Hydride Method Research Articles

オルガノコバロキシムの反応と合成への応用

Alkyl- and alkenylcobaloximes are conveniently prepared by the reaction of cobaloxime (I) with alkyl halides, vinyl halides, and acetylenes. The organocobaloximes thus obtained are convenient and versatile radical source for organic syntheses. The cobaloxime group is conveniently transformed into other functions by a variety of radicophiles. The organo radical from organocobaloxime attacks intramolecular or intermolecular olefin in the same manner as a general organo radical. Contrary to the conventional tin hydride method, an organocobaloxime gives not a reduction product but an olefinic product. The olefinic function thus formed is useful for further chemical transformation. The coexisting cobaloxime (II) radical modifies reactivity of the olefinic and arenic part of the organo radical containing sulfur function. The cobaloxime moiety activates an intramolecular diene and arene system to cause cycloaddition and aromatic substitution respectively.

Stereoselective hydrogen transfer reactions of vinyl radicals: Cyclization of alkynyl iodides by Unimolecular Chain Transfer from silicon hydrides

The cyclization of several substituted hexynyl and heptynyl iodides proceeds stereoselectively to give either E- or Z-exocyclic double bonds depending on the type of precursor and radical chain used. In UniMolecular Chain Transfer (UMCT) reactions, the intramolecular abstraction of hydrogen by the intermediate vinyl radical leads exclusively to the E-isomer while the traditional tin hydride method usually provides the Z-isomer with good selectivity.

A New Coupling Reaction of Alkyl Iodides with Electron Deficient Alkenes Using Nickel Boride (cat.)-Borohydride Exchange Resin in Methanol.

The radical addition reaction of alkyl iodides with alpha,beta-unsaturated esters, nitriles, and ketones proceeds in moderate to excellent yields (50-95%) using Ni(OAc)(2) (0.05-0.2 equiv)-BER (3-5 equiv) in methanol in 1-9 h at room temperature or at 65 degrees C. Nickel boride on borohydride exchange resin (BER) is a good alternative reagent to tributyltin hydride for the coupling of alkyl iodides with the electron deficient alkenes in methanol. Compared with tributyltin hydride method, this method has an advantage of simple workup, since nickel boride-BER can be removed readily by filtration.

The use of fuel cells to enhance the underwater performance of conventional diesel electric submarines

Air Independent Propulsion (AIP) systems have the potential to improve the underwater performance of conventional diesel electric submarines and to reduce their vulnerability. Many different types of AIP systems are being considered, either for integration into new submarines or for retrofitting to existing submarines by the insertion of an additional section or ‘plug’. Based on a generic submarine, this paper presents conceptual designs for fuel cell-based AIP plugs that could be retrofitted to an ocean-going conventional submarine of about 3 000 t displacement. The designs are based on solid polymer electrolyte fuel cells that use hydrogen and oxygen as reactants to produce a nominal 100 MWh of electrical energy. Three hydrogen storage methods are considered: metal hydrides; liquid hydrogen, or hydrogen generated from the reforming of methanol. The metal hydride method is mass limited and requires a longer plug than the other two options. The liquid hydrogen and methanol reforming methods are both volume limited and the plug displacement is much greater than the system mass. To maintain neutral buoyancy, considerable ballast has to be added to the plug, or elsewhere in the submarine. Equipped with a 600 kW fuel cell, the generic submarine's maximum speed on fuel cell alone is about 8 knots. The submarine is much harder to detect, because, at speeds below 8 knots, it does not need to snorkel. With a nominal 100 MWh of electrical energy, the submarine's maximum underwater range is increased by a factor of almost five compared with the range of a single battery charge. The maximum endurance is about 14 days. AT speeds greater than the maximum possible with the fuel cell only, the range and endurance of the submarine is increased considerably when the fuel cell and battery are used together.

