bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of green chemistry in the manufacture of oligonucleotide drugs
Authors: Sanghvi Yogesh S. , Ravikumar V. T. , Scozzari Anthony N. , Cole Douglas L. 
Published: October 2007

Abstract
We have modified the current phosphoramidite-based, solid-phase synthesis of antisense oligonucleotides to accommodate principles of green chemistry. In this article, we summarize key accomplishments that reduce or eliminate the use or generation of toxic materials, solvents, and reagents. Also discussed are methodologies that allow reuse of valuable materials such as amidites, solid-support, and protecting groups, thus improving the atom economy and cost-efficiency of oligonucleotide manufacture. Approaches to accident prevention and the use of safer reagents during oligonucleotide synthesis are also covered.
Design, synthesis, and application of chelating polymers for separation and determination of trace and toxic metal ions. A green analytical method
Authors: Sharma Rakesh K. 
Published: October 2007

Abstract
A green analytical method was developed for separation and preconcentration of trace amounts of copper from aqueous samples using aurin tricarboxylic acid-immobilized silica gel (ATA-SG). This was done by determining chemical speciation and stability constant of Cu-ATA complex. The pH-metric studies indicate strong complexation of Cu with ATA (log bCu2ATA = 19.56). Species distribution curve for Cu-ATA complex indicates almost 100% complexation of copper, with ATA forming Cu2ATA as the predominant species. Considering the selectivity and strong interaction of ATA toward copper, ATA was immobilized on the polymeric matrix of silica gel, and the conditions were optimized for the uptake of copper from the aqueous solutions. The uptake of Cu ions by ATA-SG was studied both by batch and column methods. The method was developed for the estimation of trace amounts of copper in various samples. Molecular modeling studies were also performed on ATA-immobilized silica gel for gaining an insight into the active structure of ATA on the silica surface.
Recent progress in the chemistry of multicomponent reactions
Authors: Ugi Ivar 
Published: October 2007

Abstract
The chemistry of multicomponent reactions (MCRs) and isocyanides belongs to three periods: In the century 1859­1958, isocyanide chemistry was moderately active and was separate from the classical name reactions of the MCRs. In the next period, isocyanides became well available, and MCRs of isocyanides became the most variable way of forming chemical compounds. The year 1993 began a new era of the formation and investigation of the products and the libraries of the Ugi reaction (U-4CR) and higher MCRs of the isocyanides. This chemistry is primarily accomplished in the industrial search and preparation of new pharmaceutical and plant-protecting products.
Solvent-free accelerated organic syntheses using microwaves
Authors: Varma Rajender S. 
Published: October 2007

Abstract
A solvent-free approach for organic synthesis is described which involves microwave (MW) exposure of neat reactants (undiluted) either in the presence of a catalyst or catalyzed by the surfaces of inexpensive and recyclable mineral supports such as alumina, silica, clay, or "doped" surfaces, namely, Fe(NO3)3-clay (clayfen), Cu(NO3)2-clay (claycop), NH2OH-clay, PhI(OAc)2-alumina, NaIO4-silica, MnO2-silica, and NaBH4-clay. A variety of deprotection, condensation, cyclization, oxidation, and reduction reactions are presented including the efficient one-pot assembly of heterocyclic molecules from in situ generated intermediates such as enamines and a-tosyloxyketones. The application of this solvent-free MW approach to multicomponent reactions is highlighted that can be adapted for high-speed parallel synthesis of the library of dihydropyrimidine-2(1H)-ones and imidazo [1,2-a]annulated pyridines, pyrazines, and pyrimidines.
Green twist to an old theme. An eco-friendly approach
Authors: Yadav J. S. , Meshram H. M. 
Published: October 2007

