6-Bromo-7-methoxy-1,1-dimethyl-3,4-dihydro-1H-naphthalen-2-one (Compound E1, 0.2 g, 0.71 mmol) and 3-chlorophenylhydrazine hydrochloric acid salt (0.17 g, 1.3 eq.) were dissolved in acetic acid (0.5 mL). Under nitrogen atmosphere, the reaction solution was stirred at 90° C. for 8 hr. After cooling to room temperature, the reaction solution was added with ethyl acetate, washed with water, saturated aqueous solution of sodium hydrogen carbonate and saturated brine and dried over magnesium sulfate. After filtration and concentration under reduced pressure, the residues obtained therefrom were dissolved in THF (3 mL) comprising 10% water, added with DDQ (227 mg, 3 eq.) at room temperature, and the mixture was stirred at room temperature for 2 hr. The reaction solution was added with the mixture liquid of THF/diethyl ether (1:1) and washed with 0.5 N aqueous solution of sodium hydroxide and saturated brine. After drying with sodium sulfate, the mixture was filtered and the resulting residues obtained after concentration under reduced pressure were washed with the mixture liquid of hexane/diethyl ether (1:1) to obtain the title compound (brown powder, 86 mg).
