16 results on '"Diels-Alder Reaction"'
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2. Synthetic Studies on Bilobalide.
- Author
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Shiogai, Akihiro, Toma, Tatsuya, and Yokoshima, Satoshi
- Abstract
We disclose our synthetic studies on bilobalide, which features a Diels–Alder reaction of a cyclic anhydride to form two contiguous quaternary carbon centers, desymmetrization of a symmetric diol, and construction of a cyclic acetal under acidic conditions with inversion of configuration at an allylic position. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
3. Diels-Alder-Reaktion eines elektronenarmen C-Acylimins mit Tetraethoxyethylen.
- Author
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Felderhoff, M. and Sustmann, R.
- Abstract
The synthesis of two C-acylimines and their reactivity towards electron rich dienophiles in Diels-Alder reactions is described. A [4+2] cycloadduct is obtained only in one case: from the reaction of a C-acylimine substituted by two methoxycarbonyl groups with tetraethoxyethylene. No [2+2] cycloadducts are observed. [ABSTRACT FROM AUTHOR]
- Published
- 1996
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4. Bishomocamphenilon, Bishomocamphen und Bishomocamphenilansäure: Synthesen in der Isocamphanreihe, 32. Mitt.
- Author
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Buchbauer, Gerhard, Spreitzer, Helmut, Zechmeister-Machhart, Friederike, and Pleßl, Martha
- Abstract
Syntheses of the title compounds are described and their olfactive properties discussed. Bishomocamphenilone ( 2) has been prepared by a Diels-Alder reaction of acrylonitril and cycloheptadiene-1,3 via the bicyclonitril 5 which upon geminal chlorination and alkaline oxidation furnished the bishomonorbornanone 9 which then could be transformed into 2 by twofold methylation. 14 has been prepared by action of MeLi upon 2 and bishomocamphene by dehydration of 14. Hydroboration of this olefine 3 yielded the alcohol 15, which could be oxidized to the corresponding aldehyde 13 and bishomocamphenilanic acid ( 4). The configurations of all new compounds has been ascertained. [ABSTRACT FROM AUTHOR]
- Published
- 1989
- Full Text
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5. Zur Synthese von Homocamphenilansäure.
- Author
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Buchbauer, Gerhard, Spreitzer, Helmut, and Kurz, Margit
- Abstract
Syntheses of the title compound and of some of its derivatives are described. Homocamphenilanic acid could not be obtained by a Diels-Alder reaction of cyclohexadiene with an appropriate dienophile but is easily accessible via homocamphene by hydroboration of this homoterpene and subsequent oxidation of the reaction product. [ABSTRACT FROM AUTHOR]
- Published
- 1987
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6. Oxidationsreaktionen am 1-(3,3-Dimethyl-5-norbornen-2-yl)ethanon und ein neuer Zugang zu endo-konfigurierten Isocamphanderivaten.
- Author
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Buchbauer, Gerhard, Vitek, Renate, Hirsch, Margit, Kurz, Christina, Cech, Barbara, and Vas, Eva
- Abstract
The synthesis of some new compounds with the isocamphane skeleton obtained by oxidation reactions on the bicyclic ketone 3 and its derivatives is described. Some possible routes to the endo-configurated camphenilanic acid ( 2) have been explored which yet have to be improved to furnish better yields. Separation of mixtures of the acids 1 and 2 failed. Carboxylation of camphenilone yielded only the exo-configurated isocamphenilanic acid ( 1). 2, however, an important starting material for the preparation of endo-configurated isocamphane derivatives, can be obtained easily with high yields and sterically pure by oxidation of camphene with HO/HCOOH. Thus a cheap, one-step method for the preparation of pure 2 even in larger quantities is introduced. [ABSTRACT FROM AUTHOR]
- Published
- 1982
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7. Synthesis in the isocamphane series, XVI. The regioselectivity of some lewis acids in the catalyzed Diels-Alder-reaction of cyclopentadiene and mesityloxide.
- Author
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Bachner, Johann, Huber, Ulrike, and Buchbauer, Gerhard
- Abstract
Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 1981
- Full Text
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8. Zur Synthese von Norbornanonen mit geminaler Dimethylgruppe.
