Реакция #216436

Уравнение реакции

diisopropylamine

n-butyllithium

hexane

2-thiophenecarboxylic acid

ethyl chloroformate

NaHCO3

2-thiophenecarboxylic acid

→

desired acid 35

Выход 75.1%

5-Carboethoxythiophen-2-carboxylic acid

Выход 75.1%

Растворители

THF

THF

Условия реакции

Обработка

1. 1
   workup.ADDITIONwas added slowly
2. 2
   workup.STIRRINGThe mixture was stirred for 15 min
3. 3
   workup.STIRRINGThe mixture was stirred for 30 min at -78° C.
4. 4
   Промывкаwashed with 80% ethyl acetate/hexane
5. 5
   Экстракцияextracted with 80% ethyl acetate/hexane
6. 6
   СушкаThe combined organic layers were dried over anhydrous MgSO4
7. 7
   Фильтрацияfiltered
8. 8
   Концентрированиеconcentrated
9. 9
   Другоеto afford a yellow solid

Методика

To a solution of diisopropylamine (3.6 mL, 25.75 mmol) in 10 mL of THF at -78° C. under argon was added a 1.6M solution of n-butyllithium in hexane (16.1 mL, 25.75 mmol). The mixture was stirred for 15 min, and a solution of 2-thiophenecarboxylic acid 34 (1.5 g, 11.705 mmol) (2-thiophenecarboxylic acid 34 is readily available from Aldrich) in 5 mL of THF was added slowly. The mixture was stirred for 15 min, and ethyl chloroformate (2.7 mL, 28.33 mmol) was added. The mixture was stirred for 30 min at -78° C., and warmed to 0° C. for another 30 min. The reaction mixture was poured into saturated aqueous NaHCO3, and washed with 80% ethyl acetate/hexane. The aqueous layer was acidified with acetic acid and extracted with 80% ethyl acetate/hexane. The combined organic layers were dried over anhydrous MgSO4, filtered, and concentrated to afford a yellow solid. Flash chromatography yielded the desired acid 35 (1.76 g, 75%) as a white solid: m.p. >300° C. The structure of the product was also confirmed using IR, 1H NMR and mass spectroscopy.

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