反应详情

A solution of 23.8 g of 4-nitrobutyric acid methyl ester (made in accordance with Bruson, U.S. Pat. No. 2,342,119) 39.6 g of methyl acrylate, 0.2 g triethyl amine in 200 ml of toluene is stirred and treated dropwise with 23.8 g of phenyl isocyanate. The mixture is stirred for 72 hours at room temperature and heated at 90° C. for two hours. The mixture is cooled, filtered to remove the diphyl urea, and concentrated under reduced pressure. The resulting oil is chromatographed on SiO2 (elution with hexane:ethyl-acetate; 75:25) to yield 4,5-dihydro-5-(methoxycarbonyl)-3-isoxazolepropanoic acid methyl ester as a colorless oil. NMR (CDCl3) and 4.93 (t, J=9 Hz, 1H), 3.72 (s, 3H), 3.63 (s, 3H), 3.20 (d, J-9 Hz, 2H9, 2.61 (s, 4H). IR (KBr) 2956, 2851, 1739, 1632, 1439, 1367, 1340, 1215. IR (cm-1).

1. temperatureheated at 90° C. for two hours
2. temperatureThe mixture is cooled
3. filtrationfiltered
4. customto remove the diphyl urea
5. concentrationconcentrated under reduced pressure
6. customThe resulting oil is chromatographed on SiO2 (elution with hexane:ethyl-acetate; 75:25)