Chlorosulfonic acid → 2-oxo-2,3-dihydro-1H-indole-5-sulfonyl chloride

Participants

Reaction Steps

To a 100 mL flask charged with 27 mL chlorosulfonic acid was slowly added 13.3 g 2-oxindole. The reaction temperature was maintained below 30° C. during the addition. The reaction mixture was stirred at room temperature for 1.5 hour, heated to 68° C. for 1 hour, cooled, and poured into water. The precipitate which formed was filtered, washed with water and dried in a vacuum oven to give 11.0 g (50%) of 5-chlorosulfonyl-2-oxindole which was used without further purification.

Provenance & Evidence