Albert F. Khasanov

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.

(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.

Extended cavity pyrene-based iptycenes for the turn-off fluorescence detection of RDX and common nitroaromatic explosives

Extended cavity pyrene-based iptycenes have been synthesized by using the Diels–Alder reaction between in situ generated dehydropyrenes and anthracene. The photophysical properties and the interaction of these iptycenes with nitro-explosive components were studied both in solution and in the solid state by using fluorescence spectroscopy and X-ray crystallography, respectively. Due to the presence of both the large iptycene cavity and the central pyrene core, an unprecedently high fluorescence-quenching response towards non-aromatic and non-planar 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) has been observed both in solution (with an apparent Stern–Volmer constant value aKSV up to 1.53 × 103 M−1) and in the vapor phase (50–75% fluorescence quenching of the PU films doped with chemosensors). In the case of nitroaromatic explosives, nitrobenzene (NB), 2,4-DNT, TNT, and 2,4,6-trinitrophenol (TNP or picric acid, PA), pyrene-based iptycenes also demonstrate a good fluorescence-quenching response both in solutions (with apparent Stern–Volmer constant values aKSV = 0.4–8.0 × 103 M−1) and in the vapor phase (up to 90% fluorescence quenching of the PU films doped with chemosensors). The “sphere of action” fluorescence quenching model was suggested.

Functionalized 2-(5-arylpyridin-2-yl)quinolines: synthesis and photophysical properties

An efficient approach to the synthesis of 2-(5-arylpyridin-2-yl)quinolines containing fluorine atoms and a cyclopentene fragment was suggested. Photophysical properties of new compounds were studied and compared to those of the earlier described compounds without such functional groups.

Solvent-free reaction of 3-aryl-6-(3-nitrophenyl)-1,2,4-triazines with 4-(cyclohex-1-en-1-yl)morpholine

The aza-Diels–Alder reaction of 3-aryl-6-(3-nitrophenyl)-1,2,4-triazines with 4-(cyclohex-1-en-1-yl)morpholine as dienophile was accompanied by reduction of the nitro group to amino. In the reaction of 3-(4-methoxyphenyl)-6-(3-nitrophenyl)-1,2,4-triazine with 4-(cyclohex-1-en-1-yl)morpholine, 3-[3-(4-methoxyphenyl)-1,2,4-triazin-6-yl)aniline was formed together with the cycloaddition product.

Mass spectrometric studies of self-condensation products of cyclohexanone under alkaline conditions and synthesis of dodecahydrotriphenylene and triphenylene from easily available reactants

LC-MS was used to study products of cyclohexanone self-condensation under alkaline conditions. Improved methods (as compared to those described in the literature) for the preparation of dodecahydrotriphenylene and highly pure sublimed triphenylene were suggested based on the easily available and cheap reactants. Possible reasons of the low yield of the target dodecahydrotriphenylene in the step of oligomerization of cyclohexanone were identified.

Phenylglyoxal dihydrazones as unexpected products in the synthesis of 1,2,4-triazines by interaction of α-bromoacetophenones and arylhydrazides

On interacting α-bromoacetophenones with aromatic carboxylic acid hydrazides, the formation of two reaction products was observed in certain cases, the expected 1,2,4-triazine and the phenylglyoxal dihydrazone as an unexpected product. The effect of substituents in the initial substrates and of the conditions of carrying out the synthesis on the direction of the reaction have been studied.

Solvent-free reaction of 1,2,4-triazine-5-carbonitriles with 4-(cyclohex-1-en-1-yl)morpholine. Unexpected decyanation in addition to classical aza-Diels–Alder reaction

The reaction of 1,2,4-triazine-5-carbonitriles with 4-(cyclohex-1-en-1-yl)morpholine under solventfree conditions has been found to follow two pathways: aza-Diels–Alder reaction and unexpected decyanation of the initial nitriles. The scope of the revealed decyanation reaction has been roughly estimated.