Home About us Contact
|
Home About us Contact | ||
|
|
||
Triple Bond (triple + bond)
Kinds of Triple Bond Selected AbstractsChemInform Abstract: Palladium-Catalyzed Chloroimination of Imidoyl Chlorides to a Triple Bond: An Intramolecular Reaction Leading to 4-Chloroquinolines.CHEMINFORM, Issue 46 2008Akira Isobe Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Unexpected Reactivity of 3-(Phenylethynyl)-1H-indenes Towards Nucleophiles: Noncatalytic Addition to Triple Bond with or without Double Bond Migration.CHEMINFORM, Issue 31 2007P. V. Ivchenko Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] An Unusually Robust Triple Bond: Synthesis, Structure and Reactivity of 3-Alkynylcyclopropenes.CHEMINFORM, Issue 24 2004Robert D. Gilbertson Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Cleavage of Carbon,Carbon Triple Bond of Alkyne via Hydroiminoacylation by Rh(I) Catalyst.CHEMINFORM, Issue 52 2001Chul-Ho Jun Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: The Novel Selective Reduction of the Carbon,Carbon Triple Bond Using Pd(PPh3)4 as a Catalyst.CHEMINFORM, Issue 47 2001WenXin Gu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Palladium-Catalyzed Cyanation of Carbon,Carbon Triple Bonds under Aerobic Conditions.CHEMINFORM, Issue 42 2009Shigeru Arai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] DNA Containing Side Chains with Terminal Triple Bonds: Base-Pair Stability and Functionalization of Alkynylated Pyrimidines and 7-DeazapurinesCHEMISTRY & BIODIVERSITY, Issue 5 2006Frank Seela Abstract The synthesis of a series of oligonucleotides containing 5-substituted pyrimidines as well as 7-substituted 7-deazapurines bearing diyne groups with terminal triple bonds is reported. The modified nucleosides were prepared from the corresponding iodo nucleosides and diynes by the Sonogashira cross-coupling reaction. They were converted into phosphoramidites and employed in solid-phase synthesis of oligonucleotides. The effect of the diyne modifications on the duplex stability was investigated. The modified nucleosides were used for further functionalization using the protocol of Huisgen,Sharpless [2+3] cycloaddition (,click chemistry'). [source] Electronic Structure of Linearly Coordinated EQ Complexes of the Type [(N3N)W(EQ)] [N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se, Te]: A DFT StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2007Gábor Balázs Abstract Density functional theory (DFT) calculations were carried out on the terminal EQ complexes [(N3N)W(EQ)] {N3N = N(CH2CH2NSiMe3)3; E = P, As, Sb, Bi; Q = O, S, Se Te} to clarify the bonding situation within the linear Nax,W,E,Q core. This unusual structural motif gives rise to a bonding arrangement in which the ,-electron density is delocalised over the three atoms of the W,E,Q unit. Fragment calculations and natural bond order (NBO) data indicated that the ,-bonding component of the Nax,W,E,Q unit comprises two occupied , orbitals, while the , component of bonding comprises two sets of degenerate , orbitals. In general, the , orbitals of the Nax,W,E,Q core are higher in energy compared to the , orbitals. The phosphorus monoxide (EQ = PO) complexes provide an exception to this rule, with the 1, orbitals of the W,P,O core lower in energy than the , orbitals. Generally, as the atomic number of either the pnicogen (E) or chalcogen (Q) atom increases the extent of ,-orbital delocalisation decreases, whereas the ,-orbital delocalisation increases. Fractional bond orders and Wiberg bond indices were used to establish whether localisation of the ,-electron density gives rise to a W,E or an E,Q double or triple bond. Both methods indicate a W,E as well as an E,Q double bond. The ionic nature of the complexes were analysed by inspection of the Hirschfeld charge distribution which shows only a moderate ionic character. Exceptions are the pnicogen monoxide complexes, which are more ionic. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis, Characterization and Reactivity of New (,-Aminocarbyne)diruthenium Complexes Containing Alkynylimino LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2004Luigi Busetto Abstract Addition of acetylides R,C,CLi [R, = Tol, Ph, Me3Si, nBu, C(Me)=CH2] to the diruthenium complexes [Ru2{,-CN(Me)(R)}(,-CO)(CO)(NCCMe3)(Cp)2]+ (R = Xy, 2a; Bz, 2b; Me, 2c) results in the formation of [Ru2{,-CN(Me)(R)}(,-CO)(CO){N(H)=C(CMe3)(C,CR,)}(Cp)2]+ (R = Xy, R, = Tol, 3a; R = Bz, R, = Tol, 3b; R = Me, R, = Tol, 3c; R = Xy, R, = Ph, 4a; R = Bz, R, = Ph, 4b; R = Me, R, = Ph, 4c; R = Bz R, = H, 5; R = Xy, R, = nBu, 6; R = Xy, R, = [C(Me)=CH2], 7), which contain an alkynylimino ligand, formed from addition of the acetylide to the Me3CCN ligand. Structural