Palladium on activated carbon: a valuable heterogeneous catalyst for one-pot multi-step synthesis

Abstract

Pd on activated carbon (Pd/C) is demonstrated to be active and selective as one single catalyst in a series of one-pot multi-step reactions. The carefully chosen Pd/C catalysts were successfully applied in domino and tandem reactions involving (1) Heck reactions and hydrogenations for the synthesis of (a) dibenzyl and (b) 2-styryl-phenylamine, (2) Sonogashira coupling and intramolecular heteroannulation to form indole ring systems, and (3) Heck and Suzuki coupling reactions to produce 4-styryl-biphenyl. Total yields between 72 and 93% could be achieved. All reaction steps were performed with one and the same Pd/C catalyst, solvent, and additives. Temperature and pressure were adjusted as necessary. The order of the different reactions, the consecutive addition of educt(s) and optimization of reaction conditions was found to be crucial.