bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facile synthesis of urea derivatives under mild conditions
Authors: Mizuno Takumi , Matsumoto Manabu , Nishiguchi Ikuzo , Hirashima Tsuneaki 
Published: January 2005

AbstractUrea derivatives were readily synthesized in good yields under quite mild conditions, i.e., at ambient pressure and room temperature by sulfur‐assisted carbonylation of primary amines with carbon monoxide followed by oxidation of the resulting ammonium thiocarbamates with molecular oxygen.
NMR studies of 1,1‐diphenylboroxazolidone derivatives of α‐aminoacids
Authors: Farfán Norberto , Silva David , Santillan Rosa 
Published: January 2005

AbstractA series of twelve 1,1‐diphenylboroxazolidones (1b–12b) prepared from α‐aminoacids and diphenylborinic acid were studied using one‐ and, in some cases, two‐dimensional (HETCOR) NMR techniques. Interpretation of these spectra led to definitive assignment of all carbon, hydrogen, and boron resonances.
Reaction of dichlorocarbene with 1‐(2,4,6‐tri‐t‐butylphenyl)‐1‐phosphaallenes
Authors: Yoshifuji Masaaki , Shibata Manabu , Toyota Kozo , Miyahara Ikuko , Hirotsu Ken 
Published: January 2005

Abstract1‐(2,4,6‐Tri‐t‐butylphenyl)‐1‐phosphaallene reacted with dichlorocarbene to give 2‐dichloromethylene‐1‐(2,4,6‐tri‐t‐butylphenyl)‐1‐phosphirane. The structure was confirmed by X‐ray crystal structure analysis. A similar isomerization product was obtained in the reaction of dichlorocarbene with 3‐phenyl‐1‐(2,4,6‐tri‐t‐butylphenyl)‐1‐phosphaallene.
Reactions of heteroaryllithium compounds with phosphorus trichloride, phosphorus oxychloride, and thionyl chloride. Formation of heterocyclic biaryls
Authors: Uchida Yuzuru , Echikawa Naoji , Oae Shigeru 
Published: January 2005

AbstractThe reactions of four equivalents of heterocyclic aryllithium compounds with phosphorus trichloride or phosphorus oxychloride gave symmetrical heterocyclic biaryls in good yields. A similar coupling was found in the reactions of three equivalents of the lithium compounds with thionyl chloride.
Synthesis and spectral analysis of 6‐substituted‐1,2,4,8,10,11‐hexachloro‐12H‐dibenzo[d,g][1,3,2]dioxaphosphocin 6‐oxides
Authors: Reddy B. Sankara , Reddy C. Devendranath , Reddy P. Mallikarjuna 
Published: January 2005

AbstractSynthesis of several 6‐substituted‐1,2,4,8,10,11‐hexachloro‐12H‐dibenzo[d,g][1,3,2]dioxaphosphocin 6‐oxides and their IR, 1H, 13C, and 31P NMR and mass spectral analyses are described. Observation of geminal coupling [2J(H,H) = 16.0 Hz] between bridged methylene protons (12‐CH2) suggested their non‐equivalence and is consistent with a boat‐chair form which may be in conformational equilibrium with either a boat‐boat or a distorted and extended boatlike conformation.
5‐Amino‐3H‐1,2,4‐dithiazole‐3‐thione as a synthon: New synthesis of 2‐thioureidobenzheteroazoles
Authors: Krishnaswamy N. R. , Sundaresan C. N. , Nambisan P. N. K. , Sandya K. 
Published: January 2005

AbstractNew and efficient one pot syntheses of 2‐thioureidobenzimidazole (V), 2‐thioureidobenzoxazole (VI), and 2‐thioureidobenzothiazole (VII) have been developed. The target compounds were obtained in good yields by condensing the title synthon commonly known as isoperthiocyanic acid (I) with 1,2‐diaminobenzene (II), 2‐aminophenol (III), and 2‐aminothiophenol (IV), respectively, in various organic solvent and in the solid state.
N‐alkyl‐C‐polyfluoroalkyl‐C‐chlorosulfinimides RFC(Cl)SNR
Authors: Ahlemann Jens‐Thomas , Roesky Herbert W. , Markovsky Leonid N. , Timoshenko Vadim M. , Shermolovich Yuri G. 
Published: January 2005

