反应详情

温度

-5 °C

3-Ethoxy-1-isopropyl-2-oxo-3-pyrroline-4-carboxylic acid (5b, 8 g, 0.0376 mol) in powdered form was added in small portions through a seive to a stirred mixture of 70 mL of concentrated sulfuric acid and 4.7 mL of white fuming nitric acid (90%) that had been cooled to -5° C. prior to the start of the addition of 5b. The rate of addition of 5b was controlled so as to keep the temperature of the reaction mixture from rising above -3° C. and to minimize accumulation of undissolved lumps of starting material in the mixture. Stirring was continued for 3 h at -3° C. Effervescence caused by carbon dioxide evolution began after the mixture had been stirred for a few minutes and virtually ceased after an hour of two. When the mixture was poured slowly into a stirred suspension of 1 L of crushed ice, the product separated as a white crystalline precipitate. It was collected by filtration as soon as the ice was melted and washed on the filter with a small amount of cold water. The yield was 4.9 g (61%), mp 47°-47° C. Recrystallization from acetone or benzene and petroleum ether (bp 30°-60° C.) raised the melting point to 49°-50° C.: 1H NMR (CDCl3) δ4.90 (q, 2H, OCH2CH3, J=7 Hz), 4.40 (septet, 1H, NCH(CH3)2, J=7 Hz), 4.15 (s, 2H, CH 2 of pyrroline), 1.55-1.20 (t+d, 9H, overlap of --OCH2CHc and NCH(CH3)2, J=7 Hz); IR (thin film) 3.34, 3.39, 3.47, 5.87, 6.08, 6.69, 6.92, 7.17, 7.3, 7.30, 7.38, 7.67, 7.93, 8.10, 8.40, 8.55, 8.75, 8.87, 9.05 μm; UV (95% EtOH) 293 nm (ε9800).

1. customfrom rising above -3° C.
2. stirringhad been stirred for a few minutes
3. waitvirtually ceased after an hour of two
4. customthe product separated as a white crystalline precipitate
5. filtrationIt was collected by filtration as soon as the ice
6. washwashed on the
7. filtrationfilter with a small amount of cold water
8. customRecrystallization from acetone or benzene and petroleum ether (bp 30°-60° C.)
9. temperatureraised the melting point to 49°-50° C.