Synthesis
The general procedure for the synthesis of 5-chloro-3,4-dihydronaphthalen-1(2H)-one from 5-amino-3,4-dihydro-2H-1-naphthalenone was as follows: 5-amino-3,4-dihydronaphthalen-1(2H)-one (1 g, 6.2 mmol) was dissolved in a mixture of HCl (36%, 2 mL) and EtOH (8 mL) at 0 °C, and NaNO2 was slowly added aqueous solution (0.582 g, 8.4 mmol dissolved in 1 mL of water) and stirred for 15 min. Subsequently, the reaction mixture was added dropwise to a solution of CuCl (0.3 g, 3.1 mmol) in HCl (36%, 10 mL) that was preheated to 95 °C and kept at that temperature for 15 minutes. Upon completion of the reaction, the solution was cooled to room temperature, diluted with water and extracted with EtOAc. The organic phases were combined, washed with saturated NaHCO3 solution, dried over MgSO4, filtered and purified by silica gel column chromatography with 40-50% EtOAc/hexane as eluent. The target product 5-chloro-3,4-dihydronaphthalen-1(2H)-one (0.7 g, 62% yield) was finally obtained. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 7.53 (dd, J = 7.8, 1.2 Hz, 1H), 7.14 (tt, J = 7.8, 0.7 Hz, 1H), 6.88 (dd, J = 7.8, 1.2 Hz, 1H), 3.70 (s, 2H), 2.69 (t, J = 6.2 Hz, 2H), and 2.66-2.60 (m, 2H), 2.30-2.07 (m, 2H).