AbstractThe N‐alkyl‐C‐polyfluoroalkyl‐C‐chlorosulfinimides RFC(Cl)SNR have been investigated. Some aspects of their thermal stability and their [3 + 2] and [3 + 1] cycloaddition reactions have been examined.
Heterocyclic synthesis with nitriles: Synthesis of some new thiocyanato‐substituted heterocycles from alkylidene malononitrile
Authors: Abdelrazek Fathy M. 
Published: January 2005

Abstractα‐(Thiocyanatomethyl)benzylidenemalononitrile undergoes bromination with N‐bromo succinimide to afford α‐(bromothiocyanatomethyl)benzylidenemalononitrile. This bromo derivative undergoes reactions with sodium hydrogen sulfide, thioglycollic acid, hydroxylamine hydrochloride, phenylhydrazine, and hydrazine hydrate to afford thiophene, 4H‐thiopyran, 4H‐oxazine, pyridazine, and bis(thiazol‐2‐ylidene)azine derivatives, respectively. Mechanistic explanations as well as structure elucidations are discussed.
A useful synthesis of α,β‐bis(methylseleno)alkanes and α,δ‐bis(methylseleno)alk‐2‐enes by the reactions of alkenes and 1,3‐dienes with B(SeMe)3‐Lewis acid
Authors: Yoshimatsu Mitsuhiro , Asahi Takashi , Shimizu Hiroshi , Kataoka Tadashi 
Published: January 2005

AbstractReactions of tris(methylsenleno)borane‐SnCl4 with alkenes 1a–g gave α,β‐bis(methylseleno)alkanes 2a–g, stereospecifically, and reactions with 1,3‐dienes 1i–k afforded α,β‐bis(methylseleno)alk‐2‐enes 2i–k, regioselectively.
A novel strategy for the synthesis of 4,5‐dihydroisoxazoles via conjugate additions to α‐nitroalkenes
Authors: Yuan Chengye , Li Chaozhong 
Published: January 2005

AbstractMichael condensation of α‐nitroalkenes with various nucleophiles, followed by the addition of trimethylchlorosilane, led to novel syntheses of 4,5‐dihydroisoxazoles via cycloadditions of silyl nitronates.
Electron and X‐ray diffraction studies of chemically deposited thin films of cadmium selenide following reaction with mercury(II) chloride solution
Authors: Estrada C. A. , Meyers E. A. , Zingaro R. A. , Dufner D. C. , Nair P. K. , Nair M. T. S. 
Published: January 2005

AbstractThe reaction between thin films of CdSe and aqueous HgCl2 was studied using electron diffraction (ED) powder X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). It was found that α‐Hg3Se2Cl2 is formed in the CdSe film following its reaction with 0.01 M HgCl2 for a period of 5 minutes. Upon completion of the reaction of CdSe powder with 0.01 M HgCl2, Hg2Cl2 is present in addition to α‐Hg3Se2Cl2 in a molar ratio of 1:3.1. The effect of air annealing on CdSe powder was also studied. Heating in air to 450°C for 1 hour resulted in an XRD pattern corresponding to the hexagonal form of CdSe.
Stereospecific synthesis of P‐epimeric (Rp1, Rp2)‐bis‐[O‐l‐menthylphenylphosphonothionyl] diselenide. A new variant of the stereoselective Staudinger reaction
Authors: Łopusiński Andrzej , Łuczak Leszek , Michalski Jan 
Published: January 2005

