A definitive investigation of the reaction of cyclopentadiene with cis-3,4-dichlorocyclobutene: A literature correction (original) (raw)
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Tetrahedron, 1999
Vinylcyclobutanol 7, gmexated via the ~nglct oxyganation of alkylidanecyclobutene 5, rearranges at room ~ to a solvent dependent irdxtur¢ of isomeric dicmme$10 zvl 11. Alkylidvnccyclobutane 5 was prepared in turn via an inverse Witdg addition of the isopmpyl ylids to cyciobutenone 4; in a normal addition of ketone to ylide, vinylalle~e 12 is also obtained. Finally, the corresponding WiUig reaction of 4,4-dichlorecyclobulenone 3 yields only the 2,4-dichloro isomer 13. When this reaction is carried in the presence of n-butoxide, dienone 32 is generated.
Organometallics, 1994
Two results argue against a diradical intermediate in the exchange of diosmacyclobutanes with free olefins. The diosmacyclobutane Osz(CO)&-propene) reacts with vinylcyclopropane to give as the sole product a diosmacyclobutane bearing an intact cyclopropane ring. Repeated exchange of truns-ethylene-l,Z-d2 with the same ligand in a diosmacyclobutane shows > 99.1% stereochemical excess per exchange half-life. These exchange reactions do not involve mononuclear olefin complexes. (4) (a) Bowry, V. W.; Lusztyk, J.; Ingold, K. U. (11) The assessment of stereochemistry in these compounds, and the determination of their structure, by 'H NMR in nematic phase solvents will be reported separately: Bender, B. R.; Hembre, R. T.; Norton, J. R. Manuscript in preparation. (12) (a) Golike, R. C.; Mills, I. M.; Person, W. B.; Crawford, B., Jr.
The Journal of Organic Chemistry, 1977
Aromatics: Diels-Alder Reactions of Bicyclic Dimethoxycyclobu tenes Summary: Photochemical cycloaddition of alkoxyolefins to enol acetates of 0-diketones and 0-chloroenones proceeds readily to afford the cyclobutane or derived cyclobutene. These substances, on thermolysis in the presence of a dienophile, readily eliminate the elements of mineral acid or acetic acid and/or undergo conrotatory opening to the butadiene followed by Diels-Alder reaction. This process provides a facile entry into certain polycyclic aromatic systems and highly substituted benzene derivatives. Sir: The use of photochemical cycloadditions to produce substituted cyclobutanes is well documented.'P2 We became interested in the utility of this process as a general route to substances which might serve as stable, thermal precursors of alkoxy-substituted butadienes by in situ conrotatory opening of a cyclobcltene (eq l).3 This route would provide
The stereochemistry of diels-alder reactions of cyclopropenes
Tetrahedron Letters, 1987
The stereochemistry of the Diels-Alder reactions of 3 cyclopropenes was determined unequivocally by X-ray and NOE studies. Tetrachlorocyclopropene yields exo-adducts with (r)-l-R-1,3-butadiene (R=OCH3, OCOCH3, OSiMe), with 1,4_diphenylbutadieKand with furan. 1,2-bromochlorocyclopropene yields with (E)-?-R-butadienes (R=OCH3, OSiMe) endo:exo-adducts in a ratio of 9:l. Cyclopropene + 1-methoxyFutadiene yield only the endo-ad-2 uct. The Uiels-Alder (DA) reaction is the most important method for formation of six-membered rings and it has been extensively studied.* Recently, special attention has been devoted to the study of the stereochemistry and the mechanism of this reaction.2b*c
Journal of Organic Chemistry, 1996
Polycyclic dienes having an exocyclic 1-bromobutadiene moiety react with dienophiles and fullerene-C 60 to afford exclusively dienes via a cycloaddition-elimination mechanism. Neither the primary adducts nor the double addition products derived from a second cycloaddition of the dienophile to the diene could be detected. In one case only, i.e. with 4-phenyl-1,2,4-triazoline-3,5-dione, was the double addition product formed. Contrary to expectations, X-ray diffractometric analysis shows that this adduct is formed following a contrasteric approach. † Author to whom inquiries concerning the X-ray structure analysis should be directed.
