Cope elimination template

The N-oxide oxygen takes a β-hydrogen through a five-membered cyclic transition state; the C–N bond breaks at the same time, giving styrene and N,N-dimethylhydroxylamine.

Mechanism step by step

A tertiary amine oxide loses R₂NOH on heating to give an alkene (syn)

1. Syn elimination (Ei) – O⁻ takes the β-H as the C=C forms and the C–N bond breaks: one concerted step

Key points

• The amine oxide is made from the tertiary amine with H₂O₂ or mCPBA.
• Syn elimination: the H and the N-oxide must be on the same side (compare anti E2).
• Gives mainly the less substituted alkene (Hofmann-type), like the Hofmann elimination.
• Runs at lower temperature than the Hofmann elimination and needs no strong base.

Drawn with 49 atoms, 5 arrows, 5 shapes – every one editable in MolDraw.

Sources

• Kürti & Czakó, Strategic Applications of Named Reactions in Organic Synthesis, Elsevier 2005 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook