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Free Radical Reactions of N-Heterocyclic Compounds, VI. - Radical Reactions of Cyclic 2,2-Diacyl-1-arylhydrazyls. - A New N-N Bond Cleavage Reaction
Schulz, Manfred,Kluge, Ralph,Willscher, Sabine
, p. 671 - 678 (2007/10/02)
Diacylhydrazyl radicals 5 are generated from N-(phenylamino)dicarboximides 1, 2a, b, 3a-f, and 4 by oxidation with different oxidants.The intermediates 5 react in two ways depending on the substituents in the anilino group.Dimerization of the hydrazyl radikals 5 to stable tetrazanes 8 is favoured by acceptor substituents in the Ar group.N-N bond dissoziation (α-decomposition) of the hydrazyl radicals 5 is favoured by donor substituents in the phenyl ring of the anilino group.The fragments of such reactions are imide radicals 22 and phenylnitrenes 23.The formation of these fragmentation products is proven by analysis of the reaction products.The formation of benzoxazole (25) (15percent yield) is an evidence for an intramolecular insertion reaction of the o-methoxyphenylnitrene, generated by oxidation of 3e.The hydrazyl radicals 5 are also trapped by the stable free radical 2,4,6-tri-tert-butylphenoxyl (9).The thermal decomposition of the isolated radical adducts was studied.