[C:1](=O)([O-])[O-].[Cs+].[Cs+].IC.[N:9]1[CH:10]=[CH:11][N:12]2[CH:17]=[C:16]([C:18]([OH:20])=[O:19])[CH:15]=[CH:14][C:13]=12>CN(C=O)C.[Cl-].[Na+].O>[CH3:1][O:19][C:18]([C:16]1[CH:15]=[CH:14][C:13]2[N:12]([CH:11]=[CH:10][N:9]=2)[CH:17]=1)=[O:20]Cesium carbonate (15.7 g, 48.2 mmol) and iodomethane (1.50 ml, 24.2 mmol) were added to a solution of imidazo[1,2-a]pyridine-6-carboxylic acid (2.61 g, 16.1 mmol) in DMF (100 ml). The reaction was stirred at ambient temperature overnight, then poured into brine (100 ml) and extracted with ethyl acetate (3×100 mL). The combined organics were washed with saturated sodium bicarbonate solution (25 mL), and a 1N HCl solution (25 mL) then dried over MgSO4 and evaporated to give imidazo[1,2-a]pyridine-6-carboxylic acid methyl ester as a yellow solid (1.1 g, 39%). 1H NMR (250 MHz, CDCl3): δ 8.96 (s, 1H), 7.8-7.6 (m, 4H), 3.98 (s, 3H). MS [EI+] 177 (M+H)+.
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