Abstract
Owing to present environmental awareness, attempts are being made toward the evolution of environmentally benign processes using solid-supported reagents and microwave-assisted reactions. A newly developed, nonmetallic oxidative reagent, "clayan", has been exploited for various reactions such as deprotection, oxidation, oxidative coupling, and nitration and bromination of activated and deactivated arenes. In another green chemistry endeavor, reactions such as reduction and cyclization have been successfully carried out in dry media under microwave irradiation. The nonsolvent reaction, experimental simplicity, and enhanced selectivity are the main attractive features of the approach.
Cooperative bimetallic oxidative addition reactions
Authors: Qin C. Jin , Gavrilova Anna , Bosnich and B. 
Published: October 2007

Abstract
The factors that control the oxidation of metals in bimetallic complexes are investigated in relation to the possibility of developing one-site addition two-metal oxidation reactions such as those that occur in the respiratory protein,hemerythrin. It is shown that the behavior of bimetallic complexes is not represented by the sum of the analogous monometallic parts because of metal and ligand interactions.
Asymmetric hydrogenation via architectural and functional molecular engineering
Authors: Noyori Ryoji , Koizumi Masatoshi , Ishii Dai , Ohkuma Takeshi 
Published: October 2007

Abstract
RuCl2 (phosphine) 2 (1,2-diamine) complexes, coupled with an alkaline base in 2-propanol, allows for preferential hydrogenation of a C=O function over coexisting conjugated or nonconjugated C=C linkages, a nitro group, halogen atoms, and various heterocycles. The functional group selectivity is based on the novel metal-ligand bifunctional mechanism. The use of appropriate chiral diphosphines and diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic, hetero-aromatic, and olefinic ketones. The versatility of this method is manifested by the asymmetric synthesis of various biologically significant chiral compounds.
Some newer aspects of organozirconium chemistry of relevance to organic synthesis. Zr-Catalyzed enantioselective carbometallation
Authors: Negishi Ei-ichi 
Published: October 2007

Abstract
The reaction of terminal alkenes with trialkylalanes in the presence of chiral (NMI) 2ZrCl2 has been shown to be 70-75% ee for methylalumination and 90-95% ee for ethyl- and higher alkylalumination. It must involve an acyclic bimetallic process. Its scope, limitations, and applications to some natural products syntheses are discussed.
Rational design of polymers for optoelectronic interests
Authors: Luh Tien-Yau , Chen Ruey-Min , Hwu Tsyr-Yuan , Basu Sourav , Shiau Chung-Wai , Lin Wei-Yu , Jin Bih-Yaw , Hsu Chia-Chen 
Published: October 2007

Abstract
Using organometallic catalysts, two types of polymers containing conjugated moiety and insulating linker are synthesized. The investigations on the photophysical properties of these polymers (photoluminescence, electroluminescence and nonlinear optical properties) are briefly summarized. These polymers represent a new class of materials for optoelectronic interests.
Effect of ligands on the divalent palladium- catalyzed carbon-carbon coupling reactions. Highly enantioselective synthesis of optically active g-butyrolactones
Authors: Lu Xiyan , Zhang Qinghai 
Published: October 2007

Abstract
In the palladium (II) -catalyzed enyne coupling reactions, the nitrogen-containing ligand plays the same role as the halide ion to inhibit the β-hydride elimination. Employing the pymox or bisoxazoline as ligands, the catalytic asymmetric cyclization of (Z) -4'-acetoxy-2'-butenyl 2-alkynoates initiated by acetoxypalladation was established with high efficiency (up to 92% ee) to afford the optically active γ-butyrolactones.
Chemical nitrogen fixation by using molybdenum and tungsten complexes
Authors: Hidai Masanobu , Mizobe Yasushi 
Published: October 2007

Abstract
Dinitrogen complex cis-[W (N2) 2 (PMe2Ph) 4] reacts with an excess of acidic dihydrogen complexes such as trans-[RuCl (h2-H2) (dppe) 2]BF4 (dppe = 1,2-bis (diphenylphosphino) ethane) at 55 °C under 1 atm of H2 to form ammonia in moderate yield. The reaction is presumed to proceed through nucleophilic attack of the remote nitrogen of the coordinated dinitrogen on the dihydrogen ligand. The coordinated dinitrogen is also protonated by treatment with hydrosulfido-bridged dinuclear complexes such as [Cp*Ir (m-SH) 3IrCp*]Cl (Cp* = h5-C5Me5) to afford ammonia. On the other hand, the synthetic cycle for the formation of pyrrole and N-aminopyrrole from dinitrogen and 2,5-dimethoxytetrahydrofuran has been established starting from dinitrogen complexes of the type trans-[M (N2) 2 (dppe) 2 ] (M = Mo, W).
Synthesis of oxygen heterocycles via alkynyltungsten compounds
Authors: Liu Rai-Shung 
Published: October 2007

