The effect of strain on reactivity: poor leaving groups increase strain-induced inhibition of alkene-forming elimination
作者:Luca Volta、Charles J. M. Stirling
DOI:10.1039/a807506i
日期:——
Elimination to form a carbon–carbon double bond exocyclic to a cyclopropane ring is inhibited by factors which increase from 1.4 to 104.5 as the leaving group becomes poorer; strain induced in the transition structure can amount to some 50% of the enthalpy difference between strained and unstrained products.
Reactivities of Methylenetriangulanes and Spirocyclopropanated Bicyclopropylidenes toward Bromine. Relative Stabilities of Spirocyclopropanated versus Methyl-Substituted Bromonium Ions
作者:Sergei Kozhushkov、Thomas Späth、Torsten Fiebig、Bernard Galland、Marie-Francoise Ruasse、Prince Xavier、Yitzhak Apeloig、Armin de Meijere
DOI:10.1021/jo0162686
日期:2002.6.1
rings enhances the rate of bromination and stabilizes the intermediate cyclopropyl bromonium cations against ring opening in the course of bromine addition. Calculations at the B3LYP/6-311G(d,p) level show that unsymmetrical bromoniumions are the intermediates, and that they are stabilized by the spiroannelation with cyclopropane rings. The bromoniumion derived from 1 is less stable by 6.3 kcal mol-1