Azinones activation

For pyridones, pyrones, azinones (cf. 565) and also for A-oxides (cf 566) and [3-oxidocationic rings (cf. 567) the situation is more complex. The combined effect of the heteroatoms in such compounds is to act either as an electron source or as an electron sink depending on the requirements of the reaction (see Section 3.2.1.1.4). In practice, in reactions involving neutral species, substituents a or 7 to the heteroatom in 2- and 4-pyridones, 2- and 4-pyrones, and 2- and 4-thiinones (e.g. 565) and pyridine A-oxides (566) are usually activated by electron withdrawal almost as much as they are in pyridine itself. Additional nitrogen atoms increase the reactivity as expected. 

The Michael-type addition of maleic hydrazide to activated olefins has been investigated. Maleic hydrazide when treated with methyl acrylate, acrylonitrile, methyl vinyl ketone, and other activated olefins forms monoaddition products - for which the structure as A-substituted derivatives has been determined. The exclusive formation of monoaddition products is in contrast to the saturated cyclic succinhydrazide which can form mono- and diaddition products. Additions of the foregoing type are valid also for pyrid-azinones. Low yields of addition products have been obtained when adding dihydropyran or its thio analog and dihydrofuran to pyrid-azinones or pyridazinethiones. ... 

An orientation of leaving group to azinone moiety suitable for activation or, at least, appreciable reactivity exists in various 3-pyridazinones. 6-Bromo- and 6-chloro-2-phenyl-3-pyridazinones react at 20° with methylamine. In 4,6,-dichloro-2-phenyl-3-pyridazin-one, ° inductive meta activation by the partly cationic ring-nitrogen... 

Azinium compounds, Af-allgrl-, substituent displacement, 193 formation of, 187-196 kinetics of substitution of, 194 reaction with nudeojdiiles, 193 Azinones, 192-193 activation of, 245-251 Azlactones, see 2-oxazolin-5-ones... 

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