Реакция #439079

Уравнение реакции

cyclohexanedione

ethyl bromopyruvate

KOH

hydrochloric acid

sodium hydroxide

Potassium hydroxide

→

4-oxo-4,5,6,7-tetrahydrobenzofuran-3-carboxylic acid

Выход 50.5%

Растворители

methyl alcohol

methyl alcohol

water

methyl alcohol

Условия реакции

Обработка

1. 1
   Другое4-Oxo-4,5,6,7-tetrahydrobenzofuran-3-carboxylic acid is prepared
2. 2
   Температураthen cooled in an ice water bath
3. 3
   workup.ADDITIONis added dropwise to the cold
4. 4
   Другоеto reach ambient temperature
5. 5
   ТемператураWhile cooling the reaction mixture via a water bath
6. 6
   workup.STIRRINGAfter stirring at ambient temperature for 15.5 h
7. 7
   Температураthe reaction mixture is cooled in an ice water bath
8. 8
   КонцентрированиеThe reaction mixture is concentrated in vacuo, 1 L of ice
9. 9
   workup.ADDITIONis added
10. 10
    Фильтрацияthe precipitate filtered
11. 11
    Промывкаwashed with ice water (3×200 mL)
12. 12
    Другоеdried in a vacuum oven at 75° C.

Методика

4-Oxo-4,5,6,7-tetrahydrobenzofuran-3-carboxylic acid is prepared according to the following procedure. Potassium hydroxide (345 g, 6.15 mol) is dissolved in methyl alcohol (1.2 L) then cooled in an ice water bath. A solution of cyclohexanedione (714 g, 6.15 mol) in methyl alcohol (1.2 L), dissolved using gentle heat, is added dropwise to the cold, stirred KOH solution over 2 h. A solution of ethyl bromopyruvate (1200 g, 6.15 mol) in methyl alcohol (1.5 L) is then added dropwise over 3 h. The reaction mixture is allowed to reach ambient temperature and stirred an additional 14.5 h. While cooling the reaction mixture via a water bath, a solution of sodium hydroxide (492 g, 12.4 mol) in water (984 mL) is added dropwise over 2.5 h. After stirring at ambient temperature for 15.5 h, the reaction mixture is cooled in an ice water bath, 500 g of ice added, and the resulting mixture is then acidified with concentrated hydrochloric acid (ca 1 L) to pH 1. The reaction mixture is concentrated in vacuo, 1 L of ice is added, and the precipitate filtered, washed with ice water (3×200 mL), and then dried in a vacuum oven at 75° C. to afford 4-oxo-4,5,6,7-tetrahydrobenzofuran-3-carboxylic acid (560 g). m.p. 137-138° C.

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