Reacción #7751

Ecuación de reacción

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

trimethylacetyl chloride

Dichloro-methane

→

desired product

Rendimiento 98.0%

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

Rendimiento 98.0%

Disolventes

pyridine

Condiciones de reacción

Tratamiento posterior

1. 1
   OtroThe cloudy reaction mixture
2. 2
   Concentraciónis then concentrated in vacuo
3. 3
   Otroto afford a white residue
4. 4
   Lavadothe mixture washed with a 1.0 N aqueous solution of hydrochloric acid (75 mL)
5. 5
   ExtracciónThe aqueous layer is extracted with dichloro-methane (75 mL)
6. 6
   Lavadothe combined organic layers washed with a saturated aqueous solution of NaHCO3 (75 mL), water (75 mL), brine (75 mL)
7. 7
   Otrodried
8. 8
   Filtraciónfiltered
9. 9
   Concentraciónconcentrated in vacuo
10. 10
    Otroto afford the crude product
11. 11
    OtroThe crude product is purified over silica (4:1 to 1:1 hexane/ethyl acetate)

Procedimiento

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.

Fuente