Polymer-Incarcerated Gold-Palladium Nanoclusters with Boron on Carbon: A Mild and Efficient Catalyst for the Sequential Aerobic Oxidation-Michael Addition of 1,3-Dicarbonyl Compounds to Allylic Alcohols

We have developed a polymer-incarcerated bimetallic Au-Pd nanocluster and boron as a catalyst for the sequential oxidation addition reaction of 1,3-dicarbonyl compounds with allylic alcohols. The desired tandem reaction products were obtained in good to excellent yields under mild conditions with broad substrate scope. In the course of our studies, we discovered that the excess reducing agent, sodium borohydride, reacts with the polymer backbone to generate an immobilized tetravalent boron catalyst for the Michael reaction. In addition, we found bimetallic Au-Pd nanoclusters to be particularly effective for the aerobic oxidation of allylic alcohols under base- and water-free conditions. The ability to conduct the reaction under relatively neutral and anhydrous conditions proved to be key in maintaining good catalyst activity during recovery and reuse of the catalyst. Structural characterization (STEM, EDS, SEM, and N-2 absorption/desorption isotherm) of the newly prepared PI/CB-Au/Pd/B was performed and compared to PI/CB-Au/Pd. We found that while boron was important for the Michael addition reaction, it was found to alter the structural profile of the polymer carbon black composite material to negatively affect the allylic oxidation reaction.