Bromide ion → HCID 19385718, compound

Participants

Reaction Steps

7-Methyl-2-propylimidazo[4,5-b]pyridine-5-carboxylic acid or the 2-ethyl analog is prepared from 7-methyl-2-propylimidazo[4,5-b]pyridine or the 2-ethyl analog by treatment with m-chloroperoxybenzoic acid to obtain the N-oxide which is then treated with POCl3 to give 5-chloro-7-methyl-2-propylimidazo-[4,5-b]pyridine or 2-ethyl analog. The chloride is then exchanged for a bromide by reaction of 5-chloro-7-methyl-2-propylimidazo[4,5-b]pyridine or the 2-ethyl analog with HBr in acetic acid. The resulting 5-bromo-7-methyl-2-propylimidazo[4,5-b]pyridine or 2-ethyl analog is treated with NaH in DMF followed by benzyl bromide to obtain 3-benzyl-5-bromo-7-methyl-2-propylimidazo[4,5-b]pyridine or its corresponding 2-ethyl analog which is in turn treated with CuCN in hot pyridine to obtain 3-benzyl-5-cyano-7-methyl-2-propylimidazo[4,5-b]pyridine or the corresponding 2-ethyl analog. The cyano compound is hydrolyzed to 3-benzyl-7-methyl-2-propylimidazo[ 4,5-b]pyridine-5-carboxylic acid or the corresponding 2-ethyl analog by treatment with H2SO4 --H2O. This acid is esterified by reaction with MeOH--HCl. The benzyl group is removed by hydrogenation at 1 atm. in MeOH-HCl solution using Pd(OH)2 as catalyst. This compound can be alkylated as described earlier and the product methyl ester is converted to the carboxylic acid by treatment with hydroxide.

Provenance & Evidence