Reaktion #1776939

Reaktionsgleichung

3-isopropyl-4-dimethylamino-2-oxo-but-3-enoic acid ethyl ester

2,6-dichlorophenylhydrazine hydrochloride

HCl

→

title compound

Ausbeute 52.0%

2-(2,6-Dichloro-phenyl)-4-isopropyl-2H-pyrazole-3-carboxylic acid methyl ester

Ausbeute 52.0%

Lösungsmittel

EtOH

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturby refluxing overnight
2. 2
   EinengenThe reaction mixture is concentrated
3. 3
   Sonstigethe residue is partitioned between EtOAc and 1N HCl
4. 4
   TrocknenThe organic phase is dried (Na2SO4)
5. 5
   Einengenconcentrated to a residue
6. 6
   SonstigeThe residue is purified by column chromatography (0-15% EtOAc in hexanes)

Vorschrift

To a solution of 4-methyl-2-oxo-pentanoic acid methyl ester (3.8 g, 26 mmol) in N,N-dimethylformamide dimethyl acetal (7 mL, 52 mmol) is added p-toluenesulfonic acid monohydrate (30 mg). The mixture is stirred at 80° C. overnight. The reaction mixture is concentrated under reduced pressure to give 3-isopropyl-4-dimethylamino-2-oxo-but-3-enoic acid ethyl ester as an orange oil. To a solution of 3-isopropyl-4-dimethylamino-2-oxo-but-3-enoic acid ethyl ester and 2,6-dichlorophenylhydrazine hydrochloride (2.8 g, 13 mmol) in EtOH (40 mL) is added concentrated HCl (0.5 mL). The mixture is stirred at ambient temperature for 2 h followed by refluxing overnight. The reaction mixture is concentrated and the residue is partitioned between EtOAc and 1N HCl. The organic phase is dried (Na2SO4) and concentrated to a residue. The residue is purified by column chromatography (0-15% EtOAc in hexanes) to give the title compound as an oil (2.2 g, 52%). 1H NMR (CDCl3): δ 7.76 (s, 1H), 7.43 (d, 2H), 7.34 (dd, 1H), 3.75 (s, 3H), 3.48 (m, 1H), 1.32 (d, 6H).

Quelle