To a solution of 1-(1,3-dimethoxypropan-2-yl)-6-iodo-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (Intermediate 78, 300 mg, 0.72 mmol) and 1-methylpiperazine (100 mg, 1.00 mmol) in dichloromethane (50 mL) was added hydroxybenzotriazole (HOBT) (110 mg, 0.72 mmol) and N-methylmorpholine (290 mg, 2.87 mmol). The reaction mixture was stirred for 1 h at room temperature and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC HCl) (234 mg, 1.29 mmol) was added. The resulting reaction mixture was stirred at room temperature over night. The reaction mixture was quenched with 2N hydrochloric acid (30 mL) and the layers were separated. The organic layer was washed with saturated sodium bicarbonate solution (40 mL), water (60 mL) and finally with brine successively and dried over anhydrous sodium sulphate, filtered and concentrated under vacuum to afford 1-(1,3-dimethoxypropan-2-yl)-6-iodo-3-[(4-methylpiperazin-1-yl)carbonyl]quinolin-4(1H)-one 300 mg (80%) as thick oil.
