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Unexpected ring closure reaction of α,β‐unsaturated ketones with aminoguanidine. entry into 1,3,5‐trisubstituted pyrazoles
Author(s) -
Světlík Jan,
Šallai Ladislav
Publication year - 2002
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570390220
Subject(s) - chemistry , closure (psychology) , pyrazole , ring (chemistry) , aryl , medicinal chemistry , organic chemistry , alkyl , economics , market economy
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.