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Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (5) with benzvalene (4), norbornene, and norbornadiene afforded the azo compounds 7 and 8. Theseare derivatives of 2,3-diazabicyclo[2.2.2]oct-2-ene as is azo compound 3, which had been obtained previously from 5 and 2 equiv of benzvalene (4). The photochemical extrusion of nitrogen from 3, 7, and 8 has been studied. Whereas 7 and 8 on direct irradiation in benzene gave rise exclusively to the bicyclo[2.2.0]hexane derivatives 9 and 10, respectively, from 3 in addition to the bicyclo[2.2.0]hexane 11, the diolefin 1l was formed. Diolefin 12 has cisdouble bonds in the nine-membered ring and is fixed in a boat conformation in a manner so that the two bicyclobutane systems approach each other very closely. This geometry suggests the unusual ring opening of the intermediate 1,4-cyclohexanediyl diradical from a boat conformation, which arises by inversion of the primarily generated boat conformation. Sensitized photolysis of 3 as weilasthat of ll produced the saturated isomer 13 of 11 and 12. The proximity of the bicyclobutane systems in 1l causes unprecedented reactions leading to cage compounds. When ll was heated at 90 °C, a rearrangement to the pentacyclic product 10 took place. Utilization of tetradeuteriated substrate ll-d4 supported a pathway with two diradical intermediates. Behaving in a convcntional manncr, bicyclobutane 9 and bis(bicyclobutane) 11 took up 1 and 2 equiv of thiophenol most probably in a radical-chain addition to give the thioethers 28 and 19, respectively. In contrast, bis(bicyclobutane) ll was converted by 1 equiv of thiophenol into cagc compound 30 in a process involving both the strained a systems. Heating at 80 °C subjected 30 to a reversible Copc rearrangement, resulting in a 6:1 mixture of 31 and 30. When it was treated with bromine, 11 was transformed to cage compound 38. This addition is believed to proceed via a cationic intermediate. The structure of cage compound 10 was established by a singlc-crystal X-ray analysis of dialcohol 11 prepared from 20 and methyllithium.
Das bekannte 6-0xo-2,5-diphenyl-6H-l,3,4-oxadiazin (1 a) und die neuen 2,5-Diarylderivate 1 b - g lagern Alkene an, und es entstehen stickstofIfreie Produkte. Im Falle von Cyclopropenen und Cyclobuten bilden sich die a,p-ungesättigten Siebenring-Enollactone 42 -45 bzw. das a,ß-ungesättigte Achtring-Enollacton 47. 42a und d erleiden an basischem Aluminiumoxid die H-Verschiebung zu den ß,y-ungesättigten Siebenring-Enollactonen 46a bzw. d. Bei weiteren Olefinen wurden die 'Y-Ketoketene des Typs 33 als Zwischenprodukte nachgewiesen oder sind aufgrund der Konstitution der Endprodukte wahrscheinlich. Aus 1 a werden mit Norbomen, Norbornadien, Cyc1openten, trans-Cycloocten und Styrol die Sechsring-Enollactone 10, 13, 15, 19 bzw. 21 und 22 erhalten. 10 isomerisiert mit Kalium-tert-butoxid zu 34, und die Methanolyse dieser Enollactone erbringt die diastereomeren Methy]ester 12 bzw. 35. Das y-Ketoketen 16 aus trans-Cycloocten nimmt schneller Wasser und Methanol zu 17 bzw. 18 auf als es zum Enollacton 19 cyclisiert. cis,trans-l,5-Cyc1ooctadien erbringt über die Stufe des nachgewiesenen y-Ketoketens 40 in einer intramolekularen [2 + 2J-Cyc1oaddition den Tricyclus 41. Tetracyclische Verbindungen des Typs 4 gehen aus der Umsetzung von Benzvalen (2) mit 1 hervor. Durch Röntgenstrukturanalysen wurden Konstitution und Konfiguration von 10, 19 und 41 aufgeklärt
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Phenyl(tricyclo[4.1.0.0\^(^{2,7}\)] hept-4-en-3-yl)sulfone 8 has been prepared in two steps from 4,S-dlbromohomobenzvalene (6) and deprotonated to give the title compound 9. The carbon-13 NMR spectrum of 9 reveals a considerable interaction between the allyl anion moiety and the bicyclobutane system.
