C₂ and C₁‐Symmetric Camphopyrazole Dioxomolybdenum(VI) Complexes catalyze the Epoxidation of Cyclic Olefins

Dioxomolybdenum(VI) complexes ( 1 ‐ 6 ) were prepared in good yields (≥79 %) using enantiopure C 2 and C 1 ‐symmetric bidentate N,N‐ligands ( L 1 ‐ L 6 ) derived from (+)‐camphor. The ligands and complexes were characterized by NMR spectroscopy, IR, and elemental analysis. Single crystal X‐ray diffraction analyses of complexes 3 , 4 and 6 confirmed the bidentate coordination modes of ligands L 3 , L 4 , and L 6 and revealed distorted octahedral coordination geometries around the metal center. Complexes 3 and 6 form conformational isomers depending on the orientation of the substituents of the ligand aryl groups. Preliminary evaluation of the complexes as catalysts for the epoxidation of cyclohexene (81–93 % conversion) and cis ‐cyclooctene (66–94 % conversion) with cumyl hydroperoxide and 35 % w/w aqueous hydrogen peroxide (39–73 %) demonstrated their activity for oxygen atom transfer reactions, opening the way for asymmetric epoxidations.