Réaction #8801

Équation de réaction

amide

3-nitrothiophene-2-carboxamide

Triethylamine

trifluoroacetic anhydride

→

2-cyano-3-nitrothiophene

Rendement 96.6%

Solvants

dichloromethane

Conditions de réaction

Traitement

1. 1
   Températureto warm to room temperature
2. 2
   ConcentrationThe solution was concentrated in vacuo
3. 3
   Lavagewashed successively with hydrochloric acid (1N, 2×), water (1×), saturated aqueous sodium hydrogencarbonate (2×) and brine
4. 4
   SéchageDrying over sodium sulfate and removal of solvent
5. 5
   Autregave a dark solid, which
6. 6
   Autrewas purified by flash chromatography (400 g of silica gel, petroleum ether:ethyl acetate 7:3+1% MeOH as eluent)

Mode opératoire

The amide 30 (15.5 g, 90 mmol), prepared as described above, was dissolved in dichloromethane (700 ml). Triethylamine (27.2 g, 37.6 ml, 270 mmol) was added and the solution cooled to 0° C. After dropwise addition of neat trifluoroacetic anhydride (24.6 g, 16.5 ml, 117 mmol), the reaction was allowed to warm to room temperature and stirred for 1 h. The solution was concentrated in vacuo, the residue taken into ethyl acetate and then washed successively with hydrochloric acid (1N, 2×), water (1×), saturated aqueous sodium hydrogencarbonate (2×) and brine. Drying over sodium sulfate and removal of solvent gave a dark solid, which was purified by flash chromatography (400 g of silica gel, petroleum ether:ethyl acetate 7:3+1% MeOH as eluent) yielding 2-cyano-3-nitrothiophene 31 (13.4 g, 96.5%). 1H NMR (CDCl3): δ 7.75 (1H, d, J 5.5), 7.68 (1H, d, J 5.5). An analytical sample was obtained by recrystallization from dichloromethane/n-pentane, m.p. 87–88° C.; elemental analysis, calc. for C5H2N2O2S: C, 38.96; H, 1.31; N, 18.17; S, 20.80. Found: C, 38.92; H, 1.20; N, 18.03; S, 21.31.

Source