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Jan 23, 2023 · Molecular rearrangements in which a σ-bonded atom or group, flanked by one or more π-electron systems, shifts to a new location with a corresponding reorganization of the π-bonds are called sigmatropic reactions. The total number of σ-bonds and π-bonds remain unchanged. These rearrangements are described by two numbers set in brackets ...
- Stereochemical Notations
Cycloaddition reactions and sigmatropic rearrangements both...
- Cope
The Cope rearrangement, not to be confused with the Cope...
- Ene Reactions
Contributors; The joining of a double or triple bond to an...
- Claisen Rearrangement
Mechanism; The Claisen rearrangement, not to be confused...
- Allene
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- William Reusch
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- Stereochemical Notations
All of the sigmatropic rearrangements that we have seen so far are reactions of neutral molecules. That is the case for most sigmatropic rearrangements, but charged molecules also participate in these transformations. The Wittig rearrangement is an anionic [2,3] sigmatropic rearrangement of an allylic ether to yield a homoallylic alcohol.
Sigmatropic reaction. In organic chemistry, a sigmatropic reaction (from Greek τρόπος (trópos) 'turn') is a pericyclic reaction wherein the net result is one sigma bond (σ-bond) is changed to another σ-bond in an intramolecular reaction. [1] In this type of rearrangement reaction, a substituent moves from one part of a π-system to ...
Sep 25, 2024 · A sigmatropic rearrangement, the third general kind of pericyclic reaction, is a process in which a σ -bonded substituent atom or group migrates across a π π electron system from one position to another. A σ bond is broken in the reactant, the π π bonds move, and a new σ bond is formed in the product. The σ -bonded group can be either ...
A sigmatropic rearrangement, the third general kind of pericyclic reaction, is a process in which a σ -bonded substituent atom or group migrates across a π electron system from one position to another. A σ bond is broken in the reactant, the π bonds move, and a new σ bond is formed in the product. The σ -bonded group can be either at the ...
Because a [1,5] sigmatropic rearrangement involves three electron pairs (two π bonds and one σ bond), the orbital-symmetry rules in Table 30.3 predict a suprafacial reaction. In fact, the [1,5] suprafacial shift of a hydrogen atom across two double bonds of a π system is a commonly observed sigmatropic rearrangements. For example, 5-methyl-1 ...
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Apr 22, 2023 · Sigmatropic rearrangement, a class of concerted pericyclic reactions, is controlled by orbital symmetry. During this rearrangement, a group connected by a sigma (σ) bond moves to the terminal of the neighboring pi (π)electron system. During the reaction, a σ bond appears to shift from one location to another and hence is called a sigmatropic ...
