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5 Step 5: Synthesis of 7-trifluoromethylisoquinoline
In a 500 mL three-necked flask, dissolve compound 7-(trifluoromethyl)-3,4-dihydroisoquinoline (10.5 g, 52.8 mmol) into 130 mL of toluene solution, add manganese dioxide (41.3 g, 475 mmol), the solution was heated to reflux and the reaction was stirred. The reaction was monitored by TLC. After the reaction was completed, the reaction solution was filtered with diatomaceous earth, the filter cake was rinsed with ethyl acetate (200 mL), and the organic phase was concentrated. After drying to obtain the crude product, it was further purified by column chromatography (eluent: V (petroleum ether): V (ethyl acetate) = 20/1) to obtain 5.93 g of a yellow solid compound with a yield of 57.1%.
6 Step 6: Synthesis of 5-bromo-7-trifluoromethylisoquinoline
In a 250 mL three-neck flask, add compound 7-trifluoromethyl isoquinoline (10.1 g, 51.3 mmol), dissolve in 200 mL of concentrated sulfuric acid, heat the reaction system to 75°C, add NBS (11.9 g, 66.7 mmol) in batches And stir the reaction. The reaction was monitored by TLC. After the reaction was over, 600 mL of ice water was added, and the pH of the mixed solution was adjusted to 7-9 with ammonia water. The mixture was extracted with ethyl acetate (300 mL×3), the organic phases were combined, dried over anhydrous sodium sulfate, and the organic phase was spin-dried to obtain the crude product, which was further purified by column chromatography (eluent: petroleum ether) to obtain the compound as a light yellow solid 10.1 g, the yield is 71.4%.