[Cl-].C([Al+]CC)C.Cl.[CH3:8][NH:9][O:10][CH3:11].[Br:12][C:13]1[S:17][C:16]2=[C:18]([C:21]([O:23]CC)=O)[N:19]=[CH:20][N:15]2[CH:14]=1.P([O-])([O-])([O-])=O>ClCCl>[CH3:11][O:10][N:9]([CH3:8])[C:21]([C:18]1[N:19]=[CH:20][N:15]2[CH:14]=[C:13]([Br:12])[S:17][C:16]=12)=[O:23]Diethylaluminum chloride (0.9 M hexane solution; 2.3 ml, 2.11 mmol) was added to an ice cooled solution of N,O-dimethylhydroxylamine hydrochloride (206 mg, 2.11 mmol) in dichloromethane (8 ml), and, while gradually raising the temperature, the mixture was stirred for one hr. A solution of ethyl 2-bromoimidazo[5,1-b]thiazole-7-carboxylate (116 mg, 0.42 mmol) in dichloromethane (4 ml) was added and stirred at room temperature for 15 hr. A phosphate buffer solution (10 ml) was added to the reaction solution, and the mixture was stirred at room temperature for 10 min and was filtered through Celite. The filtrate was washed with saturated brine and was then dried over anhydrous sodium sulfate, and the solvent was removed by distillation under the reduced pressure. The residue was purified by column chromatography on silica gel (ethyl acetate:methanol=30:1→10:1) to give N-methoxy-N-methyl-2-bromoimidazo[5,1-b]thiazole-7-carboxamide (113 mg, 92%) as a white solid.
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