The Bicyclo[2.2.2]octyl Carbene System as a Probe for Migratory Aptitudes of Hydrogen to Carbenic Centers
作者:Xavier Creary、Mark A. Butchko
DOI:10.1021/ja002407+
日期:2001.2.1
A series of tosylhydrazone derivatives of exo-6-substituted bicylo[2.2.2]octan-2-ones have been prepared. Thermal decomposition of the sodiumsalts of these tosylhydrazones gives carbene-derived products from 1,3-migration of either the C6 hydrogen (perturbed) or the C7 hydrogen (unperturbed), along with smaller amounts of alkenes derived from 1,2-hydrogen migration. The exo-6-substituent strongly
Inductivity and Bridging in 2-Bicyclo[2.2.2]octyl Cations. Polar Effects, Part 11
作者:Cyril A. Grob、Pawel Sawlewicz
DOI:10.1002/hlca.19840670729
日期:1984.11.7
(ρI = 0.78), probably, because in the former case bridging of C(6) is less hindered by the departing anion. The relative yields of exo- and endo-substitution products from the series 12 and 13, are in accord with graded bridging of C(6) in the incipient bicyclooctyl cations. But almost constant bridging of C(2) by C(7) is indicated in the ionization of the 2-endo-bicyclooctane series 13. Consequently
溶剂分解速率和若干6-取代的2-产品外切-和2-内型-双环[2.2.2]辛基p -toluenesulfonates,12和13分别被报道。电感,如由反应常数ρ测量余,是在相当少的外切-系列12(ρ我= -1.50)中比在相应的2-外型-norbornyl p -toluenesulfonates 1(ρ我= -2.0)。建议,出于几何原因,在双环辛烷系列12中,阳离子中心C(2)与C(6)的桥接不那么强。就像降冰片系列一样1。在另一方面,电感是在2-更高内二环辛烷系列13(ρ我= -1.0)中比在相应的2-内型-norbornane系列3(ρ我= 0.78),可能是,因为在前者的情况下桥接C(6)的原子被离去阴离子的阻碍较小。从系列12和13的exo-和内取代产物的相对产量与C(6)在初始双环辛基阳离子中的分级桥连相一致。但是在2-内膜的电离中表明了C(7)与C(2)几乎恒定的桥接-双环
The influence of captodative effect on the dienophilicity of olefins. The easy diels-alder reaction of α-methylthioacrylonitrile with cyclohexadiene
作者:Jean-Luc Boucher、Lucien Stella
DOI:10.1016/s0040-4039(01)80848-0
日期:1985.1
We show that the cycloaddition of α-methylthioacrylonitrile to cyclohexadiene is faster than that of acrylonitrile. This indicates that the captodative substitution exerts an accelerating effect on the Diels-Alder reaction despite the larger steric bulk of the methylthio group compared to hydrogen.
Evidence for 2-hexene-1,6-diyl diradicals accompanying the concerted Diels-Alder cycloaddition of acrylonitrile with nonpolar 1,3-dienes
作者:Yufei Li、Anne Buyle Padias、H. K. Hall
DOI:10.1021/jo00077a025
日期:1993.12
The spontaneous reactions of a series of alkyl 1,3-dienes with acrylonitrile (AN) were investigated. Reproducible spontaneous copolymerizations were shown to compete with the expected concerted [4 + 2] cycloadditions. For dienes which exist in s-cis/s-trans equilibrium, both copolymer and cycloadduct are formed. Kinetic measurements show that the alternating copolymerization and cycloaddition are two independent parallel second order reactions. With 1,3-cyclohexadiene and 1,2-dimethylenecyclohexane, for which s-gauche is in equilibrium with s-cis, copolymerization still competes with cycloaddition. The s-trans-locked verbenene forms only copolymer, while s-cis-locked cyclopentadiene and 1,2-dimethylenecyclopentane form only cycloadduct rapidly. Our explanation involves a 2-hexene- 1,6-diradical, formed by combination between the terminal carbons of the s-gauche or s-trans diene and acrylonitrile. This does not cyclize but initiates copolymerization. Competitively s-cis conformer undergoes classical concerted [4 + 2] addition.
Alder et al., Chemische Berichte, 1958, vol. 91, p. 1516,1523