Synthesis of 2- and 3-acetylfuran carbethoxyhydrazones and investigation of their reaction with thionyl chloride

Abstract

By the reaction of 2- and 3-acetylfurans with ethoxycarbonyl hydrazine in presence of acetic acid a series of carboethoxyhydrazones was synthesized. On the basis of the 1H NMR spectra it was shown that in the compounds obtained furyl substituent and ethoxycarbonyl group might be located both in Z- and in E-position with respect to the C=N bond. The isomer ratio for various types of substitution in the furan ring was established. It was shown that the introduction of two methyl groups in the positions adjacent to the hydrazone group leads to thermal lability of the corresponding hydrazone. 2-Acetyl-, 5-methyl-2-acetyl-, and 3-acetylfuran carbethoxyhydrazones under the action of thionyl chloride undergo cyclization to 4-furyl-1,2,3-thiadiazoles. In the case of 3-methyl-5-acetyl- and 2-methyl-3-acetylfuran a mixture of corresponding thiadiazoles and the products of chlorination of carbethoxyhyrazone fragment was formed. It was shown that the introduction of methyl group in the furan ring leads to thermal lability of furylthiadiazoles.