A one-pot procedure for the regiocontrolled synthesis of allyltriazoles via the Pd-Cu bimetallic catalyzed three-component coupling reaction of nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide

A one-pot procedure for the regiocontrolled synthesis of both 2-allyl- and 1-allyl-1,2,3-triazoles via the three-component coupling (TCC) reaction between nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide (TMSN3) under a palladium and copper bimetallic catalyst has been developed. To accomplish the regioselective synthesis of the allyltriazoles, proper choice of two different catalyst systems is needed. The combination of Pd-2(dba)(3).CHCl3- CuCl(PPh3)(3)-P(OPh)(3) catalyzes the formation of 2-allyl-1,2,3-triazoles, while the combination of Pd(OAc)(2)-CuBr2-PPh3 promotes the formation of 1-allyl-1,2,3-triazoles. The cooperative activity of palladium and copper catalysts plays an important role in the present transformations. Most probably, the palladium catalyst works as a catalyst for generating reactive azide species, pi-allylpalladium azide complex and allyl azide. The copper catalyst probably behaves as an activator of the C-C triple bond of the starting terminal alkynes by forming a copper-acetylide intermediate and thereby promotes the [3 + 2]-cycloaddition reaction between the reactive azide species and the copper-acetylide to form the triazole framework.