Unexpected high regiocontrol in Heck reaction of fluorine-containing electron-deficient olefins—Highly regio- and stereoselective synthesis of β-fluoroalkyl-α-aryl-α,β-unsaturated ketones

Treatment of (E)-4,4,4-trifluoro-1-aryl-2-buten-1-one with various aryldiazonium salts in the presence of palladium catalyst gave the corresponding α-arylated Heck adducts with high regio- and stereoselectivity in good to high yields.     

Crotylations of alpha-carbonyl radicals with crotylstannane

Electrophilic radicals undergo crotylation with crotylstannane with moderate to good efficiency. The reaction provides the syn isomer as the major product. The present methodology is complementary to Claisen protocols for the synthesis of gamma,delta-unsaturated carboxylic acid derivatives. Details of the new radical methodology are presented. [reaction: see text]     

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.     

Landmine detection: improved binding of 2,4-dinitrotoluene in a gamma-CD/metal oxide matrix and its sensitive detection via a cyclic surface polarization impedance (cSPI) method

Highly sensitive and selective detection of 2,4-DNT, a representative explosive, was achieved by the synergic effect of molecular imprinting and host (cyclodextrin)-guest interaction in ultrathin layers of TiO(2) and SiO(2) gel; the detection limit using cSPI measurements reached nM concentration.     

Pulsed laser photolysis vacuum UV laser-induced fluorescence kinetic study of the gas-phase reactions of Cl(2P3/2) atoms with C3-C6 ketones

The gas-phase reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone at 295 +/- 2 K were studied using pulsed laser photolysis vacuum UV laser-induced fluorescence (PLP-LIF) techniques. Cl(2P(3/2)) atoms were produced by photolysis of Cl2 at 351 nm and monitored by LIF spectroscopy at 134.72 nm (3p(5) 2P(3/2)-3p(4)4s 2P(3/2) transition). Rate coefficients for reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone are (2.30 +/- 0.12) x 10(-12), (4.08 +/- 0.21) x 10(-11), (1.23 +/- 0.13) x 10(-10), (8.87 +/- 0.92) x 10(-11), (2.08 +/- 0.32) x 10(-10), (1.43 +/- 0.19) x 10(-10) and (1.16 +/- 0.12) x 10(-10) cm3 molecule(-1) s(-1), respectively. The results for acetone and butanone are consistent with previous studies. The results for 2-pentanone, 3-pentanone, 2-hexanone, and 3-hexanone are approximately a factor of 2-3 higher than those from previous absolute rate studies. Likely explanations for these discrepancies are discussed. Tropospheric lifetimes of ketones with respect to reaction with Cl atoms are estimated and discussed.     

Determination of the lumped mass transfer rate coefficient by frontal analysis

The validity of measurements of the lumped mass transfer rate coefficient (k_m,L) is studied on the basis of experimental data acquired under Langmuir isotherm conditions, in reversed-phase liquid chromatography. Two different methods were used, the perturbation method and frontal analysis. Accurate values of k_m,L can be properly obtained by the perturbation method because, with this method, the chromatographic processes take place under locally linear isotherm conditions. Values of k_m,L can also be derived from the breakthrough curves obtained in frontal analysis. Because the contribution of axial dispersion to band broadening was larger than that of the mass transfer resistances, the apparent axial dispersion coefficient (D_a) was first derived from the breakthrough curve by applying the equilibrium–dispersive model. Then, the value of k_m,L was calculated from D_a. The values of k_m,L determined by the two methods were in close agreement in the range of nondimensional Langmuir equilibrium constants (r=1/[1+K_LC₀]) between 0.32 and 0.85, irrespective of the mobile phase flow velocity. Thus, frontal analysis can be used for kinetic studies of the mass transfer in chromatographic columns.     

Peak tailing and column radial heterogeneity in linear chromatography

The correlation between the radial heterogeneity of a column and the tailing of the elution profiles of chromatographic peaks was studied using a numerical method. A parabolic distribution of the linear flow velocity of the mobile phase and of the column efficiency in the radial direction were assumed. Moment analysis showed that peak tailing takes place under such experimental conditions and that it increases with increasing range of radial variations of the flow velocity and the column efficiency. It was also found that the higher the column efficiency, the larger the effect of a given degree of radial heterogeneity on the extent of peak tailing. Peak tailing behavior of columns having different efficiencies could be correlated with each other by an equation. Some characteristic features of tailing peaks were analyzed in connection with the column radial heterogeneity.     

A survey of ochratoxin A and aflatoxins in domestic and imported beers in Japan by immunoaffinity and liquid chromatography.

Analyses of ochratoxin A (OTA) and aflatoxins (AFs) in 94 imported beer samples from 31 producing countries and in 22 Japanese beer samples were performed by immunoaffinity column and reversed-phase liquid chromatography (LC) with fluorescence detection. Recoveries of OTA from beer samples spiked at 25 and 250 pg/mL were 86.1 and 88.2%, respectively. Recoveries of AFs were 98.4 and 98.9%, 95.4 and 95.5%, 101.2 and 97.8%, and 98.9 and 96.0%, respectively, from beer samples spiked at 4.1 and 41 pg AF B1, 4.45 and 44.5 pg AF B2, 4.7 and 47 pg AF G1, and 4.65 and 46.5 pg AF G2/mL. Detection limits were 1.0 pg/mL for OTA, 0.5 pg/mL for AFs B1 and B2, and 1.0 pg/mL for AFs G1 and G2. OTA was detected in 86 (91.5%) of 94 imported beer samples at a mean level of 10.1 pg/mL and in 21 (95.5%) of 22 Japanese beer samples at a mean level of 12.5 pg/mL. AF B1 was detected in 11 of 94 imported beer samples at a level of 0.5-83.1 pg/mL and in 2 of 22 Japanese beer samples at 0.5 and 0.8 pg/mL. Except for one beer sample from Peru, the samples contaminated with AFs were also contaminated with OTA. Although OTA was detected in most samples from various countries, AFs were detected in the beer samples from only a limited number of countries where AF contamination might be expected to occur because of their warm climate.     

π 0 and η Photoproduction on the Deuteron at ELPH, Tohoku University

Baryon spectroscopy is important to understand Quantum Chromodynamics at low energies. In this purpose, a series of π ⁰ and η photoproduction experiments was carried out with an electro-magnetic calorimeter FOREST at Research Center for Electron Photon Science, Tohoku University. The incident tagged bremsstrahlung photon energy ranges from 550 to 1,150 MeV. The differential and total cross sections obtained for π ⁰ and η photoproduction processes on the proton are consistent with the SAID and MAID calculations. The analysis of π ⁰ and η photoproduction on the neutron is underway.