Aerobic Oxidation of Amines Catalyzed by Polymer-Incarcerated Au Nanoclusters: Effect of Cluster Size and Cooperative Functional Groups in the Polymer

Aerobic oxidation reaction of amines to imines catalyzed by polymer-incarcerated Au nanoclusters (PI-Au) was developed. The effect of cluster size for this oxidation reaction was carefully examined using the same polymer support. We have succeeded in preparation of various PI-Au catalysts containing different size clusters by modification of standard preparation methods. The size of clusters and their distribution were analyzed by electron microscopy. Interestingly, catalysts containing relatively larger clusters (>5 nm) showed higher activity in aerobic oxidation of amines than catalysts containing smaller clusters (1-3 nm) that showed much better activity for aerobic oxidation of alcohols. In addition, novel Au nanocluster catalysts immobilized on newly prepared polymer with tertiary amine groups were developed and they showed excellent activity for aerobic oxidation of amines to imines. The relation between cluster size and catalytic activity and role of tertiary amine in polymer were discussed. These catalysts could be applied to aerobic oxidative deprotection of p-methoxybenzyl groups.