Sulfuric Acid → 9-Bromo-3,4,7,8-tetrahydro-[1,4]diazepino[7,1-a]isoquinoline-2,5-dione

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Reaction Steps

methyl 2-(5-bromo-1,2,3,4-tetrahydroisoquinolin-1-yl)acetate. MeOH (1280 mL) was cooled to −15° C. and conc. Sulfuric acid (147 mL, 2759 mmol) was added slowly (exotherm) under cooling. To this solution, methyl 2-(2-acetyl-5-bromo-1,2,3,4-tetrahydroisoquinolin-1-yl)acetate (90 g, 276 mmol) was added and the reaction mixture was stirred under reflux for 96 h. The reaction mixture was cooled to RT and slowly added to a solution of NaHCO3 (540 g) in water (1.35 L). The slightly basic aqueous solution was extracted with AcOEt (3×500 mL). The combined organic layers were washed with saturated aqueous NaHCO3 (300 mL) and brine (300 mL). The organic layer was dried with sodium sulfate, filtered and the solvent was removed under reduced pressure. The crude product was dried under high vacuo to yield the title compound as yellow foam (76 g) which was used without further purification. UPLC-MS: MS 284.1/286.1 (M+H+); UPLC rt 0.50 min.

Provenance & Evidence