Abstract
This short review article covers some useful applications of alkynyltungsten compounds to the syntheses of complex lactones. Two types of cyclizations will be emphasized: (1) cycloalkenylation of tungsten-alkynol compounds with aldehydes to give a-alkylidene oxacarbeniums, further leading to a-alkylidene lactones and (2) intramolecular [3+2]-cycloaddition of epoxides to give bicyclic lactones. The new methodologies can provide a short synthesis of enantiopure lactones such as (-) -epilitsenolide C2, (+) -listenolide C1, (+) -isodihydromahubanolide A, (+) -blastmycinone, and (-) -epi-blastmycinone.
Fullerenes covalently linked to transition metals with organic ligands
Authors: Sokolov Viatcheslav I. , Nefedova Marina N. , Potolokova Tatiana V. , Bashilov Vasily V. 
Published: October 2007

Abstract
Synthesis of molecules combining both fullerene and metallocene moieties separated by some spacer is discussed in connection with the possible intramolecular charge transfer. Two new kinds of spacers, =CH-CO- and -Pd-P-, have been introduced by using the corresponding reactions. Reaction of diazoacetyl ferrocene and cymantrene with C60 has been studied in detail and products characterized. 1,1'-Bis (diazoacetyl) ferrocene gave with C60 1:1 adduct to which the ansa-structure has been assigned on the basis of 1H and 13C NMR spectra. Palladium-h2-C60 complex with a bidentate ferrocenyl diphosphine as a ligand has been also prepared.
Lewis-acidic organometallic compounds of the lanthanides and the alkaline earth metals as catalysts for the activation of carbonyl groups
Authors: Schumann Herbert , Glanz Mario , Gottfriedsen Jochen , Dechert Sebastian , Wolff Dietmar 
Published: October 2007

Abstract
1,3-dialkyl-4,5-dimethylimidazol-2-ylidenes form adducts with various bis (alkylcyclopentadienyl) complexes of magnesium, calcium, strontium, barium, samarium, and ytterbium. The X-ray structures of selected metallocenes and carbene adducts are discussed. Liquid-crystalline homo- and block copolymers with a narrow molecular mass distribution index were obtained in high yields by living polymerization of mesogenic methacrylates with organosamarium complexes. Depending on the structure of the catalyst and the polarity of the solvent used, different, partially competitive reaction mechanisms are observed.
Asymmetric synthesis by stereocontrol
Authors: Kim Yong Hae , Kim Sam Min , Youn So Won 
Published: October 2007

Abstract
Diels-Alder cycloadditions of S-indoline chiral acrylamides with cyclopentadiene in the presence of Lewis acids proceed with high diastereofacial selectivity, giving either endo-R or endo-S products depending on Lewis acid and the structures of chiral dienophiles. Diastereo- and enantioselective pinacol coupling reactions of chiral α-ketoamides mediated by samarium diiodide afforded extremely high diastereoselectivities. Enantiopure (S,S) - or (R,R) -2,3-dialkyltartaric acid and derivatives can be synthesized. Furthermore, it was demonstrated that α,β-unsaturated amides coupled with SmI2 to dimerized products containing two chiral carbons which were first obtained as the adjacent chiral carbons.
New methods for the synthesis of transition-metal fullerene complexes
Authors: Thompson David M. , McLeod Jason , Baird Michael C. 
Published: October 2007

