[Synthesis]
A) Synthesis of methyl 4-oxo-1,2,3,4-tetrahydronaphthalene-1-carboxylate: 2-phenylglutaric anhydride (52.2 g, 0.274 mol) was mixed with concentrated sulfuric acid (274 mL) and heated in an oil bath at 70°C for 1.5 hours. Upon completion of the reaction, the mixture was cooled to room temperature, followed by slow addition to pre-cooled (ice/water bath) methanol (550 mL) over 30 minutes. After addition, the mixture was allowed to gradually warm to room temperature and stirred continuously for 20 hours. The reaction mixture was poured into 1 liter of ice water, saturated saline (500 mL) and deionized water (500 mL) were added, and then extracted with ethyl acetate (4 × 500 mL). The organic phases were combined and washed sequentially with saturated sodium bicarbonate solution (500 mL), deionized water (500 mL) and saturated saline (500 mL). The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated to afford 44.8 g (80% yield) of methyl 4-oxo-1,2,3,4-tetrahydronaphthalene-1-carboxylate as a brown oil, which could be used for subsequent reactions without further purification. The product was characterized as follows: 1H NMR (CDCl3, 400 MHz) δ 8.02 (dd, 1H, J = 7.9, 1.3 Hz), 7.48 (td, 1H, J = 7.5, 1.3 Hz), 7.35 (td, 1H, J = 7.5, 1.3 Hz), 7.29 (d, 1H, J = 7.9 Hz), 3.96 (t, 1H, J = 5.0 Hz). J = 5.0 Hz), 3.69 (s, 3H), 2.87 (ddd, 1H, J = 17.4, 11.6, 5.0 Hz), 2.60 (dt, 1H, J = 17.4, 5.0 Hz), 2.51-2.43 (m, 1H), 2.36-2.27 (m, 1H); GCMS m/z 204 (M+). |