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

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-styryi-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. (C) 2004 Elsevier B.V. All rights reserved.