- Author
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Buchbauer, Gerhard and Dworan, Erich
- Abstract
The synthesis of gem-dimethylnorbornanones is described. One synthetic pathway after a Diels-Alder reaction involves the transformation of the nitro group into the oxo group with subsequent methylation into the geminal dimethyl product. A shorter way by [4+2]-cycloaddition of cyclopentadiene with a suitable dimethylated dienophile (e.g. 2-methyl-1-nitropropene) failed, probably by steric hindrance of the dienophile. 7-Oxanorbornanones, with a gem-dimethyl group could not be prepared. A second synthetic approach to gem-dimethylnorbornanones is opened by Lewis acid catalyzed rearrangement of cyclohexenylcarbaldehydes. [ABSTRACT FROM AUTHOR]
- Published
- 1980
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9. Synthese von Cyclodextrin-Polyrotaxanen mittels Diels-Alder-Reaktionen
- Author
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Hahn, Michael and Wenz, Gerhard
- Subjects
macromolecular chemistry ,cyclopentadiene ,Polyrotaxane ,Cyclopentadien ,Polyrotaxan ,Cyclodextrine ,cyclodextrin ,Diels-Alder-Reaktion ,ddc:540 ,Makromolekulare Chemie ,ddc:620 ,Diels-Alder reaction - Abstract
Die vorliegende Arbeit behandelt eine neuartige Synthese zur Darstellung von Polyrotaxanen, die mittels Diels-Alder-Reaktion abgestoppt werden. Die Polyrotaxane basieren auf modifiziertem Polyethylenglykol und α-Cyclodextrin. Das Polyethylenglykol wurde mit endständigen Cyclopentadien-Gruppen versehen, um bei der Abstoppreaktion des Pseudopolyrotaxans eine Diels-Alder-Reaktion zu ermöglichen. Für die Abstoppreaktion wurden Cyclopentadien, das Pseudopolyrotaxan selbst sowie zwei verschiedene RAFT-Polymere eingesetzt. Als RAFT-Polymere wurden Styrol-4-sulfonsäure-Natriumsalz bzw. N,N -Dimethylacrylamid eingesetzt, die in verschiedenen Polymerisationsgraden dargestellt wurden. Die RAFT-Polymere wurden mittels NMR-Spektroskopie, UV/Vis-Spektroskopie, Viskosimetrie und Gel-Permeations-Chromatographie analysiert. Alle drei Abstoppreaktionen wurden erfolgreich durchgeführt und führten zu verschiedenen Belegungsgraden an α-Cyclodextrin. Die Verwendung von monomerem Cyclopentadien erreicht den höchsten Belegungsgrad mit 35,0 %. Der Einsatz des Poly(Styrol-4-sulfonsäure)-Natriumsalzes verringert den Belegungsgrad auf 18,0 %. Des Weiteren wurde festgestellt, dass die Reaktion von mehreren Pseudopolyrotaxanen untereinander zu einem längeren Polyrotaxan immer auch als Nebenreaktion auftritt und so teilweise sehr große Polyrotaxane mit bis zu 14 Polyethylenglykol-Einheiten pro Molekül gebildet wurden. The present work deals with a novel synthesis for the preparation of polyrotaxanes, which are stopped by Diels-Alder-reaction. The polyrotaxanes are based on modified polyethylene glycol and α-Cyclodextrin. Polyethylene glycol was modified with cyclopentadiene groups at both ends, to allow stopping of pseudopolyrotaxanes via Diels-Alder-reaction. For this stopping reaction, cyclopentadiene, the pseudopolyrotaxane itself and two different RAFT polymers were used. As RAFT polymers styrene-4-sulfonic acid sodium salt or N,N -dimethylacrylamide were used, which have been synthesized in different degrees of polymerization. The RAFT-polymers were analyzed by NMR spectroscopy, UV/Vis spectroscopy, viscometry and gel permeation chromatography. All three stopping reactions were successfully carried out and resulted in various degrees of coverage of α-Cyclodextrin. The use of monomeric cyclopentadiene achieved the highest coverage at 35.0 %. The use of the RAFT polymer poly(styrene-4-sulfonic acid sodium salt) reduced the coverage to 18.0 %. Furthermore, it was found that the intermolecular reaction of two or more pseudopolyrotaxanes always occurs to form a longer polyrotaxane as a side reaction and therefore partially very large polyrotaxanes are formed that have up to 14 polyethylene glycol units per molecule.
