Phosphorus oxybromide → 2-Bromo-5-methyl-3-phenylimidazo[1,2-A]pyridine

Participants

Reaction Steps

5-Methyl-3-phenylimidazo[1,2-a]pyridin-2-ol from step 2 (1.30 g, 5.22 mmol) were dissolved in 41 mL 1,2-dichloroethane under argon atmosphere. 5 Equivalents of phosphoryl bromide (7.48 g, 26.1 mmol) were added and the reaction mixture was stirred at reflux temperature overnight. LC/MS analysis showed incomplete conversion, therefore another 5 equivalents phosphoryl bromide were added. After stirring for 4 h at reflux temperature LC/MS analysis again showed incomplete conversion, so 5 equivalents were added again. After stirring at reflux temperature overnight the reaction mixture was allowed to cool to room temperature. The reaction mixture was neutralized with aqueous sodium bicarbonate-solution followed by extraction with dichloromethane. The organic phase was washed with brine and filtered through a Whatman-filter. Drying under high vacuum gave 801 mg (44%) of the title compound in 83% purity (LC/MS, area-%).

Provenance & Evidence