2-Nitromethyl-2-trichloromethyl-1,3-benzodioxoles and 2-nitromethyl-2-trichloromethyl-1,3-benzoxazolines: Synthesis and structure

A reaction of 1-bromo-3,3,3-trichloro-1-nitropropene with pyrocatechol, o-aminophenol, and their substituted derivatives led to 2-nitromethyl-2-trichloromethyl-1,3-benzodioxoles and 2-nitromethyl-2-trichloromethyl-1,3-benzoxazolines. The structure of the compounds synthesized was established by IR, ¹H and ¹³C NMR spectroscopy with HMQC and HMBC ¹H—¹³C experiments, and X-ray diffraction analysis.     

Stereoelectronic interactions in the fragment N-C-CN from high-resolution X-ray diffraction data and quantum chemical computations

Analysis of the experimental electron density distribution function for the crystal and quantum chemical calculations revealed some distinctive features of stereoelectronic interactions (SI) in the fragment N-C-CN. The SI-induced changes in the atomic parameters were characterized in terms of the “Atoms in Molecules” theory. These interactions were compared with competitive SI in the fragment N-C-N. The crystal packing in organic cyanides is discussed. According to the data obtained, relatively weak SI in the fragment N-C-CN can be decisive for the molecular conformation in the crystal when there are no strong competitive interactions.     

Synthesis of Diaminophosphonium Salts [Ph2(ArNH)2P]+Br− (Ar = o-MeC6H4, p-MeC6H4, p-Pr i C6H4, p-EtO2CC6H4, p-MeOC6H4)

The behavior of different anilines H₂NC₆H₄R (R = o-Me, p-Me, o-, m- and p? ⁱ Pr, p-OMe, p-CO₂Et) and 2,6-Me₂C₆H₃NH₂ towards trihalophosphoranes was studied. 2,6-Me₂C₆H₃NH₂ failed to form the diaminophosphonium salt [Ph₂PNH(2,6-Me₂C₆H₃)₂]Br, and the aminophosphine oxide Ph₂(2,6-Me₂C₆H₃NH)PO was the only isolated product. Both o- and p-toluidine gave the corresponding diaminophosphonium salts; however in the case of o-toluidine, the yield was low and a mixture with the respective aminophosphine oxide was observed. Anilines containing methoxy and ethoxycarbonyl groups in para-position form the diaminophosphonium salts in reasonable yields.     

Racemo-selective formation of ansa-zirconocene in the reaction of dimethylbis(5-phenyl-5,6-dihydroindeno[2,1-b]indol-6-yl)silane dilithium salt with ZrCl4: X-ray and DFT argumentation for stereocontrol

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Cyclic hydroxamic acids derived from α-amino acids 1. Regioselective synthesis,structure, NO-donor and antimetastatic activities of spirobicyclic hydroxamic acids derived from glycine and DL-alanine

The reactions of glycine hydroxamic and DL-alanine hydroxamic acids with triacetonamine are chemoselective and afford 1-hydroxy-7,7,9,9-tetramethyl-1,4,8-triazaspiro[4.5]decan-2-one (3) and (±)-1-hydroxy-3,7,7,9,9-pentamethyl-1,4,8-triazaspiro[4.5]decan-2-one (4), respectively. The X-ray diffraction study showed that compound 3 crystallizes as a solvate with MeCN (1: 1). As shown by ESR measurements, spiro hydroxamic acids 3 and 4 are NO donors in in vitro biological systems. The NO-donor activity of compounds 3 and 4 was found to be substantially higher in the presence of DMSO. Homologue 4 is a stronger NO donor than 3. Compound 4 also exhibits high antimetastatic activity (81%) on the B16-melanoma model.     

Peculiarities of metal—ligand bonding in europium trinitrate complexes: a viewpoint of comparative charge density analysis in crystals

The results of high-resolution X-ray diffraction studies of the charge density distribution in crystals of three europium trinitrate complexes, including those with N-donor "antenna"-ligands are summarized. It is shown that the charge transfer between lanthanide ion and "antenna" correlates with the energy of interaction between the metal and nitrate anion, and the total stabilization energy of the metal polyhedron depends weakly on the coordination number of the metal and the nature of the ligands. The statistical treatment of the crystal structural data for similar complexes and the energies of the corresponding metal—ligand interactions allowed us to suggest the stability of mer-arrangement of the coordinated nitrate anions and to propose a semiempirical relationship to estimate the energy of Eu—O interactions. The influence of vibration processes on the electron density distribution in the EuO₂NO fragment was additionally considered, and a feasibility to estimate the energy of interaction between the ligand and lanthanide ion at non-stationary points on the potential energy surface was validated.     

Sigmatropic [1,3]-boron shift (permanent allylic rearrangement) in 3-allyl-3-borabicyclo[3.3.1]nonanes

2D ¹H-¹H EXSY NMR spectroscopy show that the free energy of activation ΔG ^≠ in six 3-allyl-3-borabicyclo[3.3.1]nonane derivatives is significantly higher (72–86 kJ mol^?1) than that in typical allylboranes (48–66 kJ mol^?1). For the first member of the series, viz., 3-allyl-3-borabicyclo[3.3.1]nonane, the activation parameters of the permanent allylic rearrangement were also determined (ΔH ^≠ = 82.7±3.4 kJ mol^?1, ΔS ^≠ = ?11.8±10.3 J mol^?1 K^?1, E _A = 85.5±3.4 kJ mol^?1, lnA = 29.2±1.2).     

3,28-Bis-<Emphasis Type="Italic">O</Emphasis>-polyfluorobenzoylbetulin. Synthesis,Molecular Structure,and Cytotoxicity

Treatment of betulin with 2,3,4,5-tetrafluoro- and pentafluorobenzoyl chlorides in triethylamine afforded 3,28-bis-O-polyfluorobenzoylbetulins. According to the X-ray diffraction data, all six-membered rings in the 3,28-bis-O-pentafluorobenzoylbetulin molecule appear in a chair conformation, and the five-membered ring has an envelope conformation with the C¹⁷ atom deviating from the plane formed by the other four carbon atoms. Unlike betulin itself, the obtained bis-esters showed no cytotoxic effect on human lung adenocarcinoma cell line A549 and human glioblastoma cell line U251.     

New (S)-proline derivatives as catalysts for the enantioselective aldol reaction

(2S)-N- 2-[(R)-Hydroxy(phenyl)methyl]phenylpyrrolidine-2-carboxamide, (2 S)-N-{2-[(S)-hydroxy(phenyl)methyl]phenyl}pyrrolidine-2-carboxamide, and (S)-N-{2-[hydroxy-(diphenyl)methyl]phenyl}pyrrolidine-2-carboxamide were obtained and tested as catalysts for an asymmetric aldol reaction of 4-nitrobenzaldehyde with acetone.     

Synthesis of substituted dibenz[<Emphasis Type="Italic">b,f</Emphasis>]oxepines from 2,4,6-trinitrotoluene

1,3-Dinitro[b,f]dibenzoxepine undergoes nucleophilic substitution with O-and S-nucleophiles, the nitro group at position 1 (peri-nitro group) being selectively replaced. The factors responsible for the selectivity of the reaction are discussed.