Valence bond isomerization of fused [1,2,3]triazolium salts with bridgehead nitrogen atom. Fused azolium salts. 19

Mariann Béres, György Hajós, Zsuzsanna Riedl, Tibor Soós, Géza Timári, András Messmer

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

[1,2,3]Triazolo[1,5-a]quinolinium (7), [1,2,3]triazolo[1,5- b]isoquinolinium (8), and [1,2,3]triazolo[1,5-a]pyrazinium salts (9) when heated in trifluoroacetic acid and/or 1,2-dichlorobenzene undergo valence bond isomerization to ring-opened reactive intermediates (e.g., 8 gave 13) which can participate in (i) electrophilic substitution as nitrenium cations to yield pyrazole- and indazole-fused new heterocycles (e.g., from 13, 14, and 15 are formed), (ii) pseudoelectrocyclization (e.g., intermediate 19c leads to the pyrazolo[3,4-b]pyrazine 21), or (iii) in nucleophilic addition as carbenium cations (e.g., 1 gave the methoxy-substituted adduct 22 when heated in methanol). Comparison of these and some recent results reveals that this ring opening of fused [1,2,3]triazolium salts is a general phenomenon and is closely related to the well-known retro-electrocyclizations (called '1,5-dipolar cyclizations') of neutral fused [1,2,3]triazoles and tetrazoles.

Original languageEnglish
Pages (from-to)5499-5503
Number of pages5
JournalJournal of Organic Chemistry
Volume64
Issue number15
DOIs
Publication statusPublished - Jul 23 1999

ASJC Scopus subject areas

  • Organic Chemistry

Fingerprint Dive into the research topics of 'Valence bond isomerization of fused [1,2,3]triazolium salts with bridgehead nitrogen atom. Fused azolium salts. 19'. Together they form a unique fingerprint.

  • Cite this