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.