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0 °C

5 g (38.4 mmol) of 2-hydroxy-3,3-dimethyl-γ-butyrolactone (pantolactone) were dissolved in 118 ml of methylene chloride in a 200 ml sulphonation flask. 3.3 g (40.2 mmol) of sodium acetate and 3.6 g (15.5 mmol) of trichloroisocyanuric acid were added thereto. The mixture was cooled to 0° C. while stirring. A solution of 38.2 mg (0.24 mmol) of TEMPO in 2 ml of methylene chloride was dosed in within 10 minutes. The temperature was held at 0°-3° C. by constant cooling. After a reaction period of 7 hours the white precipitate was filtered off. The filtrate was concentrated. Chromatography of the residue (SiO2, toluene/ethyl acetate 85:15) and subsequent recrystallization of the chromatographed product gave 4.23g (86%) of ketopantolactone, m.p. 67.5°-68° C., GC content: 100% (area percent).

1. customwas dosed in within 10 minutes
2. customwas held at 0°-3° C. by constant cooling
3. customAfter a reaction period of 7 hours the white precipitate
4. filtrationwas filtered off
5. concentrationThe filtrate was concentrated
6. customChromatography of the residue (SiO2, toluene/ethyl acetate 85:15) and subsequent recrystallization of the chromatographed product