Modular synthesis of bis- and tris-1,2,3-triazoles by permutable sequential azide-aryne and azide-alkyne cycloadditions.

A modular synthetic method for bis- and tris-1,2,3-triazoles that include a benzotriazole structure was developed on the basis of sequential azide-aryne and azide-alkyne cycloadditions. The key to success was efficient halogen-metal exchange reaction-mediated generation of aryne from ortho-iodoaryl triflates bearing a base-sensitive terminal alkyne moiety, which was achieved using trimethylsilylmethyl Grignard reagent.