Nitric Acid → 6-Bromo-3-nitroimidazo[1,2-a]pyridine
Reaction equation
[Br:1][C:2]1[CH:3]=[CH:4][C:5]2[N:6]([CH:8]=[CH:9][N:10]=2)[CH:7]=1.S(=O)(=O)(O)O.[N+:16]([O-])([OH:18])=[O:17].[OH-].[K+]>>[N+:16]([C:8]1[N:6]2[CH:7]=[C:2]([Br:1])[CH:3]=[CH:4][C:5]2=[N:10][CH:9]=1)([O-:18])=[O:17]Participants
5
Procedure
A solution of 24 gms. (.122 mole) of 6-bromoimidazo [1,2-a] pyridine in 80 ml. of concentrated sulfuric acid is treated dropwise with 24 ml. of concentrated nitric acid while maintaining a temperature of 15° C. with external cooling. When the addition is complete, the reaction mixture is stirred at room temperature for 1/2 hour and poured onto 450 gm. of ice. The ph of the mixture is adjusted to ph 4 with aqueous potassium hydroxide and the resultant solids are collected by filtration. The filter cake is washed with water and dried. Recrystallization from methylene chloride-hexane yields pure 3-nitro 6-bromoimidazo [1,2-a] pyridine m.p. 160°-161° C.