Design of and Mechanistic Studies on a Biomimetic Iron–Imidazole Catalyst System for Epoxidation of Olefins with Hydrogen Peroxide

One step further in bio‐inspired catalytic epoxidation reactions was made in investigations on iron/imidazole catalyst systems (see the crystal of one example) with hydrogen peroxide as the terminal oxidant, in which it was shown for the first time that defined iron–imidazole complexes are capable of epoxidizing challenging aliphatic olefins. X‐ray studies, UV/Vis titrations, and NMR studies were carried out to clarify the mechanism. Novel iron catalysts, both defined and in situ generated, for the epoxidation of aromatic and aliphatic olefins with hydrogen peroxide as terminal oxidant are described. Our catalyst approach is based on bio‐inspired 1‐aryl‐substituted imidazoles in combination with cheap and abundant iron trichloride hexahydrate. We show that the free 2‐position of the imidazole ligand motif plays a key role for catalytic activity, as substitution leads to a dramatic depletion of yield and conversion. X‐ray studies, UV/Vis titrations, and NMR studies were carried out to clarify the mechanism. One step further in bio‐inspired catalytic epoxidation reactions was made in investigations on iron/imidazole catalyst systems (see the crystal of one example) with hydrogen peroxide as the terminal oxidant, in which it was shown for the first time that defined iron–imidazole complexes are capable of epoxidizing challenging aliphatic olefins. X‐ray studies, UV/Vis titrations, and NMR studies were carried out to clarify the mechanism.