Novel rearrangement of N-(9H-carbazol-9-yl)arylaminyl radicals

The title radicals were generated from 2-(arylazo)-2'-iodobiphenyls using the tin hydride method. When the aryl substituent has an acetyloxy or a benzoyloxy group in the ortho position, besides reduction of the hydrazyl radical, a migration of the acetyl or benzoyl from oxygen to nitrogen atom took place. The mechanism of the rearrangement is dicussed, and evidences supporting a radical pathway are reported, including EPR characterization of the intermediates

Asymmetric synthesis of 3-chloro-3-fluoro- and 3-fluoro-2,4-disubstituted tetrahydrofurans by the “fluorinated sulfoxide chiron” route

An efficient procedure for the preparation of the title compounds in moderate to high enantiomeric purity has been realized starting from olefins tethered on the fluorinated sulfinyl chiron 6, prepared from methyl 4-methylphenyl sulfoxide and ethyl dichlorofluoroacetate. Radical-promoted cyclization of intermediates 9 according to the tributyltin hydride method afforded 3-chloro-3-fluorotetrahydrofuran derivatives 12, from which the corresponding 3-fluorotetrahydrofurans 15 were obtained by reductive dechlorination. Structural assignments have been done on the basis of 1H, 13C and 19F NMR data and NOE difference experiments.

Simultaneous determination of arsenic, selenium and antimony in water by an inductively coupled plasma hydride method

Arsenic, selenium and antimony were determined using on-line hydride generation in conjunction with a simultaneous medium power inductively coupled plasma (ICP) spectrometer with conventional pneumatic nebulization. The sample, acidified with 3 mol/l hydrochloric acid was mixed with 1% (m/v) sodium tetrahydroborate and 5% (m/v) potassium iodide, the mixed stream being pumped to the nebulizer of the ICP spectrometer. Calibration curves were linear up to 1 mg/l analyte, with detection limits of 2; 3 and 3 μg/l for arsenic, antimony and selenium, respectively, for 10 s integration times and a sample uptake rate of 2.15 ml/min.

Synthesis of optically pure difluoro- or chloro,fluoro-cyclohexanols and cyclopentanols

Starting from the secondary alcohols 1, cyclohexanols 2 having three (XF) of four (XCl) chiral centres on the ring can be obtained in optically pure form by intramolecular trapping of difluoroalkyl or chlorofluoroalkyl radicals (tributyltin hydride method). ▪ The diastereoselection of the process seems to be determined mainly by the stereochemistry at the carbons bearing the sulfinyl and the hydroxyl substituents. Optically pure difluoro- or chloro, fluoro-cyclopentanols can be obtained in the same way.

Experimental and theoretical study of InP homoepitaxy by chemical vapour deposition from gaseous indium chloride and hydrogen diluted phosphine

We are reporting a theoretical and experimental study of InP homoepitaxy by chemical vapour deposition (hydride method) in a near-atmospheric pressure, open flow reactor. We determine the rate limiting reaction as being the chlorine atoms desorption from PInCl adsorbed molecules. The reactions leading to PInCl adsorption are supposed to be in a steady state because their velocities are not infinite compared to the rate limiting reaction velocity. Mass transport processes are taken into account to improve the partial pressure calculations in the gaseous phase above the substrate. The theoretical graphs calculated from those assessments are in good agreement with experiments.

Asymmetric synthesis of trisubstituted gem-difluorocyclohexanes by intramolecular trapping of difluoroalkyl radicals.

gem-Difluorocyclohexanols 8 bearing a methyl and a p-tolyl-sulphinyl substituent have been synthesized in optically pure form by intramolecular trapping of difluoroalkyl radicals on terminal double bonds. The radical intermediates have been generated by the tributyltin hydride method from 1-chloro-1,1-difluoro-3-[(4-methylphenyl)sulphinylhept-6-en-2-ols ( 4), obtained by acylating (R)-p-tolyl-ω-pentenyl sulphoxide ( 1) with ethyl chlorodifluoroacetate ( 2) and by reducing the carbonyl of the β-ketosulphoxide intermediate 3.

Kinetic processes in epitaxy of Ga xn 1−xAs on InP(100) by hydride vapour phase epitaxy

The growth of matched Ga x In 1− x As layers on InP(100) substrates using the hydride method is studied. This paper collects all detected processes that take place in the reactor: surface reactions on the substrate, non-equilibrium reactions in the vapour phase and diffusion in the vapour phase. The experimental results are consistent with the whole model.

On arsenic speciation in the Tagus estuary

New evidence is presented pointing to the presence in estuarine waters both of trimethylarsenic forms (TMA) and of an organoarsenical component refractory to the hydride method. Although not previously detected in estuarine and coastal studies, TMA concentrations were measured in the Tagus estuary in August 1984. The results are presented together with total inorganic, monomethyl (MMA) and dimethyl arsenic (DMA) species quantified in the same occasion. Further digestion of a separate water sample gave positive increments for the methylarsenicals (MMA+DMA+TMA), with special relevance for DMA, suggesting the presence of a heavier organo-arsenical, undetectable in undigested samples with our current analytical capabilities. This component seems to be present in concentrations greater than MMA and TMA. That same sample was passed through a molecular fractionation scheme to get indications of the molecular weight of that unknown component. The results suggest a molecular weight of less than 210 although the limitations of the method do not allow a definitive conclusion.

