Eu(FOD)3 induced shifts of alkyl substituted adamantanones and molecular geometries of the adducts
作者:Douglas J. Raber、Christopher M. Janks、Joop A. Peters
DOI:10.1016/s0040-4020(01)87662-6
日期:1986.1
The geometries of adducts of europium tris(fod) and a series of alkyl substituted adamantanones have been determined with the use of lanthanide induced 1H shift measurements. The position of the Eu(III) cation relative to the substrateligand appears to be strongly dependent upon steric interactions between the fodligands and the alkyl groups in the substrate. The alkyl substitution causes distortions
Electrostatic vs Hyperconjugative Effects as Stereoinductive Factors in the Adamantane Ring System
作者:William Adcock、Jason Cotton、Neil A. Trout
DOI:10.1021/jo00086a044
日期:1994.4
A series of 5-substituted (X) adamant-2-yl derivatives 1 (Y = O and CH2) have been synthesized and their C-13 NMR spectra measured. The carbonyl and ethylenic C-13 substituent chemical shifts (SCS) are shown to be proportional to substituent field effects (sigma(F)). By use of the polar field susceptibility parameter (rho(F)) for the former shifts, polar field parameters (Delta sigma(F) values) have been calculated for a series of p-SC6H4 substituents. II-Facial diastereoselectivities for the reduction (NaBH4) and methylation (MeLi) of para-substituted (S) phenyl derivatives of 1 (Y = O; X = p-SC6H4) and, as well, for the hydrochlorination of similarly substituted alkenes 1 (Y = CH2; X = p-SC6H4) have been determined and correlated successfully against polar field parameters (Delta sigma(F) values). The slopes of these plots (log(10)[Z]/[E] vs Delta sigma(F)) provide polar-field susceptibility parameters (rho(FS)) which have been deployed to calculate appropriate diastereoselectivities of the aforementioned reactions for 5-substituted (X) derivatives of 1 (Y = O and CH2) in general. A comparison of these calculated values with observed diastereoselectivities for a wide range of substituents reveals that direct electrostatic field interactions play a dominant role in governing the phenomena for nucleophilic additions of the ketones 1 (Y = O) and that it is unnecessary to invoke Cieplak's transition-state hyperconjugative model. This appears to be also the case for electrophilic additions to 1 (Y = CH2) not involving final nucleophilic capture of an intermediate cation. However, hyperconjugation clearly impinges significantly on II-facial diastereoselectivity for those reactions mediated by 2-adamantyl cations. New results for methyl-substituted derivatives of 1 (Y = O and CH2, X = CH3) reinforces the sigma-electron-withdrawing character of this substituent with respect to gamma- and delta-interactions in the neutral ground-state and cationic species.
Geluk,H.W.; Schlatmann,J.L.M.A., Recueil des Travaux Chimiques des Pays-Bas, 1969, vol. 88, p. 13 - 16
作者:Geluk,H.W.、Schlatmann,J.L.M.A.
DOI:——
日期:——
2<i>H</i>-Azirines from a Concerted Addition of Alkylcarbenes to Nitrile Groups
作者:Wolfgang Knoll、Jean-Luc Mieusset、Vladimir B. Arion、Lothar Brecker、Udo H. Brinker
DOI:10.1021/ol100703r
日期:2010.5.21
Photolysis of aziadamantanos in the presence of fumoronitrile (FN) unexpectedly afforded conjugated 2H-azirines resulting from addition of the carbene to the CN triple bond. This represents the first example of a direct azirine formation starting from an alkylcarbene for which a concerted pathway is postulated. The novel outcome if the reaction is favored by the prior formation of a carbene-alkene complex, a type of adduct that only recently has been described.