Selective aerobic oxidation of activated alkanes with MOFs and their use for epoxidation of olefins with oxygen in a tandem reaction

Abstract

MOFs with Cu²⁺ centers linked to four nitrogen atoms from azaheterocyclic compounds, i.e., pyrimidine [Cu(2-pymo)₂] and imidazole [Cu(im)₂], are active catalysts for aerobic oxidation of activated alkanes, such as tetralin, cumene and ethylbenzene. Differences in activity among the two MOFs appear to be related to differences in their ability to decompose the hydroperoxide and to coordinate to the resulting radical ˙OH species. Copper ions in [Cu(im)₂] can coordinate by expanding their coordination sphere from 4 to 5 in a reversible way, while in the case of [Cu(2-pymo)₂] it results in a displacement of one of the pyrimidine ligands. The MOFs can be used in combination with a silylated Ti-MCM-41 to catalyze the epoxidation of olefins with oxygen by means of a tandem reaction in which the MOF produces cumene hydroperoxide, which is used by Ti-MCM-41 to epoxidize the olefin.