2-Ethyl-[1,6]naphthyridin-3-ol (69 mg), 4-chloro-6,7-dimethoxyquinoline (265 mg), and 4-dimethylaminopyridine (145 mg) were suspended in o-dichlorobenzene (3 ml), and the mixture was stirred at 140° C. for 4 hr. The reaction solution was cooled to room temperature, water was then added to the reaction solution, and the mixture was extracted with chloroform. The chloroform layer was then washed with water and saturated brine and was dried over anhydrous magnesium sulfate. The solvent was removed by distillation under the reduced pressure, and the residue was purified by thin layer chromatography using chloroform-methanol to give the title compound (9 mg, yield 6%).
