Hydrochloric Acid → 6-chloro-4',5'-dihydrospiro[benzo[b]thiophene-2(3H),3'(2'H)-furan]-3,2'-dione

Participants

Reaction Steps

In 200 ml of water were dissolved 14.2 g of 4-chlorothiosalicylic acid and 20 g of sodium carbonate, and 19.1 g of α-bromo-γ-butyrolactone was added dropwise to the solution under ice-cooling. After stirring the solution at room temperature for 6 hours, 35 ml of concentrated hydrochloric acid was added to the reaction solution at room temperature to acidify. After stirring at room temperature for 3 hours, the precipitate was collected, washed with water and dried, resulting in crude α-[(2-carboxy-5-chlorophenyl)thio]-γ-butyrolactone. The crude product was dissolved in 150 ml of acetic anhydride and 30 ml of triethylamine, and heated under a stream of nitrogen at 130° C. for 10 minutes. The reaction solution was evaporated to dryness under reduced pressure, and the resulting residue was chromatographed on a column of activated carbon and silica gel. Recrystallization from ethanol of the resultant crude crystals yielded 1.60 g of 6-chloro-4',5'-dihydrospiro[benzo[b]thiophene-2(3H),3'(2'H)-furan]-3,2'-dione as colorless needles. Melting point: 157°-158° C.

Provenance & Evidence