Hydrochloric Acid → 7-Ethyl-2-methyl-4-oxo-4,7-dihydrothieno(2,3-b)pyridine-5-carboxylic acid

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Reaction Steps

A mixture of 1.4 parts of ethyl-4-hydroxy-2-methylthieno(2,3-b)pyridine-5-carboxylate, 12 parts by volume of 10% aqueous potassium hydroxide, 48 parts by volume of ethanol, 60 parts by volume of water and 1.8 parts by volume of ethyl iodide is refluxed for about 3 hours. After cooling, the reaction mixture is added to 60 parts by volume of water containing 3 parts by volume of concentrated hydrochloric acid and the resulting crystals are collected by filtration to give 7-ethyl-4,7-dihydro-2-methyl-4-oxothieno(2,3-b)pyridine-5-carboxylic acid as colorless crystals. Recrystallization from chloroform-ethanol yields colorless prisms melting at 229°-230° C.

Provenance & Evidence