反应详情

39.6 g (approximately 0.105 mol) of 4-[(2-tert.butyl-6-benzothiazolyl)-sulphonyl]-5-methyl-1,2-benzenediol and 72.3 g (0.523 mol) of potassium carbonate are stirred in 300 ml of dimethylformamide at room temperature under inert gas protection. In the course of 20 minutes there is added dropwise thereto half of a solution of 45.6 g (0.209 mol) of dibromoacetic acid in 100 ml of dimethylformamide. The reaction mixture is subsequently stirred for 21 hours at 100° and, during this time, the remainder of the dibromoacetic acid solution is added in small portions. For working up, the dimethylformamide is distilled off in a rotary evaporator under a water jet vacuum. The residue is dissoled in water and adjusted to pH 1-2 with concentated hydrochloric acid. The precipitated acid is extracted three times with ethyl acetate. The combined ethyl acetate solutions are washed once with water, dried over sodium sulphate, filtered and concentrated by evaporation. The residue is dissolved in 500 ml of ethanol, and after the addition of 0.5 ml of concentrated hydrochloric acid the solution is left to stand at room temperature for 10 days. During this time, the ethyl ester of 5-methyl-6-[(2 -tert.-butyl-6-benzothiazolyl)-sulphonyl]-1,3-benzodioxole-2-carboxylic acid is precipitated in the form of colourless crystals. The crystal suspension is cooled to 0° and the crystals are filtered off. 90 ml of 2N sodium hydroxide solution are added to the crystals, still moist with ethanol, and the mixture is stirred for 2 hours at room temperature, a solution being formed. This is acidified with concentrated hydrochloric acid and the precipitated acid is extracted three times with ethyl acetate. The ethyl acetate solutions are washed with water, dried over sodium sulphate, filtered and concentrated by evaporation in vacuo to dryness. The residue is recrystallised from ethyl acetate, yielding 5-methyl-6-[(2-tert.-butyl-6-benzothiazolyl)-sulphonyl]-1,3-benzodioxole-2-carboxylic acid in the form of colourless crystals having a melting point of 247° (decomposition), after sintering from 203°.

1. additionIn the course of 20 minutes there is added dropwise
2. distillationthe dimethylformamide is distilled off in a rotary evaporator under a water jet vacuum
3. extractionThe precipitated acid is extracted three times with ethyl acetate
4. washThe combined ethyl acetate solutions are washed once with water
5. dry with materialdried over sodium sulphate
6. filtrationfiltered
7. concentrationconcentrated by evaporation
8. dissolutionThe residue is dissolved in 500 ml of ethanol
9. additionafter the addition of 0.5 ml of concentrated hydrochloric acid the solution
10. waitis left
11. waitto stand at room temperature for 10 days
12. customDuring this time, the ethyl ester of 5-methyl-6-[(2 -tert.-butyl-6-benzothiazolyl)-sulphonyl]-1,3-benzodioxole-2-carboxylic acid is precipitated in the form of colourless crystals
13. temperatureThe crystal suspension is cooled to 0°
14. filtrationthe crystals are filtered off
15. addition90 ml of 2N sodium hydroxide solution are added to the crystals, still moist with ethanol
16. stirringthe mixture is stirred for 2 hours at room temperature
17. customa solution being formed
18. extractionthe precipitated acid is extracted three times with ethyl acetate
19. washThe ethyl acetate solutions are washed with water
20. dry with materialdried over sodium sulphate
21. filtrationfiltered
22. concentrationconcentrated by evaporation in vacuo to dryness
23. customThe residue is recrystallised from ethyl acetate