[CH3:1][S:2][C:3]1[CH:11]=[C:10]([C:12]([F:15])([F:14])[F:13])[CH:9]=[C:8]([C:16]([F:19])([F:18])[F:17])[C:4]=1[C:5](O)=[O:6].C(Cl)(=O)C([Cl:23])=O.CO>C(Cl)Cl.CN(C=O)C>[CH3:1][S:2][C:3]1[CH:11]=[C:10]([C:12]([F:15])([F:14])[F:13])[CH:9]=[C:8]([C:16]([F:19])([F:18])[F:17])[C:4]=1[C:5]([Cl:23])=[O:6]A solution of the mixture containing 2-(methylthio)-4,6-bis(trifluoromethyl)benzoic acid D54 (225 mg) in dry DCM (4 ml), containing dry DMF (1drop), was treated with oxalyl chloride (87 ul, 1.0 mmol) and stirred at room temperature for 1 hour. The solvent was removed under reduced pressure to afford a crude product which was treated with dry methanol (2 ml) and stirred at room temperature overnight. The solvent was then carefully removed under reduced pressure. The residue was chromatographed on silica gel, eluting with 0-10% ethyl acetate in pentane to afford the title product 2-(methylthio)-4,6-bis(trifluoromethyl)benzoyl chloride (60 mg). 1H NMR (CDCl3) δ: 2.62 (3H, s), 7.77 (1H, s), 7.82 (1H, s). Further elution gave methyl 2,4-bis(trifluoromethyl)benzoate (100 mg).
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