Hydrochloric Acid → Hydrochloric Acid

Participants

Reaction Steps

To a stirred solution of 15.2 g (0.08 mole) of 2,3-dihydro-3-oxothieno[2,3-d]isothiazole 1,1-dioxide (U.S. Pat. No. 4,028,373) in 200 ml of dry pyridine at 80° C. was added 15.2 g of phosphorus pentasulfide over a period of 10 minutes. The reaction mixture was stirred for a period of 45 minutes at this temperature and was then poured into 500 ml of ice water. The reaction mixture was acidified with conc. hydrochloric acid solution to pH 1. The resulting precipitate was collected on a filter and was dissolved in 20% sodium bicarbonate solution then filtered. The filtrate upon acidification with conc. hydrochloric acid gave 7.6 g of thieno[2,3-d]isothiazole-3(2H)-thione 1,1-dioxide, m.p. 185°-187° C. A second treatment of the precipitate which did not dissolve with 20% sodium bicarbonate followed by acidification gave an additional 3.7 g of product, m.p. 186°-189° C. The two crops of product were combined giving 11.3 g (69%).

Provenance & Evidence