- Published
- 2017
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10. Neue Synthesen durch Aktivierung tertiärer Carbonsäureamide mit Trifluormethansulfonsäureanhydrid
- Author
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Dettenrieder, Ralf
- Subjects
DDC 540 / Chemistry & allied sciences ,DDA-reaction ,trifluoromethanesulfonic anhydride (Tf2O) ,alkenediazonium triflates ,Trifluoroiodomethane ,bis(iminio)ether salts ,a-diazo acetoamides ,propiolic acid amides ,Trifluoromethanesulfonyloxy iminium salts ,Diels-Alder-Reaktion ,ddc:540 ,Dehydro-Diels-Alder-reaction ,Diels-Alder reaction ,Trifluormethansulfonsäure - Abstract
Treatment of propiolic acid amides with trifluoromethanesulfonic anhydride (Tf2O) leads to the formation of trifluoromethanesulfonyloxy iminium salts. These salts react with a further equivalent propiolic acid amide to bis(iminio)ether salts, which undergo a DDA-reaction. After hydrolysis 1-phenylnaphthalene-2,3-dicarboxamides were isolated in good yields. Treatment of alpha-diazo acetoamides with Tf2O leads to reactive alkenediazonium salts, which undergo an electrophilic aromatic substitution with electron-rich aromatics to form the corresponding iminium triflates.
- Published
- 2015
11. Thermoreversible networks based on cellulose derivatives
- Author
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Ax, Jennifer and Wenz, Gerhard
- Subjects
Diels-Alder-Reaktion ,ddc:540 ,Selbstheilung ,self-healing ,ddc:620 ,Cellulose ,Diels-Alder reaction - Abstract
Im Rahmen dieser Arbeit ist es gelungen eine umfangreiche Substanzbibliothek cellulosischer Diene anzulegen. Hierzu wurden Cellulose, Hydroxyethylcellulose und Hydroxypropylcellulose mit Furan-basierten Dienen umgesetzt und durch Variation der Reaktionsbedingungen der Substitutionsgrad an Dien-Substituenten eingestellt. Durch die Umsetzung der restlichen Hydroxygruppen des cellulosischen Rückgrats mit Säurechloriden, -anhydriden oder Isocyanaten wurde die Prozessierbarkeit des Polymers erhöht und dessen Eigenschaften, wie Löslichkeit, thermische Stabilität oder Beschaffenheit, beeinflusst. Als Vernetzer wurden organische Bismaleinimide mit unterschiedlichen Spacern gewählt und deren Reaktivität in Diels-Alder Reaktionen verglichen. Zudem ist es erstmals gelungen, cellulosische Dienophile zu synthetisieren. Zur Untersuchung der Netzwerkbildung bzw. -auflösung mittels Diels-Alder bzw. retro Diels-Alder Reaktion wurden UV-Spektroskopie, Rheologie und Nanoindentierung erfolgreich angewendet. Die Fähigkeit zur Selbstheilung dieser Systeme konnte anhand der thermischen Ausheilung eines zuvor zerbrochenen Formkörpers bewiesen werden. In the scope of this work, a substance library of cellulosic dienes was synthesized. For that purpose, cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose were reacted with furan-based dienes. By varying the conditions of these reactions the degree of substitution of the dienic functional group was modified. The remaining hydroxyl groups of the cellulosic backbone were reacted with acid chlorides, anhydrides or isocyanates in order to achieve a processable product. Furthermore, the properties of the polymer, like solubility, form or stability, can be influenced by this procedure. Organic bismaleimides with various spacers were chosen as cross-linkers and their reactivity in Diels-Alder reactions were compared to each other. Moreover, the synthesis of cellulosic dienophiles was developed. To monitor the cross-linking and the decoupling due to the Diels-Alder and the retro Diels-Alder reaction respectively UV spectroscopy, nano indentation and rheology were successfully applied. To confirm the self-healing ability of the systems, a sample pellet was broken and thermally re-mended by Diels-Alder and retro Diels-Alder reaction.
