A supported palladium nanocatalyst for copper free acyl Sonogashira reactions: One-pot multicomponent synthesis of N-containing heterocycles

A convenient method has been developed for the synthesis of palladium nanoparticles (PdNPs) embedded into a polymer matrix, PPS [PPS = poly(1,4-phenylene sulfide)], via the thermolysis of palladium acetate. X-ray photoelectron spectroscopy (XPS) studies confirmed the presence of strong sulfur coordination of PPS to the palladium nanoclusters. These palladium nanoparticles (PdNPs-PPS) have been used as an efficient heterogeneous nanocatalytic system for the copper free acyl Sonogashira reaction. A wide range of ynones was synthesized in high yields under mild reaction conditions. The catalyst was recovered and recycled up to four times. Transmission electron microscopy (TEM) images revealed that the catalyst maintained nanospheric dimensions for four consecutive catalytic cycles. This simple protocol was further explored in a one-pot multicomponent synthesis of 2,4-disubstituted pyrimidines and a tetrahydro-beta-carboline derivative in improved yield.