[Br:1][C:2]1[CH:3]=[C:4]2[NH:10][C:9]([CH3:11])=[N:8][C:5]2=[N:6][CH:7]=1.C(N(C(C)C)CC)(C)C.Cl[C:22]([O:24][CH2:25][CH:26]([CH3:28])[CH3:27])=[O:23]>CN(C)C=O.C(OCC)(=O)C>[Br:1][C:2]1[CH:3]=[C:4]2[N:10]([C:22]([O:24][CH2:25][CH:26]([CH3:28])[CH3:27])=[O:23])[C:9]([CH3:11])=[N:8][C:5]2=[N:6][CH:7]=1
To a solution of 6-bromo-2-methyl-1H-imidazo[4,5-b]pyridine (3.40 g, 16.0 mmol) and diisopropylethylamine (6.5 mL, 65 mmol) in N,N-dimethylformamide (20 mL) cooled in an ice bath was added dropwise isobutyl chloroformate (2.51 mL, 19.2 mmol) and the mixture was warmed to room temperature. After 1 hour the reaction was diluted with ethyl acetate (80 mL) and washed with water (60 mL), 10% aqueous citric acid (40 mL) and brine (20 mL). The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated to a slurry. The residue was triturated diethyl ether (100 mL) and the solid isolated by filtration to give isobutyl 6-bromo-2-methyl-1H-imidazo[4,5-b]pyridine-1-carboxylate (2.3 g, 46% yield). MS (EI) for C12H14BrN3O2: 313 (MH+).
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