Search results for "Triple bond"
showing 10 items of 39 documents
One-Pot Synthesis to Quinone-Based Diaza[3.3]cyclophanes
2017
A simple one-pot synthesis to [3.3]cyclophanes that involves quinone moieties was found. The protocol tolerates a variety of amines that include aliphatic and aromatic structures with different functional groups, such as hydroxy groups, amides, and terminal double and triple bonds. The straightforward synthesis can be performed by a twofold N-alkylation reaction with 2,5-bis(bromomethyl)-3,6-dimethyl-1,4-benzoquinone (1). Neither anhydrous nor inert conditions are required. Various amines can be employed without any activating groups, several functionalities at end groups are tolerated, and the cyclophanes generated can be easily modified or embedded into larger molecular architectures. The…
Versatile behavior of conjugated diynes with zirconocene reactive species
2008
Thermal decomposition of Cp2ZrPh2 in the presence of the buta-1,3-diynes RC≡CC≡CR (R = Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused seven-membered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiC≡CC≡CSiMe3 a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This α monoinsertion complex is an intermediate in the exchange of the metalated…
Chemical and Spectroscopical Properties of Medium Sizedtrans- andcis-Bicyclo[n.1.0]alk-2-ynes
1997
Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.
cis-Diazido[bis(diphenylphosphino)methane-κ2P,P′]ruthenium(II) dichloromethane 0.42-solvate
2006
Submitted by António Freitas (amsf@uma.pt) on 2019-06-13T13:44:22Z No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Made available in DSpace on 2019-06-13T13:44:22Z (GMT). No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Previous issue date: 2006 info:eu-repo/semantics/publishedVersion
Topochemical Reactions of Monomers with Conjugated Triple-Bonds VII Mechanism of Transition from Monomer to Polymer Phase During Solid-State Polymeri…
1972
The lattice-controlled solid-state polymerisation of three different modifications of 2,4-hexadiin-1,6-diol-bis(phenylurethane) was investigated by X-ray and optical methods. The polymerisation is a homogeneous reaction. The polymer grows in the form of single chains within the crystal of the monomer. The chains extend along a definite crystallographic direction. Monomer and polymer are isomorphous and monomer-polymer single crystals of various compositions are obtained up to a quantitative conversion in the case of modification I or III. Phase separation into a mesomorphic polymer and oriented monomer phase was observed on annealing partially polymerised single-crystals of modification II …
Toward an Understanding of the Molecular Mechanism of the Reaction between 1-Methylpyrrole and Dimethyl Acetylenedicarboxylate. An ab Initio Study
1998
The molecular mechanism for the reaction between 1-methylpyrrole and dimethyl acetylenedicarboxylate (DMAD) has been studied using ab initio methods. Two alternative reaction pathways have been considered, both of which correspond to stepwise processes with initial, rate-determining formation of a common zwitterionic intermediate. This intermediate is formed by nucleophilic attack of the pyrrole ring to the carbon−carbon triple bond of DMAD. Closure of this intermediate (pathway A) affords a [4 + 2] cycloadduct, whereas intramolecular proton transfer (pathway B) affords a Michael adduct. The much larger potential energy barrier of the second step in pathway B relative to pathway A is respon…
Palladium on pumice: new catalysts for the stereoselective semihydrogenation of alkynes to (Z)-alkenes
2001
Abstract High selectivities (93–99%) and excellent stereoselectivities (>99%) in the semihydrogenation of CC triple bonds were achieved using palladium on pumice with a metal loading of 0.5, 1.5 or 3.0% wt as catalyst. The reactions were carried out in ethanol or tetrahydrofuran with only 2.5% of ethylenediamine allowing a self-terminating semihydrogenation independently on the CC triple bond.
ChemInform Abstract: Palladium on Pumice: New Catalysts for the Stereoselective Semihydrogenation of Alkynes to (Z)-Alkenes.
2010
Abstract High selectivities (93–99%) and excellent stereoselectivities (>99%) in the semihydrogenation of CC triple bonds were achieved using palladium on pumice with a metal loading of 0.5, 1.5 or 3.0% wt as catalyst. The reactions were carried out in ethanol or tetrahydrofuran with only 2.5% of ethylenediamine allowing a self-terminating semihydrogenation independently on the CC triple bond.
Dithiametacyclophane mit Dreifachbindungen
1994
Dithiametacyclophanes with Triple Bonds Schemes 1 and 2 show the syntheses of dithia[8]metacyclo-phanes 4a-d and tetrathia[m.n]metacyclophanes 9, 10 by cyclization reactions applying the cesium effect. All these cyclophanes contain C—C triple bonds which influence the molecular dynamics; especially the halogen substituents in 4b-d obstruct the topomerization.
Synthese von 9‐Oxabicyclo[6.1.0]non‐3‐in
1987
Ausgehend von 1,5-Cyclooctadien (1) wird in einer siebenstufigen Synthese die Titelverbindung 9 gewonnen. Sie liegt in zwei Konformationen 9a und 9b vor, wobei in 9a eine starke sterische Wechselwirkung zwischen dem Sauerstoffatom und der gespannten Dreifachbindung auftritt. Zur Einfuhrung der Dreifachbindung dient die thermische Fragmentierung des 1,2,3-Selenadiazols 7. Der Strukturnachweis fur die regiospezifische Bildung von 7 wird mit 2D-NMR-Spektroskopie gefuhrt. Starting with 1,5-cyclooctadiene (1), the title compound 9 is gained in a synthesis of seven steps. 9 exists in two conformations 9a and 9b, of which 9a shows a strong interaction between the oxygen atom and the strained tripl…