Cope reaction: Difference between revisions

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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.   
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|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>[[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>
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]]
[[File:MethyleneCyclohexaneByCopeReaction.svg|center|389x389px|synthesis of methylenecyclohexane]]

Latest revision as of 01:26, 26 June 2025

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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.[1][2][3][4]

Cope reaction
Cope reaction

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:[5]

synthesis of methylenecyclohexane
synthesis of methylenecyclohexane

Mechanism and related eliminations

The reaction proceeds through the Ei pathway, with an intramolecular, cyclic 5-membered transition state.[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.)[6][7][8]

intramolecular Cope reaction

This organic reaction is closely related to the Hofmann elimination,[2] 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 alliums. 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.[9][10] The reaction is a form of hydroamination and can be extended to the use of unsubstituted hydroxylamine, in which case oximes are produced.[11]

References

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  1. ↑ Script error: No such module "Citation/CS1".
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  3. ↑ Script error: No such module "Citation/CS1".
  4. ↑ Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "citation/CS1".
  7. ↑ 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 Script error: No such module "doi".
  8. ↑ 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. Script error: No such module "doi".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
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