反应详情

温度

68 °C

4-Carboxymethyl-3,5-dimethyl-1H-pyrrole-2-carboxylic acid wet mixture (778 g, 3.95 mol), 880 mL of 9 N potassium hydroxide and 880 mL of water were heated to an internal temperature of 65° C., removed from the heat, and 800 mL of 10 N hydrochloric acid were slowly added with stirring to a pH of 2.5. The temperature increased to 68° C. and then decreased to 58° C. with the evolution of carbon dioxide. Thin layer chromatography (ethyl acetate:hexane:acetic acid 4:6:0.5) showed a major spot at Rf 0.7 and a small spot at the origin. The mixture was cooled to 4° C. The solids were collected by vacuum filtration and washed 3 times with 200 mL of water each time. The solid was air dried to give 240 g (40% yield) of (2,4-dimethyl-1H-pyrrol-3-yl)-acetic acid as a brown solid. 1H-NMR (dimethylsulfoxide-d6) δ 1.89, 2.06 (2×s, 2×3H, 2×CH3), 3.17 (s, 2H, CH2), 6.26 (s, 1H, pyrrole CH), 10.02 (s, 1H, NH), 11.74 (br s, 1H, COOH).

1. customremoved from the heat, and 800 mL of 10 N hydrochloric acid
2. additionwere slowly added
3. customdecreased to 58° C. with the evolution of carbon dioxide
4. temperatureThe mixture was cooled to 4° C
5. filtrationThe solids were collected by vacuum filtration
6. washwashed 3 times with 200 mL of water each time
7. customdried