تفاعل #7751

معادلة التفاعل

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

trimethylacetyl chloride

Dichloro-methane

→

desired product

المردود 98.0%

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

المردود 98.0%

المذيبات

pyridine

ظروف التفاعل

المعالجة

1. 1
   أخرىThe cloudy reaction mixture
2. 2
   تركيزis then concentrated in vacuo
3. 3
   أخرىto afford a white residue
4. 4
   غسيلthe mixture washed with a 1.0 N aqueous solution of hydrochloric acid (75 mL)
5. 5
   استخلاصThe aqueous layer is extracted with dichloro-methane (75 mL)
6. 6
   غسيلthe combined organic layers washed with a saturated aqueous solution of NaHCO3 (75 mL), water (75 mL), brine (75 mL)
7. 7
   أخرىdried
8. 8
   ترشيحfiltered
9. 9
   تركيزconcentrated in vacuo
10. 10
    أخرىto afford the crude product
11. 11
    أخرىThe crude product is purified over silica (4:1 to 1:1 hexane/ethyl acetate)

الإجراء التجريبي

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.

المصدر