Abstract
Buckminsterfullerene, C60, is readily reduced on exposure to solutions of strongly reducing transition-metal carbonylate anions to give the radical anion fulleride C60
- and the corresponding highly reactive, 17-electron neutral compounds. Three secondary reaction paths have been identified, depending on the nature of the reactants and the reaction conditions. (1) With Na+ and PPN+ salts of [Mn (CO) 5]-, thermal substitution of a CO on the metal radical by the C60-results in formation of the anionic, h2-fullerene complex [Mn (C60) (CO) 4]- . (2) With salts of [Co (CO) 4]-, the thermal reaction results in formation of a novel transition-metal fulleride NaCoC60 while (3) with Na[CpFe (CO) 2] and [CpM (CO) 3]- (M = Mo, W) , the 17-electron intermediates couple to form the 18-electron dimers, [CpFe (CO) 2]2 and [CpM (CO) 3]2. In contrast, photochemical reactions of C60 with salts of [Mn (CO) 5]-, [Co (CO) 4]-, and [CpM (CO) 3]- result in excellent yields of the complexes [Mn (C60) (CO) 4]- , [Co (C60) (CO) 3]- and [CpM (C60) (CO) 2]- , respectively; analogous complexes of C70 may be made similarly. The new complexes have been characterized crystallographically, by IR, 13C NMR, and/or Raman spectroscopy and by electrospray mass spectrometry.
Novel polymerization and copolymerization of ethylene, styrene, and/or butadiene by new organolanthanide-based catalysts
Authors: Hou Zhaomin , Kaita Shojiro , Wakatsuki Yasuo 
Published: October 2007

Abstract
Replacement of one of the two C5Me5 ligands in the samarocene (II) complex (C5Me5) 2Sm (THF) 2 with a monodentate anionic ligand (e. g. , OAr, SAr, or NR1R2) gives a unique catalytic system, which can not only polymerize styrene and ethylene, but also copolymerize them into block styrene-ethylene copolymers under the presence of both monomers. On the other hand, addition of an appropriate cocatalyst such as MMAO or AlR3/[Ph3C][B (C6F 5) 4] to the samarocene complex (C5Me5) 2Sm (THF) 2 or (C5Me5) 2Sm (m-Me) 2AlMe2 affords a novel catalytic system for stereospecific 1,4-cis living polymerization of butadiene and copolymerization of butadiene with styrene.
Isolobal displacement methodology for the synthesis of transition-metal cluster complexes containing various biscyclopentadienyl ligands
Authors: Song Li-Cheng , Guo Dian-Shun 
Published: October 2007

Abstract
The isolobal displacement methodology for the synthesis of biscyclopentadienyl-bridged transition-metal cluster complexes has been developed. This methodology involves various isolobal displacement reactions between tetrahedral cluster substrates and Mo/W-containing isolobal reagents, leading to a series of linear biscyclopentadienyl-bridged cluster complexes and cyclic biscyclopentadienyl-bridged cluster crown ethers, respectively.
Alkane activation on a multimetallic site
Authors: Suzuki Hiroharu , Inagaki Akiko , Matsubara Kouki , Takemori Toshifumi 
Published: October 2007

Abstract
Trinuclear polyhydrido complex of ruthenium effectively activates alkanes to cleave C-H bonds in a selective manner due to cooperative action of the metal centers. The reaction of (Cp´Ru) 3 (m-H) 3 (m3 -H) 2 (1) (Cp´ = h5-C5Me5) with n-alkane at 170 °C leads to the formation of a trinuclear closo-ruthenacyclopentadiene complex as a result of a successive cleavage of six C-H bonds. Introduction of a m3-sulfido ligand into the Ru3 core of the trirutheniumpolyhydrido cluster significantly modifies the regioselectivity of the alkane C-H activation. Heating of a solution of (Cp´Ru) 3 (m3-S) (m-H) 3 (4) in alkane exclusively gives a trinuclear m3-alkylidyne complex via a selective C-H bond cleavage at the less-hindered terminus of alkane molecule.
New developments in transition metal-catalyzed synthetic reactions via C-H bond activation
Authors: Fujiwara Yuzo , Jia Chengguo 
Published: October 2007

