Phenyl 3-pyridazinyl ketones

Oxidative decyanation of phenyl-3-pyridazinylacetonitriles, by passing a brisk stream of oxygen into an aqueous sodium hydroxide/DMSO solution of the substrate containing tri-ethylbenzylammonium chloride, is a convenient method for the synthesis of phenyl 3-pyridazinyl ketones (Scheme 55). Modified reaction conditions allow the one pot conversion of a-(6-chloro-pyridazin-3-yl)phenylacetonitrile into ketones with concomitant hydrolysis or methoxylation of the chloro substituent the direct one pot preparation of 3,6-dibenzoylpyridazine from 3,6-dichloro-pyridazine is achieved in 48% yield <93JHC1685>. 

Substituted 4,S-dihydropyridazin-3,6-dione 3-hydrazones were reacted with trifluoroacetic acid to yield 3-trifluoromethyl-s-triazolo[4,3-6]pyri-dazinones (19) [94M1(49)21]. Reaction of catechol derivatives with 3,4,5-tri-chloropyridazine have been shown to afford 4-chloro[l,4]benzodioxino[2,3-c]-pyridazines 20 and 21 [93JHC(30)789]. An efficient procedure for preparing phenyl 3-pyridazinyl ketones 22 has been published [93JHC(30)1685] [94SC(24)773],... 

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