反应详情

3,5-Dimethyl-2,4-pyrrole dicarboxylic acid, diethyl ester (200 g, 836 mmol) was placed in a 1 L beaker and treated with 400 mL concentrated sulfuric acid (H2SO4). The mixture was stirred, heated to 45 C with the aid of a heat gun and then maintained at 36–42 C for 25 minutes. The reaction mixture was poured into 3 L crushed ice and stirred for 30 minutes. The yellow solid was recovered by filtration and washed with 200 mL water. The solid was transferred to a 4 L Erlenmeyer flask and treated with 2 L 1 N sodium hydroxide solution (NaOH) followed by 100 mL 10 N NaOH. The basic mixture was filtered and the yellow solid residue was discarded. The filtrate was acidified with H2SO4. The resulting solid was recovered by suction filtration and washed with 2×500 mL water. After suction drying, the material was transferred to a 6 L Erlenmeyer flask and digested briefly in 4 L acetone. After standing overnight at room temperature (RT), the solid was collected by filtration and dried in a vacuum dessicator to afford 139 g, 659 mmol, 79% of the title compound. 1H NMR (DMSO-d6) δ 4.22 (q, 2H), 2.44 (s, 3H), 2.38 (s, 3H), 1.27 (t, 3H).

1. temperatureheated to 45 C with the aid of a heat gun
2. temperaturemaintained at 36–42 C for 25 minutes
3. additionThe reaction mixture was poured into 3 L
4. customcrushed ice
5. stirringstirred for 30 minutes
6. filtrationThe yellow solid was recovered by filtration
7. washwashed with 200 mL water
8. additiontreated with 2 L 1 N sodium hydroxide solution (NaOH)
9. filtrationThe basic mixture was filtered
10. filtrationThe resulting solid was recovered by suction filtration
11. washwashed with 2×500 mL water
12. customAfter suction drying
13. filtration(RT), the solid was collected by filtration
14. customdried in a vacuum dessicator