Abstract
Several novel and useful reactions involving transition metal-catalyzed C-H bond activation discovered in our laboratory have been summarized here, which includes olefin arylation, hydroarylation of alkynes, carboxylation of arenes and alkanes, and acetoxylation and aminomethylation of alkanes. Possible mechanisms of these reactions have been suggested.
Interplay of synthesis and mechanism in asymmetric homogeneous catalysis
Authors: Adams Nicholas J. , Bargon Joachim , Brown John M. , Farrington Edward J. , Galardon Erwan , Giernoth Ralf , Heinrich Hanjo , John Benjamin D. , Maeda Kenji 
Published: October 2007

Abstract
Asymmetric homogeneous catalysis forms one of the main planks of modern organic synthesis. It has developed rapidly and largely through the application of novel ligands, whose design is very much based on insight and intuition. At the same time, a better understanding of catalytic reaction mechanisms can contribute to further progress, since it can identify the intimate relationship between ligand structure and successful applications. The presentation will concentrate on the author's research with complexes of the late transition metals and include the search for superior methodologies in hydroboration, as well as ventures into the chemistry of reactive intermediates. The latter will be exemplified from work with rhodium and palladium catalysts.
Chemistry of η5-fullerene metal complexes
Authors: Nakamura Eiichi , Sawamura Masaya 
Published: October 2007

Abstract
Treatment of [60]fullerene with an organocopper reagent converts one of the pentagons of the fullerene into cyclopentadienyl anion through addition of five organic groups on every peripheral carbon atom surrounding the pentagon. Similar treatment of [70]fullerene afforded indenyl anion through regioselective tri-addition of the organic group. These anionic moieties strongly interact with the remainder of the fullerene p-system, and provide unique opportunity for exploration of organometallic chemistry of a new class of metal cyclopentadienides.
New class of metallacarboranes incorporating the η7-carboranyl ligand
Authors: Xie Zuowei 
Published: October 2007

Abstract
This article provides an overview of our work on the synthesis, molecular structure, and bonding of a novel class of 13-vertex closo-metallacarboranes incorporating the h7-carboranyl ligand. This bonding mode can only be observed in the d0/fn transition-metal ions with the proper size.
New metallocenes of early transition metals with functional groups in organic ligands. Red-ox transformations
Authors: Krut'ko Dmitrii P. , Borzov Maxim V. , Veksler Edward N. , Kirsanov Roman S. , Churakov Andrej V. , Lemenovskii Dmitri A. 
Published: October 2007

Abstract
The reduction behavior of the novel zirconocene dichlorides, (h5-C5Me5) (h5-C 5Me4CH2CH2ER 2) ZrCl2 (ER2 = NMe2, PMe2, PPh2) , (h5-C5Me4CH2 CH2PMe2) 2ZrCl 2, and (h5-C5Me4CH2 CH2PPh2) (h5-C 5Me4CH2CH2PMe 2) ZrCl2, together with the new types of intramolecular activation of inert C-H and C-heteroatom bonds are presented and discussed. A remarkably thermally stable zirconocene alkylhydryde type framework complex (h5-C5Me5) [h5 ,s-C5Me4CH2CH 2N (Me) CH2-]ZrH, zirconocene arylhydryde complex (h5-C5Me5) [h5 ,s-C5Me4CH2CH 2P (Ph) -o-C6H4-]ZrH, tetramethylfulvene hydride-type complexes (h5-C5Me5) [h6 :h1- (CH2C5Me3 ) CH2CH2PR2]ZrH (R = Me, Ph) and (h5-C5Me4CH2 CH2PPh2) [h6:h 1- (CH2C5Me3) CH 2CH2PMe2]ZrH are reported. The first unusually thermally stable zirconocene (h5,h1-C5Me4 CH2CH2PMe2) 2 Zr with the Zr (II) center stabilized by intramolecular coordination of two Me2P-groups is described.
Dynamic solvatochromism in solvent mixtures
Authors: Wetzler Diana E. , Chesta Carlos , Fernández-Prini Roberto , Aramendía Pedro F. 
Published: October 2007

