Sulfuric Acid → 3-Chloro-4,5,6,7-tetrahydro-1,2-benzisothiazol-4-one

Participants

Reaction Steps

A solution of sodium dichromate (4.4 g) in glacial acetic acid (30 mL) was added dropwise over 1 h to a solution of 3-chloro-4,5,6,7-tetrahydro-1,2-benzisothiazole 23a (2.7 g) and concentrated sulfuric acid (1.8 mL) in glacial acetic acid (80 mL). The reaction mixture was stirred at room temperature for an additional 2 h, and neutralized with a saturated solution of sodium hydrogencarbonate. Extraction with ether (3×150 mL), drying and evaporation gave an oil. Column chromatography on silica gel (eluent: toluene-ethyl acetate 1:1) eluted first 3-chloro-4,5,6,7-tetrahydro-1,2-benzisothiazol-7-one (680 mg). The later fractions contained the title compound (780 mg). Mp 84-85° C.

Provenance & Evidence