V. A. Bakulev

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

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).

Synthesis and properties of 5-amino-1,2,3-thiadiazole-4-carbothioamides

Abstract5-Amino-1,2,3-thiadiazole-4NR-carboxamides were reacted with P4S10, and 5-NR-amino-1,2,3-thiadiazole-4-carbonitriles with-H2S. The reversible rearrangement of 5-amino-1,2,3-thiadiazole-4-NR-carbothioamides to 5-NR-amino-1,2,3-thiadiazole-4-carbothioamides was discovered.

Rearrangement of 5-amino-1,2,3-thiadiazole-4-carbothioamides

ConclusionsA new rearrangement in the series of 5-amino-1,2,3-thiadiazole-4-carbothioamides was observed.

Reaction of 5-Hydrazono-1,2,3-thiadiazoles with Toluene and Xylene in the Presence of PCl5

The treatment of 5-hydrazono-1,2,3-thiadiazoles by phosphorus pentachloride in toluene or xylene leads to an anomalous Dimroth rearrangement and the reaction of the mercapto function formed with the methyl group of the solvent to give 5-benzylmercapto-1,2,3-triazole.

Synthesis and Investigation of Ring-chain Isomerism of the Derivatives of N-Amino-5-hydroxy-1,2,3-triazole-4-carboxylic Acid

A series of sodium salts of 4-substituted 1-amino-5-hydroxy-1,2,3-triazoles was obtained by the “diazo transfer” reaction to arylmethylene-protected α-ethoxycarbonyl- and α-(methylcarbamoyl)-acetohydrazides. In DMSO solution the corresponding neutral hydroxytriazoles exist in equilibrium with the isomeric diazo compounds with an open chain. Electron-donating substituents stabilize the cyclic form. A good correlation was obtained between the equilibrium constants and the Hammett σ-constants. During the diazotization of benzaldehyde α-amino-α-cyanoacetylhydrazone the initially formed diazo compound undergoes spontaneous cyclization in solution to hydroxytriazole. Removal of the arylmethylene protection leads to N-unsubstituted sodium salts of 1-amino-5-hydroxytriazoles, but acidification of the latter leads to diazoacetohydrazides with an open chain.

Synthesis and cyclization direction of 2-diazomalondiamide derivatives new rearrangement of 5-hydroxy-1,2,3-triazole-4-carboxamides

The thermal behavior of 5-hydroxy-1,2,3-triazole-4-carboxamides obtained on acidification of solutionns of triazol-5-olates has been investigated. A new rearrangement has been discovered in the 1,2,3-triazole series and the qualitative effect of the substituents in the initial triazole and of temperature have been clarified.

Study of direction of cyclization of malonodithioamides as a method of investigation of reactivity of ?-diazothioacetamides

The reaction of malonothioamides with benzene-sulfonyl azide and 2-azido-3-ethylbenzthiazolium tetrafluoroborate gave amides of 2-diazothiomalonic acid, which underwent cyclization to a mixture of 5-N-R-amino-1,2,3-thiadiazole-4-carbothioamides and 5-amino-1,2,3-thiadiazole-4-N-R-carbothioamides. The ratio of the isomeric thiadiazoles formed in this reaction is the same as in the reactions of 2-diazo-2-cyanoacetamides, 5-amino-1,2,3-thiadiazole- and 5-mercapto-1,2,3-triazole-4-carboxamides with P4S10 and of 5-amino-1, 2,3-thiadiazole-4-carbonitriles with H2S; it is characteristic of the influence of substituents on the reactivity of α-diazothioacetamides. It was found that the cyclization of the diazo compounds is accelerated when electron-acceptor substituents are attached to the nitrogen atom of the carbothioamide group.

Reaction of 2-arylhydrazono-2-cyano-N-cyclohexylthioacetamides with halocarbonyl compounds

The reaction of arylhydrazonocyanothioacetamides containing an N-cyclohexyl fragment with chloroacetone, phenacyl bromide, ethyl chloroacetate, and chloroacetonitrile was investigated. It was shown that a substituent with a large steric effect in the thioamide group alters the direction of intramolecular cyclization of the thioimidate intermediate. In contrast to the Hantsch reaction, which usually leads to the formation of thiazoles under these conditions, the only products are 3-amino-4-arylhydrazono-4,5-dihydrothiophenes.

Acylation of 2-aryl-5-imino-2,5-dihydro-1,2,3-thiadiazoles

A large series of new 5-acyl-and 5-sulfonylthiadiazolimines was prepared by acylation of 2-aryl-5-imino-2,5-dihydro-1,2,3-thiadiazoles. Compounds obtained are more stable than the initial substances and do not transform into 1,2,4-thiadiazoles.

Synthesis and heteroelectrocyclization of unsymmetrically substituted diazomalonamides

A selective procedure was developed for the synthesis of 1,2,3-triazoles and unsymmetrically substituted diazomalonamides. Cyclization of unsymmetrically substituted diazomalonamides to 1,2,3-triazoles was studied by the method of intramolecular competitive reactions. The kinetic and thermodynamic characteristics of the process were determined. Quantum-chemical calculations for the monorotatory electrocyclic and nonrotatory heteroelectrocyclic mechanisms of cyclization were carried out. N-Aryldiazomalonamides undergo cyclization according to the heteroelectrocyclic mechanism, whereas cyclization of N-alkyldiazomalonamides proceeds by the monorotatory mechanism. The experimental constant of competition between these processes is (1.3—8.3)·103 (DMSO-d6) and (45.2—72.4)·103 (CD3OD).