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

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Abstract
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 Pd2(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, π-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.

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