2-Methylbenzothiazole → 2-Methylbenzo[d]thiazole-4-sulfonyl chloride
Reaktionsgleichung
[CH3:1][C:2]1[S:3][C:4]2[CH:10]=[CH:9][CH:8]=[CH:7][C:5]=2[N:6]=1.[Cl:11][S:12](O)(=[O:14])=[O:13]>>[CH3:1][C:2]1[S:3][C:4]2[C:5](=[C:7]([S:12]([Cl:11])(=[O:14])=[O:13])[CH:8]=[CH:9][CH:10]=2)[N:6]=1Komponenten
3
Versuchsvorschrift
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.