The Initiating Effect of Vinyl Aromatic and Diene Monomers on the Polymerization of Isobutylene with VCl4

The polymerization of isobutylene with VCl₄ in n-heptane or in the bulk does not proceed in the dark at temperatures lower than -20°C, yet it may be induced by the addition of styrene, α-methylstyrene, p-divinylbenzene, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene. In these cases the polymerizations proceed with variously long induction periods depending on the type of comonomer used. The shortest induction period was observed after the addition of p-divinylbenzene and 2, 3-dimethyl-1, 3-butadiene. In a nonpolar medium the copolymerization of isobutylene with isoprene or butadiene in the dark gives rise to copolymers insoluble in heptane, benzene, and CCl₄, while co-polymers formed with the effect of light are soluble. Unlike polymerizations carried out in a nonpolar solution, the polymerization of isobutylene with VCl₄ in methyl chloride proceeds spontaneously in the absence of protonic coinitiators. Also, soluble copolymers of isobutylene with isoprene or butadiene arise in the copolymerization in methylchloride solution irrespective of the procedure used when the copolymerization is carried out (in the dark or with the effect of light). Polymerizations and copolymerizations carried out both in nonpolar and in polar solutions are inhibited by the presence of oxygen.     

Selective Reduction of the N-O Bond in Heteroaromatic N-Oxides by TiCl4/SnCl2

Heteroaromatic N-oxides bearing various functionalities are readily and selectively converted under mild conditions into the corresponding bases using TiCl₄/SnCl₂.     

Asymmetric transfer hydrogenation of imines catalyzed by a Noyori-type Ru(II) complex—a parametric study

We present, to the best of our knowledge, the first parametric study of the asymmetric transfer hydrogenation of imines catalyzed by a Noyori-type catalytic complex based on ruthenium. A model imine for this study was 1-methyl-3,4-dihydroisoquinoline, and a well-known complex RuCl(η⁶-p-cymene)((1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine) was chosen as the model catalyst. The reactions were performed in the presence of a formic acid–triethylamine mixture as the source of hydrogen.The parameters examined include general parameters, for example, concentration, temperature, and substrate-to-catalyst molar ratio, as well as parameters specific to this particular reaction, such as the amount of the hydrogenation mixture used, the ratio of its components, or the inhibitive effect of carbon dioxide. During this study, several unexpected parameters worth further investigation have emerged.     

Reactions of β-Pinene with Aromatic Aldehydes

Aromatic aldehydes add to β-pinene under Lewis acid catalyzed Prins reaction conditions and yield the corresponding homoallylic alcohols. The reactions proceed in poor yield when electron donating substituents are present on the aromatic ring.     

Cellular Fucosylation Inhibitors Based on Fluorinated Fucose-1-phosphates**

Fucosylation of glycans impacts a myriad of physiological and pathological processes. Inhibition of fucose expression emerges as a potential therapeutic avenue for example in cancer, inflammation, and infection. In this study, we found that protected 2-fluorofucose 1-phosphate efficiently inhibits cellular fucosylation with a four to seven times higher potency than known inhibitor 2FF, independently of the anomeric stereochemistry. Nucleotide sugar analysis revealed that both the α- and β-GDP-2FF anomers are formed inside the cell. In conclusion, we developed A2FF1P and B2FF1P as potent new tools for studying the role of fucosylation in health and disease and they are potential therapeutic candidates.     

σ-Porosity is separably determined

We prove a separable reduction theorem for σ-porosity of Suslin sets. In particular, if A is a Suslin subset in a Banach space X, then each separable subspace of X can be enlarged to a separable subspace V such that A is σ-porous in X if and only if A∩V is σ-porous in V. Such a result is proved for several types of σ-porosity. The proof is done using the method of elementary submodels, hence the results can be combined with other separable reduction theorems. As an application we extend a theorem of L. Zají?ek on differentiability of Lipschitz functions on separable Asplund spaces to the nonseparable setting.     

[11]Anthrahelicene on TiO2 surfaces

Helicenes are carbon-rich materials with an ordered structure that possess interesting and remarkable electronic, chiroptical, mechanical and magnetic properties either in bulk or as single molecule devices. We report on the first attempt to anchor and organize [11]anthrahelicene ([11]AH) molecules onto a metal oxide surface. Molecular structures obtained on the (110) and (011) faces of rutile titania are characterized using scanning probe microscopy. On the (110) surface, [11]AH molecules form islands that are comprised of small domains of two types that are mirror reflections of each other and have an ordered quasi-hexagonal lattice. In contrast, molecules form unordered clusters on the (011) surface. Single molecules on both faces are imaged with sub-molecular resolution.     

On the hyperreflexivity of power partial isometries

Necessary and sufficient conditions for hyperreflexivity of completely non-unitary power partial isometries are given.     

Interactions of polar hydrogen bond donor solvents with ions: a theoretical study

Structural Chemistry - Intermolecular interactions between molecules of protic solvents (water, methanol, formic acid, formamide, methylamine and ammonia) and monatomic ions (Li+, Na+, K+,...