Behaviour of 5,6-dihydrothieno[2,3-h]cinnolin-3(2H)-one and 5,6- dihydrothieno[3,2-h]cinnolin-3(2H)-one towards hydrazine. Synthesis of thienocinnolinones and of 4-aminothienocinnolinones

Stefania Villa, Giorgio Cignarella, Michela M. Curzu, Gérard A. Pinna, Elena Pini, Lucio Toma

Research output: Contribution to journalArticle

Abstract

The isomeric compounds 5,6-dihydrothieno[2,3-h]cinnolin-3(2H)-one (7a) and 5,6-dihydrothieno[3,2-h]cinnolin-3(2H)-one (7b) rapidly tautomerise to the corresponding 1,4-dihydrothienocinnolinones 8a,b when kept in refluxing hydrazine hydrate. With longer reaction times the initially formed 8a,b dehydrogenate to the thienocinnolinones 9a,b which eventually are aminated to 4-aminothienocinnolinones 10a,b. This behaviour recalls that reported for the related 5,6-dihydrobenzocinnolin-3(2H)-one (1) which under the same conditions undergoes dehydrogenation to benzo[h]cinnolin-3(2H)-one (2) followed by 4-amination to 3, but differs for the stability of the intermediates, for the mechanism of the final amination, and for the higher reaction rate. All these differences can be rationalised in terms of the heats of formation of the intermediates and products of the two series of transformations.

Original languageEnglish
Pages (from-to)1253-1257
Number of pages5
JournalJournal of Heterocyclic Chemistry
Volume36
Issue number5
Publication statusPublished - 1999

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hydrazine
Amination
Dehydrogenation
Reaction rates

ASJC Scopus subject areas

  • Organic Chemistry

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Behaviour of 5,6-dihydrothieno[2,3-h]cinnolin-3(2H)-one and 5,6- dihydrothieno[3,2-h]cinnolin-3(2H)-one towards hydrazine. Synthesis of thienocinnolinones and of 4-aminothienocinnolinones. / Villa, Stefania; Cignarella, Giorgio; Curzu, Michela M.; Pinna, Gérard A.; Pini, Elena; Toma, Lucio.

In: Journal of Heterocyclic Chemistry, Vol. 36, No. 5, 1999, p. 1253-1257.

Research output: Contribution to journalArticle

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