{{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 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|bibcode=1949JAChS..71.3929C }}</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|bibcode=1949JAChS..71.3423C }}</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|bibcode=1953JAChS..75.3212C }}</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>554px|Cope reaction|centerTypically, 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> center|389x389px|synthesis of methylenecyclohexane

==Mechanism and related eliminations== The reaction proceeds through the E<sub>i</sub> pathway, with an intramolecular, cyclic 5-membered transition state.{{ref|1}} Consequently, the elimination product is always ''syn'' and rarely occurs with 6-membered rings. (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> alt=intramolecular Cope reaction|center|261x261px This organic reaction is closely related to the Hofmann elimination,{{ref|1}} but the base is a part of the leaving group. Sulfoxides can undergo an essentially identical reaction to produce sulfenic acids, which is important in the antioxidant chemistry of garlic and other ''allium''s. Selenoxides likewise undergo selenoxide eliminations.

==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 oximes 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