[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]=1To 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 sulphuric acid (3.15 g, 32.2 mmol). The slurry was warmed to 70° C. and the resulting solution stirred for 7 h then stood 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 filtered, 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 I, CDCl3) 6.97-7.08 (1H, m), 7.38-7.54 (2H, m), 7.62-7.68 (1H, m).
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