Search results for "BOND"
showing 10 items of 3527 documents
Cycloaddition reactions of benzothiete with azomethines
1986
Obtention de diaryl-2,3 dihydro-3,4 benzothiazines-1,3 (70%) via la cycloaddition de la thiobenzoquinone methode-1,2 (obtenue par scission thermique du benzothiete) et d'arylimines de benzaldehydes. Obtention egalement de 10% du dimere (dibenzo [b, f] dithiocinne-1,5)
Umsetzungen an polyallylalkoholen ein beitrag zur strukturaufklärung der polyacroleine. Polymere acroleine. 23. mitt.
1962
Redoxpolymerisate des Acroleins wurden mit Natriumboranat reduziert und polymere Allylalkohole mit einem Restgehalt von 4 Mol-% Carbonylgruppen erhalten. Sie enthalten auserdem noch etwa 4 Mol-% C—C-Doppelbindungen. Die Polyallylalkohole wurden xanthogeniert und die Zersetzungsgeschwindigkeit im Vergleich zu Propyl- und Polyvinylalkoholxanthogenaten studiert. Neben Aldehydgruppen kommen noch 3–5 Mol-% Ketogruppen in den Redoxpolymerisaten des Acroleins vor. Die Anwesenheit von Doppelbindungen und Ketogruppen in den Polyacroleinen wird durch Nebenreaktionen bei derPolymerisation erklart. Redox-polymers of acrolein were reduced by sodium boranate and polymeric allylic alcohols were obtained w…
A Photoredox-Catalyzed Four Component Reaction for the Atom-Efficient Synthesis of Complex Secondary Amines
2020
The one-pot sulfonylation/aminoalkylation of styrene derivatives furnishing highly substituted gamma-sulfonylamines was accomplished through a photoredox-catalyzed four-component reaction. Apart from one molecule of water and the sodium counterion of the sulfinate, all atoms of the starting materials are transferred to the final product, rendering this process highly atom-efficient. The operationally simple protocol allows for the simultaneous formation of three new single bonds (C–S, C–N, and C–C) and therefore grants rapid access to structurally diverse products. The reaction proceeds under mild conditions in aqueous acetonitrile and shows a broad scope, including natural products and dru…
An Uncommon Pathway in the Biosynthesis of Acetylenic Fatty Acids in Mosses
1995
Although more than 600 acetylenic compounds of various structures have been found in plants [1], hardly anything is known about the formation of the triple bonds. The acetylenes so far known from Bryophytes, have been identified as long chain fatty acids with a characteristic arrangement of one triple bond and one to three double bonds.
Über die cyclopolymerisation einiger bis-(N-vinyl)-verbindungen
1966
Durch Umsetzung von Vinylisocyanat mitAthylenglykol, Butandiol-1,4, Hexandiol-1,6, Octandiol-1,8, Brenzcatechin, Resorcin, Hydrochinon, cis- und trans-Chinit sowie Piperazin wurden die entsprechenden Bis-(N-vinyl)-Verbindungen hergestellt. Diese Monomeren werden unter gleichen Bedingungen radikalisch polymerisiert. Der Gehalt an seitenstandigen N-Vinylgruppen ergibt sich aus der bei saurer Hydrolyse gebildeten Menge Acetaldehyd. Der auf 0% Umsatz berechnete Doppelbindungsgehalt und damit der Cyclisierungsgrad hangt von der Struktur der Monomeren ab. Die Ergebnisse stimmen uberein mit der Ringbildungstendenz bei niedermolekularen Verbindungen (z. B. Ansaverbindungen) und werden an Hand von M…
Quinonoid π-extended tetrathiafulvalenes (TTFs)
2001
Publisher Summary Tetrathiafulvalene (TTF) is a fascinating planar πelectron-donor molecule with a broad range of potential applications. TTF and its derivatives play an important role in the field of organic conductors forming charge-transfer (CT) complexes and radical cation salts (Bechgaard salts) with a huge variety of electron-acceptor molecules and anions in the search for electrically conducting and superconducting materials. The chapter focuses on highly π-extended electron donors with p-quinodimethane structures as interesting precursors of materials with non-conventional properties. The first dimeric examples of π-extended TTF derivatives connected through an oxygen atom are also …
Structural characterization in solution of multifunctional nucleotide coordination systems
2000
The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…
ChemInform Abstract: Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes.
2008
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional th…
Stereoselective Synthesis of 8,12-Furanoeudesmanes from Santonin. Absolute Stereochemistry of Natural Furanoeudesma-1,3-diene and Tubipofurane.
1996
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained by stereoselective reduction of the C(4)-C(5) double bond in 3 in the following way: hydrogenation of 3 over Pd/C followed by acidic treatment gave the cis isomer 10 as the major product; selective hydrogenation of the C(1)-C(2) double bond with the Wilkinson's catalyst followed by reduction with NaTeH yielded mainly the trans isomer 9. Compounds 9 and 10 were transformed into 4 and 5 in parallel sequences. Optical rotation and CD measurements of the synthetic produ…
ChemInform Abstract: Synthesis of α-Fucosyl Glycosides and Disaccharides Using 4- Methoxybenzyl (Mpm) Protected Fucosyl Donors.
2010
The 4-methoxybenzyl (Mpm) group removable by selective oxidation was applied as a nonneighbouring-group-active protection of fucose hydroxy functions in the stereoselective synthesis of α-fucosides of acceptors containing double bonds sensitive to hydrogenation. With this aim, the synthesis of the α-fucosyl chloride (4) carrying the acidsensitive Mpm protection was elaborated.