[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8]1[C:14]2[CH:15]=[C:16]([N+:19]([O-:21])=[O:20])[CH:17]=[CH:18][C:13]=2[NH:12][C:11](=[O:22])[C:10]([CH3:24])([CH3:23])[N:9]=1.[Br:25]N1C(=O)CCC1=O>Cl.C(O)=O>[Br:25][C:18]1[C:13]2[NH:12][C:11](=[O:22])[C:10]([CH3:24])([CH3:23])[N:9]=[C:8]([C:3]3[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=3[F:1])[C:14]=2[CH:15]=[C:16]([N+:19]([O-:21])=[O:20])[CH:17]=130 g (0.092 mol) of 5-(o-fluorophenyl)-1,3-dihydro-3,3-dimethyl-7-nitro-2H-1,4-benzodiazepin-2-one are dissolved in 600 ml of concentrated hydrochloric acid and 600 ml of formic acid, treated with 49.5 g of N-bromosuccinimide and stirred at room temperature for 48 hours. Subsequently, an additional 33 g of N-bromosuccinimide are added thereto and the mixture is stirred at room temperature for 4 days. The solution is evaporated and the residue is poured into ice and aqueous ammonia. After extracting the aqueous solution three times with methylene chloride, the organic phase is dried and evaporated. The residue is chromatographed on 2 kg of silica gel with methylene chloride and methylene chloride/ethyl acetate (20:1) as the elution agent. There is obtained 9-bromo-5-(o-fluorophenyl)-1,3-dihydro-3,3-dimethyl-7-nitro-2H-1,4-benzodiazepin-2-one of melting point 164° (ether/n-hexane).
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