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Hantzsch reaction has been successfully employed for a one-step assembling of pyranopyridine fragment to produce 5Н,9Н-pyrano[2',3':5,6]- chromeno[4,3-b]pyridine-5,9-diones which upon treatment with binucleophiles undergo chemoselective γ-pyrone ring opening with the concomitant recyclization to give five-membered cycles, providing a concise route to 6-pyrazolyl(isoxazolyl)-5H-chromeno[4,3-b]- pyridin-5-ones. [ABSTRACT FROM AUTHOR]

Three-component reactions involving 3-amino-1,2,4-triazole, aldehydes, including salicylic aldehydes, and pyruvic acids were studied in detail. The reaction pathway and products of the heterocyclizations could be changed by variation of the reaction parameters. The broad antimicrobial activity of the products was also studied. Compound 9d showed specific anti-influenza virus (A/H1N1) activity, with an IC50 of 0.57 μ M and a CC50 of >100 μ M. [ABSTRACT FROM AUTHOR]

The [3+2] cycloaddition of CF3CHN2, generated in situ, with electron-deficient alkenes/alkynes affords CF3-substituted pyrazolines/pyrazoles in quantitative yields. The one-pot three-component reaction between CF3CH2NH2 ·HCl, NaNO2, and the substrate proceeds at room temperature in dichloromethane/water. [ABSTRACT FROM AUTHOR]

Comparison of the results of Car-Parrinello molecular dynamics simulations of isolated benzene, pyrimidine and 1,2,4-triazine molecules reveals that the unusually low population of planar geometry of the benzene ring is caused by entropy effects despite its high aromaticity. The decrease in symmetry of the molecule results in smaller changes in entropy and Gibbs free energy due to out-of-plane deformations of the ring, leading to an increase in the population of planar geometry of the ring. This leads to differences in the topology of potential energy and Gibbs free energy surfaces. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Three-component heterocyclization of 4-amino-5-carboxamido-1,2,3-triazole, thiopyran-3-one-1,1-dioxide, and aromatic aldehydes under ultrasonic and microwave irradiation was studied. Regardless of the reaction parameters, 5,6,7,9-tetrahydro-4 H-thiopyrano[3,2- d][1,2,3]triazolo[1,5- a]pyrimidine-8,8-dioxides were isolated as sole reaction products whose structures were proven with help of NMR data and X-ray analysis. [ABSTRACT FROM AUTHOR]

Two isomeric conformationally restricted analogues of 4-trifluoromethylpiperidine were designed. The synthesis was performed in four steps from commercially available N-benzylmaleimide. The key reaction was the [3+2] cycloaddition between trifluoromethyldiazomethane and N-benzylmaleimide. [ABSTRACT FROM AUTHOR]

Formylation of 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5- a]pyrimidine 1a using Vilsmeier-Haack conditions yields 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5- a]pyrimidin-6-ylcarbaldehyde 3a. 5,7-Diaryl-4,7-dihydro-1,2,4-triazolo[1,5- a]pyrimidines 1b, c in this reaction apart from formylation undergo recyclization into 5-aryl-1,2,4-triazolo[1,5- a]pyrimidin-6-ylmethane derivatives 4b, c, 5b, c, and 6. The structure of the synthesized compounds was determined on the basis of NMR, IR, and MS spectroscopic data and confirmed by the X-ray analysis of the 6-(ethoxy-phenyl-methyl)-5-phenyl-[1,2,4]triazolo[1,5- a]pyrimidine 6, 5-phenyl-6-(1-phenyl-vinyl)-[1,2,4]triazolo[1,5- a]pyrimidine 11, and 7-phenyl-6-(1-phenyl-vinyl)-[1,2,4]triazolo[4,3- a]pyrimidine 12. [ABSTRACT FROM AUTHOR]

Ethyl azol-2-ylglyoxylates react smoothly with acetone in the presence of catalytic amounts of proline and trifluoroacetic acid to give the corresponding azolyl aldols in 93-98% yield. The products are easily transformed into azolyl pyridazinones in 85- 98% yield by cyclization with hydrazine hydrate. [ABSTRACT FROM AUTHOR]

The reactions of ethyl (4,5-dihydrofuran-3-yl)-2-oxo-acetate and ethyl 2-(3,4-dihydro-2H-pyran-6-yl)-2-oxoacetate, as 1,3-bielectrophiles, with N-unsubstituted 5-aminoazoles, as N-C-N-bi-nucleophiles, are the subject of this work. Regioselective heterocy-clizations of ethyl 2-(3,4-dihydro-2H-pyran-6-yl)-2-oxoacetate lead to 3-hydroxypropyl-7-ethoxycarbonyl substituted pyrazo-lo[1,5-a]pyrimidines and triazolo[1,5-a]pyrimidines whilst the cor-responding reactions of ethyl (4,5-dihydrofuran-3-yl)-2-oxoacetate result in the formation of oxodihydropyrano[4,3-e] annulated prod-ucts. [ABSTRACT FROM AUTHOR]

Heterocyclization reactions between N-arylmaleimides and 6-aminouracils were studied in detail. It was established that several directions are possible depending on the nature of reaction medium and the substituent character in the uracil component. The synthetic procedure leading to N-phenyl-2,4,7-trioxopyrido[2,3- d]pyrimidine-5-carboxamides in good-to-high yields was developed and key stages of the corresponding reaction were established. [ABSTRACT FROM AUTHOR]