and spectroscopic studies show that all these complexes contain the two Cp ligands in a relative cis arrangement, whereas two isomers arise from the different orientation of the substituents on the bridging aminocarbyne ,-CN(Me)(R) when R , Me. Addition of secondary amines to 3,7 results in a stereo- and regioselective cis amination of the C,C triple bond to give the new complexes [Ru2{,-CN(Me)(R)}(,-CO)(CO){N(H)=C(CMe3)C(H)=C(NMe2)(Tol)}(Cp)2]+ (R = Xy, 8a; Bz, 8b; Me, 8c), [Ru2{,-CN(Me)(Xy)}(,-CO)(CO){N(H)=C(CMe3)C(H)=C(NC5H10)(Tol)}(Cp)2]+(9) and [Ru2{,-CN(Me)(Xy)}(,CO)(CO){N(H)=C(CMe3)C(H)=C(NMe2)C(Me)=CH2)}(Cp)2]+ (10) containing the hitherto unknown new imino-2-en-3-amine ligand. The solid-state structures of these products have been analyzed by X-ray analysis and, in solution, by NOE spectroscopic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Lewis Acid Mediated Aminobenzannulation Reactions of ,-Ketoalkynes: Synthesis of 1-Aminocarbazoles and 9-Aminopyrido[1,2- a]indolesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2009Diego Facoetti Abstract 2-Acyl- N -propargylindoles 1 and 2-acyl-3-propargylindoles 5 undergo aminobenzannulation reactions with pyrrolidine in the presence of an appropriate Lewis acid to give 9-aminopyrido[1,2- a]indoles 6 and 1-aminocarbazoles 7, respectively. The selection of the appropriate Lewis acid, TiCl4 or GaCl3 for 1 and InCl3 for 5, allows the domino process involving the initial formation of an enamine intermediate, followed by a regioselective 6- exo - dig intramolecular nucleophilic attack of the nucleophilic terminus of the unsaturated system (the ,-carbon of the enamino moiety) to the carbon,carbon triple bond. Moreover, several features concerning the reaction mechanism and the role of both catalysts, in connection with the electronic properties of the reacting alkynes, are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Silver-Catalyzed Incorporation of Carbon Dioxide into Propargylic Alcohols,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2007Wataru Yamada Abstract The combined use of a catalytic amount of silver acetate and a stoichiometric amount of DBU efficiently catalyzed the incorporation of CO2 under mild reaction conditions into a wide range of propargylic alcohols bearing a terminal or an internal triple bond to afford the corresponding cyclic carbonates in high-to-excellent yields. All the cyclic carbonates obtained from the reaction were found to be single isomers. The geometries were determined to be (Z) by X-ray crystal structure analysis and NOE experiments.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Twisted Intercalating Nucleic Acids , Intercalator Influence on Parallel Triplex StabilitiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006Vyacheslav V. Filichev Abstract Phosphoramidites of several new twisted intercalating nucleic acid (TINA) monomers and the previously discovered (R)-1- O -[4-(1-pyrenylethynyl)phenylmethyl]glycerol (1) were synthesized and used in DNA synthesis. Stabilization of Hoogsteen-type triplexes was observed in cases of insertion of the novel (R)-1- O -[3-(naphthalen-1-ylethynyl)phenylmethyl]glycerol (2) as a bulge into homopyrimidine oligodeoxynucleotides (ONs), whereas phenylethynyl and 4-(biphenylylethynyl) derivatives of TINAs resulted in destabilization of parallel triplexes relative to the wild-type triplex. It was concluded that TINA monomers should possess at least two fused phenyl rings attached through the triple bond at the 4-position of bulged (R)-1- O -(phenylmethyl)glycerol in homopyrimidine ONs in order to stabilize parallel triplexes. Slight destabilization of DNA/DNA Watson,Crick type duplexes (,Tm = 1.0,4.5 °C) was detected for 2 inserted as a bulge, while RNA/DNA duplexes and duplexes with other TINA analogues were considerably destabilized (,Tm > 6.0 °C). In cases of double insertion of 1 opposite to base inversions in dsDNA, the thermal stabilities of the triplexes were higher than that of the wild-type triplex, which is a new solution to overcome the problem of targeting homopurine stretches with single base pair inversions. A DNA three-way junction was considerably stabilized (,Tm in a range of 10.0,15.5 °C) upon insertion of TINA monomers in the junction point as a bulge. