View source for Wagner–Meerwein rearrangement

{{Short description|Organic reaction}}
A '''Wagner–Meerwein rearrangement''' is a class of [[carbocation]] [[1,2-rearrangement]] [[rearrangement reaction|reaction]]s in which a [[hydrogen]], [[alkyl]] or [[aryl]] group migrates from one carbon to a neighboring carbon.<ref name=wagner99>{{cite journal|author=Vagner, Ye. Ye. (Wagner, G.)
| title = In "Protokol zasedaniya Otdeleniya Khimii R. F. Khimicheskago Obshchestva. 9-go sentyabrya 1899 goda [Minutes of the meeting of the Chemistry Section of the Russian Physical-Chemical Society. 9th September 1899]"
| journal = J. Russ. Phys. Chem. Soc. [Zh. Russ. Fiz.-Khim. O-va.]
| year =1899
| volume =31
| pages =680–684
| author-link = Igor Igorevich Wagner
| url = https://babel.hathitrust.org/cgi/pt?id=uc1.$b625259&view=1up&seq=732}}</ref>
<ref name=meerwein14>{{cite journal| author = Hans Meerwein
| title = Über den Reaktionsmechanismus der Umwandlung von Borneol in Camphen; [Dritte Mitteilung über Pinakolinumlagerungen.]
| journal = [[Justus Liebig's Annalen der Chemie]]
| year =1914
| volume =405
| pages =129–175
| author-link = Hans Meerwein
| doi = 10.1002/jlac.19144050202| issue = 2
| url = https://zenodo.org/record/1427621
}}</ref>  They can be described as [[cationic]] [1,2]-[[sigmatropic]] rearrangements, proceeding suprafacially and with [[stereochemical]] retention.  As such, a Wagner–Meerwein shift is a thermally allowed [[pericyclic]] process with the Woodward-Hoffmann symbol [<sub>ω</sub>0<sub>s</sub> + <sub>σ</sub>2<sub>s</sub>].  They are usually facile, and in many cases, they can take place at temperatures as low as –120&nbsp;°C. The reaction is named after the Russian chemist [[Yegor Yegorovich Vagner]]; he had German origin and published in German journals as Georg Wagner; and [[Hans Meerwein]].
Several reviews have been published.<ref name=popp58>{{cite journal|author1=Popp, F. D. |author2=McEwen, W. E. |journal=[[Chem. Rev.]]|year=1958|volume=58|pages= 375|doi=10.1021/cr50020a004|title=Polyphosphoric Acids As a Reagent in Organic Chemistry|issue=2}}</ref><ref name=cargill74>{{cite journal|journal=[[Acc. Chem. Res.]]|year=1974|volume=7|pages= 106–113|doi=10.1021/ar50076a002|title=Acid-catalyzed rearrangements of β,γ-unsaturated ketones|first1=Robert L.|last1=Cargill|first2=Thomas E.|last2=Jackson|first3=Norton P.|last3=Peet|first4=David M.|last4=Pond|issue=4}}</ref><ref name=olah76>{{cite journal|author=Olah, G. A. |journal=[[Acc. Chem. Res.]]|year=1976|volume=9|pages= 41–52|doi=10.1021/ar50098a001|title=Stable carbocations, 189. The σ-bridged 2-norbornyl cation and its significance to chemistry|issue=2|author-link=George Olah}}</ref><ref name=hogeveen79>{{cite journal|author=Hogeveen, H.; Van Krutchten, E. M. G. A.   |journal=Top. Curr. Chem.|year=1979|volume=80|pages= 89–124|doi=10.1007/BFb0050203|title=Wagner-meerwein rearrangements in long-lived polymethyl substituted bicyclo[3.2.0]heptadienyl cations|series=Topics in Current Chemistry|isbn=3-540-09309-5}}</ref><ref name=hanson91>{{cite journal|author=Hanson, J. R. |journal=Compr. Org. Synth.|year=1991|volume=3|pages= 705–719|doi=10.1016/B978-0-08-052349-1.00077-9|title=Wagner–Meerwein Rearrangements|isbn=978-0-08-052349-1}}</ref>
The rearrangement was first discovered in [[bicyclic]] [[terpene]]s for example the conversion of [[isoborneol]] to [[camphene]]:<ref>{{JerryMarch}}</ref>
[[File:Wagner-Meerwein Camphen mechanism.svg|center|Dehydration of Isoborneol to Camphene|1000px]]
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.<ref name=birladeanu00>{{cite journal|author=Birladeanu, L.  |journal=[[J. Chem. Educ.]]|year=2000|volume=77|pages= 858–863|doi=10.1021/ed077p858|title=The Story of the Wagner-Meerwein Rearrangement|issue=7|bibcode=2000JChEd..77..858B}}</ref>
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,<ref name=polito10>{{cite journal| doi=10.1021/ed9000238| title=Carbocation Rearrangement in an Electrophilic Aromatic Substitution Discovery Laboratory| year=2010| last1=Polito| first1=Victoria| last2=Hamann| first2=Christian S.| last3=Rhile| first3=Ian J.| journal=Journal of Chemical Education| volume=87| issue=9| pages=969| bibcode=2010JChEd..87..969P}}</ref> 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 <ref name=zubkov11>{{cite journal|author1=Zubkov, F. I. |author2=Zaytsev, V. P. |author3=Nikitina, E. V. |author4=Khrustalev, V. N. |author5=Gozun, S. V. |author6=Boltukhina, E. V. |author7=Varlamov, A. V. |doi=10.1016/j.tet.2011.09.099|title=Skeletal Wagner–Meerwein rearrangement of perhydro-3a,6;4,5-diepoxyisoindoles|year=2011|journal=Tetrahedron|volume=67|issue=47|pages=9148}}</ref>
:[[File:Wagner-Meerwein heterocyclic.png|Some examples of Wagner-Meerwein rearrangement in heterocyclic series|950px]]
Plausible mechanisms of the Wagner–Meerwein rearrangement of [[diepoxyisoindoles]]:
[[File:Wagner-Meerwein rearrangement of diepoxyisoindoles.svg|Plausible mechanisms of the Wagner-Meerwein rearrangement of diepoxyisoindoles|1000px]]
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]]).
== References ==
{{Reflist}}
{{DEFAULTSORT:Wagner-Meerwein rearrangement}}
[[Category:Rearrangement reactions]]
[[Category:Name reactions]]