Реакция #93191

Уравнение реакции

imidazole

3-Acetylthio-2-methylpropanoic acid

1,1'-carbonyldiimidazole

Glycolic acid

glycolic acid

→

O-[3-(Acetylthio)-2-methylpropanoyl]glycolic Acid

Растворители

tetrahydrofuran

tetrahydrofuran

triethylamine

Условия реакции

Обработка

1. 1
   workup.WAITAfter several minutes
2. 2
   workup.WAITto run overnight at room temperature
3. 3
   ФильтрацияThe crystalline salt is filtered
4. 4
   Концентрированиеthe filtrate concentrated to dryness in vacuo
5. 5
   Промывкаwashed with 1N hydrochloric acid and three times with water
6. 6
   Сушкаdried over magnesium sulfate
7. 7
   Концентрированиеconcentrated to dryness in vacuo
8. 8
   workup.DISSOLUTIONby dissolving in ether/hexane
9. 9
   Другоеprecipitating by the addition of dicyclohexylamine
10. 10
    ДругоеThe salt is recrystallized from ether, m.p. 120°-122°
11. 11
    workup.ADDITIONby adding to ethyl acetate
12. 12
    workup.ADDITIONadding 10% potassium bisulfate solution
13. 13
    Другоеcrystallizing from ethyl/hexane, yield 2.96 g

Методика

3-Acetylthio-2-methylpropanoic acid (6.48 g) is taken into 40 ml of dry tetrahydrofuran. To this 1,1'-carbonyldiimidazole (0.48 g) is added and stirred for 30 minutes at room temperature. Glycolic acid (6.08 g) and 11.2 ml of triethylamine in 60 ml of dry tetrahydrofuran are added. After several minutes, the imidazole salt of glycolic acid begins to come out of solution. The reaction is permitted to run overnight at room temperature. The crystalline salt is filtered and the filtrate concentrated to dryness in vacuo. The residue is taken up into ethyl acetate, washed with 1N hydrochloric acid and three times with water, dried over magnesium sulfate and concentrated to dryness in vacuo. This product is converted to its dicyclohexylamine salt by dissolving in ether/hexane and precipitating by the addition of dicyclohexylamine. The salt is recrystallized from ether, m.p. 120°-122°. This salt is then converted to the free acid, O-[3-(acetylthio)-2-methylpropanoyl]glycolic acid by adding to ethyl acetate, adding 10% potassium bisulfate solution, then crystallizing from ethyl/hexane, yield 2.96 g., m.p. 50°-51°.

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