Alkynyliodonium salts in organic synthesis. Preparation of 2-substituted-3-p-toluenesulfonyldihydrofurans from 1-hydroxybut-3-ynyliodonium ethers via a formal Stevens shift of a carbon group

[reaction: see text]p-Toluenesulfinate addition to 1-hydroxybut-3-ynyliodonium ethers triggers a sequence of reactions which ultimately delivers 2-substituted-3-p-toluenesulfonyldihydrofuran products along with 3-p-toluenesulfonyldihydrofuran as a major byproduct. A putative 1,2-alkyl shift within an unsaturated oxonium ylide (Stevens rearrangement) accounts for the oxygen-to-carbon transfer of the alkyl group.     

Penultimate effects in methyl methacrylate-4-vinyl pyridine copolymers

From the ¹H-NMR spectra of methyl methacrylate (M₁)-4-vinyl pyridine (M₂) radical copolymers with various monomer ratios, the reactivity ratios have been found using the penultimate model (r₁₁ = 1.51 r₂₁ = 0.10 r₂ = 0.24) and the co-isotactic alternating addition probability (σ = 0.5) as the best fit of the pentad distribution between the three parts of the methoxy signal.     

Alkali metal intercalated fullerene-like MS(2) (M = W, Mo) nanoparticles and their properties

Layered metal disulfides-MS(2) (M = Mo, W) in the form of fullerene-like nanoparticles and in the form of platelets (crystallites of the 2H polytype) have been intercalated by exposure to alkali metal (potassium and sodium) vapor using a two-zone transport method. The composition of the intercalated systems was established using X-ray energy dispersive spectrometer and X-ray photoelectron spectroscopy (XPS). The alkali metal concentration in the host lattice was found to depend on the kind of sample and the experimental conditions. Furthermore, an inhomogeneity of the intercalated samples was observed. The product consisted of both nonintercalated and intercalated phases. X-ray diffraction analysis and transmission electron microscopy of the samples, which were not exposed to the ambient atmosphere, showed that they suffered little change in their lattice parameters. On the other hand, after exposure to ambient atmosphere, substantial increase in the interplanar spacing (3-5 A) was observed for the intercalated phases. Insertion of one to two water molecules per intercalated metal atom was suggested as a possible explanation for this large expansion along the c-axis. Deintercalation of the hydrated alkali atoms and restacking of the MS(2) layers was observed in all the samples after prolonged exposure to the atmosphere. Electric field induced deintercalation of the alkali metal atoms from the host lattice was also observed by means of the XPS technique. Magnetic moment measurements for all the samples indicate a diamagnetic to paramagnetic transition after intercalation. Measurements of the transport properties reveal a semiconductor to metal transition for the heavily K intercalated 2H-MoS(2). Other samples show several orders of magnitude decrease in resistivity and two- to five-fold decrease in activation energies upon intercalation. These modifications are believed to occur via charge transfer from the alkali metal to the conduction band of the host lattice. Recovery of the pristine compound properties (diamagnetism and semiconductivity) was observed as a result of deintercalation.     

Extending Pummerer reaction chemistry. Application to the oxidative cyclization of indole derivatives

Treatment of 2-(phenylsulfinyl)indoles bearing a pendant nucleophile at C(3) with Tf(2)O/lutidine triggers a Pummerer-like cyclization to furnish 3,3-spirocyclic-2-(phenylthio)indolenine products, which can, in turn, be hydrolyzed to 3,3-spirocyclic oxindoles. [reaction: see text]     

Formation and reactions of monomeric and dimeric radical cations of aliphatic ketones in freon matrices

ESR spectra of -irradiated, at 77 K, acetone and CH₃COEt solutions /0.1–22%/ in CFCl₃ were studied. The yields of monomer and dimer radical cations of ketones and RCHCOCH₃ radicals depend on ketone concentration in CFCl₃. When exposed to light the dimeric radical cations are transformed into RCHCOMe, while the monomeric radical cations disappear without further radical production. Different types of solid phase ion-molecular reaction for monomer and dimer radical cations are discussed.     

Diazonamide synthesis studies: use of Negishi coupling to fashion diazonamide-related biaryls with defined axial chirality

The syntheses of a bis indole and an indole salicylate with the required axial chirality for diazonamide A are reported. Atropselectivity in these biaryl systems is enforced by an sp(3) stereogenic center in a lactone tether in both cases. [structure: see text]     

Spectral Characteristics and Transformations of Intermediates in Irradiated Freon 11, Freon 113, and Freon 113a

Optical absorption bands observable in Freon 11, Freon 113, and Freon 113a irradiated at 77 K were assigned to various intermediates (radical cations, radical ion pairs, and complexes of radicals with ions). The transformations of these species in thermal and photochemical reactions occurring at 77 K were studied. On the basis of experimental results, it was suggested that the radical anions of Freon 11 and Freon 113 are unstable at 77 K and the spatial distribution of the intermediates produced is inhomogeneous.     

Effect of charge density fluctuations within a droplet on dielectric polarization of ionic microemulsions

A statistical model of the dielectric polarization of ionic water-in-oil microemulsions is proposed. The model makes it possible to describe the effect of temperature and dispersed phase content on the static dielectric permittivity behavior of the microemulsions at a region far below percolation. With the help of this model, the microemulsions formed with the surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), have been analyzed. The studied systems are considered to consist of nanometer-sized spherical non-interacting water droplets of equal size with negatively charged head groups , staying at the interface and positive counterions Na⁺, distributed in the electrical diffuse double layer of the droplet interior. It can be conjectured that two different mechanisms, that provide an increase of the static dielectric permittivity as a function of temperature, may take place. These may be attributed either to the aggregation of droplets or the temperature growth of polarizability of non-interacting and therefore non-aggregating droplets dispersed in oil. The results support the hypothesis that the experimental temperature behavior of dielectric polarization far below the percolation region is only due to the polarization of a single droplet and not to an aggregation. The droplet polarizability is proportional to the fluctuation mean-square dipole moment of a droplet. It is shown that this mean-square dipole moment and the corresponding value of the dielectric increment, depend upon the equilibrium distribution of counterions within a diffuse double layer. The density distribution of ions is determined by the degree of the dissociation of the ionic surfactant. The dissociation of the ionic surfactant in the system has been analyzed numerically. The relationship between the constant of dissociation and the experimental dielectric permittivity has been ascertained.