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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 ...
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The Cope rearrangement, not to be confused with the Cope...
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Mechanism; The Claisen rearrangement, not to be confused...
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- William Reusch
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- Stereochemical Notations
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 ...
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.
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 ...
2. [1,2] Sigmatropic rearrangement: Often initialized by the formation of a reactive intermediate such as a carbocation or a carbanion to form a more stable intermediate. Many name reactions involve a [1,2] shift such as Wagner-Meerwein, Beckmann, or Stevens rearrangement. -Wagner-Meerwein rearrangement in bicyclic terpenes
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Sigmatropic Rearrangement s can also result in degenerate rearrangements of structures such as homotropilidene (47, Figure 11.50 ). 69 Perhaps the most dramatic example of a Sigmatropic Rearrangement is provided by tricyclo[3.3.2.0 4, 6 ]deca-2,7,9-triene (48, Figure 11.51 ), more commonly known by the trivial name
