4-BROMO-3-METHYL-2-THIOPHENE CARBOXYLIC ACID

Preparation

4-Bromo-3-methyl-2-thiophenecarboxylic Acid synthesis: A. From Ester Hydrolysis. To a solution of 50% NaOH (97 mL, 1.9 mol) in 1600 mL of water was added methyl 4-bromo-3-methyl-2-thiophenecarboxylate (277 g, 1.18 mol) and the slurry was heated at 65°C for 1 h. The resulting orange solution was filtered through Celite, diluted with an additional 2 L of water, and 37% aqueous HCl (178 mL, 2.15 mol) was added dropwise to precipitate the acid, resulting in a thick white slurry. The solid was collected on a funnel and rinsed with water, and dried overnight in a vacuum oven at 65°C to give 238 g (91% wt.) of 4-bromo-3-methyl-2-thiophenecarboxylic acid as a white solid, m.p. 189-190 oC (Lit. [11] 188-189°C): 13C NMR {1H} (acetone-d6): 164.0, 144.5.