- Published
- 2014
- Full Text
- View/download PDF
12. Asymmetrische Diels-Alder-Reaktion zum Aufbau des AB-Ring-Bausteins und Synthese der ABEFG-Substruktur der Chinocycline
- Author
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Breuning, Marcel André and Koert, Ulrich (Prof. Dr.)
- Subjects
natural product synthesis ,unique heterocycle structue ,cyclization reaction ,Asymmetrische Synthese ,Esterdienophil ,Chemie ,Heterocyclische Verbindungen ,Naturstoffsynthese ,Asymmetric synthesis ,Chemistry and allied sciences -- Chemie ,Organische Synthese ,Diels-Alder-Reaktion ,Cyclisation ,ddc:540 ,einzigartige Heterocyclenstruktur ,Diels-Alder reaction ,ester dienophile ,2011 - Abstract
Obwohl die Chinocycline bereits in den 1950er-Jahren aus einem Bodenbakterium isoliert werden konnten, wurde bislang kein synthetischer Zugang zu diesen strukturell sehr interessanten Naturstoffen entwickelt. Ein Ziel dieser Arbeit war es, den AB-Ring-Baustein der Chinocycline über eine enantioselektive Diels-Alder-Reaktion aufzubauen. Hierfür wurde eine breite Zahl an unterschiedlichen Dienophilsubstraten getestet, wobei sich ein Esterdienophil als geeignetes Substrat erwies. Dieses Esterdienophil konnte in einer enantioselektiven, intramolekularen Diels-Alder-Reaktion mit einem CBS-Katalysator zum gewünschten [4+2]-Cycloadditionsprodukt und in drei weiteren Stufen zum benötigten AB-Ring-Baustein umgesetzt werden. Ein weiterer wichtiger Schwerpunkt dieser Arbeit war es, einen synthetischen Zugang zur einzigartigen EF-(Pyrrolopyrrol)-Ring-Struktur der Chinocycline zu entwickeln. Hierfür wurden unterschiedliche Lösungsansätze verfolgt, wobei der Versuch, den E-Ring als letzten gerüstbildenden Schritt zu schließen, nicht den erwünschten Erfolg zeigte. Aus diesem Grund wurde der F-Ring in einer weiterentwickelten Herangehensweise als letzter gerüstbildender Schritt geschlossen. Über den hierfür entwickelten synthetischen Zugang, ausgehend von einem lithiierten Iminoether und einem Lacton, konnte der E-Ring erfolgreich eingeführt werden. Die synthetisch anspruchsvolle Cyclisierungsreaktion zum Aufbau des F-Rings war über eine säurevermittelte Ringschlussreaktion möglich, wobei die erwünschte Zielstruktur in wenigen Stufen und in ausgezeichneten Ausbeuten erhalten werden konnte., Although the Quinocyclines were isolated in the 1950´s, a synthesis of these structurally very interesting compounds has not been reported yet. One goal of this work was to develop an enantioselective access to the AB-ring building block of the Quinocyclines via an asymmetric catalyzed Diels-Alder reaction. Different dienophiles and catalysts have been tested but an intermolecular approach did not deliver the desired product. Therefore, an intramolecular approach with an ester dienophile has been investigated. With the CBS-catalyst it was possible to conduct an intramolecular enantioselective Diels-Alder reaction and to obtain the desired lactone. This [4+2]-cycloaddition product has been converted into the AB ring building block in three steps and in good yields. The second goal of this PhD thesis was to find a synthetic access to the unique EF-(pyrrolopyrrole)-ring substructure of the Quinocyclines. Different approaches have been investigated but all cyclization conditions to close the E-ring as last step failed. Based on these results, it was reasonable to introduce the E-ring in an already activated form and to close the F-ring as the last step. The activated E-Ring was introduced via the reaction of a lithiated iminoether with a lactone. The synthesis of the unique heterocycle structure was possible via an acid catalyzed cyclization with a tosylated amidine as reactant. The EF-ring heterocycle structure could be synthesized in a few steps in very good yields.
