Application and Mechanistic Studies of a Water-Oxidation Catalyst in Alcohol Oxidation by Employing Oxygen-Transfer Reagents

By using a dimeric ruthenium complex in combination with tert‐butyl hydrogen peroxide (TBHP) as stoichiometric oxidant, a mild and efficient protocol for the oxidation of secondary benzylic alcohols was obtained, thereby giving the corresponding ketones in high yields within 4 h. However, in the oxidation of aliphatic alcohols, the TBHP protocol suffered from low conversions owing to a competing Ru‐catalyzed disproportionation of the oxidant. Gratifyingly, by switching to Oxone (2 KHSO5⋅KHSO4⋅K2SO4 triple salt) as stoichiometric oxidant, a more efficient and robust system was obtained that allowed for the oxidation of a wide range of aliphatic and benzylic secondary alcohols, giving the corresponding ketones in excellent yields. The mechanism for these reactions is believed to involve a high‐valent RuV–oxo species. We provide support for such an intermediate by means of mechanistic studies. Biphasinating: The use of a dimeric ruthenium complex in the oxidation of alcohols to their corresponding carbonyl compounds in high yields with various oxygen‐transfer reagents is reported. This provides support for a mechanism that involves a high‐valent RuV–oxo species (see scheme).