Contribution a l'etude de la transformation thermique des aldazines α-ethyleniques. nouvelle voie d'acces aux pyrazoles halogenes ou substitues par des groupements phenoxy,thiophenoxy et thioethoxy en 3(5)

Azines of β-halogen-, aryloxy-, alkylthio- and arylthio-substituted acroleines when heated gave pyrazole derivatives which may be hydrolysed very easily to give N-unsubstituted pyrazoles bearing in the 3(5) position halogen, ArO, RS or ArS groups. The observed heterocyclisation was compared with thermal decomposition of cinnamald azine for which an ionic mechanism had been previously proposed, whereas we show that the involved mechanism is an internal 1,4-addition and, according to the nature of the migrating group, a thermal [1,3] or [1,5] sigmatropic rearrangement.