Reaktion #50958

Reaktionsgleichung

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

trimethylacetyl chloride

Dichloro-methane

→

desired product

Ausbeute 98.0%

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

Ausbeute 98.0%

Lösungsmittel

pyridine

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe cloudy reaction mixture
2. 2
   Einengenis then concentrated in vacuo
3. 3
   Sonstigeto afford a white residue
4. 4
   Waschenthe mixture washed with a 1.0 N aqueous solution of hydrochloric acid (75 mL)
5. 5
   ExtraktionThe aqueous layer is extracted with dichloro-methane (75 mL)
6. 6
   Waschenthe combined organic layers washed with a saturated aqueous solution of NaHCO3 (75 mL), water (75 mL), brine (75 mL)
7. 7
   Sonstigedried
8. 8
   Filtrationfiltered
9. 9
   Einengenconcentrated in vacuo
10. 10
    Sonstigeto afford the crude product
11. 11
    SonstigeThe crude product is purified over silica(4:1 to 1:1 hexane/ethyl acetate)

Vorschrift

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.

Quelle