反应详情

Acetic anhydride (8 ml, 85 mmol) was treated with nitric acid (1.020 ml, 15.98 mmol) (heating occurred upon addition); the mixture was cooled to RT and slowly added to a suspension of 1-methyl-1H-pyrrole-2-carboxylic acid (2 g, 15.98 mmol) in acetic anhydride (12 ml, 127 mmol) cooled to −30° C. The reaction was stirred at −30° C. for 0.5 hours, then at RT for 20 minutes. The mixture was cooled again to −30° C. to precipitate the desired product. The solid was quickly filtered in a frit funnel cooled in dry ice; after a few minutes at room temperature, the solid became deliquescent and resulted in a thick slurry/solution that was collected in a separate flask. The slurry was cooled at −30° C. and washed twice with a mixture of hexane (5 ml) and (iPr)2O (1 ml). The obtained solid was dried under vacuum, then treated with 2N NaOH till complete dissolution (10 ml) and precipitated again by addition of 37% HCl (20 ml). The solid was filtered, washed with water (10 ml) and finally dried under vacuum for 3 days to yield 1-methyl-4-nitro-1H-pyrrole-2-carboxylic acid (Int. 15) (540 mg, 3.17 mmol, MS/ESI+ 170.9 [MH]+).

1. temperaturecooled to −30° C
2. waitat RT for 20 minutes
3. temperatureThe mixture was cooled again to −30° C.
4. customto precipitate the desired product
5. filtrationThe solid was quickly filtered in a frit funnel
6. temperaturecooled in dry ice
7. waitafter a few minutes at room temperature
8. customresulted in a thick slurry/solution that
9. customwas collected in a separate flask
10. temperatureThe slurry was cooled at −30° C.
11. washwashed twice with a mixture of hexane (5 ml) and (iPr)2O (1 ml)
12. customThe obtained solid was dried under vacuum
13. additiontreated with 2N NaOH till complete dissolution (10 ml)
14. customprecipitated again by addition of 37% HCl (20 ml)
15. filtrationThe solid was filtered
16. washwashed with water (10 ml)
17. customfinally dried under vacuum for 3 days