AbstractAn efficient procedure is described that leads to pure (SP)‐O‐l‐menthylphenylthiophosphinate. The absolute configuration of this diastereomer was assigned by chemical correlation and confirmed by X‐ray crystallography. The reaction of the isomer with phenyl azide, leading to amidate, is a new variant of the stereoselective Staudinger reaction. Addition of elemental selenium to the (SP)‐thiophosphinate led to diastereomeric O‐l‐menthylphenylselenophosphonothioic acid, which was finally oxidized to the diastereomeric (RP1,RP2)‐bis‐[O‐l‐menthylphenylphosphonothionyl] diselenide. The diselenide structure was unambiguously confirmed by 31P NMR spectroscopy.
Synthesis of pentacoordinated germanium compounds containing a phosphonyl group
Authors: Chen Ruyu , Liu Lunzu , Zhang Zhongbiao 
Published: January 2005

AbstractThe title compounds were prepared by the reaction of germanium sesquioxides with diethyl N,N‐bis(2‐hydroxyethyl)aminomethylphosphonate in good yields (72–94%). The X‐ray analyses showed that the geometry about the germanium atom was a distorted trigonal bipyramid. © John Wiley & Sons, Inc.
Super‐resolution bright‐field optical microscopy based on nanometer topographic contrast
Authors: Huang Shu‐Wei , Mong Hong‐Yao , Lee Chau‐Hwang 
Published: January 2005

AbstractBy using an expectation‐maximization maximum likelihood estimation algorithm to improve the lateral resolution of a recently developed non‐interferometric wide‐field optical profilometer, we obtain super‐resolution bright‐field optical images of nanometer features on a flat surface. The optical profilometer employs a 365‐nm light source and an ordinary objective lens of a 0.95 numerical aperture. For objects of 100 nm thickness, lateral features about λ/7 can be resolved in the restored images without fluorescence labeling. Current image acquisition rate is 0.1 frame/sec, which is limited by the brightness of the light source. With a brighter light source, the imaging speed can be fast enough for real‐time observation of dynamic activities in the nanometer scale. Microsc. Res. Tech. 65:180–185, 2004. © 2005 Wiley‐Liss, Inc.
Single molecule studies of RNA secondary structure: AFM of TYMV viral RNA
Authors: Giro Andrea , Bergia Anna , Zuccheri Giampaolo , Bink Hugo H.J. , Pleij Cornelis W.A. , Samorì Bruno 
Published: January 2005

AbstractNowadays, the development of experimental procedures for the determination of the secondary structure of RNA molecules is taking advantage of the novel single‐molecule probing and imaging techniques. We report a method for the mapping of the secondary structure of RNA molecules spread on a flat surface by means of the atomic force microscope. Globular domains comprising groups of RNA secondary and tertiary structure elements separated by unstructured domains can be discerned in the micrographs and their position along the molecule contour can be measured directly on unstained specimens. We have analyzed the morphology of a population of single molecules of 3′ fragments of the Turnip Yellow Mosaic Virus RNA shorter than 1 kb in different temperature and electrolytic conditions. We found a satisfying agreement of the shape of the imaged structures with previously available evidence. The method we have developed can be used to map also different types of RNA molecules and has the advantage of showing the distribution of the single molecule conformations within the population. Microsc. Res. Tech. 65:235–245, 2004. © 2005 Wiley‐Liss, Inc.
Exploring molecular motors and switches at the single‐molecule level
Authors: Capitanio M. , Vanzi F. , Broggio C. , Cicchi R. , Normanno D. , Romano G. , Sacconi L. , Pavone F.S. 
Published: January 2005

AbstractSingle‐molecule techniques have propelled an impressive number of biophysical studies during the last decade. From relatively simple video‐microscopy techniques, to sophisticated manipulation and detection apparata, single‐molecule techniques are capable of tracking the movements and the reaction trajectories of single enzymatic units. By observing microspheres attached to biomolecules it is possible to follow the motion of molecular motors, or to detect conformational “switching” induced by regulatory proteins. Micromanipulation tools like optical tweezers have been widely applied to understand the mechanisms of linear molecular motors, and have allowed the measurement of the elementary steps and the forces produced by several motor proteins, including myosin, kinesin, and dynein. New experimental assays based on magnetic or optical “wrenches,” which are able to apply and detect torques on rotary motors and biopolymers, are opening new possibilities in this field. Here, established and emerging magneto‐optical manipulation and video‐tracking techniques are reviewed, in the perspective of single molecular motors and regulatory proteins studies. Microsc. Res. Tech. 65:194–204, 2004. © 2005 Wiley‐Liss, Inc.
Diffusion of microspheres in sealed and open microarrays
Authors: Rieger B. , Dietrich H.R.C. , Doel L.R. Van Den , Vliet L.J. Van 
Published: January 2005

