反应详情

2.1 g of the free 4-(2,3-dichlorophenyl)pyrrole-3-carboxylic acid obtained in (b) are dissolved in 30 ml of ethanol. The solution is made alkaline with concentrated ammonia and then evaporated to dryness. The residue is dissolved in 50 ml of ethanol. NH3 gas is added (20 atm) to this solution at room temperature in an autoclave and the reaction mixture is kept for 15 hours at 220° C. The reaction mixture, which has cooled to room temperature, is poured into ice/HCl, the precipitate is isolated by filtration and dried at 60° C. The resultant powder is heated with 17 g of polyphosphoric acid in an open vessel at 180° C., the hot mixture is dropped onto ice, made alkaline with NaOH and extracted with ethyl acetate. The combined extracts are concentrated by evaporation and the residue is purified by column chromatography (silica gel; elution with a 4:1 mixture of toluene/ethyl acetate), affording 4-(2,3-dichlorophenyl)-3-cyanopyrrole of m.p. 148°-150° C.

1. customevaporated to dryness
2. dissolutionThe residue is dissolved in 50 ml of ethanol
3. additionNH3 gas is added (20 atm) to this solution at room temperature in an autoclave
4. additionis poured into ice/HCl
5. customthe precipitate is isolated by filtration
6. customdried at 60° C
7. temperatureThe resultant powder is heated with 17 g of polyphosphoric acid in an open vessel at 180° C.
8. additionthe hot mixture is dropped onto ice
9. extractionextracted with ethyl acetate
10. concentrationThe combined extracts are concentrated by evaporation
11. customthe residue is purified by column chromatography (silica gel
12. washelution
13. additionwith a 4:1 mixture of toluene/ethyl acetate),