(NHC)copper(I)-catalyzed [3+2] cycloaddition of azides and Mono- Or disubstituted alkynes

Abstract

A versatile and highly efficient catalyst for the Huisgen cycloaddition reaction has been developed. Previously isolated or in situ generated azides yielded 1,2,3-triazoles with differently substituted alkynes in the presence of a [(NHC)CuBr] complex (NHC = N-heterocyclic carbene). Extremely high reaction rates and excel lent yields were obtained in all cases. This catalytic system fulfils the requirements of "click chemistry" with its mild and convenient conditions, nota bly in water or solvent free reactions and simple isolation with no purification step. Furthermore, for the first time, an internal alkyne was successfully used in this copper-catalyzed cyclo-addition reaction. DFT calculations on this particular system allowed for the proposition of a new mechanistic path-way for disubstituted alkynes. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.