Reaction of 3-Hydrazinylquinoxaline-2(1H)-one with 2-Hydroxyimino-1,3-dicarbonyl Compounds

Regioselective synthesis of novel nitroso-pyrazolylquinoxalines via HOAc-mediated cyclocondensation of 2-hydroxyimino-1,3-diketones with hydrazinylquinoxalines

“…Afterward, we observed the fast formation of intermediates, which were isolated and identified as the hydrazones II. 33 This is the difference between the proposed mechanism and the classical cyclocondensation of hydrazine hydrate with acetylacetone. 38…”

“…On the basis of the experimental results 33 and evidence provided in the literature, 38 the plausible mechanism of the cyclocondensation of 2-hydroxyimino-1,3-diketones with hydrazinylquinoxalines is shown in Scheme 5.…”

“…Recently, we have shown that the reaction between hydrazinylquinoxaline 1a and 1-aryl-substituted 2-hydroxyimino-1,3-butanediones leads to excellent yields of products 3ab–3ah (Scheme 3). 33 In respect that hydrazone intermediates can be used as precursors for the corresponding nitrosopyrazoles, we investigated the conditions for their cyclocondensation.…”

“…Physical, spectral data and structure for hydrazones 3aa–3ag , 5-hydroxypyrazoline 3ah were described in our recent report. 33…”

“…Recently, we have shown that the condensation between hydrazinylquinoxalin-2(1 H )-one and 2-hydroxyimino-1,3-dicarbonyl compounds is stopped when the hydrazones and 5-hydroxypyrazolines are formed (Scheme 2 (1)). 33…”