Rh<Subscript>2</Subscript>(OAc)<Subscript>4</Subscript>-catalyzed reaction of 2-(2-carbonylvinyl)-3-phenyl-2<Emphasis Type="Italic">H</Emphasis>-azirines with diazo esters

Rh₂(OAc)₄-catalyzed reaction of 2-(2-carbonylvinyl)-3-phenyl-2H-azirines with diazo esters proceeds through an intermediate generation of azirinium ylide suffering a nonstereoselective ring opening to form (3Z)- and (3E)-2-azahexa-1,3,5-trienes. The former depending on configuration of the C ⁵ =C ⁶ bond may undergo cyclization either in derivative of 2,3-dihydropyridine, or in pyrrolium ylide that isomerizes into a derivative of 1H-pyrrole. According to DFT calculation, the preferred formation of pyrroles at increasing volume of Z-substituent at the atom C ⁶ and of substituents at the atom C ¹ of 2-azahexatriene occurs due to the destabilization of more sterically loaded transition states of 1,6-cyclization.     

An alternative approach to the synthesis of [1,2,4]triazolo[1,5-a]pyridine-8-carbonitriles,their crystal structure,and DFT calculations

New representatives of [1,2,4]triazolo[1,5-a]pyridine-8-carbonitriles were synthesized via the condensation of β-diketones or β-dialdehydes and characterized using MS spectrometry, ¹H, ¹³C and, ¹⁹F NMR and IR spectroscopy. Crystal structures of two compounds were established using X-ray analysis and showed that title compounds are prone to the formation of planar molecules. The absence of band responsible for CN stretching vibration in trifluoromethyl-containing compounds was explained using the DFT calculations method, which also showed a significant influence of fluorines introducing on the energy gap between HOMO and LUMO.     

Bis(1,10-phenanthroline)lithium perchlorate: Crystal structure and dissociation in acetone

The composition of the solid phase formed in acetone at a 1,10-phenanthroline (phen):LiClO₄ concentration ratio close to 2:1 was found. According to X-ray diffraction data, the molecular structure of bis(1,10-phenanthroline)lithium perchlorate is as follows: space group Pnna, a 7.191(2), b 39.929(9), c 14.494(3) Å, Z 8, and D _x 1,490 g cm^?3. The IR spectra data show that the complex Li(phen)₂ClO₄ dissociates in acetone into a 1:1 complex and a phen molecule in the solution equilibrium with the solid phase.     

17β‐Ethoxy‐3‐methoxy‐8‐isoestra‐1,3,5(10)‐triene

The conformation of the crystal of 17β‐ethoxy‐3‐methoxy‐8‐iso­estra‐1,3,5(10)‐triene, C₂₁H₃₀O₂, (I), has been established and compared with the molecular structure of a typical steroid estrogen 8‐iso‐analogue, (II). Calculations of distances separating some of the H‐atom pairs in (I) and (II) by molecular‐mechanical and semi‐empirical methods revealed the similarity of the values to the H⃛H distances obtained from X‐ray analysis.     

Protolytic properties of 2-acylthioacetamides

Concentration acidity of 2-acylthioacetamides dissolved in DMSO-H₂O was measured by the method of pH-metric titration. The data obtained were extrapolated for the determination of pK _a values of 2-acylthioacetamides in water and DMSO. We found that in aqueous solutions the acidity of thioacetarylamide (pK _a = 5.75?C6.01) was almost independent of the nature of substituents in their N-phenyl rings, whereas in DMSO solution the nature of substituents significantly affects their ionization constants (pK _a = 7.88?C11.70). The graphs were displayed and the acidity of N-aryl-3-oxobutanethioamides dependence on the Hammett constants of meta- and para-substituents in the phenyl rings derived. Water is shown to be a leveling, and DMSO a differentiating solvent for 2-acylthioacetamides.     

Synthesis and structure of some 8α-analogs of steroid estrogens

The distances between the protons of four 8α-analogues of steroid estrogens as determined by X-ray data are consistent with the calculated values obtained by ab initio, PM3 and MM+ methods, that can be used for docking of these stereochemical analogs onto α-estrogen receptors.     

Influence of acido ligands on the structure of copper dihalide solvates with dimethyl sulfoxide and <Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide

Structures of copper dihalide solvates with dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) were determined by XRD single crystal analysis. The existence of two DMSO solvates with CuBr₂, but only one with CuCl₂, was attributed to a lower Cu-Br bond strength in comparison with Cu-Cl, and, as a consequence, by its easier breaking to form a bond with a solvent molecule. Fundamentally different structures of CuX₂·2DMF (X = Br, Cl) solvates are caused by different donor power of the acido ligands.     

The (3+2)- and formal (3+3)-cycloadditions of N-vinylpyrroles with cyclic nitrones and C,N-cyclic azomethine imines

The addition of Lewis acids changes the path of the reaction of N-vinylpyrroles with 3,4-dihydroisoquinoline-N-oxides: formal (3 + 3)-cycloaddition proceeds instead of (3 + 2)-cycloaddition. In the case of benzoyl(3,4-dihydroisoquinolin-2-ium-2-yl)amides, reaction path does not change in the same conditions, but changing of the diastereoselectivity occurs and other diastereomer of (3 + 2)-cycloaddition became predominant.     

Stereo- and regioselective synthesis of β-amino-β-tetrazolylvinylphosphonates

Addition of 5-substituted tetrazoles to dimethyl [(N,N-diisopropylamino)ethynyl]phosphonate proceeds regio- and stereoselectively to yield (Z)-[2-diisopropylamino-2-(tetrazolyl)vinyl]phosphonic acid dimethyl esters. The Z-configuration of the products was confirmed by ¹Н NMR spectroscopy and single-crystal X-ray diffraction. The reactions occur via nucleophilic attack of tetrazole involving predominantly the N-1 atom of the tetrazole ring.     

Synthesis and properties of 5-alkynyl-1,2,3-triazoles

1,3-Dipolar addition was investigated of 2-azidoethanol to diyne glycols containing primary or tertiary hydroxyethyl groups at the system of triple bonds. This reaction provided exclusively a monoadduct as a single regioisomer, namely, 5-alkynyl-1,2,3-triazole.