3-Ethyl-6-(methyloxy)-2-phenyl-3,4-dihydro-1(2H)-naphthalenone (55) (0.84 g, 3.00 mmol) was dissolved in isopropenyl acetate (30 mL). pTsOH monohydrate (100 mg) was added. The mixture was refluxed under nitrogen for 3 days. Cooled to room temperature, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (1.74 g, 7.50 mmol) was added. The resulting mixture was refluxed under nitrogen overnight. Cooled to room temperature and diluted with CH2Cl2 (150 mL). The mixture was washed with 0.2 N NaOH (4×20 mL), water (2×20 mL), brine (30 mL), dried over Na2SO4, filtered, and the filtrate was concentrated to give the crude product as a dark brown tar. The crude product was purified by flash chromatography over SiO2 with hexanes:acetone (50:1) to give 0.61 g (64%) of the title compound (56) as a white solid. 1H NMR (400 MHz, CDCl3): δ 1.11 (t, J=7.5 Hz, 3H), 1.97 (s, 3H), 2.55 (q, J=7.5 Hz, 2H), 3.93 (s, 3H), 7.10-7.16 (m, 2H), 7.20-7.25 (m, 2H), 7.30-7.45 (m, 3H), 7.57 (s, 1H), 7.62 (d, J=8.9 Hz, 1H).
