Fused Imidazoles: A Novel Synthesis of Imidazo[1,2-b][1,2,4]triazole and Imidazo[5,1-f]-[1,2,4]triazine Derivatives

The reaction of 1-amino-2-methylthio-4-phenylimidazole with isothiocyanates, followed by treatment with methyl iodide and heating in ethanol affords 1,6-disubstituted 2-methylthio-1H-imidazo[1,2-b] [1,2,4]triazoles. Starting from the same aminoimidazole, a sequence consisting of N-phosphoranylidenation with triphenylphosphine dibromide, replacement of the phosphoranylidene group by an α-chlorobenzylidene group by reaction with benzoyl chlorides, Cl/N₃ exchange with sodium azide, and reaction of the resultant N-(α-azidobenzyl) derivate with triphenylphosphine affords the N-[α-(triphenylphoranylidenamino)benzyl] derivatives which, on reaction with isocyanates are converted into 2,4,5,7-tetrasubstituted imidazo[5,1-f] [1,2,4]triazines.