The reaction mixture was prepared from 5-bromo-1,2,3,4-tetrahydroisoquinoline hydrobromide (2.24 g, 9.0 mmol, Zannan Pharma), di-tert-butyl dicarbonate (3.1 mL, 14 mmol), and triethylamine (2.8 mL, 20 mmol), which was solubilized in THF (40 mL), and the reaction mixture was stirred for 1 hour at room temperature. After completion of the reaction, the solvent was removed by vacuum concentration. Water (15 mL) was added to the residue, followed by extraction with ethyl acetate (2 x 15 mL). The organic phases were combined, dried with anhydrous sodium sulfate and concentrated again in vacuum to afford 1,1-dimethylethyl-5-bromo-3,4-dihydro-2(1H)-isoquinoline carboxylate (2.79 g, 99% yield) as an off-white solid. The obtained product could be used directly in the subsequent reaction without further purification.LCMS analysis (formate method, 5 min): retention time 3.60 min, molecular ion peak MH+ = 312/314.
