A solution of 6-chloro-4-methyl-1-trityl-1H-pyrazolo[4,3-c]pyridin-3(2H)-one (Intermediate 4B; 406 mg, 0.953 mmol) in DMF (3 mL) was charged with potassium carbonate (348 mg, 2.52 mmol) and methyl iodide (0.089 mL, 1.430 mmol) and stirred at room temperature for 1 h. The reaction mixture was diluted with water, filtered, and dried under vacuum to give 6-chloro-3-methoxy-4-methyl-1-trityl-1H-pyrazolo[4,3-c]pyridine, which was carried onto the next step without further purification. MS ESI calc'd. for C27H22ClN3O [M+1]+ 440. found 440.
