Cyclic sulfonium salts with S ... O interactions 2. Molecular structures with six-membered rings

1-[2-(N-methylcarbamoyl)phenyl]-3H-2,1-naphto-(1,8-d,e)-oxathiin-1-ium chloride (2), 1-[2-(N-methylcarbamoyl)-phenyl]-2-methyl-3-oxo-3H-1, 2-naphto-(1,8-d,e)-thiazin-1-ium chloride (3), 1-[8-(N-methylcarbamoyl)naphtyl]-2-methyl-3-oxo-3H-1, 2-naphto-(1,8-d,e)-thiazin-1-ium chloride (4) and 1-(8-carboxylatonaphtyl)-2-methyl-3-oxo-3H-1,2-naphto-(1,8-d,e)-thiazin-1-ium dipolar ion (5) cyclic sulfonium salts were prepared and their chemical properties investigated (spirosulfurane-formation, hydrolysis). The molecular structures obtained from x-ray diffraction can be described with a considerably distorted trigonal bipyramidal arrangement of the ligands about the sulfonium center, with O/N—S ... O=apical angles of 173.9, 164.9, 156.6, and 159.0°, as well as with S—O/N apical bond lengths of 1.648, 1.671, 1.664, and 1.682 Å. The structures exhibit relatively short S ... O close contacts with interatomic distances of 2.253, 2.448, 2.795, and 2.619 Å.     

Synthesis of novel tryptamine and β-carboline derivatives via palladium-catalyzed reaction of bromotryptamine with organic boronic acids

New tryptamine 5, 7 and β-carboline derivatives 3 were preparated by palladium-catalyzed coupling reaction of 5-bromotryptamine 1 with aryl boronic acids. Dedicated to Professor András Lipták on his 70^th birthday.     

Regioselectivity of Birch reductive alkylation of biaryls

[reaction: see text] The regioselectivity of the Birch reductive alkylation of polysubstituted biaryls has been investigated. Results indicate that regioselectivity is affected by the electronic nature of substituents on both aromatic rings. The electron-rich 3,5-dimethoxyphenyl moiety is selectively reduced and then alkylated, while phenols and aniline are not dearomatized under these conditions. Biaryls possessing a phenol moiety are alkylated on the second ring, providing that the acidic proton has been removed prior to the Li/NH3 reduction.     

Assessment of the Fe-Sn-Zn phase diagram at 450°C

The Fe-Sn-Zn system is of interest because Sn is one element added to the Zn galvanizing bath to overcome the drawbacks due to the presence of Si in semi-killed steels. This work has been undertaken with the aim to understand the tin effect on the microstructure and the layers growth in batch galvanized coatings on low alloyed steels. Various experimental techniques such as metallography, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDX) are used in order to characterize the microstructure and the properties of such coatings elaborated in a zinc bath enriched with tin. Solidification phenomena and layers growth mechanisms during galvanization are explained by means of the ternary phase diagram Fe-Sn-Zn at 450°C. The Calphad method allows to obtain this phase diagram from the three optimized binary phase diagrams Fe-Sn, Fe-Zn and Sn-Zn and some experimental data inside the ternary Fe-Sn-Zn system.     

Synthesis of 2′,3′-dihydrosolanesyl analogues of β-d-arabinofuranosyl-1-monophosphoryldecaprenol with promising antimycobacterial activity

Two new hydrolytically stable analogues of β-d-arabinofuranosyl-1-monophosphoryldecaprenol, the donor substrate for mycobacterial arabinosyltransferase, have been prepared. Biological evaluation of these compounds in vitro against Mycobacterium tuberculosis H₃₇Rv strain revealed a promising activity.     

Selected ion flow tube mass spectrometry analyses of stable isotopes in water: Isotopic composition of H3O+ and H3O+(H2O)3 ions in exchange reactions with water vapor

A new method has been developed for the determination of the isotope abundance ratios of deuterium, D, and oxygen-18, 18O, in water vapor (and water) using selected ion flow tube mass spectrometry (SIFT-MS). H3O+ ions are injected into the helium carrier gas where they associate with the H2O and HDO molecules in a sample of water introduced into the carrier gas. The D and 18O contents of the product cluster ions H8DO4+ and H9(18)OO3+ at m/e = 74 and 75, respectively, are determined by reference to the majority cluster ion H9O4+ at m/e = 73. Allowance is made for the contribution of the H8(17)OO3+ ions to the m/z = 74 ions. Absolute isotopic ratios are measured within seconds without the need for precalibration of the SIFT-MS instrument, currently to an accuracy of better than 2%.     

Synthesis,Crystal Structure,and Electrochemical Behaviour of an Azido μ‐bridged Ni2+ Complex

A homo‐dinuclear Ni^II complex was prepared from 2, 6‐bis(3, 5‐dimethylpyrazolyl)pyridine (Me₄‐bpp) and azide ions in nonaqueous media. It was characterized by single crystal X‐ray structural analysis, IR spectroscopy, and elemental analysis. In addition, the electrochemical properties of the compound were determined with cyclic voltammetry in DMF. The title compound crystallizes in the P2₁/n monoclinic space group, with unit cell parameters a = 8.978(1), b = 12.459(1), c = 17.764(1) Å, ß =100.603(3)°, V = 1953.0(3) ų, Z = 2. The Ni²⁺ ion has a distorted octahedral environment involving three nitrogen atoms of the Me₄‐bpp ligand, two nitrogen atoms from the bridged azide group, and one nitrogen atom from the terminal azide group. The Ni···Ni distance is 3.273(5) Å.     

Examining the balance between efficiency and resilience in closed-loop supply chains

Central European Journal of Operations Research - We study a hybrid system where the demand of customers can be satisfied by both manufacturing new products and remanufacturing used products. To...     

Triangulations and moduli spaces of Riemann surfaces with group actions

Summary We study that subset of the moduli space of stable genusg,g>1, Riemann surfaces which consists of such stable Riemann surfaces on which a given finite groupF acts. We show first that this subset is compact. It turns out that, for general finite groupsF, the above subset is not connected. We show, however, that for ℤ₂ actions this subsetis connected. Finally, we show that even in the moduli space ofsmooth genusg Riemann surfaces, the subset of those Riemann surfaces on which ℤ₂ actsis connected. In view of deliberations of Klein ([8]), this was somewhat surprising. These results are based on new coordinates for moduli spaces. These coordinates are obtained by certainregular triangulations of Riemann surfaces. These triangulations play an important role also elsewhere, for instance in approximating eigenfunctions of the Laplace operator numerically. This work has been supported by the European Communities Science Plan Project No SCI^*-CT91 (TSTS) “Computational Methods in the Theory of Riemann Surfaces and Algebraic Curves,” by Academy of Finland and by the Swiss National Science Foundation Grant 20-34099.92. We thank M. C. Petrus for providing excellent motivation for this work. This article was processed by the author using the LATEX style filecljourl from Springer-Verlag.