[H-].[Na+].[CH2:3]([C:5]1[N:14]=[C:13]([CH2:15][CH3:16])[CH:12]=[C:11]2[C:6]=1[CH:7]=[CH:8][C:9](=[O:17])[NH:10]2)[CH3:4].[N+:18]([C:21]1[CH:28]=[CH:27][C:24]([CH2:25]Br)=[CH:23][CH:22]=1)([O-:20])=[O:19].O>CN(C=O)C>[CH2:3]([C:5]1[N:14]=[C:13]([CH2:15][CH3:16])[CH:12]=[C:11]2[C:6]=1[CH:7]=[CH:8][C:9](=[O:17])[N:10]2[CH2:25][C:24]1[CH:27]=[CH:28][C:21]([N+:18]([O-:20])=[O:19])=[CH:22][CH:23]=1)[CH3:4]Sodium hydride (50% dispersion in oil; 0.2 g) was added to a stirred solution of 5,7-diethyl-1,6-naphthyridin-2(1H)-one (1.0 g) in DMF (10 ml) under argon. The mixture was stirred for 15 minutes, then 4-nitrobenzyl bromide (1.1 g) was added and the mixture was stirred for 16 hours. The reaction mixture was poured into water (50 ml) and extracted with ethyl acetate (2×30 ml). The combined extracts were washed with saturated sodium chloride solution (10 ml), dried (MgSO4) and the solvent was removed by evaporation. The residue was purified by flash chromatography eluting with ethyl acetate/dichloromethane (1:4 v/v) to give 5,7-diethyl-1-(4-nitrobenzyl)-1,6-naphthyridin-2(1H)-one (B) as yellow solid (1.4 g), m.p. 105°-106° C.; NMR (CDCl3): 1.22(t, 3H), 1.36(t, 3H), 2.77(q, 2H), 3.11(q, 2H), 5.77(s, 2H), 6.69(s, 1H), 6.77(d, 1H), 7.38(d, 2H), 8.03(d, 1H), 8.19(d, 2H); mass spectrum (+ve CI): 338 (M+H)+ ; microanalysis, found: C, 67.0; H, 5.7; N, 12.4; C19H19N3O3 requires C, 67.6; H, 5.7; N, 12.5%.
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