In Situ Generation of Brønsted Acidity in the Pd-I Bifunctional Catalysts for Selective Reductive Etherification of Carbonyl Compounds under Mild Conditions

Selective synthesis of ethers from biomass-derived carbonyl compounds is an important academic and industrial challenge. The existing processes based on strong acid or metallic catalysts cannot provide high selectivity to ethers due to the occurrence of side reactions. Hereby we propose a Pd-I bifunctional heterogeneous catalyst for the selective reductive etherification of aldehydes with alcohols. Extensive catalyst characterizations uncovered the presence of iodine species on the surface of Pd nanoparticles. Heterolytic dissociation of hydrogen on the I-Pd surface sites leads to the "in situ" generation of a Brønsted acid, which promotes the reaction toward the corresponding ethers with extremely high selectivity under very mild reaction conditions.