Abstract
Solvatochromism and thermochromism of 4-aminophthalimide and 4-amino-N-methylphthalimide were studied by absorption and steady-state and time-resolved emission spectroscopy in solvent mixtures of toluene­ethanol and toluene­acetonitrile at different temperatures. Emission spectra shift to the red upon addition of a polar solvent (PS) to toluene. Solvent mixtures show a much greater thermochromic shift to the blue in emission than the neat solvents. This is explained by the decrease in temperature of the exothermic association of the polar solvent to the excited state. Emission spectra are time dependent in solvent mixtures in the ns timescale. The time evolution of this emission is interpreted on the basis of the different solvation of the ground state and the emitting excited state. Stern­Volmer plots are obtained for the dependence of the spectral-shift characteristic time with [PS].
Tryptophan rotamers that report the conformational dynamics of proteins
Authors: Fidy Judit , Laberge Monique , Ullrich Beata , Polgar Laszlo , Szeltner Zoltan , Gallay Jacques , Vincent Michel 
Published: October 2007

Abstract
The binding of acetyl­pepstatin to the Q7K/L33I/L63I mutant of HIV-1 protease was studied by fluorescence, phosphorescence, and 500-ps molecular dynamics. The protease is a homodimer with two tryptophans per monomer. Maximum entropy method (MEM) analysis and acrylamide quenching results show two tryptophyl, tryptophan (Trp) populations in the apoenzyme that merge into one in the complex. These results are in agreement with molecular dynamics simulations indicative of Trp asymmetry in the apoenzyme as revealed by the occurrence of nonequivalent Trp42 indole rotamer interconversions, not observed for the complex. Analysis of the local Trp42B environments of the apoenzyme with respect to possible quencher groups shows that the c2 interconversions do not influence the lifetime, while the c1 interconversions do. Upon binding the inhibitor, Trp42B acquires a single conformation with the same lifetime and orientation as that of Trp42, and also with less quenching accessibility. Thus, protein conformational dynamics become constrained with inhibitor binding. This conclusion is supported by red-edge effect experiments and phosphorescence lifetime measurements. The low temperature tp (~5.8 s) is quenched to ~200 ms as protein motions become activated around the glass transition temperature. In the case of the complex, the phosphorescence lifetime data show a more cooperative activation of the quenching mechanisms.
Conjugated polymers. New materials for optoelectronic devices
Authors: Friend R. H. 
Published: October 2007

Abstract
Conjugated polymers now provide a class of processible, film-forming semiconductors and metals. We have worked on the development of the semiconductor physics of these materials by using them as the active components in a range of semiconductor devices. Polymer light-emitting diodes show particular promise, and recent developments in color range (red, green, and blue), efficiency (above 20 lumen/W for green emitters), and operating lifetime are discussed. Progress on their application to displays, with integration with active-matrix TFT drive, and with patterned deposition using inkjet printing techniques is also reviewed. The role played by interfaces between electrode and semiconducting polymer is also discussed.
Microscopy and optical manipulation of dendrimer-built vesicles
Authors: Gensch T. , Tsuda K. , Dol G. C. , Latterini L. , Weener J. W. , Schenning A. P. H. J. , Hofkens J. , Meijer E. W. , De Schryver F. C. 
Published: October 2007

Abstract
A fifth-generation poly(propylene imine) dendrimer decorated with palmitoyl- and azobenzene-containing alkyl groups forms giant vesicles in aqueous solutions with diameters from 50 nm up to 20 mm and a multilaminar onion-like structure. Dense and ordered arrangement of the azobenzene chromophores in the bilayer structure leads to fluorescence with lmax= 600 nm. The fluorescence intensity can be increased by irradiation with blue light, and at low pH a distinctive blue shift of the spectrum is observed. With the aid of a single-beam optical tweezers it is possible to trap vesicles and direct them in a billiard-like fashion against each other using forces in the range of several pN. In collision experiments, the vesicles behave like hard spheres, and merging is not observed.