Pyridazinones, amino-, diazotization

Mannich reactions, 3, 21 polymers, 1, 288 ring contraction, 3, 29 Pyridazinones, amino-diazotization, 3, 35 reaction... 

Aminopyridazines when diazotized form diazonium salts of various degrees of stability. Diazotized 3-amino-6-chloro-4-methyl-pyridazine evolves nitrogen at about 40-50°, whereas the diazotized 3-amino-6-chloro-5-methylpyridazine decomposes spontaneously at 0° 296 5-Amino-4-chloro-3(2H)-pyridazinones (96) behave differently... 

Stable diazonium salts were obtained upon nitrosation of 5-amino-2-phenyl-4-chloro-6(lW)-pyridazinone 98, whereas the diazonium salt prepared from 4-amino-5-chloro analog 99 is unstable and highly reactive (83MI15). Diazotization of 5-aminopyridazin-4-yl-p-chlorophenyl ketone gave the corresponding 4-one [86JCS(P1)169J. 

A primary amino group, after diazotization, reacts with an a-ketophosphorane function to form a pyridazinone ring but the triphenylphosphine moiety is retained and can be removed by heating with aqueous alkali. 

---