To a mixture of 5-bromo-3-nitro-4-(4-(thiazol-5-ylmethyl)piperazin-1-yl)pyridin-2-amine (0.060 g, 0.15 mmol, 1 eq), EtOH (2.6 mL) and DMF (0.35 mL), p-anisaldehyde (0.022 g, 0.165 mmol, 1.1 eq) was added followed by a freshly prepared aqueous solution of Na2S2O4 (1M; 0.45 mL, 0.45 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 aq 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 after trituration with diethyl ether as a off-white solid (0.02 g, 27%); 1H-NMR (500 Mz, DMSO-d6): δ 2.61-2.69 (m, 4H, piperazine N(CH2)2), 3.61-3.67 (m, 4H, piperazine N(CH2)2), 3.84 (s, 3H, OMe), 3.86 (s, 2H, NCH2), 7.10 (d, J=9.0 Hz, 2H, ArH, C6H4), 7.82 (s, 1H, thiazole 4-H), 8.13 (d, J=9.0 Hz, 2H, ArH, C6H4), 8.20 (s, 1H, imidazo[4,5-b]pyridine 5-H), 9.05 (s, 1H, thiazole 2-H), 13.20-13.50 (br s, 1H, imidazo[4,5-b]pyridine N—H); LC (Method B)-MS (ESI, m/z): Rt=3.34 min—485/487 [(M+H+), Br isotopic pattern, 100%]. ESI-HRMS: Found: 485.0760, calculated for C21H22BrN6OS (M+H)+: 485.0759.
