Copper (I)-catalyzed 1, 3-dipolar cycloaddition reaction of nonfluorescent 3-azidocoumarins and terminal alkynes afforded intense fluorescent 1, 2, 3-triazole products. The mild condition of this reaction allowed us to construct a large library of pure fluorescent coumarin dyes. Since both azide and alkyne are quite inert to biological systems, this reaction has potential in bioconjugation and bioimaging applications.
