Reaction between Azidyl Radicals and Alkynes: A Straightforward Approach to NH-1,2,3-Triazoles.

Abstract

Reaction between nitrogen-centered radicals and unsaturated C-C bonds is an effective synthetic strategy for the construction of nitrogen-containing molecules. Although the reactions between nitrogen-centered radicals and alkenes have been studied extensively, their counterpart reactions with alkynes are extremely rare. Herein, the first example of reactions between azidyl radicals and alkynes is described. This reaction initiated an efficient cascade reaction involving inter-/intramolecular radical homolytic addition toward a C-C triple bond and a hydrogen-atom transfer step to offer a straightforward approach to NH-1,2,3-triazoles under mild reaction conditions. Both the internal and terminal alkynes work well for this transformation and some heterocyclic substituents on alkynes are compatible. This mechanistically distinct strategy overcomes the inherent limitations associated with azide anion chemistry and represents a rare example of reactions between a nitrogen-centered radicals and alkynes.