Ruthenium‐Catalyzed Alkyne Oxidation with Part‐Per‐Million Catalyst Loadings

Using a catalytic system of the (cymene)ruthenium dichloride dimer, [Ru(cymene)Cl 2 ] 2 , (0.001 mol%) and iodine (10 mol%), a variety of alkynes bearing different functional groups were oxidized with tert ‐butyl hydroperoxide (TBHP; 70% solution in water) under mild conditions to give 1,2‐diketones in good to excellent yields. Two noteworthy features of the method are the extremely high catalyst productivity (TON up to 420,000) and scale‐up to 1 mol. Preliminary mechanism investigations showed that iodonium ion and water were involved in the transformation.