Reaction Steps
To a stirred solution of compound 34 (85 mg, 0.216 mmol) in wet benzene (2 mL, benzene: H2O=9:1) at room temperature was added 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ, 98 mg, 0.432 mmol). After being stirred vigorously for 15 min., the mixture was diluted with ethyl acetate (30 mL), washed with water (2×5 mL), dried (anhydr.MgSO4), and concentrated. Purification by flash silica gel chromatography (50% ethyl acetate in hexanes, and then ethyl acetate only) afforded the title compound 35 (6 mg, 7% yield): 1H NMR (300 MHz, CDCl3) δ 7.83 (d, J=9.0, 2H), 7.87 (br. s, 1H), 7.29 (d, J=15.6 Hz, 1H), 7.27 (d, 7.8 Hz, 1H), 7.00 (m, 1H), 6.72 (m, 2H), 6.62 (d, J=9.0 Hz, 2H), 5.97 (d, J=15.6 Hz, 1H), 5.97 (d, J=9.3 Hz, 1H), 4.34 (dq, J=9.3, 6.9 Hz, 1H), 3.03 (s, 3H), 1.87 (br. s, 3H), 1.29 (d, J=6.9 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 12.6, 17.6, 39.9, 40.8, 110.7, 118.0, 119.0, 119.3, 123.8, 124.4, 125.1, 126.9, 130.6, 132.5, 140.8, 146.2, 153.4, 164.8, 198.6.
