Реакция #7751

Уравнение реакции

4-Hydroxypyrazolidine-1,2-dicarboxylic acid 1-benzyl ester 2-tert-butyl ester

trimethylacetyl chloride

Dichloro-methane

→

desired product

Выход 98.0%

4-(2,2-dimethylpropionyloxy)pyrazolidine-1,2-dicarboxylic acid 1-benzyl ester 2-tert-butyl ester

Выход 98.0%

Растворители

pyridine

Условия реакции

Обработка

1. 1
   ДругоеThe cloudy reaction mixture
2. 2
   Концентрированиеis then concentrated in vacuo
3. 3
   Другоеto afford a white residue
4. 4
   Промывкаthe mixture washed with a 1.0 N aqueous solution of hydrochloric acid (75 mL)
5. 5
   ЭкстракцияThe aqueous layer is extracted with dichloro-methane (75 mL)
6. 6
   Промывкаthe combined organic layers washed with a saturated aqueous solution of NaHCO3 (75 mL), water (75 mL), brine (75 mL)
7. 7
   Другоеdried
8. 8
   Фильтрацияfiltered
9. 9
   Концентрированиеconcentrated in vacuo
10. 10
    Другоеto afford the crude product
11. 11
    ДругоеThe crude product is purified over silica (4:1 to 1:1 hexane/ethyl acetate)

Методика

4-Hydroxypyrazolidine-1,2-dicarboxylic acid 1-benzyl ester 2-tert-butyl ester, 28, (1.42 mg, 4.40 mmol) is dissolved in pyridine (22 mL). 4-Dimethylamino-pyridine (10 mg) is added followed by trimethylacetyl chloride (1.63 mL, 13.2 mmol). The reaction is stirred at ambient temperature for 12 hours. The cloudy reaction mixture is then concentrated in vacuo to afford a white residue. Dichloro-methane (75 mL) is added to the residue and the mixture washed with a 1.0 N aqueous solution of hydrochloric acid (75 mL). The aqueous layer is extracted with dichloro-methane (75 mL), the combined organic layers washed with a saturated aqueous solution of NaHCO3 (75 mL), water (75 mL), brine (75 mL), then dried, filtered and concentrated in vacuo to afford the crude product. The crude product is purified over silica (4:1 to 1:1 hexane/ethyl acetate) to afford 1.76 g (98% yield) of the desired product as a clear, viscous oil.

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