反应详情

Chlorine was bubbled through a solution of 6.31 g (50 mmol) of 2-acetylthiophene in glacial acetic acid (25 ml). The reaction solution which evolved heat was cooled with water and kept below 28° C. The reaction was discontinued at the stage when the reaction solution turned slight yellow by the excess chlorine, and then acetic acid was distilled off at room temperature under a reduced pressure to give crude 2-(dichloroacetyl)thiophene. This crude product was added in dropwise with vigorous stirring to a solution of 10.0 g (250 mmol) of sodium hydroxide in water (90 ml) which was kept at 50° C. The temperature of the reaction solution rose to ca. 55° C. The addition was completed after ca. 2 hr., and the mixture was stirred for another 1 hr. at the same temperature. After cooling to room temperature, the reaction mixture was washed with diethylether, then acidified (pH 1) by addition of 12 N hydrochloric acid under ice cooling. The acidic material which separated out was extracted with diethylether, and the ether layer was washed with a saturated aqueous solution of sodium chloride, and after drying with sodium sulfate, the solvent was distilled off to give 2-thiopheneglycolic acid in quantitative yield (7.9 g).

1. temperatureThe reaction solution which evolved heat
2. customkept below 28° C
3. distillationacetic acid was distilled off at room temperature under a reduced pressure
4. customto give crude 2-(dichloroacetyl)thiophene
5. customwas kept at 50° C
6. customrose to ca. 55° C
7. additionThe addition
8. washthe reaction mixture was washed with diethylether
9. additionby addition of 12 N hydrochloric acid under ice cooling
10. customThe acidic material which separated out
11. extractionwas extracted with diethylether
12. washthe ether layer was washed with a saturated aqueous solution of sodium chloride
13. dry with materialafter drying with sodium sulfate
14. distillationthe solvent was distilled off