Two groups that can be easily eliminated by cycloreversion, N2 and CO2, are present in 1, the primary adduct of the title reaction. 1 could be isolated in crystalline form. Elimination of nitrogen affords a γ-ketoketene, the subsequent reactions of which indicate that it exists in equilibrium with a dihydropyrylium-2-olate.
Abstract Die Konkurrenz von Dipolarophilen‐Paaren um Benzonitriloxid,. In situ aus Benzohydroximoylchlorid ( 4 ) freigesetzt, ergab die sich über 4 Zehnerpotenzen erstreckenden relativen Additionskonstanten von 39 Dipolarophilen. Benzonitriloxid gehört zu den 1,3‐Dipolen, die sowohl mit elektronen‐armen als auch mit elektronen‐reichen Mehrfachbindungen rascher reagieren als mit gewöhnlichen Alkenen und Alkinen. Die Kombination mit den bekannten Orientierungsverhältnissen erbrachte partielle Geschwindigkeitskonstanten der beiden Additionsrichtungen. Die Additivität der Substituenten‐Beiträge zur freien Aktivierungsenergie ist nur näherungsweise erfüllt. — Die spezifische Dipolarophilen‐Skala des Benzonitriloxids sowie die Orientierungsphänomene werden im Lichte neuer MO‐störungstheoretischer Behandlungen von Sustmann und Houk diskutiert. Die Aktivitätssequenz wird mit denjenigen des Diphenylnitrilimins und des N ‐Methyl‐ C ‐phenylnitrons verglichen.
Abstract Die Reaktion von Tetrachlordiazocyclopentadien mit Benzvalen ( 2 ) ergab das Fulven‐Derivat 3 . Dagegen führten die Umsetzungen von Diazofluoren und 5‐Diazo‐10,11‐dihydro‐5 H ‐dibenzo‐[ a , d ]cyclohepten mit 2 zu den erwarteten Spiro‐1‐pyrazolinen 4 bzw. 5 . Die photolytische Abspaltung von Stickstoff aus 4 und 5 lieferte die Spirotetracycloheptane 6 bzw. 7 . Die Röntgenstrukturanalyse von 6 beweist einen engen Kontakt zwischen je einem Wasserstoffatom der Tetracycloheptan‐ und der Fluoren‐Einheit. Dieser kurze Abstand (2.15 Å) ruft Winkelaufweitungen hervor und wird auch als Grund für starke Entschirmungen der betreffenden Protonen und eine formal über sieben Bindungen reichende 0.6‐Hz‐Kopplung zwischen ihnen angesehene. 7 ist das erste chirale Tetracycloheptan. Ursache dafür ist eine nichtebene Konformation des Siebenrings, der bei Raumtemperatur nicht invertiert. Auf der Basis von NOE‐Messungen gelang die Zuordnung der 1 H‐NMR‐Signale von 6 und 7 .
Electrophilic Additions to the Bicyclo[1.1.0]butane System of Tricyclo[4.1.0.0 2,7 ]heptane Derivatives: Halogen Electrophiles The known reactions of 8,8‐dibromotetracyclo[5.1.0.0 2,4 .0 3,5 ]octane ( 3a ) and homobenzvalene ( 7 ) with pyridinium bromide perbromide and iodine, respectively, were carried out in the presence of tetra‐ n ‐butylammonium chloride. The formation of the chloro‐substituted norpinane derivatives 6a and 9 is evidence for cationic intermediates. The same mechanism is operative in the reaction of pyridinium bromide perbromide with the dichlorotetracyclooctane 3b , which was prepared from 7 and dichlorocarbene. On exposure of tricyclo[4.1.0.0 2,7 ]heptane ( 1 ) to N ‐bromosuccinimide in acetone/water/triethylamine, the bromonorpinanol 22 , the bromonorcaranols 23 , and cyclohex‐1‐ene‐1‐carboxaldehyde ( 24 ) were obtained. On the basis of the steric course and thermodynamic considerations, the cationic intermediates generated in the above reactions by attack of the electrophiles at the bicyclobutane systems are assigned the halonium ion structure 38 and the nonclassical structures 34 and 35 , respectively. Elemental bromine and iodine converted the phenyltricycloheptane 10 into the respective diastereomeric norpinanes 11 and 12 , which were transformed smoothly into the diastereomeric methyl ethers 13 and 14 by treatment with sodium methoxide in methanol. The reactions of 10 with pyridinium bromide perbromide in pyridine, cyanogen bromide in the presence of aluminium trichloride, and N ‐bromosuccinimide in acetone/water gave rise to norpinane derivatives, i.e. the pyridinium salt 15 , the nitrile 16 , and the alcohol 18 , respectively. In the case of cyanogen iodide in acetonitrile, the solvent participated in the process to yield the 2‐(norpinylimino)propionitriles 17 . Corresponding to the configurations of the products, the attack of a halogen electrophile at 10 leads to classical 6‐phenyl‐6‐norpinyl cations 41 , which may be approached by nucleophiles from the two possible faces. As origin for the low tendency of the cations 33–35 and 41 to rearrange to norcaryl cations, the electronegativity of the halogen atoms is suggested. The reduced migratory aptitude of a CHHal relative to a CH 2 group results from its electron deficiency and from the decreased stability of 7‐halo‐2‐norcaryl relative to the parent 2‐norcaryl cations. The chlorophenyltricycloheptane 25 was prepared from 10 and treated with aqueous sulfuric acid to give the norpinanol 27 . Formed by protonation of the bicyclobutane system of 25 , the cationic precursor of 27 shows a behaviour similar to that of cations 41 .
Aus Bicyclo[2.1.1]hexan‐2‐on hergestelltes 2‐Lithiobicyclo[2.1.1]hexen ist die Schlüsselverbindung für die effiziente Synthese interessanter Bicyclo[2.1.1]‐hexan‐Derivate, z. B. 1–3 . Bemerkenswert ist die Reaktivität von 3 , das gegenüber Olefinen, z. B. Tetracyanethylen, eher als 2π‐ denn als 4π‐Elektronensystem wirkt. Darüber hinaus zeigen die neuen Verbindungen ungewöhnliche 13 C‐NMR‐Spektren. magnified image
Abstract Benzonitriloxid (I), das in situ aus Benzohydroximoylchlorid durch Einrühren in Triäthylamin gewonnen wird, reagiert mit den monosubstituierten Äthylene (II) zu den Isoxazolen (III).
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbon-13 nuclear magnetic resonance spectra of 7-heterotetracyclo[4.1.0.02,4.03,5]heptanes. Annelation effects of aziridine, oxirane, and thiirane rings. Unusual .gamma. and .delta. substituent effectsManfred Christl, Hartmut Leininger, and Erich BrunnCite this: J. Org. Chem. 1982, 47, 4, 661–666Publication Date (Print):February 1, 1982Publication History Published online1 May 2002Published inissue 1 February 1982https://doi.org/10.1021/jo00343a012RIGHTS & PERMISSIONSArticle Views45Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (703 KB) Get e-Alerts Get e-Alerts
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.