Growth of GaInAs/InP by the vapor phase epitaxy hydride method

The hydride method was used to study the GaxIn1−x As, deposition process on (100) InP - wafers. The effects of the vapor pressures of arsenic and metal chlorides on the composition x have been investigated in order to optimize the lattice matching to InP. These studies were carried out with a reactor designed to obtain sharp interfaces and to make possible an in situ surface analysis by ellipsometry.Thin film deposition on the substrate without heteronucleation at the entry of the deposit zone was achieved by using an additional HCl line.The GaxIn1−xAs layer matching to the InP substrate required a value of [In Cl][Ga Cl] ⋍ 20A preliminary theoretical approach based on the surface kinetics, the cracking of AsH3 in As2 species and an incomplete transformation of As2 in As4 molecules accounts for the experimental results. The non equilibrium reaction As2⇄As4 seems to be dependent on the equipment parameters: temperature profiles and length of the deposit zone in front of the substrate.

Recent studies on inductively coupled plasma sample introduction-1: Hydride generation

A new version of the nebulizer-hydride generator system for simultaneous determination of hydride forming and nonhydride forming elements has been developed in order to eliminate the twin problems of splashing and clogging found with the original design, and also to incorporate cyclone action into the system. The new cyclone nebulizer-hydride generator not only retains all the major advantages of the original system, but also has the advantages of being simpler in construction, experiencing minimal splashing, and providing better precision and detection limits. Hydride generation in non-aqueous media provides a possibility to combine hydride generation directly with solvent extraction. Alternatively, organic samples may be analyzed directly by the hydride method, with no need for reextraction or other means to get rid of the organic material. This paper describes studies with a continuous hydride generator used for ICP-AES, and its application to the determination of As and Sb in a Ni-Fe based alloy.

The Design and Application of Free Radical Chain Reactions in Organic Synthesis. Part 1

The successful application of free radical transformations in organic synthesis requires a basic knowledge of elementary radical reactions and an understanding of the principles of free radical chain reactions. Using illustrative examples from the recent literature as a framework, this review provides an introduction to the design and application of free radical reactions for use in organic synthesis. While a few nonchain reactions are discussed, the primary focus is on four of the most important and versatile methods to conduct radical chain reactions. These are: the tin hydride method, the fragmentation method, the thiohydroxamate ester method (the Barton method), and the atom-transfer method. Particular emphasis is placed on the selectivity requirements which must be met for the design of sequences of radical reactions. The review appears in two parts in consecutive issues. Part 1 contains Sections 1 (Introduction) and 2 (The Tin Hydride Method), and Part 2 contains Sections 3 (The Fragmentation Method), 4 (The Thiohydroxamate Ester Method), 5 (The Atom-Transfer Method), and 6 (Non-Chain Methods). Part 1 1.Introduction 1.1.Chain Reactions and Synthetic Planning 2.The Tin Hydride Method 2.1.Intramolecular Cyclizations 2.2.Intermolecular Additions 2.3.Combination Sequences Part 2 3.The Fragmentation Method 4.The Thiohydroxamate Ester Method 5.The Atom-Transfer Method 5.1.Hydrogen Atom Transfer Addition and Cyclization 5.2.Halogen Atom Transfer 5.2.1. Halogen Atom Transfer Addition 5.2.2. Halogen Atom Transfer Cyclization 5.3.3. Halogen Atom Transfer Annulation 5.3.Heteroatom-Halogen Donors 5.4.Organocobalt Group Transfer 6. Non-Chain Methods 7.Summary and Conclusions

Effect of phosphine decomposition on the growth and substrate heating of (100) InP in the hydride method

The hydride method was used to study the InP deposition process on (100) InP wafers. The surface state obtained during substrate heating as well as the growth rate appeared to depend on phosphine decomposition. Two regimes of growth were determined. In both regimes, the behavior of the growth rate indicates a deposition process limited to the chlorine desorption by H 2 as in GaAs growth by the chloride method. Surface adsorption of P 2 molecules accounts for the difference between the two regimes. A model of phosphine decomposition was developed to predict this effect regardless of experimental conditions.

