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

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.

1. additionWhen the addition
2. customthe dark reaction mixture
3. temperaturewas heated at 140°-145° C. for about 3 hours
4. temperatureto cool
5. additionwas slowly added to a large excess of ice
6. customInsoluble solids were removed by filtration
7. extractionthe aqueous layer was extracted with benzene
8. customDrying
9. customevaporation of the solvent
10. customgave an off-white solid which
11. customThis crude material was recrystallized three times from hexane
12. customto remove the 6-isomer as a white solid, m.p. 100°-102° C
13. concentrationThe combined mother liquors were concentrated
14. customto give a dark yellow oil which
15. customwas carried on to the next step without further purification

ORD record

ord-3fe9f9e2bb2d48fa8c1ec81089209487

Source dataset

uspto-grants-1987_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04643759