“…The complexes [M(O)(O 2 ) 2 (py)] (M=Cr, Mo; py=pyridine) react with electron‐rich enol ethers to yield the corresponding dioxetanes,8a but the products are formed by two consecutive mono‐oxygenation reactions and involve intermediate formation of the corresponding epoxides. Apart from mono‐oxygenation of 1,5‐cyclooctadiene,2c oxygenation of 1,5‐cyclooctadiene with [Rh(O 2 )(Cl)(PPh 3 ) 3 ], which can be prepared from dioxygen, produces 1,4‐cyclooctanedione 8b,c. However, this rare case of transition metal mediated alkene dioxygenation with O 2 is rather slow and is accompanied by competitive monooxygenation of the phosphine ligand.…”