反应详情

温度

25 °C

A solution of 2-mercaptoethanol (58.5 g.) in anhydrous ethanol (220 cc.) is added, at about 10° C. and over the course of one hour, to a solution of sodium ethoxide in ethanol [prepared by reacting sodium (17.2 g.) with anhydrous ethanol (570 cc.)]. After having heated the reaction mixture to 45°-50° C., ethyl γ-bromoacetoacetate (157 g.) is added over the course of 45 minutes, and then the reaction mixture is stirred for 2 hours at a temperature of about 25° C. After filtration, the solvent is evaporated at about 50° C. under reduced pressure (20 mm.Hg). The residue is dissolved in anhydrous toluene (1,000 cc.) and, after filtration of the resulting solution, toluene-p-sulphonic acid monohydrate (1.5 g.) is added. The reaction mixture is heated under reflux until complete dehydration has taken place (the water formed being removed in a Dean-Stark apparatus) and then toluene (200 cc.) is distilled. After cooling, the toluene solution is filtered and washed twice with a saturated aqueous solution of sodium bicarbonate (200 cc.) and then with water (2 × 200 cc.); it is then dried over sodium sulphate, treated with decolourizing charcoal, filtered and evaporated under reduced pressure (20 mm.Hg). A residue (131.9 g.) is obtained and is chromatographed on alumina (550 g.). Elution is effected using a mixture (2.5 liters) of ethyl acetate and cyclohexane (1-19 by volume) and the eluates are concentrated to dryness under reduced pressure (20 mm.Hg). Ethyl (5,6-dihydro-1,4-oxathiin-2-yl )acetate (75.7 g.) is obtained in the form of an oil.

1. temperatureAfter having heated the reaction mixture to 45°-50° C.
2. filtrationAfter filtration
3. customthe solvent is evaporated at about 50° C. under reduced pressure (20 mm.Hg)
4. dissolutionThe residue is dissolved in anhydrous toluene (1,000 cc.)
5. filtrationafter filtration of the resulting solution, toluene-p-sulphonic acid monohydrate (1.5 g.)
6. additionis added
7. temperatureThe reaction mixture is heated
8. temperatureunder reflux until complete dehydration
9. customformed
10. custombeing removed in a Dean-Stark apparatus) and then toluene (200 cc.)
11. distillationis distilled
12. temperatureAfter cooling
13. filtrationthe toluene solution is filtered
14. washwashed twice with a saturated aqueous solution of sodium bicarbonate (200 cc.)
15. dry with materialit is then dried over sodium sulphate
16. additiontreated with decolourizing charcoal
17. filtrationfiltered
18. customevaporated under reduced pressure (20 mm.Hg)
19. customA residue (131.9 g.) is obtained
20. customis chromatographed on alumina (550 g.)
21. washElution
22. concentrationthe eluates are concentrated to dryness under reduced pressure (20 mm.Hg)