Oligodentate Aminotriazole Ligands for CuAAC and Copper-Mediated Monooxygenation of Phenols: Influence of Denticity, Chain Length and N-Alkylation on Catalytic Activity

Copper complexes supported by a series of ligands containing different N-donor groups were prepared, and the influence of the ligand design on the catalytic activity towards (i) the conversion of monophenols to o-quinones and (ii) the CuAAC reaction was investigated. Increasing the number of methyltriazole moieties attached to an amine from one (TTA) over two (BTTA) to three (TTTA) decreases the catalytic mono-phenolase activity of derived Cu complexes. By contrast, replacing the methylene group between the apical and the outer N-donors of TTA with an ethylene bridge in TTEA increases the activity whereas alkylation of the amino group (dmTTEA, prlTTEA) has no positive effect on the catalytic activity. When employing the complexes in the CuAAC reaction, opposite trends in catalytic activity are observed. The results are interpreted in the context of the respective mechanistic pathways.