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 language | English |
|---|---|
| Pages (from-to) | 1253-1257 |
| Number of pages | 5 |
| Journal | Journal of Heterocyclic Chemistry |
| Volume | 36 |
| Issue number | 5 |
| Publication status | Published - 1999 |
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ASJC Scopus subject areas
- Organic Chemistry
Cite this
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 journal › Article
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TY - JOUR
T1 - 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
AU - Villa, Stefania
AU - Cignarella, Giorgio
AU - Curzu, Michela M.
AU - Pinna, Gérard A.
AU - Pini, Elena
AU - Toma, Lucio
PY - 1999
Y1 - 1999
N2 - 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.
AB - 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.
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M3 - Article
AN - SCOPUS:0032786836
VL - 36
SP - 1253
EP - 1257
JO - Journal of Heterocyclic Chemistry
JF - Journal of Heterocyclic Chemistry
SN - 0022-152X
IS - 5
ER -