[Cl:1][C:2]1[C:3]2[N:4]([C:16]([CH3:24])=[C:17]([C:19]([O:21][CH2:22][CH3:23])=[O:20])[N:18]=2)[C:5]2[C:10]([N:11]=1)=[CH:9][C:8]([C:12]([F:15])([F:14])[F:13])=[CH:7][CH:6]=2.[Br:25]N1C(=O)CCC1=O>ClC(Cl)(Cl)Cl.N(C(C)(C)C#N)=NC(C)(C)C#N>[Br:25][CH2:24][C:16]1[N:4]2[C:5]3[C:10]([N:11]=[C:2]([Cl:1])[C:3]2=[N:18][C:17]=1[C:19]([O:21][CH2:22][CH3:23])=[O:20])=[CH:9][C:8]([C:12]([F:15])([F:13])[F:14])=[CH:7][CH:6]=3A mixture of 4-chloro-2-ethoxycarbonyl-1-methyl-7-trifluoromethylimidazo[1,2-a]quinoxaline (830 g, 232 mmol), N-bromosuccinimide (68,0 g, 382 mmol) and 2,2'-azobis(2-methylpropionitrile)(200 mg, 1.2 mmol) in tetrachloromethane (1.5 l) was heated at reflux for 18 h, allowed to cool and the product collected by filtration. The product was dissolved in dichloromethane (2 l) and washed with water, dried (MgSO4), followed by purification with silica gel 60 (1 g). The organic phase was filtered and evaporated in vacuo. The residue was suspended in petroleum ether to yield 91.7 g (91%) of 1-bromomethyl-4-chloro-2-ethoxycarbonyl-7-trifluoromethyl-imidazo[1,2-a]quinoxaline which was collected by filtration. M.p. 196°-198° C.
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