C([Li])CCC.Br[C:7]1[CH:12]=[CH:11][C:10]([C:13]([F:16])([F:15])[F:14])=[CH:9][C:8]=1[S:17][CH3:18].[C:19](=[O:21])=[O:20].Cl>CCOCC>[CH3:18][S:17][C:8]1[CH:9]=[C:10]([C:13]([F:16])([F:15])[F:14])[CH:11]=[CH:12][C:7]=1[C:19]([OH:21])=[O:20]
n-Butyllithium (2.5M solution in hexane; 25 ml) was added under an inert atmosphere to a stirred solution 4-bromo-3-methylsulphenylbenzotrifluoride (16.4 g) in ether whilst maintaining the temperature below -70° C. The mixture was stirred at -70° C. for 2 hours and then poured onto solid carbon dioxide pellets. The mixture was stirred for 10 minutes and aqueous hydrochloric acid was added. The layers were separated and the aqueous layer was extracted with ether. The combined organic layers were washed with water, dried (anhydrous magnesium sulphate) and filtered. The filtrate was evaporated and the residue was triturated with cyclohexane and filtered to give 2-methylsulphenyl-4-trifluoromethylbenzoic acid (12.4 g) as a white solid, NMR [CDCl3 +DMSO-d6 ]: 2.45 (s,3H), 7.2(d, 1H), 7.3(s, 1H), 8.0 (d, 1H), 10.7-11.1 (bs, 1H).
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