反应详情

Add 2 g of 3-(5-nitro-2-furyl)-1-phenylpyrazole-4-carboxamide to 4.7 ml of concentrated sulfuric acid while cooling on ice and then add thereto a solution of 0.78 g of sodium nitrite in 2 ml of water slowly and dropwise at a temperature not exceeding 7° C. Allow the resulting mixture to stand overnight; dilute with from 4 to 5 ml of concentrated sulfuric acid and then mix it (while cooling with ice) with 0.39 g of sodium nitrite in 1 ml of water. Allow the thus-prepared solution to stand at a temperature of 0° to 5° C for 2 days in a refrigerator and then pour it onto ice. Vacuum filter to separate formed precipitate and chromatograph with chloroform/ethanol (9:1) on a silica gel column to obtain 3-(5-nitro-2-furyl)-1-phenylpyrazole-4-carboxylic acid [m.p. 250° to 252° C].

1. temperaturewhile cooling on ice
2. additionadd
3. customexceeding 7° C
4. additionmix
5. waitto stand at a temperature of 0° to 5° C for 2 days in a refrigerator
6. additionpour it onto ice
7. filtrationVacuum filter
8. customto separate
9. customformed precipitate and chromatograph with chloroform/ethanol (9:1) on a silica gel column