Novel self‐doped Pd/Cu bimetals in CMC/PANI composites: Efficient heterogeneous catalyst for cooperative Sonogashira and Sonogashira‐cyclization tandem reactions

Abstract

A new Pd/Cu bimetal catalyst supported on carboxymethylcellulose/polyaniline (CMC/PANI) composites (Pd/Cu@CMC/PANI) was fabricated to investigate the cooperative effect between Pd/Cu bimetals in Sonogashira reactions. This approach involves the self‐organization of aniline on CMC via H‐bond, enabling in situ oxidative polymerization using Pd(II) and Cu(II) ions as co‐oxidants. Subsequently, Pd and Cu are self‐deposited on the resulting CMC/PANI composites through the interaction of coordination and metathesis. The morphological and compositional analysis of the prepared catalyst was performed using various analytical tools such as ICP‐AES, FT‐IR, XPS, SEM, TEM, EDS, elemental mapping, and TGA. The Pd/Cu@CMC/PANI composite as a cooperative catalyst for the Sonogashira couplings exhibited high catalytic activity with relatively low Pd loading over its monometallic Pd counterpart, demonstrating the cooperative effect between Pd and Cu. Then, this bimetallic catalyst was successfully adapted for Sonogashira‐cyclization tandem reaction for the synthesis of benzofuran with excellent yields. Significantly, the Pd/Cu@CMC/PANI catalyst exhibited thermal stability under the reaction conditions and could be easily retrieved and reused repeatedly for five runs in the model reaction without significant discernible performance degradation.