Pyridazin-4 -ones, 1-aryl-, formation

Substituted 3,5-dihydro-4//-pyridazino[4,5-, ]indol-4-ones 50 <2001H(55)1105, 2002T10137> and 2,5-dihydro-l/7-pyridazino[4,5-7]indol-l-ones 52 <2006T121> have been synthesized from 5-(2-aminophenyl)pyridazin-3(2/0-ones 49 and 4-(2-aminophenyl)pyridazin-3(27/)-ones 51, respectively. For this purpose diazotization of the amino groups was followed by a nucleophilic substitution with sodium azide affording aryl azides. Upon heating of these compounds, the ring-closed products were obtained most probably via the formation of an electrophilic nitrene (Scheme 10). 

Yutilov et al. reported the formation of the [l,2,3]triazolo[4,5- / pyridazin-4-one ring system with simultaneous conversion of the 7-nitro into a methyl substituent, and reduction of the aryl nitro group to an amino substituent on... 

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