反应详情

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) and 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).

1. temperatureby refluxing overnight
2. concentrationThe reaction mixture is concentrated
3. customthe residue is partitioned between EtOAc and 1N HCl
4. dry with materialThe organic phase is dried (Na2SO4)
5. concentrationconcentrated to a residue
6. customThe residue is purified by column chromatography (0-15% EtOAc in hexanes)