Cobalt‐Catalyzed Wacker‐type Aerobic Oxidation of Olefins into Ketones Enabled by PMHS: Giving Value to a Chemical Waste with Optimal Atom‐Economy

Herein, it is demonstrated that a chemical waste from the silicon industry, namely polymethylhydrosiloxane (PMHS), is a suitable hydrosilane source for the challenging, selective aerobic oxidation of olefins into methyl ketones under cobalt catalysis: a first row, abundant in the Earth’s crust and cheap metal with low toxicity. The catalytic system operates under unprecedented, stoichiometric amounts of hydrosilane while the cobalt catalyst loading is kept at a very low 1 mol% with the reactions being finished in less than 1 hour with very high turnover numbers (1,340) and record-breaking turnover frequency values up to 530 h-1. Mechanistic studies highlight the key role of the porphyrin ligand for stabilizing the active cobalt species that does follow a radical-based reaction pathway under these particular conditions. These results are relevant for replacing the expensive and scarce palladium catalyst, traditionally used for Wacker-type oxidations, by first-row, Earth-abundant transition metals under green conditions including the efficient valorization of a chemical waste such as PMHS.