Iodide Ion-Promoted Highly Regioselective Triazolization of Aldehydes via Desulfonation-Associated Direct Radical Coupling

A highly efficient iodide ion (I^-)-promoted method for direct α-C(sp²)-H triazolization of aldehydes has been developed for the regioselective synthesis of <i>N</i>²-substituted triazole derivatives. The developed method features the corresponding products in good yields (up to 99%) with an excellent functional group tolerance via an intermolecular oxidative radical coupling. Experimental mechanistic investigations indicate that the reaction proceeds via an I^--promoted synergistic desulfonylation process, which provides a high regioselectivity. The developed method provides a direct, metal-free, operationally simple, and highly regioselective approach to C(sp²)-H triazolization from easily accessible aldehydes in air.