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.
|Titolo:||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|
|Autori interni:||VILLA, STEFANIA|
PINI, ELENA RENATA ELVIRA
|Settore Scientifico Disciplinare:||Settore CHIM/06 - Chimica Organica|
Settore CHIM/08 - Chimica Farmaceutica
|Data di pubblicazione:||1999|
|Appare nelle tipologie:||01 - Articolo su periodico|