Thionyl Chloride → 5-Chloro-2-oxobenzoxazoline-6-sulphonyl chloride

Participants

Reaction Steps

To a stirred mixture of 5-Chloro-2-oxo-2,3-dihydro-benzooxazole-6-sulfonic acid (˜10 g, 40 mmol) and CH2Cl2 was added thionyl chloride (5.8 cm3, 80 mmol) at room temperature, causing gas to be evolved. This was stirred at room temperature for two hours but the solid didn't dissolve and FIA only showed starting material. Therefore a few drops of DMF were added and the reaction heated to 50° C. overnight but no reaction occurred. The starting material was filtered off and then treated with neat thionyl chloride (15 cm3) and heated to 70° C. overnight, FIA now detected starting material and product, so the reaction was treated with DMF (2×1 cm3) to aid solvation, FIA showed completion of the reaction. The reaction was diluted with CH2Cl2 (100 cm3) then poured onto ice. The solid formed was filtered off and dried in vacuo yielding 5-Chloro-2-oxo-2,3-dihydro-benzooxazole-6-sulfonyl chloride (4.6 g, 43%) as a fine white solid; δH (300 MHz; D6 DMSO) 7.09 (1H, s, Ar—H), 7.69 (1H, s, Ar—H) and 11.81 (1H, s, N—H); m/z (FIANEG) 266.0 [(M−H)−, 100%] and 268.0 [(M−H)−, 67%].

Provenance & Evidence