To 1 mL of 20% HNO3 was added 28 mg of HNO2. This mixture was then added to 3-[2-mercapto-4-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-imidazol-1-yl]-4-methyl-benzoic acid methyl ester (280 mg; 0.69 mmol) suspended in 5 mL of rapidly stirring HOAc over 15 min. After stirring an additional 5 min, the solution was poured into ice-cold water. The pH was adjusted to about 7 with NaHCO3, and the mixture was extracted with EtOAc. The extract was washed once with brine, dried with Na2SO4, filtered, and concentrated. The resulting residue was chromatographed (5–60% EtOAc in hexanes) to provide 210 mg (0.56 mmol; 82%) of 4-methyl-3-[4-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-imidazol-1-yl]-benzoic acid methyl ester. ESI MS m/z 373 [C22H20N4O2+H]+.
