Editing Cope reaction

{{Short description|Reaction of N-oxide to alkene and hydroxylamine}}
{{distinguish|Cope rearrangement}}
{{Reactionbox
| Name = Cope reaction
| Type = Elimination reaction
| NamedAfter = [[Arthur C. Cope]]
| Section3 = {{Reactionbox Identifiers
   | OrganicChemistryNamed = cope-elimination
   | RSC_ontology_id = 0000539
 }}
}}
The '''Cope reaction''' or '''Cope elimination''', developed by [[Arthur C. Cope]], is the [[elimination reaction]] of an [[Amine oxide|N-oxide]] to an [[alkene]] and a [[hydroxylamine]].<ref>{{cite journal |last1=Cope |first1=Arthur C. |last2=Foster |first2=Theodore T. |last3=Towle |first3=Philip H. |author-link1=Arthur C. Cope |title=Thermal Decomposition of Amine Oxides to Olefins and Dialkylhydroxylamines |journal=[[Journal of the American Chemical Society]] |date=1949 |volume=71 |issue=12 |pages=3932–3935 |doi=10.1021/ja01180a014}}</ref><ref>{{cite journal |last1=Cope |first1=Arthur C. |last2=Towle |first2=Philip H. |author-link1=Arthur C. Cope |title=Rearrangement of Allyldialkylamine Oxides and Benzyldimethylamine Oxide |journal=[[Journal of the American Chemical Society]] |date=1949 |volume=71 |issue=10 |pages=3423–3428 |doi=10.1021/ja01178a048}}</ref><ref>{{cite journal |last1=Cope |first1=Arthur C. |last2=Pike |first2=Roscoe A. |last3=Spencer |first3=Claude F. |author-link1=Arthur C. Cope |title=Cyclic Polyolefins. XXVII. cis- and trans-Cycloöctene from N,N-Dimethylcycloöctylamine |journal=[[Journal of the American Chemical Society]] |date=1953 |volume=75 |issue=13 |pages=3212–3215 |doi=10.1021/ja01109a049}}</ref><ref>{{cite encyclopedia|volume=6|year=1991|pages=1011–1039|encyclopedia=Comprehensive Organic Synthesis|title=The Cope Elimination, Sulfoxide Elimination and Related Thermal Reactions |author=Peter C. Astles |author2=Simon V. Mortlock |author3=Eric J. Thomas|doi=10.1016/B978-0-08-052349-1.00178-5|isbn=978-0-08-052349-1}}</ref>[[Image:CopeReaction.png|554px|Cope reaction|center]]Typically, the amine oxide is prepared from the corresponding [[amine]] with a [[peroxy acid]] or comparable [[oxidant]].  The actual elimination requires just heat.  
Illustrative is a synthesis of [[methylenecyclohexane]]:<ref>{{cite journal |last1=Cope |first1=Arthur C. |author-link1=Arthur C. Cope |last2=Ciganek |first2=Engelbert |date=1963 |title=Methylenecyclohexane and N,N-Dimethylhydroxylamine Hydrochloride |journal=[[Organic Syntheses]] |volume=4 |page=612 |doi=10.15227/orgsyn.039.0040}}</ref>
[[File:MethyleneCyclohexaneByCopeReaction.svg|center|389x389px|synthesis of methylenecyclohexane]]

==Mechanism and related eliminations==
The reaction proceeds through the [[Ei mechanism|E<sub>i</sub> pathway]], with an intramolecular, cyclic 5-membered [[transition state]].{{ref|1}}  Consequently, the elimination product is always [[syn elimination|''syn'']] and rarely occurs with [[piperidine|6-membered rings]].  ([[Pyrrolidine|Rings with 5]] or 7 or more members undergo the reaction just fine.)<ref>{{cite book |last1=March |first1=Jerry |url=https://archive.org/details/marchsadvancedor00smit_198 |title=March's advanced organic chemistry: reactions, mechanisms, and structure. |last2=Smith |first2=Michael B. |publisher=Wiley-Interscience |year=2007 |isbn=978-0-471-72091-1 |edition=6th. |page=[https://archive.org/details/marchsadvancedor00smit_198/page/n1541 1525] |url-access=limited}}</ref><ref>''Amine Oxides. VIII. Medium-sized Cyclic Olefins from Amine Oxides and Quaternary Ammonium Hydroxides'' Arthur C. Cope, Engelbert Ciganek, Charles F. Howell, Edward E. Schweizer [[J. Am. Chem. Soc.]], '''1960''', 82 (17), pp 4663–4669 {{doi|10.1021/ja01502a053}}</ref><ref>''Amine Oxides. VII. The Thermal Decomposition of the N-Oxides of N-Methylazacycloalkanes'' Arthur C. Cope, Norman A. LeBel; [[J. Am. Chem. Soc.]]; '''1960'''; 82(17); 4656-4662. {{doi|10.1021/ja01502a052}}</ref>  
[[File:CopeReactionJACS82-4656.svg|alt=intramolecular Cope reaction|center|261x261px]]
This [[organic reaction]] is closely related to the [[Hofmann elimination]],{{ref|1}} but the [[base (chemistry)|base]] is a part of the [[leaving group]].  [[Sulfoxide]]s can undergo an essentially identical reaction to produce [[sulfenic acid]]s, which is important in the antioxidant chemistry of garlic and other [[Allium|''allium''s]]. [[Selenoxide]]s likewise undergo [[selenoxide elimination]]s.

==Reverse reaction==
The reverse or retro-Cope elimination has been reported, in which an N,N-disubstituted hydroxylamine reacts with an alkene to form a tertiary N-oxide.<ref>{{cite journal |last1=Ciganek |first1=Engelbert |last2=Read |first2=John M. |last3=Calabrese |first3=Joseph C. |title=Reverse Cope elimination reactions. 1. Mechanism and scope |journal=The Journal of Organic Chemistry |date=September 1995 |volume=60 |issue=18 |pages=5795–5802 |doi=10.1021/jo00123a013}}</ref><ref>{{cite journal |last1=Ciganek |first1=Engelbert |title=Reverse Cope elimination reactions. 2. Application to synthesis |journal=The Journal of Organic Chemistry |date=September 1995 |volume=60 |issue=18 |pages=5803–5807 |doi=10.1021/jo00123a014}}</ref> The reaction is a form of [[hydroamination]] and can be extended to the use of unsubstituted hydroxylamine, in which case [[oxime]]s are produced.<ref>{{cite journal |last1=Beauchemin |first1=André M. |last2=Moran |first2=Joseph |last3=Lebrun |first3=Marie-Eve |last4=Séguin |first4=Catherine |last5=Dimitrijevic |first5=Elena |last6=Zhang |first6=Lili |last7=Gorelsky |first7=Serge I. |title=Intermolecular Cope-Type Hydroamination of Alkenes and Alkynes |journal=Angewandte Chemie |date=8 February 2008 |volume=120 |issue=8 |pages=1432–1435 |doi=10.1002/ange.200703495|bibcode=2008AngCh.120.1432B }}</ref>

==References==
{{Reflist}}
{{Alkenes}}
{{Organic reactions}}
{{DEFAULTSORT:Cope Reaction}}
[[Category:Elimination reactions]]
[[Category:Olefination reactions]]
[[Category:Name reactions]]