Dimethyl Sulfoxide → 4-Benzoyloxy-1-methoxy-2,2,6,6-tetramethylpiperidine

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Reaction Steps

A solution of 5.9 g (52 mmol) of 30% aqueous hydrogen peroxide is added dropwise, under nitrogen, over 90 minutes to a mixture of 10.0 g (36.2 mmol) of 4-benzoyloxy-1-oxyl-2,2,6,6-tetramethylpiperidine, 11.2 g (40.3 mmol) of ferrous sulfate heptahydrate, and 135 ml of dimethyl sulfoxide which is initially at 24° C. The reaction temperature increases to 37° C. as the peroxide is added. After the addition is complete, the reaction mixture is stirred for 1.75 hours at ambient temperature. The mixture is cooled in an ice-water bath and diluted with water (80 ml). A solution of 5 g of sodium hydroxide in 45 ml of water is added to make the reaction mixture basic. The mixture is extracted with methylene chloride (250 ml, then 2×150 ml), and the combined organic layers are concentrated at reduced pressure to obtain a light orange liquid. Purification of the crude product by flash chromatography on silica gel (20:1 heptane/ethyl acetate) affords 8.5 g (81% yield) of the title compound, a white solid, mp 67°-69° C.

Provenance & Evidence