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A very important example of a [3,3] sigmatropic reaction is the Claisen rearrangement of an allyl aryl ether or an allyl vinyl ether (Section 18-4). Heating an allyl aryl ether to 250 o C causes an sigmatropic rearrangement to produce an o -allylphenol.
Two other important sigmatropic reactions are the Claisen rearrangement of either an allyl aryl ether (H 𝟐 C═CHCH 𝟐 ─O─Ar) or an allyl vinyl (H 𝟐 C═CHCH 𝟐 ─O─CH═CH 𝟐) ether, and the Cope rearrangement of a 1,5 hexadiene to an isomeric 1,5-diene. These two rearrangements, along with the Diels–Alder reaction, are ...
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.
Sigmatropic rearrangements are intramolecular reactions involving the migration of a sigma bond across a pi system. Examples include hydrogen atoms migrating across dienes upon heating (some even do this spontaneously at room temperature) and hydrogen atoms migrating across alkenes with light.
Sep 25, 2024 · This section covers sigmatropic rearrangements, a type of pericyclic reaction where sigma bonds break and reform while the molecular structure rearranges. The examples illustrate the mechanisms and …
Sigmatropic reactions often have transition-metal catalysts that form intermediates in analogous reactions. The most well-known of the sigmatropic rearrangements are the [3,3] Cope rearrangement, Claisen rearrangement, Carroll rearrangement, and the Fischer indole synthesis.
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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 \(\pi\) electron system from one position to another.
