An efficient preparation of vinamidinium hexafluorophosphate salts

Substituted acetic acids or acetyl chlorides react with phosphorus oxychloride in DMF to yield the vinamidinium salts 3a-j in moderate to excellent recrystallized yields (28-90%). The cations are conveniently isolated as their hexafluorophosphate salts, which are easily handled nonhygroscopic solids. The nitro compound 3l is prepared in 91% yield by nitration of the parent vinamidinium 3k. The X-ray crystal structure is reported for the 2-phenyl isomer 3e and displays minimal overlap of the two pi-systems.     

Genes involved in <Emphasis Type="Italic">Drosophila</Emphasis>glutamate receptor expression and localization

Background  

A clear picture of the mechanisms controlling glutamate receptor expression, localization, and stability remains elusive, possibly due to an incomplete understanding of the proteins involved. We screened transposon mutants generated by the ongoing Drosophila Gene Disruption Project in an effort to identify the different types of genes required for glutamate receptor cluster development.     

Removal, recovery, and recycling of triarylphosphonium-supported tin reagents for various organic transformations

Phosphonium-supported tin reagents and catalysts were prepared and were shown to be effective in Stille couplings, radical dehalogenations, radical cyclizations, and carbonyl allylations. Not only could the tin residues be removed from the crude reaction mixture through a phase separation process but also they could be recovered and recycled.     

A practical synthesis of alpha-aryl methyl ketones via a transition-metal-free Meerwein arylation

We report herein a simple, scalable, transition-metal-free approach to the synthesis of alpha-aryl methyl ketones from diazonium tetrafluoroborate salts under mild conditions. This methodology uses easily accessible and nontoxic starting material and was applied to the multi-kilogram-scale preparation of 1-(3-bromo-4-methylphenyl)propan-2-one.     

Stereoselective preparation of a cyclopentane-based NK1 receptor antagonist bearing an unsymmetrically substituted sec-sec ether

A highly efficient synthesis of the potent and selective NK-1 receptor antagonist 1 is described. The key transformation involved the etherification reaction between cyclopentanol 12 and chiral imidate 30 which was catalyzed by HBF4 to initially give ether 14 as a 17:1 mixture of diastereomers and in 75% combined yield. The diastereoselectivity was upgraded to 109:1 by crystallization of the triethylamine solvate 44 which was isolated in 54% yield from 12. Mechanistic studies confirmed that the etherification reaction proceeds through an unprecedented S(N)2 reaction pathway under typical S(N)1 reaction conditions.     

Determination of Chlorinated Solvent Sorption by Porous Material—Application to Trichloroethene Vapor on Cement Mortar

Experiments have been performed to investigate the sorption of trichloroethene (TCE) vapor by concrete material or, more specifically, the cement mortar component. Gas-flow experiments were conducted using columns packed with small pieces of cement mortar obtained from the grinding of typical concrete material. Transport and retardation of TCE at high vapor concentrations (500 mg L \(^{-1})\) was compared to that of a non-reactive gas tracer (Sulfur Hexafluoride, SF \(_{6})\) . The results show a large magnitude of retardation (retardation factor \(=\) 23) and sorption (sorption coefficient \(=\) 10.6 cm \(^{3}\)  g \(^{-1})\) for TCE, compared to negligible sorption for SF \(_{6}\) . This magnitude of sorption obtained with pollutant vapor is much bigger than the one obtained for aqueous-flow experiments conducted for water-saturated systems. The considerable sorption exhibited for TCE under vapor-flow conditions is attributed to some combination of accumulation at the air-water interface and vapor-phase adsorption, both of which are anticipated to be significant for this system given the large surface area associated with the cement mortar. Transport of both SF \(_{6}\) and TCE was simulated successfully with a two-region physical non-equilibrium model, consistent with the dual-medium structure of the crushed cement mortar. This work emphasizes the importance of taking into account sorption phenomena when modeling transport of volatile organic compounds through concrete material, especially in regard to assessing vapor intrusion.     

Lie ideals in triangular operator algebras

We study Lie ideals in two classes of triangular operator algebras: nest algebras and triangular UHF algebras. Our main results show that if is a closed Lie ideal of the triangular operator algebra , then there exist a closed associative ideal and a closed subalgebra of the diagonal so that .