Unexpected regio- and stereoselective [4 + 3] cycloaddition reaction of azomethine ylides with benzylidene thiazolidinediones: synthesis of pharmacologically active spiroindoline oxazepine derivatives and theoretical study

Molecular Diversity - An unexpected regio- and stereoselective [4?+?3] cycloaddition reaction of azomethine ylides with 5-benzylidenethiazolidine-2,4-diones has been successfully...     

Recent advances in 1,3-dipolar cycloaddition reactions on solid supports

Solid-phase methods are of a great significance in organic synthesis. Recent developments of these methods are providing new ways to construct libraries of small organic molecules. Five-membered heterocyclic compounds, which can be utilized in a variety of applications, are formed in the 1,3-dipolar cycloaddition reaction between dipolarophiles and dipoles. This review deals with the solid-phase synthesis of heterocycles via [3+2] cycloaddition reaction. Cycloaddition reactions of polymer-bound dipoles and polymer-bound dipolarophiles and intramolecular solid-phase cycloadditions are discussed in separate sections. Reactions of dipolarophiles such as alkenes, alkynes, and imines with dipoles such as azomethine ylides, azomethine imines, nitrile imines, azides, nitrones, and nitrile oxides are described. The recent literature up to December 2003 is covered.     

A facile and efficient ultrasound-assisted synthesis of novel dispiroheterocycles through 1,3-dipolar cycloaddition reactions

A facile and efficient one-pot three-component procedure for synthesis of novel dispirooxindolecyclo[pyrrolo[1,2-c]thiazole-6,5′-thiazolidine] derivatives without any catalysts under ultrasonic condition has been developed. Combining with the advantages of sonochemistry, such as mild reaction conditions, good yield and short reaction times, we have made a progress on construction of novel disiproheterocyclic compounds via the 1,3-dipolar cycloaddition of azomethine ylides. Several experiments were especially carried out for investigating the acceleration mechanism of ultrasound on the cycloaddition.     

Kinetics and mechanism of gas‐phase pyrolysis of ylides. Part 3.1 Thermal reactivity of α‐carbonyl‐ and thiocarbonyl‐stabilized methylenetriphenylphosphoranes

Fourteen ketone/thione‐stabilized triphenylphosphonium methylides were subjected to conventional gas‐phase and flash vacuum pyrolysis (FVP). The kinetics of the first‐order thermal gas‐phase reactions of all these compounds were investigated over 360–653 K temperature range. The values of the Arrhenius log A and energy of activation of these ylides averaged 11.52 ± 0.34 s^?1 and 133.20 ± 3.14 kJ mol^?1, respectively. The products of sealed‐tube (static) and FVP were analyzed and compared. A mechanism is proposed to account for the products of reaction. The rate constants [k (s^?1)] of the substrates at 500 K were calculated and used to substantiate the proposed mechanism of pyrolysis, and to rationalize the thermal gas‐phase reactivities of the ylides under study. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of oxime phosphoranes from reaction between triphenylphosphine and acetylenic esters in the presence of oxime derivatives

A new one-pot, simple and effective procedure is presented for the preparation of O-containing phosphorus ylides by the Michael addition reaction of N-methylpyrrole-2-carbaldehydoxime, pyridin-2-carbaldehydoxime or acetophenonoxime with acetylenic esters.     

Diastereoselective synthesis of fused [1,3]thiazolo[1,3]oxazins and [1,3]oxazino[2,3-b][1,3]benzothiazoles

An efficient diastereoselective synthesis of 7-ethyl 5,6-dialkyl 7H-[1,3]thiazolo[2,3-b][1,3]oxazin-5,6, 7-tricarboxylates and 2-ethyl 3,4-dialkyl 2H-[1,3]oxazino [2,3-b][1,3]benzothiazole-2,3,4-tricarboxylates via reaction of thiazole and benzothiazole with dialkyl acetylenedicarboxylates in the presence of ethyl pyruvate is described.     

Ylide stabilized carbenes: a computational study

High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕ_S–T), broader band gap (ΔΕ_HOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd.     

Newby shift ofK=0 rotational bands in odd-odd rare-earths

A data set of 29 experimentally determined Newby shifts in rare-earth nuclei is examined for the reliability of each values. Using this data set, Newby shifts are obtained which are free from the Coriolis and the particle-particle coupling effects. These new empirical values help resolve the failure of a recently proposed rule for the sign of the Newby shift in the {5/2[413]p − 5/2[642]n} configuration of¹⁶⁰Tb and the {5/2[402]p − 5/2[512]n} configuration of¹⁷⁴Lu. Also the Newby shifts are significantly modified in two other cases namely the {1/2[411]p − 1/2[521]n} configuration in¹⁶⁸Tm and the {1/2[541]p − 1/2[521]n} configuration in¹⁷²Lu. Only marginal changes are seen in the rest of the cases in the rare-earth nuclei.     