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of the Salicylihalamide Core Structure from Epichlorohydrin, Laying the Foundation to Macrolactone CollectionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2005Christian Herb Abstract Starting from (R)-epichlorohydrin, two successive carbon,carbon bond formations, one with acetylide and the other with cyanide, led to the 3-hydroxynitrile 20. This compound was further elaborated to the enynol 29 via an Evans aldol reaction of the derived aldehyde 22 with the pentenoyloxazolidinone 23 and conversion of the carboxyl to a methyl group after the aldol reaction. Mitsunobu esterification of the enynol 29 with the benzoic acid 5 gave rise to the ester 30 with two double bonds and one triple bond. After protection of the terminal triple bond with a TIPS group, the ring closing metathesis proceeded in good yield. The macrolactone E -33 was converted into the vinyl iodide 34 and the pyridin containing salicylihalamide analog 36. The described sequence, the two-sided elongation of epichlorohydrin appears as a general route to secondary alcohols that can be further elaborated to functionalized macrolactones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Catalytic 1,2-Dicyanation of Alkynes by Palladium(II) under Aerobic ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Shigeru Arai Abstract A stereoselective 1,2-dicyanation of various alkynes in the presence of trimethylsilyl cyanide (TMSCN) by palladium(II) catalysis under aerobic conditions is investigated. This reaction includes two cyanation pathways, syn - and anti -cyanopalladation to alkynes that are activated by Pd(II). High syn -selectivity was observed in the reaction using terminal alkynes that have bulky substituents at a propargyl position and aliphatic internal alkynes. Furthermore, a dramatic acceleration was observed with substrates having an N -arenesulfonyl functionality at a propargyl position, this indicates that both sulfoxide and carbon-carbon triple bond act as Lewis bases to Pd(II). [source] Thiophenol-Mediated 1,5-Hydrogen Atom Abstraction: Easy Access to Mono- and Bicyclic CompoundsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005Florent Beaufils Abstract A thiophenol-mediated method for cyclization of alkynes is described. The reaction cascade involves the intermolecular addition of a phenylthiyl radical to a terminal triple bond generating an alkenyl radical, followed by a 1,5-hydrogen atom transfer and a 5- exo- trig radical cyclization. This very efficient tin-free procedure allows one to prepare highly functionalized cyclopentane derivatives as well as fused bicyclic and spirocyclic compounds from easily available precursors. During this cyclization process, a phenylthio moiety is incorporated into the final cyclized products. This functionalization is particularly attractive for further transformation of the products. [source] C,H..., interactions in cocrystals of bis(trimethylsilyl)acetylene and diphenylacetylene with benzeneACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Frank Meyer-Wegner We present here the crystal structures of two acetylene derivatives cocrystallized with benzene, namely bis(trimethylsilyl)acetylene benzene solvate, C8H18Si2·C6H6, (I), and diphenylacetylene benzene solvate, C14H10·C6H6, (II). In (I), both molecules belong to the symmetry point group C2h and are located about special positions with site symmetry 2/m. In (II), both molecules show crystallographic inversion symmetry. In both structures, there are C,H..., contacts between aromatic H atoms and the ,-electrons of the triple bond. In addition to these, in (II) there are C,H..., contacts between aromatic H atoms and the ,-electron cloud of the benzene molecules. [source] Ionization potentials of heteroalkenes: a comparative studyAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2004Anna Chrostowska Abstract Methanimine, methylenephosphine and methylenearsine have been prepared in the gas phase and the gaseous flow has been analyzed by spectroscopy. Photoelectron spectra have been recorded and we report here a comparative study on these spectra. This comparison has been extended to the corresponding derivatives with a triple bond: hydrogen cyanide and methylidynephosphine. Estimation by theoretical calculations of the ionization potentials of the unknown methylidynearsine has been proposed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Oligosubstituted Pyrroles Directly from Substituted Methyl Isocyanides and AcetylenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2009Alexander Abstract The formal cycloaddition of ,-metallated methyl isocyanides 1 onto the triple bond of electron-deficient acetylenes 2 represents a direct and convenient approach to oligosubstituted pyrroles 3. The scope and limitations of this reaction (24 examples, 25,97,% yield) are reported along with an optimization of the reaction conditions and a rationalization of the mechanism. In addition, a related newly developed CuI -mediated synthesis of 2,3-disubstituted pyrroles by the reaction of copper acetylides derived from unactivated terminal