AbstractIn several experiments, we study the diffusion of microspheres with different radii in microarrays filled with a variety of aqueous solutions of ethylene glycol. We study diffusion in open and closed (sealed) microarrays. In sealed nanoliter wells, the tracers show pure diffusion, whereas in open reactors, a radial outward‐directed evaporation‐induced liquid flow is superimposed onto the diffusion. In general, one of the following quantities can be calculated if the others are known: the temperature, the viscosity of the medium, the radius of the microbeads, or the diffusion constant. The estimated diffusion constants in closed microarrays are in good agreement with theoretical predictions based on the Brownian motion. We monitor the motion of the microbeads under a microscope and extract their paths in time from the digital recordings. Ambiguous paths due to the crossing of two trajectories can be detected. We show that low microsphere concentrations or high viscosities do not hamper a robust estimation of the diffusion parameters. Microsc. Res. Tech. 65:218–225, 2004. © 2005 Wiley‐Liss, Inc.
Recent work on entropically‐driven ring‐opening polymerizations: some potential applications
Authors: Hodge Philip , Colquhoun Howard M. 
Published: January 2005

AbstractThe entropically‐driven ring‐opening polymerization of macrocyclic monomers (>ca. 14 ring atoms per repeat unit) and/or macrocyclic oligomers is a relatively new method of polymer synthesis that exploits the well‐known phenomenon of ring‐chain equilibria. It attracts interest because of its novel features. For example, these ring‐opening polymerizations emit no volatiles and little or no heat. This review considers the principles of entropically‐driven ring‐opening polymerizations, gives selected examples and discusses potential applications. The latter include micromolding, high throughput syntheses and the synthesis of supramolecular polymers. Copyright © 2005 John Wiley & Sons, Ltd.
Nanostructuring polymers with cyclodextrins
Authors: Rusa Cristian C. , Wei Min , Bullions Todd A. , Shuai Xintao , Uyar Tamer , Tonelli Alan E. 
Published: January 2005

AbstractBulk solid polymer samples formed by the coalescence of guest polymer chains from their inclusion compounds (ICs) formed with host cyclodextrins (CDs) can result in significant reorganization of their phase structures, morphologies, and even chain conformations from those more commonly produced from randomly‐coiled, entangled polymer solutions and melts. When the cyclic host CDs are threaded by polymer chains to form crystalline polymer‐CD‐ICs, the guest polymers become highly extended due to the narrow host CD diameters (∼5, 7, and 9 Å for α‐, β‐, and γ‐CDs) and are segregated from neighboring guest polymer chains by the CD‐IC channel walls. As a consequence, when polymer‐CD‐IC crystals are treated with CD solvents that do not dissolve the guest polymers or are treated with amylase enzymes, the resulting coalesced bulk polymer samples often display properties distinct from those of normally produced bulk samples of the same polymers. In this article the CD‐IC processing of polymers to generate novel polymer microstructures and morphologies are described, to control the phase separation of immiscible blocks in block copolymers, and to form well‐mixed intimate blends of two or more polymers that are normally incompatible. The thermal and temporal stabilities of polymer samples coalesced from their ICs formed with CDs will also be mentioned, and it is suggested that the range of polymer properties can be greatly expanded by their CD‐IC processing. Copyright © 2005 John Wiley & Sons, Ltd.
Composition, preparation procedure and physical properties of linear homogeneous polyurethanes for membranes
Authors: Laporta Marcello , Pegoraro Mario , Bianchi Fiorenzo , Consolati Giovanni , Zanderighi Luciano 
Published: January 2005

