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Stage #1: C8H5BrN2O2 With 1,1'-carbonyldiimidazole In N,N-dimethyl-formamide at 20℃; for 0.5h;
Stage #2: (Z)-N'-hydroxy-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzimidamide In N,N-dimethyl-formamide at 70℃; for 10h;
General procedure of synthesis of oxadiazole derivatives:
General procedure: Acid 1 (0.5 mmol) and CDI (Carbonyl diimidazole) (0.5 mmol) were dissolved in 3.0 mL of DMF and stirred at room temperature. After 30 min, amidoxime (0.5 mmol) was added and the reaction mixture was stirred at 70-80 oC for 10 h (monitored by TLC). Then the mixture was poured into water (20.0 mL), extracted by ethyl acetate (3 X 15.0 mL), and the combined organic solvent was dried over Na2SO4, filtered and concentrated in vacuo. The crude product was purified by silica-gel chromatography to give the oxadiazole product.
Stage #1: 3-bromoimidazo[1,2-a]pyridine-7-carboxylic acid With 2-chloro-1-methyl-pyridinium iodide; N-ethyl-N,N-diisopropylamine In dichloromethane at 20℃; for 0.25h;
Stage #2: methanesulfonamide With 4-dimethylaminopyridine In dichloromethane
C66.1 Step 1: 3-bromo-N-(methylsulfonyl)imidazo[1,2-a]pyridine-7-carboxamide
To a solution of 3-bromoimidazo[1,2-a]pyridine-7-carboxylic acid (0.241 g, 1 mmol) in DCM (3 mL) were added 2-chloro-1-methylpyridinium iodide (0.306 g, 1.2 mmol) followed by DIEA (0.52 mL, 3 mmol). Resulting reaction mixture was stirred at RT for 15 min. Then methanesulfonamide (0.285 g, 3 mmol) followed by catalytic amount of DMAP (0.005 g) was added, and reaction mixture was stirred for overnight. Then the reaction mixture was diluted with DCM (5 mL) and washed with water. The organic phase was dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified by SiO2 column chromatography (DCM / MeOH) to give 0.082 g of the title compound (Yield : 25%). LC/MS m/z: 319.93 (M+H)+
25%
Stage #1: 3-bromoimidazo[1,2-a]pyridine-7-carboxylic acid With 2-chloro-1-methyl-pyridinium iodide; N-ethyl-N,N-diisopropylamine In dichloromethane at 20℃; for 0.25h;
Stage #2: methanesulfonamide With 4-dimethylaminopyridine In dichloromethane
C66.1 Step 1: 3-bromo-N-(methylsulfonyl)imidazo[1,2-a]pyridine-7-carboxamide
To a solution of 3-bromoimidazo[1,2-a]pyridine-7-carboxylic acid (0.241 g, 1 mmol) in DCM (3 mL) were added 2-chloro-1-methylpyridinium iodide (0.306 g, 1.2 mmol) followed by DIEA (0.52 mL, 3 mmol). Resulting reaction mixture was stirred at RT for 15 min. Then methanesulfonamide (0.285 g, 3 mmol) followed by catalytic amount of DMAP (0.005 g) was added, and reaction mixture was stirred for overnight. Then the reaction mixture was diluted with DCM (5 mL) and washed with water. The organic phase was dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified by SiO2 column chromatography (DCM / MeOH) to give 0.082 g of the title compound (Yield : 25%). LC/MS m/z: 319.93 (M+H)+
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