6H-SiC（0001）-6[KF（]3[KF）]×6[KF（]3[KF）]R30°重构表面的同步辐射角分辨光电子能谱研究

利用同步辐射角分辨光电子能谱（SRARPES）对6H-SiC（0001）-6[KF（]3[KF）]×6[KF（]3[KF）] R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上（2.1±0.1）eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48 eV（S₀）,-1.62 eV（S₁）和-4. 关键词： 角分辨光电子能谱 碳化硅（SiC） 电子结构 表面态     

Updating the effective range expansion of low-energyN \bar N-scattering

Low energyN¯N scattering is reanalyzed using the new data on annihilation cross-sections from CERN [1], the¯np-absorption measurement from BNL [2] and the annihilation width of the 2p state in antiprotonic hydrogen [3]. Imposing the condition that the imaginary part of the effective range is negative we find low energy scattering parameters which interpolate between the existing ITEP [4] and CERN/Heidelberg [5] values.Supported by the BMFT-grant 06 HD 756     

A mild and efficient method for the synthesis of a new class of furo[3,2-c]chromenes in aqueous media

An efficient synthesis of 2-hydroxy-3-[2-oxo-2-phenylethylidene]-2-phenyl-2, 3-dihydro-4 H-furo[3, 2-c]chromene-4(2H)-one is described. This involves the reaction between dibenzoylacetylene and 4-hydroxycoumarine in the presence of NaH (10 mol %) in nearly quantitative yield. Treatment of this heterocyclic system with trimethyl chlorosilane in CHCl₃ leads quantitatively to 4-oxo-3-[2-oxo-2-phenylethylidene]-2-phenyl-3H, 4H-furo[3,2-c]chromene-1-ium chloride. Direct addition of nucleophiles, such as alcohols, amines or trialkyl phosphites to this salt in water as the solvent produces functionalized 2-phenyl-4H-furo[3,2-c] chromen derivatives in excellent yields.     

3H-Streptomycin durch Wilzbach-Reaktion

Zur Klärung spezieller Fragen des Transportes von Streptomycin in Pflanzen sollte radioaktiv markiertes Streptomycin eingesetzt werden. In der Mehrzahl der in der Literatur publizierten Untersuchungen (Engelberg und Artman [1]; Davey und Papavizas [2]; Hancock [3]; Das, Chatterjee und Roy [4]; Goodman [5]; u. a.) wurde ein [¹⁴C]-Streptomycin-CaCl₂-Komplex von MERCK, SHARP und DOHME Research Laboratories, USA benutzt. André [6] berichtete über die Herstellung von [³H]-Dihydrostreptomycin durch katalytische Anlagerung von ³H an Streptomycin. Bonventre, Hayes und Imhoff [7] arbeiteten mit uniform ³H-markiertem Streptomycin von Nuclear Research Chemicals, Orlando. Über Herstellung und Reinigung wurden keine Angaben gemacht.     

Abnormal thermal conductivity of [720]‐oriented BaTiO3 single crystal

The 3ω ‐scanning thermal microscopy and piezoresponse force microscopy techniques were combined to characterize the local thermal conductivity (λ) of ferroelastic domains in [720]‐oriented and [001]‐oriented BaTiO₃ single crystal. The [720]‐oriented BaTiO₃ showed a local λ value of 3.39 W/m·K, while it was 5.95 W/m·K for [001]‐oriented BaTiO₃. The underlying mechanism for such drastic thermal conductivity reduction in [720]‐oriented BaTiO₃ is ascribed to a stronger phonon‐scattering effect due to the high strains appearing in [720]‐oriented BaTiO₃ single crystals. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A note on <Emphasis Type="Italic">q</Emphasis>-Bernstein polynomials

Recently, Simsek-Acikgoz [17] and Kim-Jang-Yi [9] have studied the q-extension of Bernstein polynomials. In the present paper, we suggest q-extensions of Bernstein polynomials of degree n which differ from the q-Bernstein polynomials of Simsek-Acikgoz [17] and Kim-Jang-Yi [9]. Using these q-Bernstein polynomials, we derive fermionic p-adic integral representations of several q-Bernstein-type polynomials. Finally, we investigate identities between q-Bernstein polynomials and q-Euler numbers.     

Space-time aspects of superconductivity

A set of electromagnetic responses of superconductivity, [A] the zero-resistivity and [B] the perfect diamagnetism, has been reconsidered both electrodynamically and quantum mechanically. We point out an equivalence between the London gauge with the boundary condition or his “rigidity” of wave function and the phase locking in the BCS-type macroscopic wave function Φ_macro or the Ginzburg- Landau order parameter at T= 0 K. By reexamining the macroscopic wave function of condensed pairs Φ_macro at the ground state with the Josephson concept of coherent phase locking and the energy spectrum of quasi-particle excitation, we realize that the electric response [A] and magnetic response [B] can be decoupled and separable as independent with each other in the limits of an electrostatic field and of a uniform magnetic field rather than in an electrodynami-cal consideration. They are equally substantial in the physics of superconductivity. We recognize first a proper view to simultaneously account for [A] the zero-resistivity and [B] the perfect diamagnetism in the space-time aspects. By supplementing these space-time aspects with a concept of the gauge field theory, we can reach a further consistent and finally complete understanding of the theory of superconductivity.     

