Wagner–Meerwein rearrangement

A Wagner–Meerwein rearrangement is a class of carbocation 1,2-rearrangement reactions in which a hydrogen, alkyl or aryl group migrates from one carbon to a neighboring carbon.{{cite journal|author=Vagner, Ye. Ye. (Wagner, G.) | author-link = Igor Igorevich Wagner | author-link = Hans Meerwein

Several reviews have been published.

The rearrangement was first discovered in bicyclic terpenes for example the conversion of isoborneol to camphene:

The story of the rearrangement reveals that many scientists were puzzled with this and related reactions and its close relationship to the discovery of carbocations as intermediates.

In a simple demonstration reaction of 1,4-dimethoxybenzene with either 2-methyl-2-butanol or 3-methyl-2-butanol in sulfuric acid and acetic acid yields the same disubstituted product, the latter via a hydride shift of the cationic intermediate: :[[File:Carbocation rearrangement polito 2010.svg|Carbocation rearrangement Polito 2010]]

Currently, there are works relating to the use of skeletal rearrangement in the synthesis of bridged azaheterocycles. These data are summarized in

:[[File:Wagner-Meerwein heterocyclic.png|Some examples of Wagner-Meerwein rearrangement in heterocyclic series|950px]]

Plausible mechanisms of the Wagner–Meerwein rearrangement of diepoxyisoindoles:

The related Nametkin rearrangement, named after Sergey Namyotkin, involves the rearrangement of methyl groups in certain terpenes. In some cases the reaction type is also called a retropinacol rearrangement (see pinacol rearrangement).