General procedure for the synthesis of 5-(4-bromophenyl)-3-methyl-isoxazole-4-carboxylic acid from ethyl 5-(4-bromophenyl)-3-methyl-isoxazole-4-carboxylate: to a stirred THF/H2O (79/35 ml) solution of ethyl 5-(4-bromophenyl)-3-methyl-isoxazole-4-carboxylate (3.2 g, 0.010 mol) was added lithium hydroxide ( 2.4 g, 0.010 mol). The reaction mixture was stirred at room temperature overnight and the THF solvent was removed from the reaction mixture under reduced pressure. The residue was diluted with water and washed with ether (2 x 50 ml). Subsequently, the aqueous phase was acidified to pH 4 with saturated aqueous NaHCO3 and extracted with ethyl acetate (2 x 75 ml). The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give the pure product 5-(4-bromophenyl)-3-methyl-isoxazole-4-carboxylic acid 2.8 g (96% yield). Product characterization data: 1H NMR (DMSO-d6): δ 2.52 (3H, s), 7.37 (2H, dd), 7.91 (2H, dd), 12.42 (1H, br s). 13C NMR (DMSO-d6) δ 12.0,110.0,126.6,127.2,131.7,132.5,162.4. 164.4,172.7. mass spectrum (MH+) = 282.
