Reacción #59806

Ecuación de reacción

HCl

LiOH

pyrazole triester

1-tert-butoxycarbonylmethyl-1H-pyrazole-3,5-dicarboxylic acid diethyl ester

→

1-tert-butoxycarbonylmethyl-1H-pyrazole-3,5-dicarboxylic acid 3-ethyl ester

Rendimiento 53.0%

triester

1-tert-butoxycarbonylmethyl-1H-pyrazole-3,5-dicarboxylic acid diethyl ester

Disolventes

ethyl acetate

tetrahydrofuran

water

Condiciones de reacción

Tratamiento posterior

1. 1
   ExtracciónThe organic extract
2. 2
   Lavadowas washed with brine
3. 3
   Secadodried over sodium sulfate
4. 4
   Otroevaporated to a residue which
5. 5
   Otrowas chromatographed on silica gel (1% methanol in dichloromethane, followed by 90:9:1 dichloromethane:methanol:acetic acid)

Procedimiento

According to a related procedure (Lee, H. H.; Cain, B. F.; Denny, W. A.; Buckleton, J. S.; Clark, G. R. J. Org. Chem. 1989, 54, 428-431) a solution of 9.6 g (29.4 mmol) of pyrazole triester (2) in 250 mL of tetrahydrofuran and 50 mL of water was cooled to −10° C. and 30 mL (30 mmol) of a chilled 1M LiOH solution was added dropwise. The reaction mixture was slowly allowed to warm to 0° C., then was stirred at 0° C. for an additional hour. The mixture was then diluted with 600 mL of ethyl acetate and acidified to pH=1 with 1 N HCl solution. The organic extract was washed with brine, dried over sodium sulfate, and evaporated to a residue which was chromatographed on silica gel (1% methanol in dichloromethane, followed by 90:9:1 dichloromethane:methanol:acetic acid) to give 4.66 g (53%) of desired 1-tert-butoxycarbonylmethyl-1H-pyrazole-3,5-dicarboxylic acid 3-ethyl ester L3), as well as 2.3 g of recovered starting triester (2). 1H NMR of 3 (300 MHz, CDCl3) δ 7.49 (s, 1H), 5.28 (s, 2H), 4.42 (q, J=7.1 Hz), 1.45 (s, 9 H), 1.40 (t, J=7.2 Hz, 3H).

Fuente