A useful, reliable and safer protocol for hydrogenation and the hydrogenolysis of o-benzyl groups: The in situ preparation of an active Pd ~0/C catalyst with well-defined properties

摘要

A simple, highly reproducible protocol for the hydrogenation of alkenes and alkynes and for the hydrogenolysis of O-benzyl ethers has been developed. The method features the in situ preparation of an active Pd~0/C catalyst from Pd(OAc)_2 and charcoal, in methanol. The mild reaction conditions (25°C) and low catalyst loading required (0.025 mol%), as well as the absence of contamination of the product by palladium residues (<4 ppb), make this a sustainable, useful process for organic chemists. Alternatively, the protocol can be carried out under microwave activation, to shorten the reaction times, with cyclohexene as the hydrogen source. Pd~0/C: It's a kind of magic! A sustainable, simple and highly reproducible protocol for the hydrogenation of alkenes and alkynes (see scheme) and for the hydrogenolysis of O-benzyl ethers has been developed with an in situ generated Pd~0/C catalyst. The homemade Pd~0/C catalyst allows mild reaction conditions (25°C, 1 atm H_2) and low catalyst loading (as low as 0.025 mol%), without any contamination of the product by palladium residues (<4 ppb).