Pyrimidines Chichibabin amination reaction

In 1972, Zoltewicz and Helmick reported the first evidence of anionic o-adducts in the Chichibabin amination reaction. The parent diazines a-adduct complex (pyrimidine, pyridazine and pyrazine) in KNH2-NH3/KMn04 (at low temperature 0 to 0 °C) are shown below. Despite the fact that the parent pyrimidine has three possible amination spots, 18 is the adduct formed and similarly for pyridazine and pyrazine, adducts 19 and 20 are formed under the aforementioned conditions. The regio-chemical outcome changes when these rings are substituted. 

It has been established by experimental data that the Chichibabin amination of pyrimidine proceeds either by an Sn(AE) or Sn(ANRORC) mechanism. Each mechanism is favored according to substituents, substitution pattern and reaction conditions. In turn, the region-chemical outcome for the reaction depends on the mechanism course the reaction follows. 2-bromo-4-phenylpyrimidine (21) reaction with KNH2-NH3... 

Extensive investigation of amide-induced amination of purine and its derivatives has shown that the parent compound (purine) as well as its 2-methyl and 8-methyl derivatives react with potassium [ - Njamide in ammonia to undergo exclusive amination at C6 without incorporation of the N label into the ring (Chichibabin reaction). Amination of 2-fluoro-, 2-chloro-, and 2-(methylsulfanyl)purine 7, and 2-chloro-6-phenylpurine with potassium [ N]amide in ammonia, however, gives purin-2-amines with complete incorporation of the N label in the pyrimidine ring. 

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