To a mixture of ethyl [(6-bromo-5,6,7,8-tetrahydro-5-oxo-1-naphthalenyl)oxy]acetate (1.10 g, 3.36 mmol), N-(diphenylmethyl)thiourea (900 mg, 3.70 mmol), and ethanol (15 mL) was added triethylamine (0.51 mL, 3.70 mmol), and the mixture was refluxed for 6 hours. After cooling, the reaction mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed with 1N-hydrochloric acid, saturated aqueous sodium chloride solution, and water, dried over MgSO4, and filtered. The filtrate was concentrated under reduced pressure. To a solution of this concentration residue (0.79 g, 1.70 mmol) in tetrahydrofuran (16 mL)-methanol (4 mL) was added 1N-aqueous sodium hydroxide solution (2.0 mL) dropwise and the mixture was stirred at room temperature for 10 minutes. The solvent was then distilled off under reduced pressure and the residue was recrystallized from acetic acid-water to provide 0.49 g of the title compound. Yield 33%.
