A. I. Chernyshev

Oxidation of 1-aminobenzimidazoles. Synthesis and properties of 1,1′-azobenzimidazoles

Abstract1-Amino-2-R-benzimidazoles are oxidized by lead tetraacetate to give, depending on the substituent in the 2-position, either to 1,1′-azobenzimidazoles (R=H, CH3, C6H5, Cl, N(CH3)2) or 3-R-benzo-1,2,4-triazines (R=NH2, NHCH3, NHC6H5, OH). The factors affecting the course of the reaction are discussed. The physicochemical properties of the 1,1′-azobenzimidiazoles obtained have been examined.

Purines, pyrimidines and condensed systems based on them. 10. Reactivity of 1,3-dimethyl-6-chlorolumazine with respect to amines: Competition of aminodechlorination and aminodehydrogenation reactions

Abstract1,3-Dimethyl-6-chlorolumazine reacts with secondary alkylamines and hydrazine to form 1,3-dimethyl-6-amino(hydrazino) derivatives in good yields. At the same time, 6-chloro-7-amino-1,3-dimethyllumazines are formed by the action of primary amines and liquid ammonia, in addition to the nucleophilic substitution products of chlorine.

Synthesis of pyrido[2,3-d]pyrimidine-2,4-diones from pyrimido-[4,5-e]-1,2,4-triazine-6,8-diones by reversed azadiene synthesis

It was shown that pyrimido[4,5-e]-1,2,4-triazine-6,8-diones enter the reversed azadiene synthesis reaction with ketones and vinyl ethyl ether in the presence of diethylamine or boron trifluoride etherate, and also with enamines. As a result of the reaction, pyrido[2,3-d]pyrimidine-2,4-diones are formed in good yield. Pyrimido[5,4-e]-1,2,4-triazine-5,7-diones do not undergo such reactions with acetone. The reasons for the unique behavior of the isomeric pyrimidotriazinediones in the reaction with acetone are discussed.

Protonation of pyrimidotriazinediones by1H and13C NMR spectroscopy

On the basis of an analysis of the changes in the chemical shifts of the signals in the1H and13C NMR spectra on the pyrimidotriazinedione and trifluoric acid concentrations in CDCl3 it was established that the protonation of rheumycin and fervenulin takes place at the N(2) atom, whereas the protonation of isofervenulin takes place competitively at the N(1), N(2), and O(6) atoms. The equilibrium constants of the investigated protonation processes were measured.

3-Halo-1-aminoindazoles: An unusual oxidation reaction in chloroform solution

Abstract1-Amino-3-chloro-, 1-amino-3-bromo-, and 1-amino-3-iodoindazoles were prepared by reacting hydroxylamine-O-sulfonic acid with 3-haloindazoles in basic medium. It was found that on standing in air in chloroform solutions, these amines undergo a complex transformation which includes the stage of oxidation of a N-amino group, and are slowly converted into 4-(3-haloindazolyl-1)-aminobenzo-1,2,3-triazines. A similar transformation takes place in carbon tetrachloride, but not in toluene or tetrahydrofuran, which suggests that halomethanes participate in the elementary stages of the oxidation reaction.

Diethylamine and triethylamine as sources of the dienophile component in the reverse azadiene synthesis with dimethylpyrimido[4,5-e]- and-[5,4-e]-1,2,4-triazinediones and 1,2,4,5-tetrazines

Diethylamine (DEA) and triethylamine (TEA) can function as sources for the two-carbon component in the reverse azadiene synthesis. Reaction of 5,7-dimethylpyrimido[4,5-e]-1,2,4-triazine-6,8-dione, 6,8-dimethylpyrimido-[5,4-e]-1,2,4-triazine-5,7-dione, or 1,2,4,5-tetrazine with an excess of DEA or TEA gives, respectively, the pyrido[2,3-d]pyrimidine-2,4-dione,pyrido[3,2-d]pyrimidine-2,4-dione, or pyridazine. The presence of an oxidant (atmospheric oxygen, MnO2, or an electron-acceptor solvent) is required for the reaction to occur. Reaction of 5,7-dimethylpyrimido[4,5-e]-1,2,4-triazinedione with piperidine, morpholine, or under certain conditions DEA, results in opening of the triazine ring to give uracils with an amidine group in the 6-position.

Purines, pyrimidines, and condensed systems based on them. 9. Concerning the synthesis of 1-r-pyrazolo[3,4-d]pyrimidine-4,6-diones

Abstract1-Ethyl-3-aryl-5-methylpyrazolo[3,4-d]pyrimidine-4,6-diones are formed in small amounts, together with the expected hydrazones, in the reaction of 3-methyl-6-(1-ethylhydrazino)uracil with aromatic aldehydes in ethanol The yield of these diones increases substantially when the reaction is carried out in acetic acid and sodium nitrite is subsequently added to the mixture. A change in the temperature conditions makes it possible to direct this reaction toward the formation of 1-ethyl-3-aryl-6-methylpyrimido[5,7-e]as-triazine-5,7-diones.

Purines, pyrimidines, and condensed systems based on them: 6. Reactivity of 7- and 9-aminoxanthines toward oxidizing agents and some electrophiles. Synthesis of the antibiotics fervenulin and rheumycin

The action of various oxidizing agents on 7- and 9-aminotheophyllines and also on 1-methyl-9-aminoxanthine was studied. 7-Aminotheophyllines are oxidized by almost all the oxidizing agents to 6,8-dimethylpyrimido[4,5-e]-as-triazine-5, 7(6H,8H)-dione (40–90%). 1-Methyl-9-aminoxanthine and 9-aminotheophylline are oxidized with greater difficulty. The best results are obtained with hydrogen peroxide, which transforms these amines with yields of −40% into the antibiotics rheumycin and fervenulin, respectively. Under certain conditions the action of bromine and nitric acid leads to the bromination and nitration of the N-aminoxanthines at position 8. A series of the physicochemical characteristics of the N-aminoxanthines were investigated. The factors which affect their behavior toward oxidizing agents and electrophiles are discussed.

Structures of the covalent hydrates and products of acidic hydrolysis of rheumycin and fervenulin

It is shown that pyrimido[5,4-e]-1,2,4-triazinediones are hydrated at the N(4)-C(4a) bond in aqueous acidic media. The equilibrium constants of these processes were measured by PMR spectroscopy. The structure of the covalent adduct of fervenulin was established by x-ray diffraction analysis. Formic, 5-diazo-3-methylbarbituric, and methylparabanic acids were identified among the products of destruction of the hydrates in acidic media.

Purines, Pyrimidines, and Fused Systems Thereof. Part 4. Formation of Pyrido(2,1‐f)xanthines from 7‐Aminotheophylline and Ketones.

7-Aminotheophylline (I) reacts with acetone (IIa) or, in better yields, with mesityl oxide (IIb) to give the pyridoxanthines (IIIa).