[CH2:1]([O:3][C:4]([C:6]1[NH:7][CH:8]=[C:9]([N+:11]([O-:13])=[O:12])[CH:10]=1)=[O:5])[CH3:2].[CH3:14][CH2:15][O-].[Na+].[CH3:18]I.O>CCO.C(Cl)(Cl)Cl>[CH2:1]([O:3][C:4]([C:6]1[N:7]([CH2:18][CH2:15][CH3:14])[CH:8]=[C:9]([N+:11]([O-:13])=[O:12])[CH:10]=1)=[O:5])[CH3:2]4-Nitro-1H-pyrrole-2-carboxylic acid ethyl ester (5 g) was dissolved in 50 ml of dry EtOH, 50 ml of 1M sodium ethylate was added followed with 10 ml of CH3I. The reaction mixture was heated at 80° C. for 4 hours, cooled down to room temperature and distributed between water and chloroform. The organic phase was washed with water, dried with sodium sulfate and evaporated. The residue was recrystallized from hexane to yield 4.72 g (77%) of 1-propyl-4-nitro-1H-pyrrole-2-carboxylic acid ethyl ester 232. H1-NMR (DMSO-d6): 0.79 (t, 3H, CH3), 1.25 (t, 3H, CH3), 1.68 (m, 2H, CH2), 4.17-4.28 (m, 4H, 2CH2), 7.23 and 8.24 (d, 1H, pyrrole)
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