[Cl:1][C:2]1[N:3]([C:9]2[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=2[CH3:15])[C:4](=[O:8])[N:5]([CH3:7])[N:6]=1.[Br:16]N1C(=O)CCC1=O.C(OOC(=O)C1C=CC=CC=1)(=O)C1C=CC=CC=1>C(Cl)(Cl)(Cl)Cl>[Br:16][CH2:15][C:10]1[CH:11]=[CH:12][CH:13]=[CH:14][C:9]=1[N:3]1[C:2]([Cl:1])=[N:6][N:5]([CH3:7])[C:4]1=[O:8]Preparation of ##STR16## a) 8.95 g of 5-chloro-2-methyl-4-(o-tolyl)-2,4-dihydro[1,2,4]triazol-3-one (prepared according to WO 95/14009) and 7.83 g of N-bromosuccinimide are placed in 50 ml of carbon tetrachloride, and a catalytic amount of dibenzoyl peroxide is added. The suspension is then stirred under reflux with illumination (a 500 W photographic lamp) for 11/2 hours. The suspension is concentrated by evaporation and the residue is chromatographed directly on silica gel using hexane/ethyl acetate (6:4). Recrystallization from toluene/heptane (1:1) gives 4-(2-bromomethylphenyl)-5-chloro-2-methyl-2,4-dihydro[1,2,4]triazol-3-one as white crystals of m.p. 131.5-133° C.
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