[CH3:1][C:2]1[N:3]([C:13]2[CH:18]=[CH:17][CH:16]=[C:15]([C:19]([F:22])([F:21])[F:20])[CH:14]=2)[C:4](=[O:12])[C:5]([C:8]([O:10][CH3:11])=[O:9])=[N:6][CH:7]=1.FC(F)(F)C(O)=O.[I:30]N1C(=O)CCC1=O.[Al]>O.C(Cl)Cl>[I:30][C:7]1[N:6]=[C:5]([C:8]([O:10][CH3:11])=[O:9])[C:4](=[O:12])[N:3]([C:13]2[CH:18]=[CH:17][CH:16]=[C:15]([C:19]([F:22])([F:20])[F:21])[CH:14]=2)[C:2]=1[CH3:1]Methyl 5-methyl-3-oxo-4-[3-(trifluoromethyl)phenyl]-3,4-dihydropyrazine-2-carboxylate (1.5 g, 4.8 mmol), dry DCM (7.0 mL), trifluoroacetic acid (3.0 mL) and N-iodosuccinimide (1.0 g, 4.5 mmol) were mixed and stirred at RT in the dark (flask covered with aluminum foil). After 5 h, water (5 mL) was added and the mixture was concentrated by rotary evaporation. Water (3 mL) was added once more and the mixture was concentrated as described above. The resulting mixture was diluted with acetonitrile to a total volume of 50 mL. Purification by preparative HPLC with acetonitrile-water as eluent (neutral eluent) gave methyl 6-iodo-5-methyl-3-oxo-4-[3-(trifluoromethyl)phenyl]-3,4-dihydropyrazine-2-carboxylate (0.905 g, 46%) as a yellow crystalline solid.
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