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The Cope rearrangement is the prototypical example of a concerted sigmatropic rearrangement. It is classified as a [3,3]-sigmatropic rearrangement with the Woodward–Hoffmann symbol [π 2 s + σ 2 s + π 2 s] and is therefore thermally allowed.
[11] [12] [13] This rearrangement is a useful carbon-carbon bond-forming reaction. An example of Claisen rearrangement is the [3,3] rearrangement of an allyl vinyl ether, which upon heating yields a γ,δ-unsaturated carbonyl. The formation of a carbonyl group makes this reaction, unlike other sigmatropic rearrangements, inherently irreversible.
The reverse or retro-Cope elimination has been reported, in which an N,N-disubstituted hydroxylamine reacts with an alkene to form a tertiary N-oxide. [ 9 ] [ 10 ] The reaction is a form of hydroamination and can be extended to the use of unsubstituted hydroxylamine, in which case oximes are produced.
The aza-Cope rearrangements are predicted by the Woodward-Hoffman rules to proceed suprafacially. However, while never explicitly studied, Overman and coworkers have hypothesized that, as with the base-catalyzed oxy-Cope rearrangement, the charged atom distorts the sigmatropic rearrangement from a purely concerted reaction mechanism (as expected in the Cope rearrangement), to one with partial ...
In organic chemistry, the oxy-Cope rearrangement is a chemical reaction. It involves reorganization of the skeleton of certain unsaturated alcohols. It is a variation of the Cope rearrangement in which 1,5-dien-3-ols are converted to unsaturated carbonyl compounds by a mechanism typical for such a [3,3]-sigmatropic rearrangement. [1] [2]
The cis isomer exclusively yields cis,trans-hexa-2,4-diene whereas the trans isomer gives the trans,trans diene: [2] This reaction course can be explained in a simple analysis through the frontier-orbital method : the sigma bond in the reactant will open in such a way that the resulting p-orbitals will have the same symmetry as the HOMO of the ...
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The divinylcyclopropane-cycloheptadiene rearrangement is an organic chemical transformation that involves the isomerization of a 1,2-divinylcyclopropane into a cycloheptadiene or -triene. It is conceptually related to the Cope rearrangement , but has the advantage of a strong thermodynamic driving force due to the release of ring strain.