Chemoselective sequential click ligations directed by enhanced reactivity of an aromatic ynamine

Aromatic ynamines or N-alkynylheteroarenes are highly reactive alkyne components in Cu-catalyzed Huisgen [3 +2] cycloaddition (“click”) reactions. This enhanced reactivity enables the chemoselective formation of 1,4-triazoles using the representative aromatic ynamine N-ethynylbenzimidazole in the presence of a competing aliphatic alkyne substrate. The unique chemoselectivity profile of N-ethynylbenzimidazole is further demonstrated by the sequential click ligation of a series of highly functionalized azides using a heterobifunctional diyne, dispelling the need for alkyne protecting groups.