- Published
- 2011
13. Synthese von Benzo[f]pyrido[2,1-a]isoindol-Heterocyclen durch Cycloisomerisierung von 2-Phenylethinyl-1-propargylpyridinium-Salzen
- Author
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Jäger, Ulrich
- Subjects
DDC 540 / Chemistry & allied sciences ,N-Propargylierung ,Isomerization ,Dehydro-Diels-Alder-Reaktion ,Cyclisation ,ddc:540 ,Pyridin ,Isoindol ,Diels-Alder reaction - Abstract
In dieser Arbeit wurde eine neue Synthese für Pyrido[2,1-a]isoindolium-Salze ausgearbeitet und zu einer präparativ wertvollen Methode optimiert. Im speziellen konnten dadurch Benzo[f]pyrido[2,1-a]isoindolium-Salze durch intramolekulare Dehydro-Diels-Alder-Reaktion aus N-Propargyl-substituierten Pyridinen dargestellt werden. Diese ließen sich quantitativ zu den neutralen Benzo[f]pyrido[2,1-a]isoindolen umsetzen, welche eindeutig identifiziert und NMR-spektroskopisch charakterisiert werden konnten. Diese hochreaktiven Spezies konnten wiederum mit Acetylencarbonsäureestern und anschließender Oxidation zu den neuartigen Benzo[f]indolizino[3,4,5-ab]isoindolen umgesetzt werden, welche durch ihre bemerkenswerten Fluoreszenzeigenschaften auffallen.
- Published
- 2006
14. Synthese enantiomerenreiner Polycyclen an einem chiralen Templat
- Author
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Wolter, Martina
- Subjects
Polycyclische Verbindungen ,Dewey Decimal Classification::500 | Naturwissenschaften::540 | Chemie ,indoloquinolizinones ,ddc:540 ,Asymmetrische Synthese ,Diels-Alder reaction ,Template-Effekt ,polycyclic cyclohexenones - Abstract
[no abstract]
- Published
- 2000
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15. Bis(pentamethylcyclopentadienyl)methanol: Synthese, Struktur und Derivatisierung
- Author
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Peter Jutzi, Hans-Georg Stammler, Tanja Lindermeier, Beate Neumann, and Andreas Mix
- Subjects
chemistry.chemical_classification ,Ketone ,Chloroformate ,Intramolecular reaction ,Alcohol ,Medicinal chemistry ,Adduct ,Inorganic Chemistry ,Tosylate ,intramolecular ,chemistry.chemical_compound ,Pentamethylbenzene ,bis(pentamethylcyclopentadienyl)methanol ,chemistry ,Pyridine ,Organic chemistry ,Methanol ,Diels-Alder reaction - Abstract
Bis(pentamethylcyclopentadienyl)methanol: Synthesis, Structure, and Derivatization Bis(pentamethylcyclopentadienyl) ketone (1) reacts at low temperatures with LiAlH4 to form in good yields (pentamethylcyclopentadienyl)methanol (2) and its corresponding intramolecular Diels-Alder product 3 in a ca. 2:1 ratio. The alcohol 2 is separated from the tetracyclic compound 3 by crystallisation at −70°C from hexane/pyridine as pyridine adduct. The pyridine-free alcohol 2 is available by repeated dissolving of the adduct in hexane and removal of the volatile components in vacuo. The alcohol tends to intramolecular [4 + 2] cycloaddition even at room temperature with formation of 3. A derivatization of 2 is possible by deprotonation with alkyllithium compounds, which leads to the alcoholate 4, and subsequent treatment with phosgen and tosyl chloride, thus affording the chloroformate 6 and the tosylate 7, respectively, in good yields. The thermolabile tosylate 7 decomposes to pentamethylbenzene or, under basic conditions, to the pentacyclic compound 7.
- Published
- 1994
16. Oxidationsreaktionen am 1-(3,3-Dimethyl-5-norbornen-2-yl)ethanon und ein neuer Zugang zuendo-konfigurierten Isocamphanderivaten: Synthesen in der Isocamphanreihe, 18. Mitt.
- Author
-
Buchbauer, Gerhard, Vitek, Renate, Hirsch, Margit C., Kurz, Christina, Cech, Barbara, and Vas, Eva Maria
- Published
- 1982
- Full Text
- View/download PDF
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