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Updated: May 28, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Cascade cyclization, dipolar cycloaddition of azomethine imines for the synthesis of pyrazolidines
Hélène D S Guerrand1, Harry Adams, Iain Coldham
1Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, UK S3 7HF.
Abstract:
A tandem multi-step, one-pot reaction of aldehydes with hydrazines has been used for the preparation of tetrahydropyrazoles and dihydropyrazoles. The chemistry involves condensation then cyclization, followed by inter- or intramolecular dipolar cycloaddition of the resulting azomethine imine intermediates. The intramolecular cycloaddition gives fused tricyclic compounds as single diastereoisomers. The intermolecular cycloaddition was successful with a variety of activated alkene and alkyne dipolarophiles.
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