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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 60 mg (0.28 mmol) of TEMPO derative B in 2 ml of methylene chloride was dosed in within 10 minutes. The temperature was held at 0°-3° C. by constant cooling. The reaction had finished after 3 hours. The white precipitate was filtered off and the filtrate was treated with sodium bisulphite solution in order to reduce the excess trichloroisocyanuric acid. Working up of the reaction mixture and subsequent recrystallization of the crude product gave 3.5 g (71%) of ketopantolactone, GC content: 99.6% (area percent).

1. customwas dosed in within 10 minutes
2. customwas held at 0°-3° C. by constant cooling
3. filtrationThe white precipitate was filtered off
4. additionthe filtrate was treated with sodium bisulphite solution in order
5. customWorking up of the reaction mixture and subsequent recrystallization of the crude product