Recent Developments in Azide-Free Synthesis of 1,2,3-Triazoles

1,2,3-Triazoles, as one of the most significant nitrogen-containing heterocycles due to their extensive use in biology, material science and organic synthesis, have aroused great interest. 1,2,3-Triazoles are commonly synthesized by metal-catalyzed azide-alkyne cycloaddition and organocatalytic azide-carbonyl cycloaddition, which indispensably employ the toxic and potentially explosive azides. The azide-free synthetic approaches provide a powerful and straightforward alternative to the assembly of diverse 1,2,3-triazoles without the use of azides. In this review, we summarize the recent development of the construction of 1,2,3-triazoles under azide-free conditions.