Abstract:The decomposition of tricyclo[3.2.2.02~4]nonane-6-diazonium ions 20 ( e m ) and 22 (endo) has been studied to elucidate the effect of neighbouring cyclopropyl in deamination reactions. In contrast to the solvolysis of the corresponding sulfonate 49 no products indicating participation of the cyclopropane ring were obtained from 20. Direct displacement with retention of configuration was the major reaction of 20 whereas Wagner-Meerwein rearrangement predominated with 22. The endo-configuration of the major prod… Show more
“…Capture of this cation anti to the C9Br gives 2 . The stereochemistry of nucleophilic attack reflects either the orientation of the vacant p orbital at C5 and/or electronic or steric interaction of the incoming nucleophile with the C9 bromine substituent 1 Reaction of 1 with bromine in CCl 4 attack of Br + anti to the cyclopropane. 2 Reaction of 1 with bromine in CCl 4 attack of Br + syn to the cyclopropane. …”
In carbon tetrachloride reaction of 1 with bromine occurs at the double bond and is favored from the less hindered face, anti to the cyclopropane ring, to give 2 and 3 (2:1) over reaction from the syn face or at the corner of the cyclopropane to give 5. In the solvent methanol, corner attack of bromine at the cycloproane to give 30, 16, 17, and 37 competes with reaction at the double bond anti to the cyclopropane to give 18, 19, and 2.
“…Capture of this cation anti to the C9Br gives 2 . The stereochemistry of nucleophilic attack reflects either the orientation of the vacant p orbital at C5 and/or electronic or steric interaction of the incoming nucleophile with the C9 bromine substituent 1 Reaction of 1 with bromine in CCl 4 attack of Br + anti to the cyclopropane. 2 Reaction of 1 with bromine in CCl 4 attack of Br + syn to the cyclopropane. …”
In carbon tetrachloride reaction of 1 with bromine occurs at the double bond and is favored from the less hindered face, anti to the cyclopropane ring, to give 2 and 3 (2:1) over reaction from the syn face or at the corner of the cyclopropane to give 5. In the solvent methanol, corner attack of bromine at the cycloproane to give 30, 16, 17, and 37 competes with reaction at the double bond anti to the cyclopropane to give 18, 19, and 2.
Eingegangen a m 13. Mirz 1974 Die Addition aliphatischer Diazoverbindungen an Carbonylgruppen 2 ) (GI. 1) ist eine Reaktion, die zur Kettenverllngerung und Ringerweiterung3) haufig prapardtiv genutzt wird. Die Umkehrung dieser Reaktion wird in der Literatur selten diskutiert4). Wir berichten hier iiber ein Beispiel, bei dem die Retroaldol-Spaltung durch die Ringspannung des P-Oxidoalkandiazonium-Ions unterstiitzt wird.
Die Addition von Sauren an Bicyclo[5.1.0]octa-2,4-diene kann unter Umlagerung zu Bicyclo-[3.2.l]oct-2-enen verlaufen. Ein Donor-Substituent an C-8 ist Voraussetzung fur diese Umwandlung, wie aus der abnehmenden Tendenz von 1 (NHCOCH3), 19 (OCH3) und 33 (H) zur Bildung von Bicyclo[3.2. Iloctenen hervorgeht. In einer konkurrierendem Reaktion entstehen Cycloheptadienylmethyl-Derivate. Unabhangig von der Konfiguration des Ausgangsmaterials (19a. b) werden 4-exo-8-anti-substituierte Bicyclo[3.2.l]oct-2-ene erhalten. Die Konfigurationen wurden durch NMR und eindeutige Synthese von 25 festgelegt. Die Reaktion beginnt wahrscheinlich mit der Protolyse des Cyclopropanrings zum Homoallylkation 36, das zu 38 cyclisiert (formal eine 1.4-Verschiebung). Rearrangement of Bicyclo[S. l.Olocta-l,4diene Derivatives by Acids The addition of acids to bicyclo[5.1.0]octa-2,4-dienes may proceed with rearrangement to bicyclo-[3.2.l]oct-2-enes. A donor substituent at C-8 is essential for this transformation, as shown by the decreasing tendency of 1 (NHCOCH3), 19 (OCH,), and 33 (H) to form bicyclo[3.2.l]octenes. Cycloheptadienylmethyl derivatives are formed in a competing reaction. Regardless of the configuration of the starting material (19s, b), 4-exo-8-anti-substituted bicyclo[3.2.l]oct-2-enes are obtained. Configurations were established by n. m. r. and by unequivocal synthesis of 25. The reaction is thought to involve protolysis of the cyclopropane ring to a homoallyl cation 36 which undergoes cyclization to 38 (formally a 1.4 shift). Kohlenstoffverschiebungen der Ordnung [I l.j] haben theoretische und synthetische Bedeutung 'I. Besonders griindlich wurden thermische Umlagerungen studiert; einige dieser Untersuchungen stieDen auf die Grenzen des Orbitalsymmetrie-Prinzips und fuhrten zur Entwicklung neuer Konzepte 'I. Bei Carbokationen fand man neben zahllosen 1.2-Verschiebungen bisher nur wenige Umlagerungen hoherer Ordnung ''. Die vorliegende Arbeit behandelt ein Beispiel dieses Reaktionstyps. 1970 fanden Liisberg und Hurter3', daB die Addition von Chlorwasserstoff an N-(Bicyclo[5.1.0]octa-2.4-dien-8-exo-yl)acetamid (1) unter Umlagerung verlauft. Das HCI-11 I d R. B. Woodward und R. Hofmann, Die Erhaltung der Orbitalsymmetrie, Kap. 7, Verlag Chemie, Weinheim 1970. -Ib) G. Maier, Valenzisomerisierungen, S . 64-73, Verlag Chemie, Weinheim 1972. -N. i'kony Ank, Die Woodward-Hoffmann-Regeln und ihre Anwendung, Kap. 5, Verlag Chemie, Weinheim 1972. J . A. B e r m und L. Salem, J. Amer. Chem. SOC. 94,891 7 (1 972); J. A. Berson, Acc. Chem. Res. 5, 406 (1972). -2b) Wu.E.Doering und K . Sachdeu, J. Amer. Chem. SOC. 96, 1168 (1974).
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