acetonitrile and cyclohexane, and the combined organic layers are washed with sodium hydroxide solution. To the organic layer are added 6 ml of t-butyl alcohol, 6 ml of water, 0.4 g of sodium hydroxide, and 0.70 g of sodium borohydride. The mixture is stirred for 3 hours, and the aqueous layer is extracted with ethyl acetate. The combined organic layers are washed with aqueous citric acid, aqueous sodium bicarbonate, and then concentrated. Purification by flash chromatography with 1:1 heptane-ethyl acetate affords 5.10 g (69% yield) of the title compound as a light yellow syrup, GC assay 93%.

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