An efficient clean and sustainable methodology for catalytic C-C coupling process over a Pd-free magnetically recoverable cobalt catalyst

The Suzuki and Sonogashira coupling reactions are important processes in organic synthesis. However, to date, these reactions have been extensively examined using Pd-based catalysts in toxic organic solvents. Therefore, developing clean and inexpensive methodologies for these reactions remained a major challenge. Herein, by taking the advantages of thiol-ene click reaction, an easy and robust strategy for surface modification of magnetic graphene oxide with a dendrimer structure was successfully developed. Dendrimer-functionalized magnetic graphene oxide was then applied for the immobilization of Co nanoparticles. Transmission electron microscopy exhibited a homogeneous distribution of Co nanoparticles with the size of about 3 nm. The resultant nanocomposite revealed high efficiency in catalytic Suzuki and Sonogashira reactions in non-hazardous and sustainable deep eutectic solvents (DESs). The DES and catalyst were simply recycled five times with gradual slight decrease in the yield of the reactions. More importantly, the catalyst was magnetically isolated at the end of the recycling process. Overall, the utilization of DES as an environmentally friendly and recoverable reaction medium, as well as replacing the low-cost cobalt catalyst as an alternative to expensive Pd catalyst along with the facile catalyst isolation by employing an external magnetic field, make the present protocol promising from economic and green chemistry points of view for the clean C-C coupling reactions.