Sodium hydride → 6-((3H-imidazo[4,5-b]pyridin-3-yl)methyl)-2-(methylthio)benzo[d]thiazole

To a solution of 3H-imidazo[4,5-b]pyridine (2.99 g, 25 mmol) in DMF (100 mL) was added sodium hydride (60% in mineral oil, 1.0 g, 25 mmol) slowly at 0° C. After the reaction mixture was stirred at rt for 20 min, it was treated with a solution of 6-(chloromethyl)-2-(methylthio)benzo[d]thiazole from Step 3 of this Example (4.8 g, 21 mmol) in DMF (20 mL) at 0° C. The reaction mixture was then stirred at rt overnight. The mixture was quenched with 3 mL of saturated aq NH4Cl and concentrated under reduced pressure. The residue was diluted with 600 mL of EtOAc and washed with water and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure The crude product was purified on a silica gel column using a mixture of MeOH—CH2Cl2 (1:30, v/v) as eluent to give 6-((3H-imidazo[4,5-b]pyridin-3-yl)methyl)-2-(methylthio)benzo[d]thiazole as a tan solid (2.5 g, 38%). The regiochemistry of the alkylation was determined by a 2-dimensional nuclear Overhauser effect (NOE) experiment. 1H NMR (300 MHz, DMSO-d6) δ 8.65 (s, 1H), 8.38 (dd, J=1.2, 4.8 Hz, 1H), 8.11 (dd, J=1.3, 8.1 Hz, 1H), 8.00 (d, J=1.1 Hz, 1H), 7.81 (d, J=8.3 Hz, 1H), 7.46 (dd, J=1.6, 8.4 Hz, 1H), 7.30 (dd, J=4.8, 8.0 Hz, 1H), 5.62 (s, 2H), 2.77 (s, 3H). LCMS (ESI) m/z 313 (M+H)+.