Search results
1 RearrangementReactions. 1. Rearrangement ReactionsA rearrangement reaction is a board class of organic reactions in which an atom, ion, group of atoms, or chemical unit migrates from one atom to another atom in the same or different species, resulting in a structural isomer o.
- 2MB
- 68
The Baeyer-Villager Oxidation/Rearrangement O O O O RH O O R1 R2 O R1 R2 O OO O R Criegee intermediate O R1O R2+ O OR Alkyl group that migrates does so with retention of configuration More electron-rich (most substituted) alkyl group migrates in preference Mechanism: RO3H For a review, see: M. Renz, B. Meunier, Eur. J. Org. Chem. 1999, 737.
- 961KB
- 45
- 8.1 Types of Rearrangements
- 8.2 Rearrangement to Electron Deficient Carbon
- Features of this migration
- Isobornyl chloride
- Examples:
- 8.3.2 Curtius Rearrangement
- 8.3.4 Beckmann Rearrangement
- 8.4.1 Baeyer Villiger Reaction
- 8.5 Rearrangement to Electron-Rich Carbon
- A number of rearrangements occur in aromatic compounds of the type:
- 8.6.1 Intermolecular Migration from Nitrogen to Carbon
- 8.6.1.2 N-Alkyl-N-nitrosoanilines (Fisher-Hepp Rearrangement)
- 8.6.2 Fries Rearrangement
Rearrangements are divided into intramolecular and intermolecular processes. In intramolecular process, the group that migrates is not completely detached from the system in which rearrangement is taking place. In contrast, in intermolecular process, the migrating group is first detached and later re-attached at another site.
These reactions are classified according to the nature of group that migrates.
The carbocation may be produced by a variety of ways. Hydrogen can also migrate in this system. X Me Me Me Me heat Me + HX Aryl groups have a greater migratory aptitude than alkyl group or hydrogen due to the formation of lower-energy bridged phenonium ion. Me Me Cl Me H Me H Phenonium ion Me Me -H Me Me Rearrangements in bicyclic systems are com...
The rearrangement is stereosepecific Two or more rearrangements may take place simultaneously. Me Me Me H H H Me H Me
Me Me Me H Me Me OAc Me Me Me Me Me Me HO H Me H Me Me H Me Me Me Me HO Me Me -Amyrin
This rearrangement describes the transformation of acyl azide into isocyanate by decomposition on heating and its application for the synthesis of primary amines, urethanes and ureas as presented in Hofmann rearrangement. Cl
Oximes rearranges in acidic conditions to give amides. The reaction is intramolecular and stereospecific: the substituent trans to the leaving groups migrates. R' R O
Treatment of ketones with peroxyacid gives ester. The reaction is effective with acid or base and the mechanism is closely related to pinacol rearrangement: nucleophilic attack by the peroxyacid on the carbonyl group gives an intermediate that rearranges with the expulsion of the anion of the acid.
This group of reaction has been less explored, and is less of synthetic importance compared to the rearrangements to electron deficient carbons. The rearrangements to electron deficient hetero atom may be generally explained as:
Y X XH Y XH + Y X is usually nitrogen or oxygen. Both intermolecular and intramolecular migrations are known.
Aniline derivatives readily proceed rearrangement on treatment with acid. First, the formation of conjugate acid of the amine takes place which then eliminates the electrophilic species that reacts at the activated ortho or para position of the aromatic ring. Treatment of N-chloroacetanilide with hydrochloric acid affords a mixture of ortho and par...
The conjugate acid of the amine releases nitrosonium ion which reacts at para-position to give the p-nitroso product. Me N H Me N Me H N O N -NO Me H N NO -H N=O : NO H R H N NO R H -H ON ON intramolecular transfer of NO NHR R N .. H + NO
Aryl esters with Lewis acid undergo rearrangement to give phenols having keto substituent at ortho and para positions. The complex between the ester and Lewis acid gives an acylium ion which reacts at the ortho and para positions as in Friedel-Crafts acylation. O Lewis acid Protic workup R OH or OH R O In general, low temperature favors the forma...
Dec 30, 2022 · (A) rearrangement of α chain and (B) β chain (C) protein structure of TCR. The enzyme that produces this diversity is a complex called the V(D)J recombinase. The recombination occurs in two parts: first double-stranded breaks are made at re- combination signal sequence (RSS) sites, then the breaks are repaired by the general double-stranded break repair mechanism.
a [3,3]-sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl. Discovered in 1912, the Claisen rearrangement is the first recorded example of a [3,3]-sigmatropic rearrangement. Many reviews have been written. Mechanism The Claisen rearrangement is an exothermic, concerted (bond cleavage and recombination) pericyclic reaction.
Jun 14, 2022 · Structural chromosomal rearrangements result from different mechanisms of formation, usually related to certain genomic architectural features that may lead to genetic instability. Most of these rearrangements arise from recombination, repair, or replication mechanisms that occur after a double-strand break or the stalling/breakage of a replication fork. Here, we review the mechanisms of ...
People also ask
How do structural rearrangements occur?
What is a rearrangement reaction?
What causes chromosomal rearrangement?
What are structural chromosomal rearrangements?
What is a 1 2 rearrangement?
What is Beckmann rearrangement?
The study of rearrangement mechanisms obviously benefits from the development of new techniques to observe the rearrangements and breakpoints with a higher resolution. In the past, fluorescence in situ hybridization (FISH) has defined the duplications and deletions with resolution to about one BAC clone (150 to 200 kb) and accelerated the discovery of NAHR and NHEJ mechanisms.
