To a suspension of 33 (212 mg, 0.80), Cs2CO3 (260 mg, 0.80) in DMF (15 ml), 39 (200 mg, 0.89 mmol) was added portionwise and the mixture was stirred at room temperature for 2 days. H2O (30 ml) was added and the suspension was extracted with CH2Cl2 (70 ml). The organic phase was dried over Na2SO4 and the solvent was evaporated under reduced pressure. The crude was purified by flash chromatography (CH2Cl2/MeOH 9:1) affording 40 (56 mg, 17%) as yellow-brown solid. 1H NMR (300 MHz, DMSO d6): δ 8.78 (m, 2H), 8.12 (bs, 1H), 8.05-7.78 (m, 3H), 7.67 (m, 1H), 4.72 and 4.69 (s, 2H), 4.10 (q, 2H), 3.92 and 3.90 (s, 2H), 1.19 (t, 3H). ESI+MS: calcd for C19H16N6O5: 408.38; found: 409.1 (MH+).
