Sulfuric Acid → 7-Fluoroisatin

Participants

Reaction Conditions

Reaction Steps

31.3 g of the product of Step A were added at 75°-77° C. over 65 minutes to 155 ml of concentrated sulfuric acid and the mixture was heated over 10 minutes to 90° C. and held there for 10 minutes and then cooled to 20° C. The mixture was poured into 750 g of ice and the mixture was stirred until the ice melted and was filtered. The filtrate was saturated with sodium chloride and was extracted several times with ethyl acetate. The combined organic phases were washed with aqueous saturated sodium chloride solution until the wash water was neutral, dried, filtered and evaporated to dryness under reduced pressure. The residue was dissolved in 350 ml of xylene at reflux and the hot solution was filtered and the filter was washed with 20 ml of boiling xylene. The filtrate was iced and vacuum filtered. The product was washed with xylene and dried under reduced pressure at 80° C. to obtain 12.85 g of 7-fluoro-1 H-indole-2,3-dione melting at 198° C.

Provenance & Evidence