New syntheses on the basis of ethyl 2-oxotetrahydrofuran-3-carboxylates

Alkylation of 5-substituted ethyl 5-methyl-2-oxotetrahydrofuran-3-carboxylates with alkyl halides in the presence of sodium ethoxide gave the corresponding 3-alkyl derivatives which were converted into 3,5-substituted 5-methyl-N-(4-nitrophenyl)-2-oxotetrahydrofuran-3-carboxamides and 5-methyltetrahydrofuran-2-ones. Reactions of the latter with hydrazine hydrate led to the formation of 4-hydroxypentanoic acid hydrazides which were treated with isothiocyanates to obtain the corresponding thiosemicarbazides whose intramolecular cyclization in the presence of aqueous alkali gave previously unknown 1,2,4-triazole-3-thiol derivatives.