A mixture of 3-(4-(cyclopropanecarbonyl)piperazine-1-carbonyl)benzaldehyde (286 mg, 1 mmol) and (E)-4-(benzylideneamino)isobenzofuran-1(3H)-one (237 mg, 1mmol) in ethyl propionate (7.5 mL) was cooled to 0° C. Then a solution of sodium methoxide in methanol [sodium (92 mg, 4 mmol) in methanol (7.5 mL)] was added dropwise. After the addition, the mixture was stirred at 25° C. for 18 hr. The mixture was quenched with water (10 mL) and solvent was removed in vacuum. The residue was dissolved in water, and then extracted with ethyl acetate (50 mL×3). The combined organic layers were washed with brine, dried over anhydrous sodium sulfate, and concentrated to give crude product. The crude product was purified by chromatography (silica gel, petroleum ether/ethyl acetate=10:1 to 1:10) to give methyl 3-(3-(4-(cyclopropanecarbonyl)piperazine-1-carbonyl)phenyl)-4-oxo-2-phenyl-1,2,3,4-tetrahydroquinoline-5-carboxylate (64 mg, yield 12%). LC-MS (ESI) m/z: 538 (M+1)+.
