Oxidative decarboxylation of the 3-methyl-2-carboxynorbornanes with lead tetraacetate

. The ionic addition of molecular bromine to tetracycl0[3.2.0.O'~~.O~~~]heptane (quadricyclene) has been investigated in a variety of solvent systems. Depending upon the nature of the solvent, three or more of six dibromo and five solvent-incorporated adducts are isolable. A mechanism involving a series of ion-pairs and competitive edge-on vs. corner (end-on) attack is proposed. DENNIS G. GARRATI. Can. J. Chem. 58, 1327 (1980). On a etudie I'addition ionique du brome moleculaire sur le tetra~~cl0[3.2.0.0z7.0".~]heptane (quadricyclkne) dans plusieurs systemes de solvants. Dependant de la nature du solvant, on a pu isoler un minimum de 3 de 6 adduits dibromks et de 5 adduits lncorporant le solvant. On propose un mecanisme impliquant une sene de paires d'ions et des attaques competitives par le c6tC ou par le sommet (end-on).[ terms of an exo bromine atom, 3a (2,4). Br COOH COOHThe results, while indicative of apparently 3a 36stereospecific inversion of configuration at carbon during both electrophilic cleavage and subsequent nucleophilic attack, contrast with other reports (5) of more varied stereochemical pathways. For example, Skell and co-workers (6) have reported the ionic bromination of dehydroadamantane, 4, in the presence of isoamyl nitrite to give a 59:41 mixture of the isomeric 2,6-dibromoadamantanes, 5 and 6. They argued that since all aspects of ionic brominations of cyclopropanes point to formation of a 1-bromo-3-carbonium ion, it is reasonable to attribute to the second step, the reaction with bromide ion, the proportioning between axial and equatorial approach. An alternative rationalization of their data, however, would be a competitive attack by bromine, both from the edge and the corner, followed by stereospecific attack by bromide ion with inversion of configuration at carbon.In their detailed mechanism, Skell and co-

Section: Resultscontrasting

confidence: 78%

Electrophilic cleavage of cyclopropanes. III. The reaction of molecular bromine with tetracyclo[3.2.0.0^2,7.0^4,6]heptane^1,2

Garratt¹

1980

“…-CH(C6H& 9 C(CH3)?. This is attributable to a 6 deshielding effect by these substituents, an effect that has been observed previously for hydroxyl substituents and attributed, at least in part, to steric interaction (32,33). Since y-gauche substituents produce upfield shifts and sterically interacting 6 substituents produce small downfield shifts, the shielding effect of a gauche tert-butyl group is expected to be less than that of a gauche methyl group (34), as observed.…”

Section: C Nuclear Magnetic Resonance Spectrasupporting

confidence: 68%

Aliphatic diazo compounds. XIV. The synthesis of 7-substituted 3-diazo-2-norbornanones and the infrared and proton and carbon-13 nuclear magnetic resonance spectra of these diazo ketones and their precursors

