Directing the Cleavage of Ester C−O Bonds by Controlling the Hydrogen Availability on the Surface of Coprecipitated Pd/Fe3O4

The ready availability of esters from natural sources makes them promising substrates for the sustainable production of key intermediates of the chemical industry. In this context, methods to selectively cleave the alkoxy or ester C-O bond to obtain either alkane+acid or alcohol+aldehyde were investigated. Using Pd/Fe3O4 (r) [(r)=reduced] as the catalyst of choice and either 2-propanol-as indirect H source-or molecular hydrogen-as ample H source-the hydrogen coverage on the surface of the catalyst was controlled. This enabled selective cleavage of either the alkoxy C-O bond or the ester C-O bond in aromatic esters as shown for the hydrogenolysis of 2-phenylethylacetate as model substrate. Noteworthy, hydrogenation of the aromatic ring was not observed. Thus, an exceptionally high chemoselectivity of Pd/Fe3O4 (r) to hydrogenolysis of the ester group is combined with the option to readily direct the regioselectivity.