Evidence that the platelet plasma membrane does not contain a ( [formula omitted])-dependent ATPase

The present study was designed to determine the subcellular distribution of the platelet ( Ca 2+ + Mg 2+ )-ATPase. Human platelets were surface labeled by the periodate-boro[ 3H]hydride method. Plasma membrane vesicles were then isolated to a purity of approx. 90% by a procedure utilizing wheat germ agglutinin affinity chromatography. These membranes were found to be 2.6-fold enriched in surface glycoproteins compared to an unfractionated vesicle fraction and almost 7-fold enriched compared to intact platelets. In contrast, the isolated plasma membranes showed a decreased specific activity of the ( Ca 2+ + Mg 2+ )-ATPase compared to the unfractionated vesicle fraction. This decrease in specific activity was found to be similar to that of an endoplasmic reticulum marker, glucose-6-phosphatase, and to that of a platelet inner membrane marker, phospholipase A 2. We conclude, therefore, that the ( Ca 2+ + Mg 2+ )-ATPase is not located in the platelet plasma membrane but is restricted to membranes of intracellular origin.

Effect of monensin on the assembly of Uukuniemi virus in the Golgi complex.

The effect of the carboxylic ionophore monensin on the maturation of Uukuniemi virus, a bunyavirus, and the transport of its two membrane glycoproteins, G1 and G2, were studied in chicken embryo fibroblasts and baby hamster kidney cells. Virus maturation, which occurs in the Golgi complex (E. Kuismanen, K. Hedman, J. Saraste, and R. F. Pettersson, Mol. Cell. Biol. 2:1444-1458, 1982; E. Kuismanen, B. Bång, M. Hurme, and R. F. Pettersson, J. Virol. 51:137-146, 1984), was effectively inhibited by the drug (1 or 10 microM) as studied by electron microscopy and by assaying the release of infectious or radiolabeled virus. Immunoelectron microscopy showed that association of viral nucleocapsids with the cytoplasmic surface of glycoprotein-containing Golgi membranes, a prerequisite for virus budding, was unaffected by monensin. In the presence of the drug, the virus glycoproteins assembled into long, tubular structures extending into the lumen of Golgi-derived vacuoles, suggesting that monensin inhibited a terminal step in the assembly of the virus. Intracellular transport and expression of the virus membrane glycoproteins G1 and G2 at the cell surface were not inhibited by monensin as studied by immunocytochemical and radiolabeling techniques. Pulse-chase experiments in the presence of monensin showed that intracellular G1 acquired only partially endo-H-resistant glycans. The sialylation of G1 appearing on the cell surface in the presence of the drug was decreased, whereas sialylation of G2 apparently was inhibited to a lesser extent, as shown by external labeling of the cells with the periodate-boro[3H]hydride method. Thus, monensin exerted a differential effect on the terminal glycosylation of G1 and G2. Unlike several membrane and secretory glycoproteins, both G1 and G2 could enter a functional transport pathway in the presence of monensin and become expressed at the cell surface.

Solid-phase radiolabeling of glycolipids with galactose oxidase and sodium boro[ 3H]hydride

Neutral glycosphingolipids immobilized on plastic surfaces were specifically radiolabeled with the galactose oxidase-sodium boro[ 3H]hydride method. Glycolipids could be immobilized in the absence of any other lipids such as phosphatidylcholine and cholesterol. Rather, the presence of these lipid components decreased the efficiency of radiolabeling. Glycolipids having more than four carbohydrate moieties with terminal galactosyl residues were effectively radiolabeled and could be easily recovered by elution from the plastic with ethanol in one step. This method will be suitable for analysis of small samples of “upper-phase” neutral glycolipids having terminal galactose or N-acetylgalactosamine.

Detectors for spectrometry of the X-ray emission from germanium obtained by the hydride method

This paper investigates certain characteristics of p-n structures, prepared on a base of germanium obtained by the hydride method. The purpose of the study is to estimate the degree of purity of the germanium and its applicability for the preparation of the detectors with a high energy resolution. Monocrysstals of the p type were used. On completion of diffusion of the lithium in the samples by means of the procedure described, a protective groove was cut out. The apparatus spectra of Fe-55 and Am-241 are shown. The characteristics of the detectors obtained confirm the excellent quality and high purity of the germanium hydride.