Das exo/endo--lsomerenverhältnis Ja: Jb bei der bekannten [2 + 2]-Cycloaddition von Styrol an 1,2-Cyclohexadien (2) wurde als tempcraturabhingiaaefunden. Der Einsatz von (Z)-Dcutcriostyrollicfene den Beweis der Zweistufiakeit dieser Reaktion, und das Diradikal 4 wird als wahrscheinlichste Zwischenstufe anaesehen. Erhitzen von Jb auf 140-170°C führte zur Binstellung des thermodynamischen Gleichgewichts mit Ja (Ja:3b = 93:7), wobei wieder das Diradikal4 als Zwischenstufe fungieren dürfte. Mit Hilfe kinetischer Messungen ermittelte man die Aktivierungsparameter für das System Ja~ 3b. - Aus 2 und den Abfangreagenzien p-Methoxystyrol, 1,1-Diphenylethylen sowie 1-Phenylpropen gingen mit bescheidenen Ausbeuten die Titelverbindungen 6a, b, 7 bzw. 8 hervor. Analoa zu 2 wurde sein l-Methylderivat 13 aus 6,6-Dibrom-1-methylbicyclo[3.1.0]hexan (9) durch Methyllithium freigesetzt. In Gegenwart von Styrol entstand neben den Abfanaprodukten 14a, b auch das Dimere 12 von lJ. - Die 1H-NMR-Spektren der Titelverbindungen belegen eine starre Halbsesselkonformation des Cyclohexentcils mit äquatorial anellienem Cyclobutanring.
Abstraction of an allylic hydrogen atom in homobenzvalene (4) either in solurion by photolyticaßy generated tert-butoxyl radicals or in an adamantane matrix by X-rays produces the homobcnzvalenyl radical (5). which tbennally rearranps · to tbe tropylium ndical (1). In solution tbe activation cnergy for the rate determined step of the reaction sequence was detennined· to be 13.4 ± O.S kcal/mol.
The 1-oxoketenes, which are accessible from methyl 1,3,4-oxadiazin-6-one-2-carboxyIate 1 and cycloalkenes, are shown to undergo an intramolecular [2+2] cycloaddition either on heating or on photolysis to give different sterecisemers of ß-lactones of the 3-oxo-2-oxabicyclo[ 2.2.0]hexane-type.
The γ-oxoketenes, which are formed from oxadiazinone Ja and strained cyclopentene der1vat1ves, are shown to undergo a pericyclic ring enlargement to give the title compounds 2a, 2b, and 5. In the case of 5, two configurations, one having a cis and the other a trans Iactone functionality, are in equilibrium.
4-Bromoctavalen und zwei (Brommethylen)homobenzvalene anstelle eines erwarteten Bromoctabisvalens
(1988)
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By means of the BC NMR spectra of tricyclo{2.2.0~rfJ6Jhexane and thirteen of its derivatives the effects of substituents in endo-3- and endo-5-positions on the HC chemical shifts have been determined. The y-anti effects are at least as Jarge as in monosubstituted cyc1obutanes, where the shielding values of second-row hetero substituents exceed those in unstrained systems by far, and higher-row and carbon substituents still cause substantial upfield shifts. In the title system the y-anti effect of a substituent in the endo-3- and endo-5-position are operative additively, and thus shift the absorption of C-J upfieJd by a maximum of 27 ppm with respect to the unsubstituted hydrocarbon.
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The 130 chemical shifts were determined of the carbons in 12 cycloheptanes, 21 cycloheptanols, and 8 cycloheptanones. In some cyc1oheptanols and cyc1oheptanones, the assignments have been obtained unambiguously by the synthesis of deuterated derivatives and the use of paramagnetic-shift reagents. Substituent effects for the different types of groups have been calculated. The most informative data about the cyc10heptane conformations were provided by the relatively well understood I' effects. The results are generally in,good agreement with predictions based on the twist-chair form, which has been predicted by Hendrickson to be the most stable conformation. Pairs of cis-trans isomers are found to have rather characteristic differences in their 130 spectra. This fact was used to assign the resonances found for cis-trans mixtures of methyl-substituted cyc1oheptanols to specific isomers.
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7-Azatetracyclo[4.1.0.0<sup>2,4</sup>.0<sup>3,5</sup>]heptan - ein neues Valenzisomeres des Azepins
(1979)
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Cycloaddition an Benzvalen
(1973)
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