To a solution of ethyl 1-(4-fluorophenyl)-2-mercapto-1H-imidazole-5-carboxylate (3) (4.09 g, 15.34 mmol) in THF (70 mL) was added triethyl amine (4.50 mL, 32.29) and triphenylmethyl chloride (4.67 g, 16.76 mmol) and the solution was stirred for 1 hour at room temperature. The reaction was concentrated in vacuo and the residue was purified by flash column chromatography on silica gel (10%-40% EtOAc in hexanes) to give ethyl 1-(4-fluorophenyl)-2-(tritylthio)-1H-imidazole-5-carboxylate. A solution of ethyl 1-(4-fluorophenyl)-2-(tritylthio)-1H-imidazole-5-carboxylate (6.34 g, 12.47 mmol), sodium hydroxide (0.74 g, 18.39 mmol), methanol (10 mL), THF (20 mL), and water (10 mL) was stirred at room temperature for 16 hour and was then concentrated in vacuo. The aqueous was extracted with ethyl acetate. The combined organic extracts were dried over sodium sulfate, filtered, and the filtrate was concentrated in vacuo to yield 1-(4-fluorophenyl)-2-(tritylthio)-1H-imidazole-5-carboxylic acid (6).
