[F:1][C:2]1[CH:3]=[C:4]([C:16]#[N:17])[C:5]([C:8]2[C:13]([F:14])=[CH:12][CH:11]=[CH:10][C:9]=2[F:15])=[CH:6][CH:7]=1.[Br:18]N1C(C)(C)C(=O)N(Br)C1=O.S(=O)(=O)(O)O.O>C(#N)C>[Br:18][C:12]1[C:13]([F:14])=[C:8]([C:5]2[C:4]([C:16]#[N:17])=[CH:3][C:2]([F:1])=[CH:7][CH:6]=2)[C:9]([F:15])=[CH:10][CH:11]=1
To a slurry of 4,2′,6′-trifluorobiphenyl-2-carbonitrile (5.0 g, 21.4 mmol) and 1,3-dibromo-5,5-dimethylhydantoin (3.37 g, 11.8 mmol) in acetonitrile (45 ml) was added concentrated sulfuric acid (3.15 g, 32.2 mmol). The slurry was warmed to 70° C. and the resulting solution stirred for 7 h then aged at ambient temperature for 18 h. Water (45 ml) was added dropwise to the solution over 15 min. The layers were allowed to settle and the product rapidly crystallised. The slurry was left to stir for 0.5 h then the solid was collected by filtration, washed with 1:1 acetonitrile:water (10 ml) and left to air dry, which gave 3′-bromo-4,2′,6′-trifluorobiphenyl-2-carbonitrile (6.3 g, 94%) as a white solid: δH (360 MHz, CDCl3) 6.97–7.08 (1H, m), 7.38–7.54 (2H, m), 7.62–7.68 (1H, m).
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