Probing the diastereotopicity of methylene protons in strychnine using residual dipolar couplings

Residual dipolar couplings were successfully used to distinguish between the two diastereotopic protons on C-20 of strychnine dissolved in an organic liquid crystal (PBLG/CDCl(3)). The results presented here strongly suggest that this method will be of help in organic structure determination, making the determination of relative stereochemistry in the absence of NOE data possible.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXVIII. Zur Benzylierung der Acetylacetonate des dreiwertigen Titans,Vanadiums und Chroms

Contribution to the Chemistry of Transition Metal Alkyl Compounds. XXVIII. Benzylation of the Trivalent Titanium, Vanadium, and Chromium Acetylacetonates BzCr(acac)₂, 2Bz(Vacac)₂ · Mg(acac)₂ and 3BzV(acac)₂ · Al(acac)₃ were obtained in definite form by reaction of Cr(acac)₃ and V(acac)₃ with Bz₃Al, Bz₂Mg, and BzMgCl. Ti(acac)₃, reacts with Bz₂Mg and BzLi forming deep green Bz₃Ti, which could'nt be isolated free of impurities (Bz = C₆H₅CH₂, acacH = acetylacetone).     

Kinetik der unkatalysierten Urethanbildung

Summary The kinetics of the reaction of phenylisocyanate with 1-butanol have been studied at low concentrations in carbon tetrachloride solution at three temperatures. The present paper describes the relation between the reaction rate and the concentration of the alcohol dimer and the 1:1 alcoholurethane associate. Therefrom we conclude that the monomeric alcohol does not play any significant part in the reaction. We explain the observed rate equation with the second-order term of the reactants with the equality of the productsk _AA K _AA andk _AU K _AU (rate constant and association constant of alcohol dimer and 1:1 alcohol-urethane associate).For the reaction of alcohol dimer H =45.4 kJ mol^–1 and S =– 142J mol^–1K^–1. We interpret this result in terms of a six-cyclic transition state.

     

Intramolekulare C?H-Aktivierung bei der Reaktion von Bis(benzylcyclopentadienyl)zirconiumdichlorid mit Vinyllithium — Bildung eines Crotyl-zirconacyclus

Intramolecular C? H Activation at Reaction of Bis(benzylcyclopentadienyl)zirconium Dichloride with Vinyllithium — Formation of a Crotyl Zirconacyclus Bis(benzylcyclopentadienyl)zirconium dichloride, (C₆H₅CH₂? C₅H₄)₂ZrCl₂ ( V ), reacts with vinyl lithium with formation of the chiral compound (C₆H₅CH₂? C₅H₄)? ? CH₂CH=CHCH₃ ( IX ) as the product of vinyl group coupling and an orthometallation reaction. The reaction mechanism and the ¹³C n.m.r. spectrum are discussed.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXXV. Zum Reaktionsverhalten von Tetrabenzyltitan gegenüber Lithiumalkylen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXV. Reactions in Tetrabenzyl Titanium/Alkyllithium Systems Organotitanium(IV) complexes of the type Li[(C₆H₅CH₂)₄TiR] (R = CH₃, C₂H₅, n-C₄H₉) were isolated from tetrabenzyl titanium and lithium alkyls at deep temperature. The reddish brown, crystalline compounds decompose between ?30 and 0°C with formation of benzyltitanates(II) which composition differs between Li₂[Ti(CH₂C₆H₅)₄] and Li[Ti(CH₂C₆H₅)₃]. From these complexes pure dibenzyl titanium can be isolated. The reaction mechanism is discussed. Experiments for isolation of a benzyl titanium(III) compound from (C₆H₅CH₂)₄Ti/RLi systems failed in all cases. Recent informations about stable tribenzyl titanium obtained from tetrabenzyl titanium and ethyl lithium could not be confirmed.     

Register für the Bände 401–410

Chemistry and Structure Chemistry of Phosphides and Polyphosphides. XI. Lanthanum Diphosphide LaP₂; Preparation, Structure, and Properties LaP₂ is formed by heating (1 080°C) lanthanum metal and red phosphorus with small amounts of iodine. It crystallizes monoclinic in the space group Ia? C₈⁴ with a = 8.883, b = 13.942, c = 8.825 Å, β = 90.15° and Z = 16 formula units. Structural characteristics are three and five membered chains of phosphorus P and P, which justify the formula La₄P₃P₅. LaAs₂ (above 750°C) has the same structure.     

Die Kristallstruktur der Hexaquomagnesiumhexahalogeno-dimercurate [Mg(OH2)6][Hg2X6] (X = Br,I)

Crystal Structure of the Hexaquomagnesiumhexahalogenodimercurates [Mg(OH₂)₆][Hg₂X₆] (X = Br, I) Hexaquodimercurates [Mg(OH₂)₆][Hg₂X₆] (X = Br, I) were obtained by crystallization from aqueous solutions of HgX₂ and MgX₂. The crystal structure of the monoclinic compounds consists of binuclear Hg₂X₆ anions and octahedral Mg(OH₂)₆ cations.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 50. Eine ungewöhnliche Organolanthanverbindung

Contributions to the Chemistry of Transition Metal Alkyl Compounds. 50. A non-common Organolanthanum Compound Lanthanum reacts with dibenzyl mercury in tetrahydrofuran as a solvent with splitting of solvent molecules and with formation of ethylene and a benzyl hydrido vinyloxide lanthanum complex of the composition C₆H₅CH₂La(H)OCH?CH₂ · 2 THF. This complex, primary well soluble in tetrahydrofuran, is extremely sensitive against air and moisture and undergoes a fast coordination polymerisation with a strong decrease of the solubility. The compound was characterized by elementary analysis, the hydrolysis and deuterolysis reaction, and by the i.r. spectra.     

Polymer mediated self-assembly of magnetic nanoparticles

We present a simple polymer-mediated process of assembling magnetic FePt nanoparticles on a solid substrate. Alternatively absorbing the PEI molecule and FePt nanoparticles on a HO-terminated solid surface leads to a smooth FePt nanoparticle assembly with controlled assembly thickness and dimension. Magnetic measurements show that the thermally annealed FePt nanoparticle assembly as thin as three nanoparticle layers is ferromagnetic. The magnetization direction of this thin FePt nanoparticle assembly is readily controlled with the laser-assisted magnetic writing. The reported process can be applied to various substrates, nanoparticles, and functional macromolecules and will be useful for future magnetic nanodevice fabrication.