alkynes with substituted methyl isocyanides is described (11,examples, 5,88,%yield). [source] Synthesis and Photoinduced Electron-Transfer Properties of Phthalocyanine,[60]Fullerene ConjugatesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2008Maurizio Quintiliani Dr. Abstract A series of three novel ZnPc,C60 conjugates (Pc=phthalocyanine) 1,a,c bearing different spacers (single, double, and triple bond) between the two electroactive moieties was synthesized and compared to that of ZnPc,C60 conjugate 2, in which the two electroactive moieties are linked directly. The synthetic strategy, towards the preparation of 1,a,c, involved palladium-catalyzed cross-coupling reactions over a monoiodophthalocyanine precursor 4 to introduce the corresponding spacer, and subsequent dipolar cycloaddition reaction to C60. Detailed photophysical investigations of 1,a,c and 2 prompted an intramolecular electron transfer that evolves from the photoexcited ZnPc to the electron-accepting C60. In particular, with the help of femtosecond laser photolysis charge separation was indeed confirmed as the major deactivation channel. Complementary time-dependent density functional calculations supported the spectral assignment, namely, the spectral identity of the ZnPc.+ radical cation and the C60., radical anion as seen in the differential absorption spectra. The lifetimes of the correspondingly formed radical ion-pair states depend markedly on the solvent polarity: they increase as polarity decreases. Similarly, although to a lesser extent, the nature of the linker impacts the lifetime of the radical ion-pair states. In general, the lifetimes of these states tend to be shortest in the system that lacks any spacer at all (2), whereas the longest lifetimes were found in the system that carries the triple-bond spacer (1,a). [source] Intramolecular Reactions in Pseudo-Geminally Substituted [2.2]Paracyclophanes,CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2007Lidija Bondarenko Dr. Abstract A selection of pseudo-geminally substituted [2.2]paracyclophanes, the alkynes 6, 7, 10, 11,a, and 11,b and the alkenes 8 and 9 were prepared for the study of intraannular reactions between functional groups in direct juxtaposition. Whereas 9 and 10 provide the corresponding cyclobutane and cyclobutene derivatives on irradiation (12 and 13, respectively), the bis-alkynes 7 and 11,b do not lead to a cyclobutadiene intermediate. In the latter case the "half-closed" butadiene derivative 17 was isolated. A Paterno,Büchi reaction took place on irradiation of 8 and 6, although the oxetene intermediate 21 produced in the second example did not survive the reaction conditions (ring-opening to 22). Bromine addition to 9, 10, and 7 occurred with high stereoselectivity (formation of the dibromides 27, 30, and 33, respectively), and is rationalized by postulating the formation of the cationic intermediates 26, 29, and 32, respectively. To study the interaction of a carbocation with a facing triple bond, the alcohol 34 was prepared from 6. On acid treatment ring closure to the triply-bridged phane 38 took place, accompanied by the hydration of the triple bond to the ketoalcohol 37. In an interesting intraannular [2+3]cycloaddition reaction the bis-acetylene 11,a, on treatment with n -butyl lithium, provided the cyclopentadiene derivative 42. That the two triple bonds of a pseudo-geminal diacetylene can engage in a cyclization reaction leading to the cyclopentadienone complex 44 was also shown by treating 11,b with iron pentacarbonyl. [source] Comment on "Disproving a Silicon Analog of an Alkyne with the Aid of Topological Analyses of the Electronic Structure and Ab Initio Molecular Dynamics Calculations"CHEMPHYSCHEM, Issue 4 2006Gernot Frenking Prof. Dr. Bond order of a silicon-silicon bond (1): The statement that the recently synthesized compound RSiSiR (1) (RSi[C(SiMe3)3]2CHMe2) has rather a double than a triple bond is challenged. Arguments are given which support the interpretation of the bonding situation in terms of two donor,acceptor bonds which are enhanced by one , bond (see picture). [source] Disproving a Silicon Analog of an Alkyne with the Aid of Topological Analyses of the Electronic Structure and Ab Initio Molecular Dynamics CalculationsCHEMPHYSCHEM, Issue 9 2005Carlo A. Pignedoli Dr. Abstract A silicon compound has recently been synthesized that was claimed to exhibit the first realization of a silicon,silicon triple bond. We debate this classification on the basis of a thorough investigation of the nature of the chemical bond, using the rigorous topological analysis of the electron density as developed in Bader's atoms-in-molecules theory, that of the electron localization