[F:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[N:8]=[CH:7][NH:6][C:5]2=S.O.[NH2:14][NH2:15].[CH:16]([O-])([O-])OC>O1CCCC1>[F:1][C:2]1[CH:11]=[CH:10][C:9]2[N:8]=[CH:7][N:14]3[N:15]=[CH:16][N:6]=[C:5]3[C:4]=2[CH:3]=13. 2.9 g of crude 6-fluoro-3H-quinazoline-4-thione are suspended in 75 ml of tetrahydrofuran. 7.9 ml of hydrazine hydrate are then added at room temperature while stirring. A solution results for a short time after about 15 min., then a precipitate separates. The mixture is stirred at room temperature for 3 h., 75 ml of methyl orthoformate are then added thereto and the tetrahydrofuran is distilled off. The residual suspension is stirred at room temperature for 3 h. The reaction solution is evaporated in a vacuum. The residue is taken up in 300 ml of water, stirred at room temperature for 1 h. and then cooled to 15° C. The crystals are filtered off and dried in a vacuum, 2.9 g of crude product are obtained. 2.4 g of 9-fluoro-1,2,4-triazolo[1,5-c]quinazoline of m.p. 193°-195° C. are obtained after recrystallization from ethanol.
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