Procedure for the synthesis of 1,8-dichloroisoquinoline: To a solution of 8-chloroisoquinoline (11 g, 54 mmol) in dichloromethane (200 mL) was added m-chloroperoxybenzoic acid (MCPBA, 25 g, 112 mmol) in batches. The reaction mixture was stirred for 3 hours and then ether (400 mL) and hexane (1 L) were added. The mixture was stirred overnight and subsequently concentrated under vacuum. Ether (200 mL) and hexane (400 mL) were added to the concentrate and stirred again overnight. The precipitate was collected by filtration, air dried and mixed with silica gel (20 g) and toluene (150 mL). The mixture was heated to reflux for 3 hours and neutralized with sodium bicarbonate (NaHCO3) when the reaction was complete. The reaction mixture was extracted with dichloromethane (CH2Cl2) and the organic layer was dried over anhydrous sodium sulfate and concentrated in vacuum to give 1,8-dichloroisoquinoline (8 g, 72% yield). Mass spectrum (MS): 198.
