Synthesis and cation-binding properties of poly-and bis(thiacrown ether)s

Poly- and bis(thiacrown ether) derivatives in which some oxygen atoms of benzocrown ether moiety are replaced by sulfur atoms have been synthesized. Their cation-binding abilities were investigated by using the solvent extraction method. The poly- and bis(benzothiacrown ether)s showed great affinity for silver ion, being more excellent in the affinity than the corresponding monocyclic analogs. They, however, possess very poor cation-binding ability for alkali and alkaline-earth metal ions. The poly- and bis(thiacrown ether)s also bind mercuric ions effectively, whereas the corresponding monomeric analogs do not at all.     

An intramolecular diels-alder approach to quassinoids—a stereoselective construction of a-aromatic klaineanone

Thermolysis of a benzocyclobutene derivative ($\text{20}$) prepared from norcamphor produced stereoselectively a tetracyclic compound ($\text{2}$), which was converted to a lactone ($\text{21}$) having correct stereochemistry at C₇, C₈, C₉, C₁₁, C₁₃, and C₁₄ positions of (±)-klaineanone.     

Study on the structures of 2-substituted iminothiazolidine derivatives

The reaction of 2-bromoethylamine 1 with methylisothiocyanate 2 under mild condition gave 2-methyl-amino-2-thiazoline 3 as the major product together with two kinds of byproducts, 3-(N-methylthiocar-bamoyl)-2-methyliminothiazolidine 4 and N,N′-dimethyl-N-(2-thiazolin-2-yl)thiourea 5. Thermal isomer-ization of 5 to 4 was observed. The structures of the byproducts were confirmed by X-ray crystallography.     

Enantioselective reduction of ketones with optically active 2,2′-diamino-6,6′-dimethylbiphenyl-lithium aluminum hydride complex

Enantioselective reductions of prociral ketones with chiral hydride reagent prepared from optically active 2,2′-diamino-6,6′-dimethylbiphenyl and lithium aluminum hydride were accomplished in O.Y. more than 50%.     

Electrochemical control of CO/NO ligand exchange in a triruthenium cluster monolayer assembled on a gold electrode surface

A highly selective ligand exchange reaction is realized in the self-assembled monolayer (SAM) of a triruthenium cluster on a gold electrode surface under precise electrochemical potential control. CO as well as NO molecules, which are known to play key roles in many chemical, biological, and environmental systems, can be efficiently introduced into the SAM by electrochemically tuning the electronic state of the Ru site. These unique surface reactions are more convenient and efficient than conventional ligand exchange reactions in solution and could be used for the elucidation of the electron-transfer mechanism in a biological system as well as in the development of molecular sensors and devices.     

Asymmetric synthesis of the hydronaphthalene moieties of mevinic acids

The hydronaphthalene moieties of mevinic acids are synthesized enantioselectively by using the asymmetric intramolecular Diels-Alder reaction catalyzed by a chiral titanium reagent.     

Insertion of pyridine into an iron-silicon bond: structure of the product Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2

Heating a toluene solution of Cp*(CO)(C5H5N)FeSiMe2NPh2 led to insertion of pyridine into the iron-silicon bond to form Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2].     

Liquid-liquid extraction of copper (I) and copper (II) as ion-paired complexes with acyclic 2-thienyl-containing polythioether and triphenylmethane dye anion

Three acyclic polythioethers containing 2-thienyl units at both ends were synthesized and the effect of substituent on the extraction of copper(II) was studied. The methyl groups in the terminal thiophene ring have imparted an appreciable degree of increase in the percent extraction of copper(II), while the introduction of chlorine atoms into the 2-thienyl unit resulted in the reverse effect. Among the counter dye anions examined, tetrabromophenolphthalein ethylester was the best one for copper(II) extraction. The composition of extracted species was evaluated to be 122 (Cu(II)/polythioether/dye anion). Quantitative extraction of copper(I) was attained as complexes with various triphenylmethane dyes, i.e., bromocresol green, bromothymol blue, bromo-phenol blue and pyrogallol red. Copper(I) in organic phase was completely back-extracted with 2 mole/l sulfuric acid containing 10% hydrogen peroxide.     

Use of high molecular weight amines for end-point indication in the complexometric titration of Iron(III) with thiocyanate as indicator

Summary A new type of end-point indication for the complexometric titration of iron(III) is proposed. A 10% carbon tetrachloride solution of Amberlite LA-1 is applied for the extraction of the thiocyanate complexes. Very sharp color change of the organic phase from red to pale yellow gives the accurate end point for titrations with 0.01M EDTA as in the Variamine Blue B method.

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Zusammenfassung Eine neue Methode zur Endpunktanzeige bei der komplexometrischen Titration, von Eisen(III) wird vorgeschlagen. Eine 10%ige Tetrachlorkohlen-stofflösung von Amberlite LA-1 wird zum Ausschütteln der Thiocyanatkomplexe angewendet. Ein sehr scharfer Farbumschlag der organischen Phase von rot nach blaßgelb zeigt den Endpunkt für Titrationen mit 0,01-m ÄDTA so genau wie bei der Variaminblau-B-Methode an.

     

Crystallization in low-energy deposition of titanium ions

To investigate crystallization in the ion beam deposition process, titanium ions were deposited on silicon wafers at 105 and 55 eV. As titanium is an active metal, titanium compounds are formed by absorbing backfilled or residual gas. At energy levels of 105 or 55 eV, titanium crystallizes in a NaCl-type titanium compound with the backfilling of air. In all samples, (110)-oriented crystals grew with a rectangular lattice arrangement of titanium atoms. The open channel <110> of preferentially oriented crystal growth was parallel to the direction of incident ions normal to the substrate surface.