Phosphorus oxychloride → 8-Bromo-4-chloroquinoline

A suspension of 2-bromoaniline (20.9 g) and 5-(methoxymethylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (22.6 g) in 2-propanol (240 ml) was heated to reflux for 1 hour. The reaction solution was cooled to 0° C., and the deposit was then filtrated to obtain a pale yellow solid (35.0 g). A suspension of the obtained pale yellow solid (10.0 g) in Dowtherm (100 ml) was heated at 210° C. for 1 hour. After cooling, hexane (100 ml) was added to the reaction solution, and the deposit was filtrated to obtain 8-bromoquinolin-4(1H)-one (6.3 g). Phosphorus oxychloride (5.9 ml) was added to 8-bromoquinolin-4(1H)-one (9 g), and the mixture was heated to reflux for 2 hours. The solvent was distilled off under reduced pressure, and chloroform was added to the residue. The reaction solution was neutralized with an aqueous sodium hydroxide solution with cooling in an ice bath and partitioned into organic and aqueous layers. The organic layer was washed with brine. The organic layer thus washed was dried over anhydrous sodium sulfate. Then, the solvent was distilled off, and the residue was purified by neutral silica gel column chromatography (chloroform/methanol) to obtain 8-bromo-4-chloroquinoline (8.3 g) as a white solid.