Carbon-13-proton coupling constants in carbocations. 7. Application of the .DELTA.J equation to polycyclic systems including bicyclo[2.2.1]hept-2-yl cations

Kelly, David P.; Aherne, Kathryn; Delgado, Florencio; Giansiracusa, J. J.; Jensen, Wendy A.; Karavokiros, K.; Mantello, R. A.; Reum, Monica E.

doi:10.1021/ja00078a044

Cited by 10 publications

(4 citation statements)

References 2 publications

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“…The 3,4,4-trisubstituted β-lactone 17 , based on the adamantylidene skeleton, showed only a modest solvent dependence (Table , entries 7 and 8), reflecting the greater degree of substitution of the intermediate cation than that derived from the acyclic counterpart 11 (Table , entries 5 and 6). The higher degree of substitution in the adamantylidene system provides additional stabilization to any intermediate cation and shields it to a greater extent from the surrounding medium, thereby reducing dependence on solvent polarity, consistent with earlier work documenting the lack of solvent participation in the solvolysis of 2-adamantanyl derivatives and with the greater stability of the 2-adamantanyl cations than simple tertiary aliphatic carbenium ions. − Interestingly, however, a significant solvent dependence returned with the tetrasubstituted system 20 , which is nevertheless based on the adamantylidene framework (Table , entries 9 and 10) to which we return below.…”

Section: Resultssupporting

confidence: 84%

Chemistry of the β-Thiolactones: Substituent and Solvent Effects on Thermal Decomposition and Comparison with the β-Lactones.

2014

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The synthesis of a series of di-, tri-, and tetraalkyl β-thiolactones and β-lactones is described as well as their thermal decomposition with extrusion of carbon oxysulfide and carbon dioxide in two solvents of opposite polarities. The β-thiolactones are considerably more thermally stable than the β-lactones and require higher temperatures for efficient decomposition in both solvents, whatever the degree of substitution. The results are interpreted in terms of a zwitterionic mechanism for fragmentation with a change in the rate-determining step between the two series.

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Section: Resultssupporting

confidence: 84%

Chemistry of the β-Thiolactones: Substituent and Solvent Effects on Thermal Decomposition and Comparison with the β-Lactones.

2014

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“…Double hyperconjugation is facilitated by pyramidal distortion of the reaction center. The latter effect in 2-adamantyl cations was first proposed on the basis of NMR data, and there is accumulating experimental ,4a, and theoretical 8b, evidence to corroborate the idea. Thirdly, the diastereoselectivities for the σ-electron donor groups (Tables and ) are markedly suppressed compared to the stereochemical outcome of reactions mediated by the corresponding metalloidal substituted secondary 2-adamantyl cations ( 1 , R = H). 2a,4a Furthermore, the marked propensity of the latter tin species ( 1 , R = H and X = SnMe 3 ) to undergo fragmentation 2a,4a is effectively “tamed” by the presence of the methoxy group at C2.…”

Section: Resultsmentioning

confidence: 85%

Diastereofacial Selectivity in Reactions of 5-Substituted (X) Adamant-2-yl Cations: Manifestations of Electron Demand

et al. 1997

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A series of 5-substituted (X) 2,2-dimethoxyadamantanes (4, X ) F, Cl, Br, COOCH 3 , OCH 3 , CH 3 , C 6 H 5 , p-NO 2 C 6 H 4 , p-BrC 6 H 4 , SiMe 3 , and SnMe 3 ) as well as 2-methylene-5-tert-butyladamantane (6, Y ) CH 2 ; X ) C(CH 3 ) 3 ) have been synthesized and characterized. Reduction of the ketals 4 under ionic conditions with triethylsilane and phenylsilane provide π-facial diastereoselectivities for hydride trapping of 5-substituted (X) 2-methoxyadamant-2-yl cations (1, R ) OCH 3 T 5). A comparison of this data with known diastereoselectivities for nucleophilic capture of tertiary and secondary 5-substituted (X) 2-adamantyl cations highlights that stereoselectivity in these systems is a function of electron demand. Diastereoselectivities for the hydrochlorination of 6 (Y ) CH 2 , X ) C(CH 3 ) 3 ) in CH 2 Cl 2 and NO 2 CH 3 have been determined and compared with the corresponding data for the silicon analogue (6, Y ) CH 2 ; X ) SiMe 3 ). Low electron demand coupled with the stereoelectronic requirement of double hyperconjugation appears the most likely explanation, rather than a long-range steric factor, for the total lack of stereoselectivity in the Clcapture of the 2-methyl-5-(trimethylsilyl)adamant-2-yl cation (1, Y ) CH 2 ; X ) SiMe 3 ) in NO 2 CH 3 as solvent.

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“…First, the SbCl 5 -complexed 5-phenyl-2-adamantanone is distorted according to a X-ray structure analysis by Laube . Secondly, there are mounting evidence that the tertiary carbocation 6 is pyramidalized …”

Section: Resultsmentioning

confidence: 99%

Distortion in the Structures of 5-Azaadamantanone and Its N-Oxide: Implication on Diastereofacial Selectivity

Gung

Wolf

1996

J. Org. Chem.

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Ab initio molecular orbital studies of adamantanone (1), 5-azaadamantanone (2), and 5-azaadamantanone N-oxide (3) show that 2 and 3 have distorted structures. The torsional angle τ OCCRC in the C 2v symmetric adamantanone 1 is 120.6°. τ OCCRC is 124.0°in the piperidinedione ring of 3 and 117.8°in the cyclohexanone ring of 3, indicating a significant distortion. The corresponding values for 2 are 122.5°and 120.3°indicating a slightly distorted structure. These structural results are consistent with the previously observed π-facial selectivity in NaBH 4 reduction of 2 and 3, but contradict with the suggestion that they are symmetrical.

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Carbon-13-proton coupling constants in carbocations. 7. Application of the .DELTA.J equation to polycyclic systems including bicyclo[2.2.1]hept-2-yl cations

Cited by 10 publications

References 2 publications

Chemistry of the β-Thiolactones: Substituent and Solvent Effects on Thermal Decomposition and Comparison with the β-Lactones.

Chemistry of the β-Thiolactones: Substituent and Solvent Effects on Thermal Decomposition and Comparison with the β-Lactones.

Diastereofacial Selectivity in Reactions of 5-Substituted (X) Adamant-2-yl Cations: Manifestations of Electron Demand

Distortion in the Structures of 5-Azaadamantanone and Its N-Oxide: Implication on Diastereofacial Selectivity

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