General procedure for the synthesis of 5-(trifluoromethyl)-3,4-dihydronaphthalen-1(2H)-one from 4-(2-(trifluoromethyl)phenyl)butyric acid: 4-(2-(trifluoromethyl)phenyl)butyric acid (246 mg, 1.06 mmol) was dissolved in chlorosulphonic acid (2 mL) at 0 °C, and the reaction mixture was kept stirred for 1 hour at 0 °C. Upon completion of the reaction, the reaction solution was slowly poured into ice water to quench the reaction. The organic phase was extracted with ethyl acetate, and the organic layer was washed sequentially with saturated aqueous sodium bicarbonate solution and saturated sodium chloride solution, then dried with anhydrous magnesium sulfate and filtered. The solvent was removed by distillation under reduced pressure to afford the target compound 5-(trifluoromethyl)-3,4-dihydronaphthalen-1(2H)-one as a colorless oil (160 mg, 70% yield).1H NMR (CDCl3, 500 MHz) data were as follows: δ 2.16-2.21 (2H, m), 2.70 (2H, dd, J = 6.4, 6.8 Hz), 3.14 (2H, t, J = 6.4 Hz), 7.43 (1H, t, J = 7.8 Hz), 7.83 (1H, d, J = 7.8 Hz), 8.27 (1H, d, J = 7.8 Hz).
