1. 3-Methoxyaniline (1.23 g) and 5-methoxymethylene-2,2-dimethyl-[1,3]dioxane-4,6-dione (1.90 g) were dissolved in 2-propanol (40 ml), and the reaction was stirred at 70 °C for 1 hour. After completion of the reaction, the solvent was removed by distillation under reduced pressure and the residue was washed with ether to afford 5-[(3-methoxyphenylamino)-methylene]-2,2-dimethyl-[1,3]dioxane-4,6-dione (1.22 g, 44% yield).
2. 5-[(3-methoxyphenylamino)-methylene]-2,2-dimethyl-[1,3]dioxane-4,6-dione (1.22 g) was suspended in diphenyl ether (15 ml) with biphenyl (5.1 g) and reacted with stirring at 220 °C for 1.5 hrs. The reaction mixture was purified by column chromatography in methanol-chloroform system to afford 7-methoxy-1H-quinolin-4-one (394 mg, 51% yield).
3. 7-Methoxy-1H-quinolin-4-one (394 mg) was suspended in diisopropylethylamine (3 ml), phosphorus trichloride (1 ml) was added, and the reaction was stirred at 100 °C for 1 hour. After completion of the reaction, water was added under cooling in an ice bath, the aqueous layer was neutralized with aqueous sodium bicarbonate and the organic layer was extracted with ethyl acetate. The ethyl acetate layer was washed with water and dried with anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure and the residue was purified by column chromatography in acetone-chloroform system to afford 4-chloro-7-methoxyquinoline (312 mg, 72% yield).