On the Fate of Methanol and Ethanol in Cotton Plant

O-Methylester groups constitute a part in a variety of well-known organophosphorus insecticides. Such compounds, e.g. Dipterex and Rogor [1], were found to undergo in vivo [2–4] as well as in vitro [5]P—OCH₃ cleavage, thus liberating methanol. The degradation of methanol in mammals has been extensively studied [6, 7] and more recently its fate in the cotton leaf worm has been investigated [8].     

К вопросу мобилизации почвенного азота при внесенин азотных удобрений на дерново-подзолнстых почвах

Untersuchungcn zur Korngrenzenselbstdiffusion in Kadmium wurden von Wajda und Mitarb. [1] bereits 1955 vorgenommen. Jedoch haben die mit der Näherungsmethode von Fisher [2] ausgewerteten Experimente mehrfach zur Kritik Anlaβ gegeben [3,4,5]. Wir haben deshalb erneut Messungen zur Korngrenzenselbstdiffusion in Kadmium vorgenommen, die auf Grund verbesserter Versuchstechnik und exakter Auswertungsverfahren [3, 4, 5, 6] höheren Genauigkeitsansprüchen genügen.     

Mass Spectral Fragmentation Patterns of Some Substituted 10,Ll-Dihydro-5H-Dibenzo[A,D] Cycloheptene-5-One and 9,10-Dihydro-4H-Benzo [4,5]Cyclohepta[1,2-B]Thiophene-4-One

Electron impact mass spectra of some substituted 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-one and 9,10-dihydro-4H-benzo[4,5] cyclohepta[1,2-b] thiophene-4-one have been recorded and the identity of various ions in the mass spectra established. Substituted dibenzosuberones (2-6) exhibit one main fragmentation route, which include the elimination of the tropolone molecule from the dibenzosuberone fragment cation. Their monothiophene analogues(7-11) exhibit characteristic CO elimination from the molecular ion and formation of corresponding naphtho[1,2-b]thiophene radical cation which after elimination of CS or HCS from the thiophene nuclei give rise to the benzotrophyne radical cation.     

A Method for q-Calculus

Abstract

We present a notation for q-calculus, which leads to a new method for computations and classifications of q-special functions. With this notation many formulas of q-calculus become very natural, and the q-analogues of many orthogonal polynomials and functions assume a very pleasant form reminding directly of their classical counterparts.

The first main topic of the method is the tilde operator, which is an involution operating on the parameters in a q-hypergeometric series. The second topic is the q-addition, which consists of the Ward–AlSalam q-addition invented by Ward 1936 [102, p. 256] and Al-Salam 1959 [5, p. 240], and the Hahn q-addition.

In contrast to the the Ward–AlSalam q-addition, the Hahn q-addition, compare [57, p. 362] is neither commutative nor associative, but on the other hand, it can be written as a finite product.

We will use the generating function technique by Rainville [76] to prove recurrences for q-Laguerre polynomials, which are q-analogues of results in [76]. We will also find q-analogues of Carlitz’ [26] operator expression for Laguerre polynomials. The notation for Cigler’s [37] operational calculus will be used when needed. As an application, q-analogues of bilinear generating formulas for Laguerre polynomials of Chatterjea [33, p. 57], [32, p. 88] will be found.     

Gold(I)-assisted catalysis – a comprehensive view on the [3,3]-sigmatropic rearrangement of allyl acetate

ABSTRACT

The unified reaction valley approach (URVA) combined with the local mode, ring puckering and electron density analysis is applied to elucidate the mechanistic differences of the non-catalysed and the Au[I]-N-heterocyclic carbene (NHC)-catalysed [3,3]-sigmatropic rearrangement of allyl acetate. Using a dual-level approach (DFT and DLPNO-CCSD(T)), the influence of solvation, counter-ions, bulky and electron withdrawing/donating substituents as well as the exchange of the Au[I]-NHC with a Au[I]-phosphine catalyst is investigated. The catalyst breaks up the rearrangement into two steps by switching between Au[I]–π and Au[I]–σ complexation, thus avoiding the energy-consuming CO cleavage in the first step. Based on local stretching force constants k^a(C=C), we derive for the first time a quantitative measure of the π-acidity of the Au[I] catalyst; in all catalysed reactions, the bond order n(C=C) drops from 2 to 1.65. The ring puckering analysis clarifies that all reactions start and end via a six-membered ring with a boat form. All Au[I]–σ-complex intermediates show a considerable admixture of the chair form. The non-catalysed [3,3]-sigmatropic rearrangement goes through a maximum of charge separation between the allyl and acetate units at the transition state, while all catalysed reactions proceed via a minimum of charge separation reached in the region of the Au[I]–σ-complex.