To a suspension of 52 (823 mg, 1.82 mmol) in DMF (10 ml) was added morpholine (317 mg, 3.65 mmol) and the reaction mixture was heated for 4 hours at 60° C., the solvent was removed under reduced pressure and the residual solid was triturated with EtOAc and collected by filtration. It was further washed with EtOAc until no color was observed in the filtrate, to form the title compound 53 (800 mg, 94% yield), which was used without additional purification. 1HNMR (DMSO) δ (ppm): 8.57 (d, J=4.7 Hz, 1H), 8.46 (dd, J=2.7 and 10.4 Hz, 1H), 8.18 (m, 1H), 8.07 (s, 1H), 7.83 (d, J=12.2 Hz, 1H), 7.71 (t, J=8.02 Hz, 1H), 7.42 (d, J=8.2 Hz, 1H), 6.91 (d, J=5.3 Hz, 1H), 3.56 (m, 4H), 3.51 (m, 2H), 3.33 (m, 3.33 (m, 2H), 2.50 (m, 2H).