function and the related orbital-independent definitions of the bond order. Our results refer both to the ground-state geometry and to nonequilibrium configurations, which are accessed by the system in a room-temperature ab initio molecular dynamics simulation. We also use the reciprocal compliance force constant as an independent chemical descriptor. All the above procedures are in agreement and do not support the classification of the silicon,silicon central bond as triple. The characterization which consistently emerges from the present study is one in which two electron pairs participate in the bonding and the other pair belongs mainly to nonbonding regions. [source] Comparison of Isoelectronic Heterometallic and Homometallic Binuclear Cyclopentadienylmetal Carbonyls: The Iron,Nickel vs. the Dicobalt SystemsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2008Jun D. Zhang Abstract The heterometallic binuclear cyclopentadienylironnickel carbonyl compounds Cp2FeNi(CO)n (n = 3, 2, 1; Cp = ,5 -C5H5) have been studied by density functional theory (BP86) for comparison with the isoelectronic homometallic dicobalt derivatives Cp2Co2(CO)n. The FeNi tricarbonyl is shown to be the doubly bridged isomer Cp2Fe(CO)Ni(,-CO)2 with an Fe,Ni distance of 2.455 Å (BP86), in accord with experiment and in contrast to Cp2Co2(CO)3 where singly and triply bridged but not doubly bridged isomers are found. The dicarbonyl compounds Cp2FeNi(,-CO)2 and Cp2Co2(,-CO)2 both have analogous doubly bridged structures with M=M distances around 2.35 Å, suggesting formal M=M double bonds. The monocarbonyl compounds have analogous singly bridged axial structures Cp2FeNi(,-CO) and Cp2Co2(,-CO) with metal,metal distances in the range 2.05 Å (M2 = Co2) to 2.12 Å (M2 = FeNi) consistent with the formal M,M triple bonds required for the favored 18-electron configuration. Open-shell states of Cp2FeNi(,-CO) are found to have even lower energies than the closed-shell structure, which indicates that the ground state of Cp2FeNi(,-CO) might be a high spin structure. However, the global minimum for the monocarbonyl is found to be a singlet "hot dog" perpendicular Cp2NiFe(CO) structure with a terminal CO group bonded to the iron atom. Other higher energy perpendicular structures are also found for Cp2FeNi(CO)n (n = 3, 2, 1) with terminal CO groups and bridging Cp rings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Titanocene(II)-Promoted Cross-Coupling of Unsaturated CompoundsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2006Akitoshi Ogata Abstract Vinyl pivalate in the presence of the titanocene(II) reagent Cp2Ti[P(OEt)3]2 reacts both with nonpolar C,C triple bonds and with polar C=O double bonds, to produce conjugated dienes and allylic alcohols, respectively. Similar alkenylation also takes place when (Z)-alkenyl sulfones are treated with alkynes and carbonyl compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Catalytic Dicyanative 5- exo- and 6- endo -Cyclization Triggered by Cyanopalladation of AlkynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Shigeru Arai Abstract A stereoselective dicyanative 5- exo- and 6- endo -cyclization using various enynes has been investigated. The mode of cyclization is critically controlled by the structure of the substrates. For example, N -allyl derivatives prefer 5- exo -cyclization, while methacryloyl amides are transformed to the corresponding lactams with tetra -substituted carbons at the alpha-position via 6- endo -cyclization. Both reactions include syn -cyanopalladation to carboncarbon triple bonds in the initial step, and sequential cyclization followed by reductive elimination in one operation enables the construction of the highly functionalized nitrogen heterocycles. The scope of suitable substrates and a proposed mechanism are also described. [source] domain averaged Fermi holes;JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2003chemical bond; The recently proposed approach based on the analysis of domain-averaged Fermi holes was applied to the study of the nature of metalmetal bonding in transition metal complexes and clusters. The main emphasis was put on the scrutiny of the systems assumed to contain direct multiple metalmetal bonds. The studied systems involve: (1) systems of the type M2X6 (M = Mo, W, X = CH3) anticipated to contain metalmetal triple bonds; (2) the molecule of W2Cl8(4,) as the representative of the systems with quadruple metalmetal bonding; (3) diatomic molecules Mo2 and V2 considered as the potential candidates for higher than quadruple metalmetal bonding. Although the resulting picture of bonding has been usually shown to agree with the original expectations based on early simple MO models, some examples were also found in which the conclusions of the reported analysis display dramatic sensitivity to the quality of the wave function used for the generation of the Fermi holes. In addition to this we also report some examples where the original theoretical predictions of multiplicity of metalmetal bonds have to be corrected. