Reaction #2467989

Reaction equation

2-aminothiophene-3-carboxamide

sodium nitrite

→

solid

Yield 18.5%

3H-Thiopheno[2,3-d]1,2,3-triazin-4-one

Yield 18.5%

Solvents

sulfuric acid

sulfuric acid

Conditions

Workup

1. 1
   workup.ADDITIONwhile adding
2. 2
   Othershould keep between −5-0° C.
3. 3
   workup.ADDITIONAfter addition
4. 4
   workup.ADDITIONThe mixture was poured
5. 5
   Otherinto crushed ice slowly
6. 6
   workup.STIRRINGwith stirring for 15 min
7. 7
   workup.STIRRINGstirred at the same temperature for 15 min
8. 8
   ExtractionThe solution was extracted with ethyl acetate (4×200 mL)
9. 9
   Washthe combined EtOAc layer was washed with water, brine
10. 10
    Dryingdried over sodium sulfate
11. 11
    FiltrationThe solution was filtered
12. 12
    Otherevaporated the solvent
13. 13
    OtherThe residue was chromatographed over silica gel column

Procedure

To an ice cold solution (0° C.) of 2-aminothiophene-3-carboxamide (5 g, 35.21 mmol) in concentrated sulfuric acid (40 mL) was added a cold (0° C.) solution of sodium nitrite (2.5 g, 35.21 mmol) in concentrated sulfuric acid (30 mL) for 30 min (while adding, the temperature should keep between −5-0° C.). After addition, the mixture was stirred at the same temperature (0° C.) for 3 h. The mixture was poured into crushed ice slowly with stirring for 15 min and stirred at the same temperature for 15 min. The solution was extracted with ethyl acetate (4×200 mL) and the combined EtOAc layer was washed with water, brine and dried over sodium sulfate. The solution was filtered and evaporated the solvent. The residue was chromatographed over silica gel column using chloroform-methanol (95:5) as eluents to give the product as a pale red color solid (1.0 g, 18%), mp 175-176° C. 1H NMR (400 MHz, DMSO-d6): δ 15.18 (1H, s), 8.16 (1H, d, J=5.6 Hz), 7.64 (1H, d, J=5.6 Hz); 13C NMR (100 MHz, DMSO-d6): δ 159.1, 153.8, 132.0, 126.1, 121.2; LC-MS (negative ion mode): m/z 152 (M−H)−.

Source