反应详情

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-%).

1. temperatureat reflux temperature overnight
2. stirringAfter stirring for 4 h
3. temperatureat reflux temperature LC/MS analysis again showed incomplete conversion
4. additionso 5 equivalents were added again
5. stirringAfter stirring
6. temperatureat reflux temperature overnight the reaction mixture
7. extractionfollowed by extraction with dichloromethane
8. washThe organic phase was washed with brine
9. filtrationfiltered through a Whatman-filter
10. customDrying under high vacuum