Applicability of a fiber-supported catalyst on a buchwald-hartwig Amination reaction

The applicability of four different heterogeneous palladium catalysts has been evaluated for the Buchwald-Hartwig amination reaction between p-bromotoluene and piperazine in the presence of the base NaO-t-Bu. The catalyst that provided the highest selectivity toward the desired amination reaction was found to be a polymer-supported palladium dichloride/triphenylphosphine catalyst. Experimental investigations of the catalyst in a reactor setup showed that the undesired reduction reaction of the aryl halide was dominant when the catalyst was reused and washed in solvent prior to reaction and when additional reactants were added to an already reacted reaction mixture. A significant washout of triphenylphosphine and palladium from the catalyst was also identified during the course of reaction and separation.