To a mixture of 5-bromo-3-nitro-4-(4-(thiazol-5-ylmethyl)piperazin-1-yl)pyridin-2-amine (0.030 g, 0.076 mmol, 1 eq), EtOH (1.95 mL) and DMF (0.29 mL), 4-(morpholinomethyl)-benzaldehyde (0.017 g, 0.083 mmol, 1.1 eq) was added followed by a freshly prepared aqueous solution of Na2S2O4 (1M; 0.23 mL, 0.23 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; 94:6). The title compound was obtained as a solid after trituration with diethyl ether (0.022 g, 26%); 1H-NMR (500 Mz, DMSO-d6): δ 2.35-2.41 (m, 4H), 2.61-2.67 (m, 4H), 3.54 (s, 2H, NCH2), 3.59 (t, J=4.8 Hz, 4H), 3.63-3.69 (m, 4H), 3.87 (s, 2H, NCH2), 7.48 (d, J=8.0 Hz, 2H, ArH, C6H4), 7.82 (s, 1H, thiazole H-4), 8.14 (d, J=8.0 Hz, 2H, ArH, C6H4), 8.24 (s, 1H, imidazo[4,5-b]pyridine 5-H), 9.05 (s, 1H, thiazole H-2), 13.47 (br s, 1H, imidazo[4,5-b]pyridine N—H); LC (Method B)-MS (ESI, m/z): Rt=2.10 min—554/556 [(M+H+), Br isotopic pattern, 100%]. ESI-HRMS: Found: 554.1342, calculated for C25H29BrN7OS (M+H)+: 554.1338.
