O. N. Chupakhin

RECENT ADVANCES IN THE CHEMISTRY OF as-TRIAZINIUM SALTS

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Ethyl cyanoacetate as 1,3-bifunctional reagent in the pyrimidine to pyridine ring transformations

Abstract By using of the double-labelled C * N * - CH 2 - COOEt compound it has been proved that transformation of 6-nitro-1,2,4-triazolo[1,5-a]pyrimidine into 2-triazolylamino-3-carbethoxy-5-nitropyridine proceeds with incorporation of the C-C-N fragment of ethyl cyanoacetate into the pyridine ring.

Cyclizations of 1,2,4-triazinium salts with bifunctional nucleophiles - a new route to condensed 1,2,4-triazines☆

Abstract The reaction of 1,2,4-triazinium salts with amides of acetoacetic acid yielding 1,4,4a,5,7,7a-hexahydro-6H-pyrrolo[3,2-e]-1,2,4-triazin-6-ones exemplifies the first direct annelation to the 1,2,4-triazine ring based on the diaddition of bifunctional nucleophiles at C-5 and C-6.

Preparation of Pyridyl-substituted Monoazatriphenylenes

Azatriphenylene derivatives are of considerable interest due to their promising photophysical and coordinating properties [1] and to their presence in the composition of natural compounds [2, 3]. Azatriphenylenes are important in inorganic biochemistry thanks to their use as intercalating ligands [4, 5]. In addition, azatriphenylenes have shown promise as luminescent chemosensors of organic anions and nitroaromatic compounds [6]. The most frequently used method for preparing azatriphenylenes is the Skraup synthesis [7, 8] which demands the use of forcing conditions. Contemporary synthetic methods broadly use a cycloaddition reaction of hard to obtain alkenes or arylacetylenes with aromatic substrates catalyzed by transition metal salts [9, 10]. Finally, the cyclocondensation of phenanthrenequinone with hydrazones of (hetero)aromatic carboxylic acid amides leads to the corresponding aryl[11, 12] and hetaryl-substituted [13] triazatriphenylenes. In this report, we propose an efficient method for the synthesis of cycloalkene-annelated derivatives of monoazatriphenylenes based on an aza-Diels–Alder reaction of the previously uncharacterized 3-(pyridin2-yl)phenathro[9,10-e][1,2,4]triazine (1) [14] with 1-morpholinocycloalkenes. A method for preparing different pyridine derivatives through reaction of the corresponding mononuclear 1,2,4-triazines has been known for some time [15-17]. In our work, we have used this method for the first time in a single-stage synthesis of the poorly available pyridyl-substituted monoazatriphenylenes 2a,b.

Aryne intermediates in the synthesis of polynuclear heterocyclic systems (Review)

Published examples of the polynuclear fused heterocyclic systems production by cycloaddition reactions involving aryne intermediates generated in situ are reviewed.

(Benzo[h])Quinolinyl-Substituted Monoazatriphenylenes: Synthesis and Photophysical Properties

We propose a method for the synthesis of quinolinyl- and benzo[h]quinolinylmonoazatriphenylenes through 1,2,4-triazine intermediates with subsequent transformations in aza-Diels–Alder reaction. The photophysical properties of these new compounds were examined, and the effects due to additional fused aromatic rings were explored.

The Extension of Conjugated System in Pyridyl-Substituted Monoazatriphenylenes for the Tuning of Photophysical Properties

We propose a method for the synthesis of diaryl-substituted pyridylmonoazatriphenylenes by the heterocyclization reaction of dihalosubstituted phenanthrenequinones with pyridine-2-carboxylic acid amidrazone, followed by aza-Diels–Alder reaction and Suzuki cross coupling. The obtained compounds showed more promising photophysical properties, compared to non-arylated analogs.

2-Azido-5-nitropyrimidine: Synthesis, Molecular Structure, and Reactions with N-, O-, and S-Nucleophiles

We describe the synthesis of 2-azido-5-nitropyrimidine and its azido-tetrazole tautomerism in various solvents and in the crystalline state. It was established that on interacting with N-nucleophiles the attack occurred at the C-2 carbon atom. The O- and S-nucleophiles attacked C-4 position of pyrimidine ring, resulting in tetrazole ring closure.

Unusual dimerization of 1-ethyl-1,2,4-triazinium salts into 4a,4b,9,10-tetrahydro-1,3,6,8,8a,10a-hexaazaphenanthrenes

Abstract 1- Ethyl-3-alkylthio-5-phenyl-l,2,4-triazinium tetrafluoroborates were found to undergo an unusual dimerization on treatment with triethylamine in methanol or ethanol solution. A mechanism for the formation of 4a,4b,9,10-tetrahydro-l,3,6,8,8a,l0a-hexaazaphenanthrenes is proposed.

Nitroazines. 7. Alkylation of 6-nitro-7-oxo-4,7-dihydroazolo[5,1-c][1,2,4]-triazines and identification of the products

Reaction of 6-nitro-7-oxo-4,7-dihydroazolo[5,1-c][1,2,4]triazines with methyl iodide or dimethyl sulfate affords the N-methyl derivatives, no O-alkylation products being found. The effect of the alkylating agent, solvent, and the azole moiety on the course of the reaction has been examined.