To a mixture of 1-(4-(2-amino-5-bromo-3-nitropyridin-4-yl)piperazin-1-yl)-2-phenoxyethanone (0.048 g, 0.11 mmol), and ethanol (4.0 ml) was added 4-dimethylaminobenzaldehyde (0.021 g, 0.14 mmol) followed by a freshly prepared aqueous solution of Na2S2O4 (1M; 0.44 ml, 0.44 mmol). The reaction mixture was heated at 70° C. for 4 h, then allowed to cool to room temperature and concentrated in vacuo. The residue was triturated with water, the precipitate was collected by filtration, washed with water, ethanol, and diethyl ether to afford the title compound as a pale yellow solid (0.027 g, 46%); 1H-NMR (500 MHz, DMSO-d6) 3.00 (s, 6H, N(CH3)2), 3.58 (br s) and 3.70 (br s) (8H, 2× piperazine N(CH2)2), 4.92 (s, 2H, COCH2O), 6.95 (m, 3H) and 7.30 (m, 2H) (ArH), 6.82 (d, J=9.02 Hz, 2H) and 8.02 (d, J=8.92 Hz, 2H) (3,5-C6H4NMe2 and 2,6-C6H4—NMe2), 8.19 (s, 1H, imidazo[4,5-b]pyridine 5-H), 13.23 (s, 1H, imidazo[4,5-b]pyridine N—H);
