Synthesis of Tetrazino‐tetrazine 1,3,6,8‐Tetraoxide (TTTO)

This study presents the first synthesis and characterization of a new high energy compound [1,2,3,4]tetrazino[5,6‐e][1,2,3,4]tetrazine 1,3,6,8‐tetraoxide (TTTO). It was synthesized in ten steps from 2,2‐bis(tert‐butyl‐NNO‐azoxy)acetonitrile. The synthetic strategy was based on the sequential closure of two 1,2,3,4‐tetrazine 1,3‐dioxide rings by the generation of oxodiazonium ions and their intramolecular coupling with tert‐butyl‐NNO‐azoxy groups. The TTTO structure was confirmed by single‐crystal X‐ray.     

Electrophilic reactivity of the zwitterionic titanocene monohalides Cp[η-C5H4B(C6F5)3]TiX (X = Cl, Br): Reactions with water and methanol

The paper reports new data evidencing for a high electrophilicity of the positively charged titanium atom in the previously described zwitterionic titanocene monochloride Cp[η⁵-C₅H₄B(C₆F₅)₃]TiCl (1) and titanocene monobromide Cp[η⁵-C₅H₄B(C₆F₅)₃]TiBr (2), containing a B(C₆F₅)₃ group in one of the C₅ rings. It has been established that on a contact of a toluene solution of these zwitterions with water vapour at 20 °C under Ar, a rapid protolytic cleavage of the otherwise inert B-C₆F₅ bond in the tris(pentafluorophenyl)borane moiety occurs to afford pentafluorobenzene and the corresponding halogenide hydroxide complex of titanocene Cp[η⁵-C₅H₄B(C₆F₅)₂]TiX(μ-OH), where X = Cl (3), Br (4). An X-ray diffraction study of the complexes has shown that the hydroxide group in 3 and 4 is bonded via the oxygen atom both to the titanium and boron atoms. Under similar conditions, the interaction of zwitterion 1 with methanol gives rise to pentafluorobenzene and the chloride methoxide complex of titanocene Cp[η⁵-C₅H₄B(C₆F₅)₂]TiCl(μ-OCH₃). It has been suggested that the driving force of the protolysis of the B-C₆F₅ bond in 1 and 2 is a sharp increase in the acidity of water or methanol molecule as a result of their complexation with the positively charged titanium centre in the starting zwitterion.     

Structures of oxidation products of 4,6-di-tert-butylpyrogallol

Oxidation of 4,6-di-tert-butylpyrogallol gave two dimeric products instead of the expected 4,6-di-tert-butyl-3-hydroxy-1,2-benzoquinone (2). It was established by X-ray diffraction analysis that the first product has the structure of tetra-tert-butyl-6, 10a-dihydroxy-1,2-dioxo-3,4a,7,9-1,2,4a, 10a-tetrahydrodibenzo-1,4-dioxine. From this it follows that compound 2 undergoes regio- and stereospecific dimerization according to the [2π+4π]-cycloaddition mechanism,viz, the hetero Diels—Alder reaction. The double intensities of the signals in the¹H NMR spectrum are indicative of a symmetrical structure of the second product, 2,6,4′, 6′-tetra-tert-butyl-4,4′-dihyroxy-3,5,3′,5′-tetraoxo-4,4′-bi(cyclohexene), which is a racemate of enantiomers formed upon recombination (r+r orl+l) of the intermediate of oxidation of pyrogallol, namely, of ther,l-stereogenic 3,5-di-tert-butyl-1-hydroxy-2,6-dioxocyclohex-3-enyl radical. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 139–146, January, 1999.     

First synthesis of 1,5-diazabicyclo[3.1.0]hexane complexes with cadmium salts

Complexes of bicyclic diaziridines 6,6′-bi(1,5-diazabicyclo[3.1.0]hexane) (L ¹ ) and 6-(4-methoxyphenyl)-1,5-diazabicyclo[3.1.0]hexane (L ² ) with the salts Cd(NO₃)₂ · 4H₂O and Cd(ClO₄)₂ · 6H₂O have been synthesized. The fact of complexation has been established by cyclic voltammetry. The crystal structure of complex L ¹ with Cd(NO₃)₂ (the coordination number of cadmium is 8) has been studied by X-ray diffraction.     

Insertion of carbon disulfide and the nitrile group into the diaziridine ring of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in ionic liquids catalyzed by BF<Subscript>3</Subscript> · Et<Subscript>2</Subscript>O

The present study revealed two new reactions resulting in the diaziridine ring expansion, viz., the insertion of the CS₂ molecule and the CN group of activated nitriles into the C—N bond of the diaziridine fragment of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes. These reactions can be performed only in ionic liquids in the presence of BF₃ · Et₂O as the catalyst. Based on these reactions, we developed simple one-pot methods for the synthesis of 3-aryldihydro-5 H-pyrazolo[1,2- c][1,3,4]thiadiazole-1-thiones and 1-aryl-6,7-dihydro-1 H,5H-pyrazolo-[1,2-a][1,2,4]triazoles in high yields. Dipolar intermediates of new reactions, which are direct precursors of the final products, were detected by NMR methods. One of the intermediates was isolated and characterized. The reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with benzoyl cyanide affords (2-benzoyrpyrazolidin-1-yl)(aryl)acetonitriles.     

A planar chiral non-metallocenic analogue of the most popular N,N-dimethylbenzylaminate palladacycle

A racemic planar chiral tertiary amine pCp-CH₂NMe₂ (HL¹, pCp = [2.2]paracyclophane-4-yl) was prepared by aminomethylation of the bromide pCp-Br with Eschenmoser’s salt. Direct cyclopalladation of this new ligand with palladium(II) acetate results in the formation of the racemic CN-dimer rac-3 in a moderate yield of 64%. The enantiomerically pure dimer (S_pl, S_pl)-3 was obtained by the standard procedure of racemic palladacycle resolution using (S_C)-prolinate as a chiral derivatising agent. The ortho-palladated structure, absolute configuration of the chiral plane and stereochemical peculiarities of the new CN-palladacycle were established by means of NMR spectroscopy and an X-ray diffraction study of its (S_C)-prolinate derivative.     

Fano resonances in semiconductor superlattices

We use semiconductor superlattices as a model system for the investigation of Fano resonances. In absorption the excitonic transitions of the Wannier–Stark ladder show the typical asymmetric line shape due to coupling to the continuum of lower-lying transitions. The unique feature of these Fano resonances is that they allow to continuously tune the key parameter – the coupling strength Γ between the discrete state and the degenerate continuum – by varying the bias voltage. Using this feature, we directly show that the Fano coupling leads to a fast polarization decay. We also investigate the dependence of the Fano parameters on the structure of the superlattice and compare with an extensive theoretical model of the resonances.     

N‐phosphorylated 3,5‐bis(arylidene)4‐piperidones: Synthesis,X‐ray structure,and evaluation of antitumor activity

In a search for cytotoxic fluorescent materials, a series of N‐phosphorylated compounds 2a–c were prepared by phosphorylation of 3,5‐bis(4‐N,N‐dimethylbenzylidene)‐4‐piperidone 1 . According to X‐ray investigations, molecule 2a is E,E‐isomer with axial position of the P(O)(OCH₂CF₃)₂ substituent. Fluorescence of compounds 2a–c was found to be similar to fluorescence of nonphosphorylated compound 1 . The cytotoxicity of the compounds 2a–c was estimated on several human tumor cell lines (H9, K562, and MCF7). © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:497–502, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20147