Azines hydrazino derivatives

Hydrazino nitrogen heterocycles are readily converted into 1,2,4-triazolo[/ ]-fused systems, as exemplified by Scheme 54 <1971JOC10>. A similar approach has been used for the synthesis of triazoloindole derivative 91 (Scheme 55) <2005BMC1847, CHEC-III(11.03.9.1)117>. Oxidation of the 2-pyrazolyl hydrazones 92 with lead tetraacetate gives, via azines 93, the 3//-pyrazolo [5,12,-4-triazoles 94 (Scheme 56) <1979TL1567>. 

This section covers primary, secondary, tertiary, and quaternary aminopyrazines (both nuclear and extranuclear) but not (functionally substituted amino)pyrazines such as hydrazino-, hydroxyamino-, or azidopyrazines. General discussions have appeared on the spectra of 2-pyrazinamine,255 257 991 the proton-sponge properties of 2,3,5,6-tetra(pyridin-2-yl)pyrazine in relation to its fine structure,925 the fluorescene properties of 3,6-diamino-2,5-pyrazinedicarboxylic acid derivatives in relation to their fine structures,1646,1659 the basic properties of aminopyrazines and other such azines in relation to their electronic structures,412,928 and the fine structures of 3-amino-2-pyrazinecarboxylic acid1340 and l,4-diacetyl-2,3-diphenylpiperazine.559... 

All experimental data on the behavior of 3,5-disubstituted 1,2,4-tri-azines in the SN reactions indicate a greater reactivity of the C-5 position. An exception is the reaction between ethyl-3,5-dimethylthio-l,2,4-tria-zine-6-carboxylate (80) and hydrazine or amines, which results in a mixture of 3- and 5-hydrazino (amino) derivatives, 81 and 82 (Scheme 50) (76JCS(P2)2521, 76JMC845 77JHC729 87MI4). 

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