Reaction Steps
Compound 3b (4.75 g, 10.75 mmol) was suspended in dry DME (100 mL) and cooled to −10° C. POCl3 (3.1 mL, 33.1 mol) was added and a mixture of Et3N (7.5 mL, 53.8 mmol) in DME (10 mL) was dropped slowly to the reaction mixture. After stirring for 2 h at −5° C., the reaction mixture was poured into ice water. The water phase was extracted with ethyl acetate, the organic phase was washed with saturated aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated in vacuum. By refrigeration over night a brown solid crystallized from the residue, which was collected and dried in vacuum. Yield: 2.75 g (6.71 mmol, 62%); brown solid of mp 109-110° C.; νmax (ATR)/cm−1 2915, 2135, 1593, 1569, 1489, 1452, 1420, 1325, 1295, 1275, 1238, 1199, 1136, 1081, 1048, 1003, 862, 826, 759, 705, 670; 1H NMR (300 MHz, CDCl3) δ 2.47 (3H, s), 3.81 (3H, s), 3.86 (3H, s), 5.46 (1H, s), 6.81 (1H, d, J=2.2 Hz), 7.01 (1H, d, J=2.2 Hz), 7.35 (2H, d, J=8.3 Hz), 7.64 (2H, d, J=8.3 Hz); 13C NMR (75.5 MHz, CDCl3) δ 321.8, 56.2, 60.7, 75.5, 111.5, 117.8, 123.2, 125.0, 129.9, 130.0, 130.5, 146.9, 148.5, 153.6, 166.6; m/z (EI) 256 (52), 254 (45), 244 (78), 242 (100), 200 (30), 123 (48), 91 (31).
