To a mixture of 5-bromo-3-nitro-4-(4-(thiazol-2-ylmethyl)piperazin-1-yl)pyridin-2-amine (0.088 g, 0.22 mmol) and EtOH (2.5 mL), 4-(morpholinomethyl)-benzaldehyde (0.045 g, 0.24 mmol) in EtOH (2.5 mL) was added, followed by a freshly prepared aqueous solution of Na2S2O4 (1M; 0.66 mL, 0.66 mmol). The reaction mixture was heated at 85° C. for 24 h, then allowed to cool to room temperature and diluted with DCM and a few drops of aqueous NH3 until complete dissolution was observed. This solution was deposited on two preparative silica TLC plates and eluted with DCM/MeOH (v/v; 96:4) to give the title compound as a solid (0.049 g, 40%); 1H-NMR (500 Mz, DMSO-d6): δ 2.33-2.43 (m, 4H), 2.72-2.79 (m, 4H), 3.54 (s, 2H, NCH2), 3.59 (t, J=4.5 Hz, 4H), 3.70 (t, J=4.5 Hz, 4H), 3.95 (s, 2H, NCH2), 7.48 (d, J=8.5 Hz, 2H, ArH), 7.69 (d, J=3.5 Hz, 1H, thiazole 5-H), 7.75 (d, J=3.0 Hz, 1H, thiazole 4-H), 8.15 (d, J=8.0 Hz, 2H, ArH), 8.24 (s, 1H, imidazo[4,5-b]pyridine 5-H), 13.49 (br s, 1H, imidazo[4,5-b]pyridine N—H); LC (Method B)-MS (ESI, m/z) 2.37 min—554/556 [(M+H)+, Br isotopic pattern]. ESI-HRMS: Found: 554.1341, calculated for C25H29BrN7OS (M+H)+: 554.1338.
