反应详情

Ethanedithiol (94 g) and ethyl alpha-chloroacetoacetate (164.5 g) were dissolved in benzene (500 g), a trace of p-toluenesulfonic acid added, and the whole solution refluxed under a Dean-Stark trap for one hour, when 16 cc of water had collected. The solution was cooled, washed with ice-cold dilute caustic soda and the benzene removed in vacuo. Ethanolic caustic soda (80 g in the minimum amount of ethanol) was added and the solution refluxed for 30 minutes, then cooled, diluted with water (one volume), and made acid with dilute HCl. The thick white precipitate was filtered, washed with water and recrystallized from ethanol to give 5,6-dihydro-3-methyl-1,4-dithiin-2-carboxylic acid as long white needles, m.p. 173°-175°, yield 92 g (52%).

1. temperaturethe whole solution refluxed under a Dean-Stark trap for one hour
2. customwhen 16 cc of water had collected
3. temperatureThe solution was cooled
4. washwashed with ice-cold dilute caustic soda
5. customthe benzene removed in vacuo
6. additionEthanolic caustic soda (80 g in the minimum amount of ethanol) was added
7. temperaturethe solution refluxed for 30 minutes
8. temperaturecooled
9. additiondiluted with water (one volume)
10. filtrationThe thick white precipitate was filtered
11. washwashed with water
12. customrecrystallized from ethanol