2-Methylbenzothiazole → 2-Methylbenzo[d]thiazole-4-sulfonyl chloride

Participants

Reaction Steps

2-Methylbenzothiazole (50 g) was added in a slow, dropwise manner to 86 mL of chlorosulfonic acid at room temperature. When the addition was complete, the dark reaction mixture was heated at 140°-145° C. for about 3 hours. The solution was allowed to cool and was slowly added to a large excess of ice. Insoluble solids were removed by filtration and the aqueous layer was extracted with benzene. Drying and evaporation of the solvent gave an off-white solid which was shown by 1H NMR analysis to consist of a mixture of sulfonyl chlorides, presumably the 4-, 6-, and 7-isomers. This crude material was recrystallized three times from hexane to remove the 6-isomer as a white solid, m.p. 100°-102° C. The combined mother liquors were concentrated to give a dark yellow oil which was carried on to the next step without further purification.

Provenance & Evidence