Catalytic enantioselective indium-mediated allylation of hydrazones

[reaction: see text] A facile and highly selective indium-mediated allylation of hydrazones utilizing BINOL ligands is described. Chiral (R)-3,3'-bistrifluoromethylBINOL afforded homoallylic amines in up to 97% ee with stoichiometric ligand. Employing only 10 mol % ligand afforded selectivity of up to 92% ee.     

Synthesis of (±)-aporphine utilizing Pictet-Spengler and intramolecular phenol ortho-arylation reactions

A synthesis of the alkaloid (±)-aporphine is reported. The initial key step of the synthesis involves a Pictet-Spengler cyclization of N-tosyl tyramine with 2-bromophenylacetaldehyde in trifluoroacetic acid. This step was followed by the second strategic transformation a palladium-mediated intramolecular phenol ortho-arylation reaction utilizing tricyclohexylphosphine as co-catalysts in the presence of cesium carbonate. Finally, de-oxygenation of the phenol, removal of the tosyl group and methylation gave the desired alkaloid.     

Synthesis and characterization of crosslinked polydiacetylene and its two-component interpenetrating polymer networks

The synthesis of crosslinked polydiacetylenes and its two-component interpenetrating polymer networks (IPNs) was carried out utilizing its polar and flexible substituent groups. Polydiacetylenes were crosslinked by the formation of allophanate linkages utilizing urethane groups in the substituent groups of the polydiacetylenes. Elemental analysis, DSC, TMA, solvent resistance, and IR spectra are presented as evidence for the formation of crosslinked polydiacetylenes. IPNs of polydiacetylenes and an epoxy resin (diglycidyl ether of bisphenol A) were synthesized by using simultaneous and sequential methods of synthesis. A study of phase morphology of the simultaneous and sequential IPNs was carried out using electron microscopy, TMA, and DSC.     

Multifunctional redox catalysts as selective enhancers of oxidative stress

Certain cancer cells proliferate under conditions of oxidative stress (OS) and might therefore be selectively targeted by redox catalysts. Among these catalysts, compounds containing a chalcogen and a quinone redox centre are particularly well suited to respond to the presence of OS. These catalysts combine the specific electrochemical features of quinones and chalcogens. They exhibit high selectivity and efficiency against oxidatively stressed rat PC12, human Jurkat and human Daudi cells in cell culture, where their mode of action most likely involves the catalytic activation of existent and the generation of new reactive oxygen species. The high efficiency and selectivity shown by these catalysts makes them interesting for the development of anti-cancer drugs.     

Host-guest interactions template: the synthesis of a [3]catenane

Formation of a [3]catenane containing dibenzo-24-crown ether wheels and a large dipyridiniumethane ring is templated by formation of a host-guest adduct between the [3]catenane and the external crown ether.     

A systematic nomenclature for cascade polymers

Cascade (dendritic) polymers are discrete, highly branched, monodisperse polymers that possess branching patterns described by a mathematical progression. A systematic nomenclature that accurately represents these molecules is described. © 1993 John Wiley & Sons, Inc.     

(η5-C5R5)2Fe2(CO)2(μ-CO)(μ-CH2) (R = H,CH3): A convenient one-pot synthesis using chloromethyl pivalate

The compounds (η⁵-C₅R₅)₂Fe₂(CO)₂(μ-CO)(μ-CH₂) (R = H, CH₃) have been prepared through the reaction of chloromethyl pivalate with the appropriate metal anions, η⁵-C₅H₅Fe(CO)₂K and η⁵-C₅Me₅Fe(CO)₂K.     

Detection of VX contamination in soil through solid-phase microextraction sampling and gas chromatography/mass spectrometry of the VX degradation product bis(diisopropylaminoethyl)disulfide

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) sampling and analysis method was developed for bis(diisopropylaminoethyl)disulfide (a degradation product of the nerve agent VX) in soil. A 30-min sampling time with a polydimethylsiloxane-coated fiber and high temperature alkaline hydrolysis allowed detection with 1.0 microg of VX spiked per g of agricultural soil. The method was successfully used in the field with portable GC-MS instrumentation. This method is relatively rapid (less than 1 h), avoids the use of complex preparation steps, and enhances analyst safety through limited use of solvents and decontamination of the soil before sampling.     

Dialing in color with rare earth metals: facile photoluminescent production of true white light

Combining polymeric architectures with metal ions produces hybrid materials with extremely rich properties. We are studying polymers containing terpyridine in the side chain. In this report, the chelation of lanthanide ions, Eu³⁺, Tb³⁺, and Dy³⁺ resulted in metal functionalized copolymers that exhibited excellent emission of red, green, and blue light respectively. The polymer architecture easily allows incorporation of all three colors into the material, which leads to the facile production of true white light in solution or the solid state. Quantum efficiencies for the polymer systems were determined. The white light system had an efficiency of 5%. Various combinations of colors were achieved from the basic RBG colors by simply varying the metal ion ratios in the polymer backbone. This easy tuning of the color makes these systems attractive. Copyright © 2007 John Wiley & Sons, Ltd.     

A high resolution mass spectrometric measurement system for a vacuum fusion apparatus

A high resolution mass spectrometric read-out system for a vacuum fusion apparatus is described. Rapid analyses are possible and the rate at which various gases are evolved can be monitored. Gas mixture assays are accomplished by scanning the nominal mass 28 peak. Serial measurements of CO⁺, N₂⁺ and C₂H₄⁺ are made. Thus detection and measurement of evolved hydrocarbons are possible. The results for silver and tin from a conventional vacuum fusion apparatus and the mass spectrometer apparatus are compared.