To a mixture of 2-(4-(2-amino-5-chloro-3-nitropyridin-4-yl)piperazin-1-yl)-N-(3-methylisoxazol-5-yl)acetamide (0.036 g, 0.09 mmol) and ethanol (4 ml) was added 4-dimethylaminobenzaldehyde (0.018 g, 0.11 mmol) followed by a freshly prepared 1M aqueous solution of Na2S2O4 (0.36 ml, 0.36 mmol). The reaction mixture was stirred at 70° C. for 4.5 h, then allowed to cool to room temperature and concentrated in vacuo. The residue was triturated with water (4 ml); the brown precipitate was collected by filtration, washed with water (3×2 ml), ethanol (3×2 ml) and diethyl ether (2×5 ml). This solid was absorbed on silica gel, and the free-running powder was placed on a 10 g isolute silica column which was eluted with ethyl acetate/dichloromethane (v/v; 1:1), and 4% methanol in ethyl acetate/dichloromethane (v/v; 1:1). The title compound was obtained as a yellow solid after trituration with diethyl ether (0.007 g, 16%). 1H-NMR (500 MHz, DMSO-d6) 2.19 (s, 3H, isoxazole CH3), 2.73 (s, 4H, piperazine N(CH2)2), 3.00 (s, 6H, N(CH3)2), 3.31 (s, 2H, NCH2CO), 3.71 (s, 4H, piperazine N(CH2)2), 6.18 (s, 1H, isoxazole C—H), 6.82 (d, J=8.9 Hz, 2H) and 8.01 (d, J=8.9 Hz, 2H) (3,5-C6H4NMe2 and 2,6-C6H4NMe2), 8.03 (s, 1H, imidazo[4,5-b]pyridine 5-H), 11.45 (br s, 1H, CONH), 13.15 (br s, 1H, imidazo[4,5-b]pyridine N—H);
