The general procedure for the synthesis of 6-bromo-3,4-dihydronaphthalen-1(2H)-one from 6-amino-1,2,3,4-tetrahydro-1-naphthalenone was as follows: an aqueous solution (10 mL) of NaNO2 (2.35 g, 34 mmol) was added slowly and dropwise at 0°C to a 6-amino-1,2,3,4-tetrahydronaphthalen-1-one (5.0 g, 31 mmol) in a 25% HBr (16 mL) solution. Subsequently, the resulting suspension was transferred to a stirred mixture of 48% HBr (30 mL) of CuBr (8.9 g, 62 mmol) at 0 °C. The reaction mixture was gradually warmed to room temperature and stirred continuously for 1 hour. After completion of the reaction, the mixture was extracted with EtOAc and the organic phase was dried and concentrated with Na2SO4. The residue was purified by silica gel column chromatography (elution gradient: 0%-60% EtOAc/Hex) to afford 5.6 g (80% yield) of 6-bromo-3,4-dihydronaphthalen-1(2H)-one as a light yellow oil.1H NMR (400 MHz, CDCl3) δ: 2.10-2.16 (2H, m), 2.64 (2H, t, J = 6.4 Hz), 2.94 (2H, t, J = 6.0 Hz), 7.42 (1H, s), 7.44 (1H, s), 7.87 (1H, d, J = 8.9 Hz). Mass spectral analysis: [M + H]+ calculated value C10H9BrO: 225,227; measured value: 225,227.
