[Br:1][C:2]1[S:3][C:4]([C:16]([O:18]CC)=[O:17])=[C:5]([C:7]2[CH:12]=[C:11]([Cl:13])[CH:10]=[CH:9][C:8]=2[O:14][CH3:15])[N:6]=1.[OH-].[K+].Cl.C(Cl)Cl>C1COCC1.O>[Br:1][C:2]1[S:3][C:4]([C:16]([OH:18])=[O:17])=[C:5]([C:7]2[CH:12]=[C:11]([Cl:13])[CH:10]=[CH:9][C:8]=2[O:14][CH3:15])[N:6]=1A mixture of ethyl 2-bromo-4-(5-chloro-2-methoxyphenyl)thiazole-5-carboxylate (1.40 g, 3.72 mmol), potassium hydroxide (278 mg) in THF (40 mL) and water (10 mL) was stirred for 20 hours at ambient temperature. The mixture was treated with 1M HCl aq. (ca. 8 mL, 2 eq.), DCM was added, and the organics separated and evaporated to dryness to give 1.23 g (95%) of 2-bromo-4-(5-chloro-2-methoxyphenyl)thiazole-5-carboxylic acid as a yellow solid. LCMS (ESI) m+H=350.1. 1H NMR (400 MHz, DMSO-d6): δ 7.47 (dd, 1H); 7.39 (d, 1H); 7.13 (d, 1H); 3.73 (s, 3H).
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