Yates¹,

Kronis²

1984

. 62, 1751 (1984).syn-and anti-7-lsopropyl-2-norbornanone (5 and 6) were prepared by catalytic hydrogenation of 7-isopropylidene-2-norbornanone; syri-and anti-7-benzhydryl-2-norbornane (9 and 10) were prepared in analogous fashion. Kctones 5 and 6 and syrl-and arlti-7-tert-butyl-2-norbornanone (7 and 8) were converted to the corresponding 3-diazo-2-norbornanones 1-4 via the monotosylhydrazones 44-47 of the corresponding a-diketones 40-43. The 'H and "C nmr spcctra of 1-10,40-47, and thcir precursors have been analyzed. The 'H nmr spectra of the diazo ketones 1-4 have their C-I and C-4 bridgehead proton signals shifted to higher and lower field, respectively, relative to the bridgehead signals of thc corresponding dikctones. Thc "C nmr spectra of all pairs of bicyclic epimers shown y-garrche shielding effects by the 7-substitucnt at (sp3) C-3 in thc syrl compounds and at C-5 and C-6 in the arlti compounds. A converse effect is found at (sp') C-2 (and C-3 in the diketoncs). Comparison of the magnitude of the shielding effects of C-7 methyl, isopropyl, benzhydryl, and tert-butyl substituents gives evidence of 6 deshielding effects at C-3 in the syrl compounds and at C-5 and C-6 in thc onti compounds by methyl substitucnts on C-8.PETER YATES et JOHN DAVID KRONIS. Can. J. Chem. 62, 1751 (1984.On a prCparC Ics isopropyl-7 norbornanones-2 syrl et anti (5 et 6) par hydrogenation catalytique de I'isopropylidene-7 norbornanone-2; on a prCparC les benzhydryl-7 norbornanones-2 syrl et nrlti (9 et 10) d'unc manikre semblablc. On a transform6 les cCtones 5 et 6 ainsi que les tert-butyl-7 norbornanones-2 sytl et anti (7 et 8) en leurs diazo-3 norbornanones-2 correspondantes (1-4) par le biais des monotosylhydrazones 44-47 des a-dicCtones correspondantes 40-43. On a analysC les spectrcs rmn du ' H et du "C des composCs 1-10 et 40-47 et de leurs prCcurseurs. Dans les spectres rmn du 'H des diazocCtones 1-4, les signaux des protons en tCte de pont (C-l et C-4) sont dCplacCs respectivcment vers des champs plus haut et plus bas, par rapport aux signaux des protons dans les positions Cquivalentes des dicttones correspondantes. Les spectrcs rmn du '.'c de chacune des paires d'Cpimkres bicycliques prtsentent tous des effets de blindage y-gauche, dus aux substituants en position 7 et affectant la position C-3 (sp3) des composCs syrl et les positions C-5 et C-6 dcs composts anti. On observe un effet inverse au niveau de C-2 (sp') (et de C-3 dans les dicttones). Une comparaison de I'amplitude dcs cffets de blindage provoquCs par les substituants mCthyle, isopropyle, benzhydrylc et tert-butyle en C-7 suggkre que les substituants mCthyles cn C-8 provoquent des effets de dtblindage 6 en C-3 dans les composCs syn et en C-5 et C-6 dans les composCs anti.[Traduit par le journal]In connection with our studies on the acid-catalyzed decomposition of a-diazo ketones (1, 2), we required pairs of 3-diazo-2-norbornanones with bulky syt7-and anti-7 substituents. We describe here the synthesis of the diazo ketones 1-4, prepared for this purpose, and di...

“…Des blindages de cette nature ont dtja Ct C relevCs pour des cCtones cyclohexaniques (31). Le carbone C, en position 6 par rapport a l'oxygene du groupement carbonyle est blind6 de 2.1 ppm, ce qui est cohkrent avec ce que l'on observe en serie bicyclooctanique oh des blindages sont notCs pour des carbones situts en position 6 par rapport B l'oxygene d'un groupement C=O (13,15).…”

Section: Autres Effets Observksunclassified

“…En particulier les dtplacements chimiques B champ fort de rarbones situts en y de groupes mtthyles et tclipsts par ceux-ci sont dus des interactions steriques (4). L'influence du groupe hydroxyle a t t t ttudite dans les systkmes bicycliques conformationnellement fixes (strie bicyclo[2.2.1]-heptanique ou -[2.2.2]octanique, strie de l'adamantane) ou peu flexibles (strie bicyclo[3.2.1 Ioctanique) (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Dans des series de dtcalols (17) et de sttroides (17,18), l'influence du groupe OH sur les carbones en y et en 6 de ce substituant a aussi t t t ttudite; des effets y de -3.3 B -7.3 ppm ont pu ainsi Etre mis en tvidence.…”

Section: Introductionunclassified

Résonance magnétique nucléaire du carbone-13 de composes oxa- et azabicyclo[3.3.1]- et -[4.2.1]nonaniques

Barrelle¹,

Apparu²,

Gey³

1978

.l]nonan-2-ols, provide supplementary inforniation regarding the previously studied structures of these types. Shielding and deshielding due to y and 6 steric interactions wereobserved depending on the substituent. The study of the oxabicyclo[4.2.1]nonanes, substituted or not substituted in positions 2 and 7 by hydroxyl groups, and of the azabicyclo[4.2.1]-nonanes substituted in position 2 by the same group, yields interesting results on the conformational equilibria in these compounds which is caused by the flexibility of the sevenmembered ring. The conformational equilibrium is displaced toward the boat form of the seven-membered ring for the unsubstituted compounds. Goirche conformations are proposed for the other compounds in order to account for the experimental observations; the pure chair and boat forms are excluded. Two ketones also have been studied.[Journal translation] Introduction Les effets de substituants sur les dtplacements chimiques en rmn du 13C ont t t t trts ttudits et peuvent apporter d'importants renseignements d'ordre sttrtochimique (1-3). En particulier les dtplacements