反应详情

温度

70 °C

A suspension of 25.0 g (90 mmol) of ethyl 2-bromo-3-nitro-5-thiophenecarboxylate (Tetrahedron 21 (1965) 1061) and 29.0 g (450 mmol) of sodium azide in 300 ml of methanol is stirred at room temperature for 4 hours in 300 ml of ethanol. The mixture is poured into 4 l of ice-water, the precipitate is filtered off and the residue is heated at 70° C. for 3 hours in 700 ml of toluene. Subsequent purification by flash chromatography yields 6.5 g (34%) of ethyl thieno[2,3-c][1,2,5]oxadiazole-5-carboxylate-1-oxide and -3-oxide, m.p. 72°-74° C.

1. filtrationthe precipitate is filtered off
2. customSubsequent purification by flash chromatography