Pericyclic reactions in the synthesis of new 5-aryl-5,6-dihydroquinolino[2,1-b]quinazolin-12-ones

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Composition, structure, and properties of pharmacologically active silicon dimethylglycerolates

¹H and ²⁹Si NMR spectroscopy showed that the product of the reaction of dimethyldiethoxysilane with glycerol in the molar ratio 1: 2 is an equilibrium mixture of dimethyldiglyceroxysilane and low-molecular-weight condensation products. The change of viscosity of silicon dimethylglycerolates, synthesized using different excesses of glycerol, versus time was studied by viscosimetry. Composition of products of hydrolysis and condensation of silicon dimethylglycerolates is determined by their concentration in the starting aqueous solutions.     

Unusual heterocyclization of chalcone podands with 3-amino-1,2,4-triazole

A new type of intramolecular cyclization of 1,5-bis[2-(E-3-oxo-3-phenylprop-1-enyl)-phenoxy]-3-oxapentane with 3-aminotriazole promoted by potassium ions was discovered. A cascade mechanism for the formation of crownophane with 4,7-dihydro[1,2,4]triazolo[1,5-a]-pyrimidine fragment was suggested. Effects of oligooxyethylene fragment of the chalcone podand and acid-base catalysis on the selectivity of the cyclocondensation processes and degree of oxidation of triazolopyrimidine fragments were studied. The product structures were confirmed by IR, ¹H and ¹³C NMR spectroscopy and X-ray diffraction study.     

Pre-organization of diarylideneacetonyl crownophanes in single crystals to photochemical transformations

Specific features of crystal packings and pre-organization of diarylideneacetonyl crownophane molecules to solid-phase photochemical transformations were studied on the basis of X-ray diffraction data using methods of simulation of molecular crystal packings. The tendency of the most part of the synthesized macrocyclic E,E-isomers to the formation of homochiral crystals (P2₁2₁2₁) was revealed, while (23E,26E)-11,12,14,15-tetrahydro-8H-dinaphtho-[2,1-k:1′,2′-r][1,4,7,10]tetraoxacyclononadecine-23,26-dien-25(9H)-one is prone to polymorphism. A phenomenon of solid-phase stereospecific photochemical dimerization of molecules according to the syn-head-to-tail type without crystal destruction (single crystal—single crystal transformation) was found for one of the modifications of this crownophane.     

Highly diastereoselective 1,3-dipolar cycloaddition of nonstabilized azomethine ylides to 3-nitro-2-trihalomethyl-2H-chromenes: synthesis of 1-benzopyrano[3,4-c]pyrrolidines

Reactions of 3-nitro-2-trifluoro(trichloro)methyl-2H-chromenes, including 2-unsubstituted derivatives, with N-alkyl-α-amino acids (sarcosine, proline) and paraformaldehyde proceed diastereoselectively to give 1-benzopyrano[3,4-c]pyrrolidines in good yields as a result of a 1,3-dipolar cycloaddition of the intermediate nonstabilized azomethine ylide at the Δ³-bond of the chromene system.     

Synthesis of chromeno[3,4-c][1,2]oxazine-N-oxides via formal [4+2] cycloaddition of 3-nitro-2-trihalomethyl-2H-chromenes with cyclohexanone and pinacolone enamines

3-Nitro-2-trichloro(trifluoro)methyl-2H-chromenes undergo a formal [4+2] cycloaddition reaction to cyclohexanone and pinacolone enamines, producing chromeno[3,4-c][1,2]benzoxazin-6-oxides with high diastereoselectivity and in good yields. In addition, some novel 2,3,4-trisubstituted chromanes were obtained. The stereochemistry of the products was established based on a 2D NOESY experiment and an X-ray diffraction study.     

Synthesis and structure of fluorine-containing 3-pyrazolin-5-ones

Noncatalyzed reaction of α-acetyl-γ-butyrolactones containing a polyfluoroalkyl substituent in the γ-position with hydrazine hydrate and thiosemicarbazide in methanol leads to the formation of substituted 3-pyrazolin-5-ones that in (CD₃)₂SO solution and in the solid state exist in the NH-tautomeric form.     

Novel methods for synthesis and sorption properties of N,O-(2,3-dihydroxy)propylchitosan

The direct addition of glycidol to chitosan in a gel medium under exposure to ultrasound afforded the chelating aminopolymer N,O-(2,3-dihydroxy)propylchitosan with a degree of substitution up to 2.3. The sorption characteristics of the crosslinked aminopolymers with respect to boron-containing ions were estimated.     

Photochemical transformations of chalcone-podands into cyclobutane-containing benzocrown ethers

A method for the synthesis of cyclobutane-containing benzocrown ethers by the template photocycloaddition of the corresponding chalcone-podands in solutions was developed. It was shown by X-ray diffraction analysis, ¹H and ¹³C NMR, and UV spectroscopy that the intramolecular [2π+2π] photocycloaddition (PCA) is stereoselective with the predominant formation of structures of the β- and γ-truxinic type. The PCA rate was shown to depend on the size of the oxyethylene spacer and stereoorientation of the chalcone fragments in the podands. The selectivity of the PCA process can be controlled by a change in the concentration of the template (alkaline metal ions) and variation of the wavelength range of irradiation.     

Isomerism and tautomerism of 5-fluoroalkyl-substituted 3-acetyldihydrofuran-2(3H)-ones

Russian Journal of General Chemistry - The geometric isomerism and tautomeric equilibrium of 5-fluoroalkyl-3-acetyldihydrofuran-2(3H)-ones obtained by condensation of (perfluoroalkyl)methyloxiranes...