Rearrangements in Heterocyclic Synthesis: A Novel Translocation of an (N-Amino-N-methylamino)methylene Group from a Heterocyclic N-Amino-N-methylformamidine Side Chain to the Vinylogous Nitrile Function

Article abstract of DOI:10.1021/jo00237a028

Reaction of the imidate 1-benzyl-4-cyano-5<(methoxymethylene)amino>imidazole (5) with an equivalent of hydrazine provided 1-amino-9-benzyl-6-iminopurine (6), which, upon treatment which excess hydrazine, rearranged to 9-benzyl-6-hydrazinopurine (7).Reaction of 5 with methylhydrazine gave N-amino-N-methyl-N'-(1-benzyl-4-cyanoimidazol-5-yl)formamidine (8b).Thermolysis of 8b in refluxing toluene-methanol, catalyzed by trifluoroacetic acid, provided an equimolar mixture of 5-amino-1-benzyl-4-cyanoimidazole (9) and 3-(5-amino-1-benzylimidazol-4-yl)-1-methyl-1,2,4-triazole (10).Compound 9 was recycled to 8b via 5.The structure of 10 was established by spectral data coupled with an unequivocal synthesis.The conversion 8b to 10 represents a novel "translocative" rearrangement involoving the transfer of an NH2N(Me)CH= group from the imidazole 5-position to the nitrile function at position 4.Successful application of the rearrangement to the analogous pyrazole system is demonstrated.The rearrangement carries useful practical implications in the synthesis of the otherwise not easily accessible heterocycles of potential biological and medicinal significance.