Regioselective α-alkylation of ketones with alkyl chlorides and fluorides via highly nucleophilic magnesium enamides

A magnesium enamide derived from N-2-(N′,N′-dimethylamino)ethyl imine reacts with primary and secondary alkyl chlorides and fluorides to give an α-alkylated ketone in good to excellent yields upon hydrolysis of the imine moiety. Reactions of the highly nucleophilic magnesium enamide derived from an unsymmetrical ketone take place regioselectively. In addition, the C-C bond formation is stereospecific: a substantial inversion of stereochemistry at the electrophilic carbon center (Walden inversion) was observed, proving its potential utility for the production of optically active compounds.     

Ferromagnetic behavior of formyl-group-carrying stable thioaminyl radicals

Four formyl-group-carrying thioaminyl radicals were generated, and one radical could be isolated as radical crystals. Magnetic susceptibility measurements of the isolated radical showed a ferromagnetic regular linear-chain interaction of 2J/k(B) = 3.2 K, which was explained in terms of the X-ray crystallographic results.     

Fabrication of organic–inorganic nano-complexes using ABC type triblock copolymer and polyoxotungstates

New organic–inorganic nano-complexes were produced from a micelle of tri-block polymers; poly(styrene)-b-poly(2-vinylpyridine)- b-poly (ethylene oxide) (PS-PVP-PEO) and tungsten compounds such as tungstate (W₁²⁻), undecatungstophospate (PW₁₁⁷⁻) and undecatungstosilicate (SiW₁₁⁸⁻) in acidic aqueous solutions. The size and morphology of the complexes were characterized by measurements of dynamic light scattering, atomic force microscopy, and scanning electron microscopy. This complex is assembled mainly by the charge interaction between the inorganic polyanions and the positively charged PVP block in the PS-PVP-PEO molecule, which was confirmed by zeta-potential and fluorescence spectroscopic studies. In the absence of the inorganic anions, the zeta-potential of the micelle was +11 mV at pH 3 due to the positive charge of the PVP block. When the inorganic anion was mixed with the PS-PVP-PEO micelle, decrease in the zeta-potential due to charge neutralization occurred with incorporation of inorganic anions into the PS-PVP-PEO micelle. The minimum zeta-potential was 0, −33, and −35 mV for W₁²⁻ /PS-PVP-PEO, PW₁₁⁷⁻ /PS-PVP-PEO, and SiW₁₁⁸⁻ /PS-PVP-PEO complexes, respectively. Excess negative charge which occurred in the latter two complexes indicates that PS-PVP-PEO molecules bound PW₁₁⁷⁻ and SiW₁₁⁸⁻ by forces other than charge interaction. In addition, the incorporation of an inorganic polyanion into the micelle gave a new morphology to the micelle. In the absence of the polyanion, the PS-PVP-PEO micelles showed an extended conformation due to repulsive forces working among the positively charged PVP blocks. Addition of the polyanion caused the formation of shrunken forms of the micelles, since the charge repulsion was cancelled by the polyanion. This feature may be useful in developing a new type of functioning micelle.     

Generation and consumption rates of OH radicals in sonochemical reactions

In this study, a KI aqueous solution or Methyl Orange (MO) aqueous solution was irradiated by an ultrasonic wave under the same experimental condition. The rates of oxidation of KI and MO by OH radicals differed by an order of magnitude. When the consumption of OH radicals by chemical reactions with species other than KI or MO is taken into account, numerical analysis of chemical kinetics model yields the same generation rate of OH radicals by the action of an ultrasonic wave for the experiments of KI and MO solutions.     

Characteristics and Dynamics of Superexcited States of Molecules

Characteristics and dynamics of superexcited states of molecules are interpreted by emphasizing their significant roles in various molecular dynamic processes. The states are expected to open a new field of physics and chemistry; but because of their complexity, they should be investigated by using the possible multifarious means from the various view points. The interplays between theory and experiment and also between the two theories, dynamics theory and quantum chemistry, are crucial to reveal this world. More systematic studies are required for the superexcited states of polyatomic molecules.     

