Double Regioselective Thermal Azide–Alkyne Cycloaddition of 1,3-Diynes

A double regioselective cycloaddition reaction of 1,3-diynes
with
azide is reported to synthesize fully substituted 5-alkynyl-1,2,3-triazoles
without any catalyst, metal, or other factor. Computational studies
revealed that the 5-alkynyl-1,2,3-triazole derivative is both kinetically
and thermodynamically favorable irrespective of the nature of the
substituents at the alkyne termini in 1,3-diynes. The simplicity of
the reaction, extremely high regioselectivity under metal-free conditions,
wide substrate scope, and good to excellent yields might inspire further
studies of the cycloaddition of 1,3-diynes in addition to click chemistry.