Reactions of methyl 4-hetaryl-2,4-dioxobutanoates with a mixture of aminoazole and aromatic (heteroaromatic) aldehyde

Abstract

We previously described methods of synthesis of methyl 6-acyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-5-carboxylates and methyl 6-acyl-7-aryl-4,7dihydrotriazolo[1,5-a]pyrimidine-5-carboxylates by reactions of methyl acylpyruvates with a mixture of an aromatic aldehyde and 5-aminotetrazole [1] or 3-amino-1,2,4-triazole [2], respectively. With a view to further study how the structure of heterocyclic amine affects the direction of these reactions in the present work we examined reactions of methyl 4-(2-thienyl)and 4-(2-furyl)-2,4-dioxobutanoates with mixtures of aromatic (heteroaromatic) aldehydes and 5-amino-1methyltetrazole, 3,5-diamino-1,2,4-tetrazole, and ethyl 5-amino-1H-imidazole-4-carboxylate. By heating for a short time a mixture of methyl 4-(2-thienyl)or 4-(2-furyl)-2,4-dioxobutanoate, 5-amino-1-methyltetrazole, and thiophene-2-carbaldehyde, benzaldehyde, or pyridine-3-carbaldehyde in acetic acid we obtained the corresponding 5-aryl(hetaryl)-4-hetaroyl-3-hydroxy-1-(1-methyltetrazol-5yl)-2,5-dihydro-1H-pyrrol-2-ones Ia–Ic (Scheme 1). Compounds Ia–Ic are colorless or slightly colored crystalline substances, which are readily soluble in DMF and DMSO, soluble in ethanol and acetic acid on heating, and insoluble in water. They give rise to a positive color test (cherry color) with an alcoholic solution of FeCl3. The H NMR spectra of Ia–Ic contain signals from aromatic protons, hydroxy proton, CH proton in the 5-position of the pyrrole ring (δ 6.13–6.48 ppm), and protons in the methyl group (δ 4.27–4.33 ppm, s). In the IR spectra of Ia–Ic we observed absorption bands due to vibrations of the ketone carbonyl group (1607–1620 cm), lactam carbonyl group (1701– 1755 cm), and enol OH group (3250–3269 cm).