To a stirred suspension at room temperature of VIII (150 mg, 0.46 mmol) in anhydrous CH2Cl2 (10 ml) under nitrogen were added Et3N (194 μl, 1.39 mmol) and 3,4,5-trimethoxyaniline (94 mg, 0.51 mmol) or ArNH2(1.1–1.2 equiv.), respectively. The reaction mixture was heated to 60° C. After 20 h, the reaction mixture was concentrated, diluted with AcOEt, and successively washed with a saturated aqueous solution of NH4Cl, H2O and brine, dried over MgSO4, filtered and concentrated. The crude product was purified by flash chromatography on silica gel (AcOEt/CH2Cl2:15/85→20/80) to give the title product IXa (130 mg, 0.35 mmol, 75% yield) as a yellow solid. 1H NMR (300 MHz, acetone-d6) δ(ppm): 9.42 (bs, 1H), AB system (δA=8.09, δB=7.78, J=8.1 Hz, 4H), 7.75 (d, J=15.6 Hz, 1H), 7.21 (s, 2H), 7.00 (d, J=15.8 Hz, 1H), 3.94 (s, 3H), 3.85 (s, 6H), 3.73 (s, 3H).
