Step 1. 6-Bromo-1,2,3,4-tetrahydroquinoline (5 g, 23.7 mmol) was dissolved in 60 mL of tetrahydrofuran (THF) under stirring conditions. Subsequently, a solution formed from sodium hydroxide (1 g, 25 mmol) dissolved in 30 mL of water was added to this solution. Next, di-tert-butyl dicarbonate (5.37 g, 25 mmol) was added. The reaction mixture was stirred continuously for 12 hours at room temperature. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The aqueous phase was extracted with ethyl acetate (50 mL x 3). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, concentrated and purified by column chromatography to afford Boc-protected tert-butyl 6-bromo-3,4-dihydroquinoline-1(2H)-carboxylate (3 g, 40.7% yield) as a colorless solid.1H NMR (300 MHz, CDCl3): δ 7.56-7.53 (m, 1H), 7.24- 7.19 (m, 2H), 3.70-3.66 (m, 2H), 2.75-2.71 (m, 2H), 1.92-1.88 (m, 2H), 1.52 (s, 9H).
