反应详情

温度

25 °C

A solution of 2-mercaptoethanol (38.2 g.) in anhydrous ethanol (146 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 (11.2 g.) with anhydrous ethanol (350 cc.)]. After heating the reaction mixture to a temperature of 45°-f 50° C., ethyl 3-bromo-3-formylpropionate (102.8 g.) is added over the course of 20 minutes. The reaction mixture is stirred for 15 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 (500 cc.); the solution is filtered and toluene-p-sulphonic acid monohydrate (1.5 g.) is then 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 the solvent is evaporated at about 50° C. under reduced pressure (20 mm.Hg). The residue is taken up in diethyl ether (700 cc.); some insoluble matter appears and is removed by filtration through "Supercel". The ether solution is washed three times with water (total 600 cc.), then dried over sodium sulphate, treated with decolourizing charcoal and filtered. The solution is concentrated to dryness under reduced pressure (20 mm.Hg); a residue (65 g.) is obtained and is chromatographed on alumina (600 g.). Elution is effected using a mixture (2.6 liters) of ethyl acetate and cyclohexane (1-19 by volume). After concentration to dryness under reduced pressure (20 mm.Hg), ethyl (5,6-dihydro-1,4-oxathiin-3-yl )acetate (16.8 g.) is obtained in the form of an oil.

1. additionis added over the course of 20 minutes
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 (500 cc.)
5. filtrationthe solution is filtered
6. additiontoluene-p-sulphonic acid monohydrate (1.5 g.) is then 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 the solvent
11. customis evaporated at about 50° C. under reduced pressure (20 mm.Hg)
12. customis removed by filtration through "Supercel"
13. washThe ether solution is washed three times with water (total 600 cc.)
14. dry with materialdried over sodium sulphate
15. additiontreated with decolourizing charcoal
16. filtrationfiltered
17. concentrationThe solution is concentrated to dryness under reduced pressure (20 mm.Hg)
18. customa residue (65 g.) is obtained
19. customis chromatographed on alumina (600 g.)
20. washElution
21. concentrationAfter concentration to dryness under reduced pressure (20 mm.Hg)