[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([O:19][CH3:20])=[C:6]([C:8]2[N:9]=[C:10]([CH3:18])[S:11][C:12]=2[C:13]([O:15]CC)=[O:14])[CH:7]=1.[OH-].[K+].Cl>C1COCC1.O>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([O:19][CH3:20])=[C:6]([C:8]2[N:9]=[C:10]([CH3:18])[S:11][C:12]=2[C:13]([OH:15])=[O:14])[CH:7]=1A mixture of ethyl 4-(5-chloro-2-methoxyphenyl)-2-methylthiazole-5-carboxylate (520 mg, 1.67 mmol) and potassium hydroxide (125 mg) in THF (18 mL) and water (4.5 mL) was stirred for 20 hours at room temperature and then at 75° C. for a further 8 hours. The solution was treated with 1M HCl aq. (pH 2) and extracted with DCM. The organics were evaporated to dryness to give 450 mg (95%) of 4-(5-chloro-2-methoxyphenyl)-2-methylthiazole-5-carboxylic acid as a white solid. LCMS (ESI) m+H=284.3; 1H NMR (400 MHz, DMSO-d6): δ 7.43 (dd, 1H); 7.31 (d, 1H); 7.10 (d, 1H); 3.71 (s, 3H); 2.69 (s, 3H).
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