Facile [3+2] dimerization and formal dehydrogenative coupling mode of a cyanophenylphosphaallene

Due to a facile head-to-tail [3+2] dimerization, even a sterically demanding group such as the Mes^∗ (2,4,6-tri-tert-butylphenyl) group around the PCC moiety did not allow us to isolate 3-(4-cyanophenyl)-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaallene from the elimination reaction of 2-bromo-3-(4-cyanophenyl)-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaprop-1-ene with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and the corresponding 1,4-diphosphafulvene containing cyano groups was obtained and characterized. Theoretical studies on the [3+2] dimerization of phosphaallene characterize possible intermediates affording 1,4-diphosphafulvenes and also suggest the cyano group effect to facilitate the saturation of the PC double bonds. On the other hand, 1,2-bis(4-cyanophenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene was obtained from 2-bromo-3-(4-cyanophenyl)-3-trimethylsiloxy-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaprop-1-ene together with the 3-(4-cyanophenyl)-1-phosphaallene.     

Phosphorus Version of the Fritsch-Buttenberg-Wiechell Reaction

Abstract

Utilizing phosphorus version of the Fritsch-Buttenberg-Wiechell (FBW) reaction, arylphosphaalkynes are prepared from 2,2-dihalo-1-aryl-1-phosphaalkenes, and theoretical calculations were carried out to obtain some basic insight into intramolecular rearrangement in the phosphorus system of interest.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Density functional theory (DFT) and ab initio MP2 calculations.]

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon for the following free supplemental files: Additional tables, figures, and references.]     

Evaluation study on properties of isohexyl-BTP/SiO2-P resin for direct separation of trivalent minor actinides from HLLW

In order to develop a direct separation process for trivalent minor actinides from fission products in high level liquid waste (HLLW) by extraction chromatography, a novel macroporous silica-based 2,6-bis(5,6-diisohexyl)-1,2,4-triazin-3-yl)pyridine resin (isohexyl-BTP/SiO₂-P resin) was prepared. The content of isohexyl-BTP extractant in the resin was as high as 33.3 wt%. The resin exhibited much higher adsorption affinity for Am(III) in 2–3 M (mol/L) HNO₃ solution over U and FP which are contained in HLLW. The kinetic data were analyzed using pseudo-second-order equation. The results suggested that the Eu(III), Gd(III), and Dy(III) adsorption was well explained by the pseudo-second-order equation. Quantitative desorption for adsorbed elements was achieved by using H₂O or thiourea as eluting agents. However, the kinetics of adsorption and desorption were rather slow and this drawback needs to be resolved. Stability of the resin against HNO₃ was also examined. It was found that the resin was considerably stable against ≤4 M HNO₃ solution for the reasons of an extremely small leakage of the extractant into the solution from the resin and the adsorption performance keeping for rare earths in 3 M HNO₃ solution.     

Expression of heme oxygenase-1 due to intracellular reactive oxygen species induced by ultrasound

The present study was undertaken to elucidate the mechanism by which ultrasound induces the expression of heme oxygenase-1 (HO-1). When human lymphoma U937 cells were exposed to a 1 MHz continuous wave for 1 min, HO-1 expression examined by real-time quantitative polymerase chain reaction and immunoblotting was observed at intensities above the cavitational threshold. No induction of HO-1 expression was observed in the cells exposed for 1 min to 42 degrees C, a temperature higher than that during sonication. When a potent antioxidant, N-acetyl-l-cysteine, was added to the culture medium before or after sonication, the induction was attenuated, indicating that reactive oxygen species (ROS) are involved. However, the addition of catalase did not affect the induction, and no HO-1 was observed on the addition of pre-sonicated medium, suggesting that hydrogen peroxide due to the recombination of hydroxyl radicals generated extracellularly was not involved. The addition of free radical scavengers, glutathion-monoethyl ester, dimethyl sulfoxide and D(-)-mannitol, suppressed the induction. A decrease in mitochondrial membrane potential and the generation of superoxide were also observed in the sonicated cells, suggesting that mitochondria were the source of intracellularly generated ROS. These results indicate that superoxide secondarily generated from damaged mitochondria, not hydroxyl radicals generated in medium directly by sonication, give rise to intracellular oxidative stress inducing HO-1 expression.     

Vanadyl C and N-capped tris(phenolate) complexes: influence of pro-catalyst geometry on catalytic activity

Vanadyl complexes of C or N-capped tripodal ligands, possessing distorted tetrahedral geometry at vanadium, serve as extremely active, thermally robust pro-catalysts for ethylene homo- and ethylene/propylene copolymerisation, whereas pseudo-octahedral pro-catalysts produce far lower activities.