7-chloro-3-ethyl-5-methyl-3H-imidazo[4,5-b]pyridine-6-carboxylic acid, ethyl ester → 3-butyl-7-ethoxy-5-methyl-3H-imidazo[4,5-b]pyridine-6-carboxylic acid, ethyl ester

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Reaction Steps

By replacing 7-chloro-3-ethyl-5-methyl-3H-imidazo-[4,5-b]pyridine-6-carboxylic acid, ethyl ester in Example 1 e with 3-butyl-7-chloro-5-methyl-3H-imidazo[4,5-b]pyridine-6-carboxylic acid, ethyl ester, 3-butyl-7-ethoxy-5-methyl-3H-imidazo[4,5-b]pyridine-6-carboxylic acid, ethyl ester is obtained. Yield 81%, b.p. 200°-210°/0.01. An equivalent of aqueous sodium hydroxide is added to an ethanol solution of the ethyl ester and refluxed for one hour. The reaction mixture is then taken to dryness, the residue is suspended in water and HCl to pH 4 is added. The precipitated solid is filtered off to obtain the free carboxylic acid. The sodium salt is obtained by dissolving this product in one equivalent of aqueous sodium hydroxide and freeze drying.

Provenance & Evidence