Perfluorinated diazines

Valence-bond isomers of perfluorinated diazine derivatives have been extensively studied by Chambers group. 

Fluorocarbon organometallic compounds have been discussed more generally elsewhere.351 Lithium derivatives and Grignard reagents352-354,240.270,280,297 may obtained as indicated in Scheme 32. These compounds are unstable relative to elimination of metal fluoride, but can be used at lower temperatures for a variety of transformations. Attempts to generate corresponding lithium or magnesium derivatives of perfluorinated diazines resulted in tars.286,355... 

Tetrafluoropyrimidine Perfluorinated diazines (pyrimidine, pyrazine, and pyridazine) are typically 1000 times more reactive toward nucleophiles than pentafluoropyridine. Various reactions of tetrafluoropyrimidine with a small range of nucleophiles have been reported (Fig. 8.15) and, in all cases, nucleophilic substitution occurs selectively at the 4-position, consistent with the mechanistic principles discussed above. 

Tetrafluoropyrazine Reactions of tetrafluoropyrazine with nucleophiles occur readily (Fig. 8.16) and, of course, there are no issues regarding regioselectivity of the first nucleophilic substitution process due to the symmetry of this system. The reduced reactivity of tetrafluoropyrazine compared to the other perfluorinated diazines reflects the absence of highly activated sites para to ring nitrogen. 

Therefore in the literature there are some N NMR data of ring fluorinated diazines. The N NMR of perfluorinated diazines are summarized in Table 7 [144], Also recently few works devoted to theoretical calculations of couphng constants in fluorinated azines were published [145,146],... 

Clark DT, Abu-Shbak MM (1984) Plasma polymerization. XL A comparison of the plasma polymerization of the isomeric perfluorinated diazines. J Polym Sd Polym Chem Ed 22 17-28... 

---