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.

2023年1月23日 · 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 …

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.

Sigmatropic Rearrangements 1. Introduction - A class of concerted pericyclic reactions governed by orbital symmetry. - One bond is being broken while another bond is being formed across a π system. - Migrating group remains the same face with the system: suprafacial. Migrating group moves to opposite face of the system: antarafacial.

Sigmatropic rearrangements can occur on one face of the molecule (think top or bottom, like a syn addition to an alkene) which is called a suprafacial reaction or from one face to the other (think from top to bottom or vice versa, like an anti addition to an alkene) which is called antarafacial.

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.

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-1,3- cyclopentadiene rapidly rearranges at room temperature to yield a mixture of 1-methyl-, 2- …

2022年1月31日 · In a sigmatropic reaction a σ bond 'migrates' across a conjugated system to a new site. If ' [n, m] sigmatropic rearrangement' has n = 1, then one end of the bond that moves remains attached to its original atom — the n refers to the fact that the other end of the bond migrates across n atoms.

2023年4月22日 · 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.

2024年9月25日 · 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.