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Unexpected ring closure reaction of α,β-unsaturated ketones with aminoguanidine. entry into 1,3,5-trisubstituted pyrazoles

✍ Scribed by Jan Světlík; Ladislav Šallai

Publisher: Journal of Heterocyclic Chemistry
Year: 2002
Tongue: English
Weight: 42 KB
Volume: 39
Category: Article
ISSN: 0022-152X
DOI: 10.1002/jhet.5570390220

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✦ Synopsis

Abstract

Cyclizations of α,β‐unsaturated ketones with aminoguanidine under neutral conditions were examined. In contrast to literature reports of 1,2,4‐triazines as reaction products, formation of 5‐aryl‐4,5‐dihy‐dro‐3‐methyl‐1__H__‐pyrazole‐1‐carboximidamides and carboxamides was observed. An explanation based on the Hard‐Soft Acid‐Base principle is presented and the probable causes of divergent reaction pathways are discussed.

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