AbstractLinear polyurethanes (PUs) were prepared in solution in two steps. In the first step, toluene‐diisocyanate (TDI) 80:20 (T) was reacted with a short‐chain poly(oxypropylene) diol (V) to obtain prepolymers characterized by various ratios of R = [T]°/[V]°. In the second step, the prepolymers were reacted with the extender 1,4‐cyclohexanedimethanol (E) with various extension ratios RE = (R − 1)[V]°/[E]°. The PU properties were analyzed by various techniques. In particular, the molecular weights determined by gel permeation chromatography (GPC), the thermal properties such as glass transition temperature Tg and specific heat variation ΔCp measured by differential scanning calorimetry (DSC), the chemical composition of the PUs and the various types of hydrogen bonds present in the polymers evidenced by Fourier‐transform infrared (FTIR) spectroscopy, the monophasic structure evidenced by small‐angle X‐ray scattering (SAXS), and the existence of only one Tg confirmed that these PUs were linear, amorphous and monophasic. Positron annihilation lifetime spectroscopy (PALS) analysis showed that the mean volume of the nanoholes increased with increasing temperature, but was not dependent on the composition, as expected for a monophasic system. A stoichiometric semi‐empirical model was proposed that relates the PU blocks' micro‐composition to the R and RE macro‐parameters, chosen for the synthesis. The polymer assumes various expressions of the general formula X[(TV)k(TE)n]mX for different values of the R and RE ratios. The micro‐parameters k and m have a direct connection with the experimental mean molecular weights of the prepolymer and the polymer, respectively: n depends only on R. The model could foresee the density of hydrogen bonds and distinguished the bonds connected to either V or E, which could be shown by FTIR analysis. This paper shows that, when using stereo‐irregular diols and blends of 2,4‐ and 2,6‐TDI, non‐stereoregular PUs are obtained. If low‐molecular‐weight diols are used and R < 3.3, it is quite improbable that the PU blocks separate into macrophases and therefore monophasic amorphous PUs are obtained. Monophasic PUs can be useful for applications such as in the field of membrane gas and vapour separation. Copyright © 2005 Society of Chemical Industry
Dynamic rheological properties of Yam starch/hectorite composite gels
Authors: Wilhelm Helena‐M , Sierakowski Maria‐R , Reicher Fany , Wypych Fernando , Souza Gabriel P 
Published: January 2005

AbstractThe rheological properties of composite gels of starch extracted from Yam roots (Discorea sp) and hectorite (a mineral clay belonging to the smectite group) were studied in aqueous solutions as a function of hectorite concentration. The elastic (G′) and viscous (G″) moduli of the composite gels were dependent on the clay content, and for all samples G′ was greater than G″. Composite gels with clay contents of <30% presented higher G′, G″ and viscosities |η*| when compared with pure starch gel, while those with a content of 50 % showed lower values. The addition of hectorite significantly inhibited the creeping properties in relation to pure starch at 25 °C but, after heating/cooling cycles between 25 and 85 °C, this effect was not observed and the composite gel showed similar behavior to that of pure starch. Copyright © 2005 Society of Chemical Industry
Ethenediylidene‐2,2′ ‐bis(1,3‐dithiole) and butatriene‐1,4‐diylidene‐2,2′‐bis(1,3‐dithiole)
Authors: Awaji Hiroshi , Sugimoto Toyonari , Yoshida Zen‐Ichi 
Published: January 2005

AbstractThis paper describes the synthesis and electrochemical behavior of dicationic salts of ethenediylidene‐2,2′ ‐bis(1,3‐dithiole) (3) and butatriene‐1,4‐diylidene‐2,2′ ‐bis(1,3‐dithiole) (4). These are expected as donor components for developing organic conducting and superconducting materials, on the grounds of high electron donating ability and of rigid skeletal structure with two and four cumulenic carbons inserted between two 1,3‐dithioles. These salts were obtained in good overall yields by several steps starting from (2‐morpholino‐4,5‐dimethyl or ‐diphenyl)‐1,3‐dithiolylium salt. From the 1H and 13C NMR, and electronic spectra it is suggested that the π conjugation between two 1,3‐dithiolylium ions through an acetylenic bond is less effective than that through an olefinic bond of the corresponding salts of ethanediylidene‐2,2′ ‐bis(1,3‐dithiole) (1) and 2‐butene‐1,4‐diylidene‐2,2′‐bis(1,3‐dithiole) (2). The cyclic voltammetric study shows that the corresponding radical cations, and in particular 3 and 4, are less stable even at −40°C, thus providing reasons for our current lack of success in isolation of 3 and 4. From comparison of the first redox potentials of neutral species, it is deduced that the donating ability increases in the order of TTF < 1 ⋍ 2 ≲ 3 ≪ 4.
Intramolecular orientation at the micellar interface: Control of norrish type I and type II reactivity of benzoinalkylethers via conformational effects
Authors: Devanathan S. , Ramamurthy V. 
Published: January 2005

