Stability of some aryllithiums in the presence of cyano group: synthesis of biaromatic cyanoarylboronic acids and silanes

Lithium diisopropylamine (LDA)‐mediated deprotonation reactions of halogenated cyanobenzyloxy‐benzenes and cyanobiphenyls were investigated. The resultant organolithium derivatives were converted into the corresponding arylboronic acids or silanes. It was found that the stability of the obtained aryllithiums towards isomerization to the respective benzyllithiums depends strongly on the number of fluorine atoms in the phenyl ring and on the position of the cyano group. Halogenated cyanobiaryls were selectively deprotonated in the position flanked by two halogen atoms; however, the yield depended strongly on the reaction conditions. Addition of LDA to the cyano group was observed on the lithiation of 4‐cyano‐3′,5′‐dichlorobiphenyl rather than deprotonation. Copyright © 2012 John Wiley & Sons, Ltd.     

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O2 Activation and the First Monomeric Well-Defined Magnesium Alkylperoxide

Despite decades of extensive studies on the reactivity of magnesium alkyls towards O₂, the isolation and structural characterization of discrete products of these reactions still remains a challenge. Although the formation of the most frequently encountered magnesium alkoxides through unstable alkylperoxide intermediates has commonly been accepted, the latter species have been elusive for over 100 years. Probing the oxygenation of a seemingly simple well-defined neo-pentylmagnesium complex stabilized by a β-diketiminate ligand, (^dippBDI)MgCH₂CMe₃, we report on the isolation and structure characterization of both a dimeric magnesium alkoxide [(^dippBDI)Mg(μ-OCH₂CMe₃)]₂ and the first example of monomeric magnesium alkylperoxide [(^dippBDI)Mg(thf)OOCH₂CMe₃] (^dippBDI=[(ArNCMe)₂CH]⁻ and Ar=C₆H₃iPr₂-2,6). The formation of monomeric magnesium alkylperoxide demonstrates a crucial role of an additional Lewis base for stabilizing the most elusive oxygenation products likely due to increasing of the electron density on the metal centre. Moreover, the ¹H NMR studies at −80 °C revealed that the dissociation of a coordinated Lewis base from the solvated complex (^dippBDI)Mg(L)CH₂CMe₃ (where L=thf or 4-methylpyridine) is likely not required prior to the effective attack of an O₂ molecule on the metal centre and the four-coordinate alkylmagnesium complex reacts smoothly with O₂ under these conditions. The results can be expected to aid future engineering of various organomagnesium/O₂-based reaction systems.     

Obtaining Granules from Waste Tannery Shavings and Mineral Additives by Wet Pulp Granulation

This paper presents the results of research on the granulation process of leather industry waste, i.e., tanning shavings. It is economically justified to granulate this waste together with mineral additives that are useful in the processes of their further processing. Unfortunately, the granulation of raw, unsorted shavings does not obtain desired results due to their unusual properties. In this study, the possibilities of agglomeration of this waste were examined by a new method consisting of the production and then the granulation of wet pulp. During granulation, no additional binding liquid is added to the granulated bed. As part of this work, the specific surface of granulated shavings, the granulometric composition of the obtained agglomerates, and their strength parameters were determined. The use of a vibrating disc granulator, the addition of a water glass solution (in the pulp), dolomite, and gypsum made it possible to obtain durable, mechanically stable granules.     

5,7,12,14-Tetrafunctionalized 6,13-Diazapentacenes

The synthesis, property evaluation, and single crystal X-ray structures of four 5,7,12,14-tetrafunctionalized diazapentacenes are presented. The synthesis of these compounds either starts from tetrabromo-N,N-dihydrodiazapentacene or from a diazapentacene tetraketone. Pd-catalyzed coupling or addition of a lithium acetylide gave the precursors that furnish, after further redox reactions, the diazapentacenes as stable crystalline materials. The performance of the tetraphenyl-substituted compound as n-channel semiconductor was evaluated in organic field effect transistors.     

Alienation of two general linear functional equations

Aequationes mathematicae - We study the alienation problem for two general linear equations i.e. we compare the solutions of the system of equations $$\begin{aligned} \left\{ \begin{array}{l}\sum...     

Preparation of new imidazol-2-yl-(amino)methylphosphonates,phosphinates and phosphine oxides and their unexpected cleavage under acidic conditions

The efficient synthesis of new imidazol-2-yl-(amino)methylphosphonic acids, phosphonates phosphinate esters and phosphine oxides is described. The synthetic methodology is based on nucleophilic addition of phosphorus species to imidazole-2 derived imines. Additionally, it was discovered that heating the imidazol-2-yl-(amino)methylphosphonates with aqueous HCl or H₂SO₄ leads to their decomposition resulting in a rupture of the C–P bond, elimination of the phosphorous-containing fragment and formation of the corresponding secondary imidazole-2 alkylamines. A mechanistic pathway for the cleavage is postulated.     

Growth and EPR properties of KSm(WO4)2 and KEr(WO4)2 single crystals

Growth conditions and electron paramagnetic resonance investigations of two well oriented KSm(WO₄)₂ and KEr(WO₄)₂ single crystals have been presented and discussed. Hyperfine structure of Sm³⁺ ion was detected and analyzed for angular and temperature dependences. EPR spectra of KEr(WO₄)₂ and its angular dependence showed the presence of 5 magnetically nonequivalent Er centers in the crystal. A change in the type of magnetic interactions was analyzed using mixed (Gaussian and Lorentzian) fits of the EPR spectra.     

EPR and optical properties of KYb(WO4)2 and KTb0.2Yb0.8(WO4)2 single crystals

Well oriented KYb(WO₄)₂ and KTb_0.2Yb_0.8(WO₄)₂ single crystals have been investigated for their magnetic and optical properties using the Raman and EPR techniques. The registered EPR signal is dominated by three lines ascribed to ytterbium ions: one main and two satellites. Tb ions, although non-paramagnetic, distinctly modify magnetic properties of the KYb(WO₄)₂ single crystal. Basic parameters of the spin Hamiltonian, including Zeeman and hyperfine terms (g and A matrices) as well the spatial orientation between principal and crystallographic axes systems were determined for both crystals.