Novel tridentate ligands and their molybdenum complexes in oxidation reactions

With the aim of developing novel organometallic catalysts suitable for asymmetric epoxidation and sulfoxidation, we have focused on molybdenum complexes bearing novel tridentate chiral ligands. The rigid diaryloxy-pyridine framework has been chosen as the ligand backbone. After observing good catalytic activities of the parent cis-MoO2 diphenyloxy-pyridine complex, we have explored the chiral inducing effect of ligands bearing axial chirality in their phenolic fragments. Various synthetic strategies have been developed for the formation of such ligand structures. After a detailed study of these pathways on the synthesis of achiral model ligands, chiral diaryloxy-pyridines have been prepared using suitable enantiopure biphenyl fragments. The corresponding, chiral cis-MoO2 complexes have then been formed, isolated and characterized. During the oxidation tests, an interesting structure-reactivity relationship has been revealed.