Nucleophilic displacement by classical SAE mechanism

There are also examples where intended substitution of a halogen does not lead to the desired reaction product. For instance, Haider reported that reaction of l-chloro-4-methyl-5//-pyridazino[4,5-/ ]indole with hydrazine (solvent and nucleophile) gave 4-methyl-5//-pyridazino[4,5- ]indole in 50%. Mechanistically, the initially formed hydrazine is oxidized by air oxygen under the SisjAr reaction conditions (oxidative dehydrazination) yielding reduced compound. Interestingly, by exclusion of oxygen the desired hydrazino-substituted compound could be obtained in 99% yield 

Ar = 4-Bu C6H4, 4-MeCgH4, 4-MeOCgH4, 4-CF2CIOCgH4, 4-CICgH4, 3,4-CICgH3 

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