AbstractThe photolysis of benzoinalkylethers 1‐5 solubilized in detergents show a significant deviation from the course of reaction in isotropic organic solvents. Remarkable difference in photobehaviour is noticed between the short chain (1‐3) and the long chain (4 and 5) benzoinalkylethers in the micellar media. However, the influence of the micellar media on the photobehaviour of alkyldeoxybenzoins 6 and 7 was small. The importance of ‘cage effect’ in controlling the product distribution was evident from its dependence on the micellar size and on the occupancy number. More importantly, a comparative analysis of the photobehaviour of the ketone 1‐7 reveals that the micellar interface can be used to control the conformations of organic molecules.
Oxygen induced reduction: Reaction of benzeneselenol with aromatic aldehydes in the presence of oxygen
Authors: Masawaki Teruyuki , Ogawa Akiya , Kambe Nobuaki , Murai Shinji , Sonoda Noboru 
Published: January 2005

AbstractReduction of aromatic aldehydes by benzeneselenol is found to be promoted by molecular oxygen to give corresponding alcohols in good yields. No reduction took place without oxygen.A free radical process involving SH2 reaction at the selenium atom is proposed where the phenylseleno radical attacks the selenium atom of selenohemiacetal, the adduct of benzeneselenol to aldehyde, to give the ketyl radical which then abstracts hydrogen from benzeneselenol. The intermediacy of selenohemiacetal is supported by a quantitative reduction of α‐methoxybenzyl phenyl selenide, which is used as a model compound of the intermediate.
ESR studies of photochemical reaction of 2‐methyl‐3‐acetylquinoxaline N,N′‐dioxide(MAQO)
Authors: Wang Hanqing , Feng Liangbo 
Published: January 2005

AbstractThe photochemical reaction of MAQO with various aromatic amines were studied by ESR. The results show that nitroxide radicals are stable productrs of the photooxidation of both diphenylamines and phenylamines. The photolyzed phenothiazine does not yield nitroxide as the final product, instead it gives the neutral radical as the stable final product.
2,3:5,6‐bis(ethylenedithio)‐ and bis(trimethylenedithio)‐N,N′‐ dicyanoquinonediimines as new electron acceptors
Authors: Otsubo T. , Nobuhara Y. , Kanefuji K. , Aso Y. , Ogura F. 
Published: January 2005

AbstractIn order to examine the substituent effect of ethylenedithio and trimethylenedithio groups on electron acceptors, the two title compounds were prepared in one step from the corresponding quinones. These species behave as weak π‐electron acceptors owing to the electronic and sterical effects of the fused groups. Only the bis(ethylenedithio) derivative formed a charge‐transfer complex with tetrathiotetracene, which showed a moderate electric conductivity of 2·0 × 10−2 S cm−1. In addition, both species oxidized copper, sodium, and potassium iodides to give the corresponding deeply colored metal salts, most of which were semiconductive. The naphtho analogs were similarly studied, but hardly served as electron acceptors.
Extrusions of dibromocarbene under neutral conditions
Authors: Warner Philip M. , Lu Shih‐Lai , Gurumurthy R. 
Published: January 2005

AbstractThe thermal and photochemical decompositions of 5 have been studied. Both reactions lead to CBr2 transfer in good to high yields. With the 2‐pentenes as substrates, CBr2 transfer is stereospecific in the classical singlet carbene manner.magnified image