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1829,1838, 2003 [source] Synthesis of tritium labelled 3(R)-HETE and 3(R),18(R/S)-DiHETE through a common synthetic routeJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2004Natalya V. Groza Abstract An efficient procedure for the synthesis of 3-hydroxyoxylipins labelled with tritium on all double bond positions is reported. The synthetic scheme involves a joint route for the formation of tetraacetylenic precursors followed by stereoselective reduction of the triple bonds either with hydrogen or tritium. The final tritiated products were obtained with specific activities ranging from 1.65 to 1.80 Ci/mmol. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of Lewis base coordination on boryl radical reactivity: investigation using laser flash photolysis and kinetic ESRJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2009Jacques Lalevée Abstract The effect of Lewis base coordination on boryl radical reactivity (L,BH where L is triethylamine, 2-picoline, 4-dimethylaminopyridine, quinoline and diphenyl phosphine) is examined. Direct detection of the different boryl radicals, their transient absorption spectra, their interaction with double or triple bonds, oxygen, oxidizing agent, alkyl halides and their hydrogen lability have been studied using laser flash photolysis (LFP), kinetic ESR (KESR), ESR spin trapping and MO calculations. For example, a strong decrease of both the bond dissociation energy (BDE)(BH) (33.8,kcal,mol,1) and the addition rate constant to MA (1300 105 to,>105 M,1,s,1) was noted when going from the triethylamine borane to the quinoline borane complex, in line with the spin delocalization (1.04 vs. 0.19). These structures are also proposed as new highly efficient co-initiators for the acrylate photopolymerization. Copyright © 2009 John Wiley & Sons, Ltd. [source] Radical Polymerisation of 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol Acrylates and Methacrylates: A New Family of Fluorinated PolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2004Ana Robert Estelrich Abstract Summary: The preparation of a new family of acrylic esters with a perfluorinated chain directly bonded to one or two conjugated triple bonds from 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol is reported. Their solution homopolymerisation was studied in the presence of a radical initiator and it was found that the polymerisation process bore more similarity to that observed with the analogous hydrocarbonated monomers containing triple bonds rather than that observed with polyfluorinated monomers without any alkyne groups. Furthermore, under the reaction conditions used, the triple bonds remained unchanged as there was no cross-linking process. The homopolymers obtained were characterised by NMR, infrared spectroscopy and gel permeation chromatography whenever possible. Structure of new fluorinated homopolymers. [source] Nitridation and reoxidation of high- k metal oxide thin films using argon excimer sourcesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006J. J. Yu Abstract We report for the first time the nitridation and reoxidation of metal oxide films with the active nitrogen and oxygen species produced by argon excimer sources. Preliminary results on 9 nm Ta2O5 films using this method exhibited excellent electrical properties with the leakage current density being up to 3 orders of magnitude lower than the as-deposited films. Breakdown fields were found to be greater than 13 MV/cm. Accumulation capacitance with the nitrided film increased by 25% compared with the as-deposited film. Optical transmittance was as high as 99% in the visible region and more than 74% in the UV region. The refractive index at 632.8 nm was high up to 2.2. The Ar excimer source emitted energetic VUV photons which could break nitrogen triple bonds to produce active nitrogen species and photodissociate O2 to form strong oxidant O3 and highly reactive O (1S) atoms, leading to the nitridation and reoxidation of Ta2O5 without the need for the use of H2O, NH3 and high temperature substrate heating. The nitridation process for a specific film thickness can be optimised by adjusting the VUV irradiation time to achieve increased accumulation capacitance and improved leakage property simultaneously. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||