Reaction of Diethyl Chloroethynylphosphonate with 3-Amino-1,2,4-triazoles

A series of new 6-phosphonylated 1 H -imidazo[2,1- c ][1,2,4]triazoles was synthesized by the reaction of diethyl chloroethynylphosphonate with 2-substituted 3-amino-1,2,4-triazoles followed by 5- endo-dig cyclization. It was found that 3-amino-5-bromo-1,2,4-triazole reacts in another way, leading to the formation of the corresponding symmetric amidine, diethyl {2-[(3-bromo-1-methyl-1 H -1,2,4-triazol-5-yl)amino]-2-[(3-bromo-1-methyl-1 H -1,2,4-triazol-5-yl)imino]ethyl}phosphonate.