Computational studies on CuAAC reaction mechanism with [CuX(PPh3)]; X = I, Br, Cl for the synthesis of 4- and 5-halo-1,2,3-triazoles

A complementary catalytic system was investigated for the [3 + 2] cycloaddition of azides and halo-alkynes. These are based on three copper complexes with [CuX (PPh3)]; X = I, Br, Cl, which are active at low metal loadings (the PPh 3 system). The computational MN12-L approach showed acceptable results with levels of Def2-TZVPfor Cu and Def2-SVP for other elements. In general, all the computational results indicate that the cycloaddition reaction favors the formation of the observed 1,4-regioisomer (5-halo-triazoles) through a direct π-activation mechanism. Graphical abstract