A micellar alignment effect in the photodimerizations of N-ω-carboxyalkyl-2-pyridones and their 4-alkyl derivatives in micelle or reversed micelle

The photoreaction of N-ω-carboxyalkyl-2-pyridones at 7.2–22.4mM concentrations in micellar and reversed micellar systems gave the ratio of cis to trans dimer increasing with decreasing length of the alkyl chain and in their 4-alkyl derivatives, only cis dimer was obtained.     

Thermomechanical analysis of calcium alginate hydrogels in water

Spherical hydrogels of Ca alginate (CaAlg) were prepared by conversion of Na alginate (NaAlg) to CaAlg in CaCl₂ aqueous solution. The degree of conversion was varied by changing the conversion times. NaAlg samples with mannuronic and guluronic component ratios (M/G ratio) 0.21 and 0.88 were used. The degrees of conversion and water contents (W_c=mass of water in CaAlg/mass of dry CaAlg) were measured by weighing. The degrees of conversion from NaAlg to CaAlg increased with increasing immersion time and the content of G. W_c of CaAlg hydrogels decreased with increasing immersion time and levelled off at 75 g g^-1 when immersion time exceeded about 10 min. Viscoelastic properties of CaAlg hydrogels in water were measured using a thermomechanical analyzer (TMA) equipped with a quartz compression probe. Dynamic modulus (E') of CaAlg with M/G=0.88 increased with increasing immersion time when immersion time is less than 5 min. When immersion time exceeded 5 min, E' reached a constant value at 4.5*10⁴ Pa. In contrast, E' of CaAlg with M/G=0.21 increased with increasing immersion time. This suggests that densely crosslinked hydrogels are formed when the guluronate sequence of the samples is rich and Na ions are fully converted to Ca ions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrostatic manipulation of enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylate within gamma-cyclodextrin cavity through chemical modification. inverted product distribution and enhanced enantioselectivity

In the enantiodifferentiating supramolecular photocyclodimerization of 2-anthracenecarboxylate using gamma-cyclodextrin with a dicationic side chain, a dramatic switching of the product selectivity and a significant enhancement of the enantiomeric excess were achieved by introducing a flexible dicationic sidearm to native gamma-cyclodextrin and also by lowering the temperature and solvent polarity.     

Cobalt-catalyzed intramolecular Heck-type reaction of 6-halo-1-hexene derivatives

[reaction: see text] Treatment of 6-iodo-1-hexene derivatives with trimethylsilylmethyl Grignard reagent in the presence of CoCl(2)(dppb) in refluxing THF affords Heck-type products, methylenecyclopentanes, in good yields.     

Analysis of crystalline phases in airborne particulates by grazing incidence X-ray diffractometry

Amounts of crystalline phases of airborne particulates collected on a silicon wafer (10 x 10 mm) using a high-volume air sampler were analyzed by grazing incidence X-ray diffractometry (GIXD). Airborne particulates were classified into five size ranges (1.09-10.5 microm) with a cascade impactor attached on the sampling ports of the high-volume air sampler. GIXD was used throughout this analysis to obtain better sensitivity for small amounts of airborne particulates on the silicon wafer. Calibration standards on the silicon wafer for the diffractometric determination were prepared by the suspension droplet method of the crystalline standards dispersed in cyclohexane. Analytical lines were (020) for gypsum, (101) for quartz, (104) for calcite, (200) for halite, and (110) for sal ammoniac. The sample and the calibrating standards were heated at 350 degrees C for 2 h to avoid mutual interference with gypsum (041 and 221) when calcite and halite were determined. The GIXD method enables us to determine 0.23-13.2 microg of gypsum, quartz, calcite, halite and sal ammoniac in 0.110-0.233 mg of airborne particulates on the silicon wafer.