Heterocyclization reactions between derivatives of 5- aminopyrazoles and N-arylmaleimides were studied and it was established that several directions are possible. Cyclizations involving 1,3-unsubstituted 5-aminopyrazoles yielded mixtures of two regioisomeric compounds, pyrazolo[1,5-a]pyrimidine-7-carboxamides and pyrazolo[3,4-b]pyridine-4-carboxamides. Reactions of 4-substituted 5-aminopyrazoles in boiling acetic acid or N,N-dimethylformamide in most cases gave pyrazolo[1,5-a]pyrimidine-7- carboxamides as the sole product. The treatment of 1-substituted 5- aminopyrazoles with maleimides possesses high selectivity only in N,N-dimethylformamide yielding pyrazolopyridines while in acetic acid the formation mixtures with pyrrolopyrazolones is observed. The key intermediates of the reaction studied were isolated and discussed. [ABSTRACT FROM AUTHOR]

Abstract: The introduction of a hydrazine functionality into 2-(2-cyanovinyl)-3-oxo-cyclohex-1-ene enolates results in their spontaneous cyclizations with participation of the hydrazine moiety. Depending on the reaction conditions used, the hydrazine-derived enolates are transformed into derivatives of 1-arylpyridine-2-one-3-carbonitriles or pyrazoloquinolinones in a one-pot synthesis. They also react with anilines to give the corresponding N1-substituted pyridine-2-one-3-carboxamides. Product characterization was performed by means of spectroscopic and X-ray diffraction studies. In addition, for structure elucidation purposes, a counter synthesis of 1-arylaminopyridine-2-one-3-carboxamide was also carried out. [Copyright &y& Elsevier]

Abstract: Based on the spectral studies of 1-aminoisoindole we have observed that in solution the isoindolenine tautomer predominates. In spite of this fact but, taking into account the Curtin–Hammett principle, we undertaken the first study of the Diels–Alder reaction for 1-aminoisoindole as a typical representative of simple isoindoles in isoindoline form. We have studied the interaction of 1-aminoisoindole with maleimide derivates and demonstrated that the products are rearranged 1:2 composition adducts. We have proposed a rearrangement mechanism, detected and identified the intermediate Diels–Alder products containing both endo- and exo adducts. [Copyright &y& Elsevier]

Abstract: A series of novel indolo[1,2-c]azolo[1,5-a]quinazoline-8,10-diones was obtained by a multi-component reaction between cyclic 1,3-diketones, α-aminoazoles, and glyoxal. The unexpected cyclization process was established by NMR spectroscopy and X-ray diffraction measurements. [Copyright &y& Elsevier]

Abstract: Three-component reactions of 5-aminopyrazoles and salicylic aldehydes with pyruvic acids were studied. The method of tuning of the selectivity of the heterocyclizations allowing to change its direction by variation of the reaction parameters was worked out. The treatment involving pyruvic acid can be selectively directed to the formation to either 3-aryl-10,11-dihydro-4,10-methano-pyrazolo[4,3-c][1,5]benzoxazocine-4-carboxylic acids or 3,6-diarylpyrazolo[3,4-b]pyridine-4-carboxylic acids, while the reaction involving arylpyruvic acid leads only to 7-hydroxy-2,5,6-triaryl-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrimidine-7-carboxylic acids. Antimicrobial activity of the compounds obtained was also studied: Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) were found sensitive to the substances tested, however, only in the highest concentration. [Copyright &y& Elsevier]

Abstract: A convenient synthesis of isothiochromen-4-one 2,2-dioxide was carried out via cyclisation of o-cyanobenzyl thioacetate by a Thorpe reaction. The reactions of isothiochromen-4-one 2,2-dioxide with nitrogen-containing nucleophilic reagents have been investigated. [Copyright &y& Elsevier]

Abstract: Multicomponent heterocyclizations of 3-amino-1,2,4-triazoles/5-aminopyrazoles with acetoacetamides and aromatic aldehydes were studied in detail using conventional thermal heating, ultrasonication, and microwave irradiation. Several different synthetic pathways for these cyclocondensations occurring under either kinetic or thermodynamic control were established depending on the temperature regime and building block selection. The experimental data obtained and the procedures developed allow tuning selectivity of the multicomponent reactions studied. [Copyright &y& Elsevier]

Hexahydro-2H-thieno[2,3-c]pyrrole is proposed as a low molecular weight polar scaffold to construct compound libraries used in the search for new drugs. Practical syntheses of derivatives of this bicyclic scaffold were developed, based on [3+2] cycloaddition of the ylide generated from N-benzyl-1-methoxy-N-((trimethylsilyl)-methyl)methanamine and 4-substituted 2,3-dihydrothiophene 1,1-dioxides. All of the 3-substituted hexahydro-2H-thieno[2,3-c] pyrrole 1,1-dioxide derivatives were obtained as single diastereomers. Conformational properties of the hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives were explored using X-ray diffraction studies. The potential of the scaffold to generate libraries of 3D-shaped molecules was demonstrated. [ABSTRACT FROM AUTHOR]

A variety of 2H-1,5-benzoxathiepin-3(4H)-one derivatives and one example of 5H-4,1-benzoxathiepin-3(2H)-ones (XIX) are synthesized. [ABSTRACT FROM AUTHOR]