[C:1]([O:5][C:6](=[O:16])[C:7]1[CH:12]=[CH:11][C:10]([CH3:13])=[C:9]([F:14])[C:8]=1[F:15])([CH3:4])([CH3:3])[CH3:2].[Br:17]N1C(=O)CCC1=O.CC(N=NC(C#N)(C)C)(C#N)C.CC(OC)(C)C>C(Cl)(Cl)(Cl)Cl.C1CCCCC1>[C:1]([O:5][C:6](=[O:16])[C:7]1[CH:12]=[CH:11][C:10]([CH2:13][Br:17])=[C:9]([F:14])[C:8]=1[F:15])([CH3:4])([CH3:2])[CH3:3]
A solution of 2,3-difluoro-4-methyl-benzoic acid tert-butyl ester (17.3 g, 75.9 mmol) and N-bromosuccinimide (13.5 g, 75.9 mmol) in carbon tetrachloride (250 mL) was degassed for 10 minutes. AIBN (1.2 g, 7.32 mmol) was added and the reaction mixture was stirred at reflux for 18 hours before being cooled to room temperature and filtered. The filtrate was concentrated in vacuo to give a residue which was subjected to flash chromatography (Si—PPC, gradient 0% to 10%, TBME in cyclohexane) to afford the title compound as a colourless oil (16.7 g, contaminated by 25% of starting material). 1H NMR (CDCl3, 400 MHz) 7.61 (1 H, ddd, J=8.3, 6.4, 2.1 Hz), 7.18 (1 H, ddd, J=8.1, 6.4, 1.8 Hz), 4.49 (2 H, d, J=1.3 Hz), 1.59 (9 H, s).
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