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Updated: Mar 18, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Competitive Ring Expansion of Azetidines into Pyrrolidines and/or Azepanes
Bruno Drouillat1, Igor V Dorogan2, Mikhail Kletskii3
1Institut Lavoisier de Versailles, UMR 8180, Université de Versailles St-Quentin-en-Yvelines, Université Paris Saclay - 45 , av. des Etats-Unis, 78035 Versailles Cedex, France.
Abstract:
Azetidines fitted with a 3-hydroxypropyl side chain at the 2-position undergo intramolecular N-alkylation after activation of the primary alcohol, and the produced 1-azonia-bicyclo[3.2.0]heptane is opened by different nucleophiles (cyanide, azide, or acetate anions) to produce mixtures of ring expanded pyrrolidines and azepanes, or a unique type of compound. Distribution of produced five- or seven-membered rings depends on the substitution pattern on the azetidine ring and on its side chain, together with the nature of the nucleophile used in the expansion process. Observed regioselectivities for nucleophilic opening are rationalized by quantum mechanical DFT calculations and are in good agreement with experimental results.
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