Groupes de départ inhabituels lors de cyclisations dans la série des quinoxalines,II [1]

Quinoxaline-3-ketones substituted by different groups in position 2 (I) are easily cyclized by hydroxylamine and phenylhydrazine to form isoxazolo4, 5-b] quinoxalines (II) and pyrazolo 3, 4-b] quinoxalines (III) respectively. The reactions proceed via the oximes resp. phenylhydrazones. Groups displaced are not only the customary leaving groups of aromatic S_N2 reactions (halogens, OH), but likewise H, COOH, CONH₂, CO-Ar, and, less easily, benzyl groups; methyl and phenyl groups were not displaced. The displacement of hydride ion in the presence of excess of hydroxylamine resp. phenylhydrazine is explained in terms of an extension of the theory of osazone formation.