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 percent 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