Canadian Journal of Chemistry, 1988
Model studies for a general intramolecular Diels-Alder approach to the tricyclo[6.3.0.0'~6]undecene~keleton common to the capnellene marine sesquiterpenes are described. Suitably functionalized cyclopentadiene systems 14 and 21 were synthesized and their cycloaddition reactivity examined. Triene 1 4 cyclized to the tricyclic adducts 15 and 16. In contrast, the anticipated product 22 from intramolecular cycloaddition of triene 21 was not formed in isolatable yield. Instead the minor adduct (10% yield) possessed an exocyclic double bond and was assigned structure 30 based on its relative stability, as determined by MM2 type calculations, and nuclear magnetic resonance data. X-ray analysis established that the major adduct (40% yield) was a tetracyclic[6.3.1 .0'~6.0'.'o]dodecene system corresponding to 32, and which arose from competitive isomerization of the initial diene and cyclization via an e.ro transition state. JOCELYNE HELLOU, GERVAIS B~R u B~, MICHAEL J. NEWLANDS, ALEX G. FALLIS, et ERIC J. GABE. Can. J. Chem. 66, 439 (1988). On dtcrit des Ctudes modkles effectukes dans le but de dCterminer I'utilitt des rCactions de Diels-Alder intramolCculaires comme mCthode gCnCrale de synthCtiser le squelette du tricyclo[6.3.0.0'~6]undCctne qui est commun aux sesquiterpknes marins du capnelltne. On a synthCtisC les systtmes cyclopentadiCniques 14 et 21 substituCs d'une f a~o n approprite et on a examine leur rCactivitC vis-a-vis la cycloaddition. Le tritne 14 se cyclise pour donner les produits tricycliques 15 et 16. Par opposition, le produit 22 qui devrait se former par cycloaddition intramolCculaire du tritne 21 n'a pu &tre isolC. I1 se forme plut6t un adduit mineur (rendement de 10%) qui posskde une double liaison exocyclique et on lui a attribuC la structure 30 en se basant sur des donnCes de rCsonance magnttique nuclCaire et sur sa stabilitC relative telle que dCterminCe par des calculs du type MM2. Une Ctude par diffraction des rayons-X a permis d'Ctablir que le produit principal (rendement de 40%) est un systkme tCtracyclo[6.3.1.0'~~,0'~~~]dodCctne correspondant au composC 32 qui se forme par une isomCrisation compttitive du dikne initial et d'une cyclisation via un Ctat de transition exo.
The Journal of Organic Chemistry, 1986
Chlorophenylcyclobutanone 11, prepared by chlorophenylketene addition to cyclohexene, reacts readily with simple and hindered carboxylic acids in a cine substitution to produce keto esters 14. The acyloxy and phenyl substituents in 14c are shown by X-ray diffraction to be cis oriented; nevertheless 14 reacts with NaOMe at 20 O C by an unusual ester-ether interchange to produce 15 and the released carboxylate RC02-. These reactions apparently proceed via an oxyallyl cation intermediate. The behaviors of related cyclobutanones 4, 6, and 11 with methoxide are contrasted.
The reaction of norbornadiene with cyclopentadiene affords a good yield of 1,4,4a,5,8,8a-hexahpdro-1,4,5,8-exo-endodimethanonaphthalene, whose configuration was established through semihydrogenation followed by degradation to dicarboxylic acids of known structure, and through complete hydrogenation to the known saturated tetracyclic hydrocarbon. Oxidation of hexahydrodimethanonaphthalene furnished cis-bicyclo[3.3.0]octane-cis,cis,trans,trans-2,4,6,8-tetracarbo~~~~c acid.
Helvetica Chimica Acta, 1981
The preparations of 1-acetylvinyl arenecarboxylates H2C=C (COCH,)OCOR with R = phenyl, p-nitrophenyl, 2,4-dinitrophenyl, u-and P-naphthyl are described (3). The Diels-A Ider reactivity of these dienophiles toward cyclopentadiene is evaluated and compared with that of methyl vinylketone, 3-trimethylsilyloxy-, 3-ethoxy-and 3-acetoxy-3-buten-2-ones. The stereoselectivity of the cycloadditions of these dienophiles with 2,3,5,6-tetramethylidene-7-oxanorbornane (1) and 5,sdimethoxy-l,4-epoxy-2,3-dimethylidene-I, 2,3,4-tetrahydroanthracene (2) is studied. In principle, the dienophiles 3 allow direct functionalization of the position C(9) of the A-ring of daunomycinone analogs by Diels-Alder additions to exocyclic dienes such as 1 and 2. Introduction.-Anthracyclinones are aglycones of very important antibiotics and anti-tumor drugs [l]. They can be prepared readily [2] [3] by two successive 3a-i R' 1 2a R1=R2=OCH3 R = a Me3Si f 2,4-(NO2)2-C6H3CO h RI=R2=H b Et g a-naphthyl-CO c R1=OCH3, R2=H c CH3CO h 8-naphthyl-CO d C~H S C O i CH3 e 4-(N02)-C6HdCO j H Diels-Alder additions [4] to 2,3,5,6-tetramethylidene-7-oxanorbornane (1) [5]. The A-ring of daunomycinone (4) [6] bears a hydroxy group at C(9), adjacent to the carbonyl function of the side-chain. This OH group can be introduced, in principle I)