Diethyl Ether → 1-Benzyl 2-(tert-butyl) 4-hydroxypyrazolidine-1,2-dicarboxylate

Temperature

-78 °C

4-Oxo-pyrazolidine-1,2-dicarboxylic acid 1-benzyl ester 2-tert-butyl ester, 27, (5.0 g, 15.6 mmol) is dissolved in tetrahydrofuran (150 mL) and the solution cooled to −78° C. A 5.0 M solution of borane-dimethyl sulfide complex in ether (6.24 mL, 31.2 mmol) is added dropwise via syringe. After 40 minutes at −78° C., the reaction is quenched by slow addition of a saturated aqueous solution of ammonium chloride (20 mL). The cooling bath is removed, and the mixture allowed to warm to ambient temperature with vigorous stirring. The solvent is removed in vacuo and the residue diluted with dichloromethane (200 mL). The mixture is washed with water (150 mL) and saturated aqueous sodium bicarbonate solution (150 mL), water and brine. The combined aqueous layers are extracted with dichloromethane (200 mL), water (150 mL), NaCl (sat.) (200 mL), dried over sodium sulfate, filtered and concentrated in vacuo to afford 4.66 g (93% yield) of the desired product as a clear, viscous oil.

1. customthe reaction is quenched by slow addition of a saturated aqueous solution of ammonium chloride (20 mL)
2. customThe cooling bath is removed
3. temperatureto warm to ambient temperature with vigorous stirring
4. customThe solvent is removed in vacuo
5. additionthe residue diluted with dichloromethane (200 mL)
6. washThe mixture is washed with water (150 mL) and saturated aqueous sodium bicarbonate solution (150 mL), water and brine
7. extractionThe combined aqueous layers are extracted with dichloromethane (200 mL), water (150 mL), NaCl (sat.) (200 mL)
8. dry with materialdried over sodium sulfate
9. filtrationfiltered
10. concentrationconcentrated in vacuo

ORD record

ord-7586e21a40db43ebb5b8ee6044639131

Source dataset

uspto-grants-2004_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06730668B2