Anchored palladium nanoparticles onto single walled carbon nanotubes: Efficient recyclable catalyst for N-containing heterocycles

A convenient process has been developed to decorate palladium nanoparticles onto carboxylic acid functionalized single walled carbon nanotubes (SWNTs) via the thermolysis of palladium acetate. This single walled carbon nanotube-palladium nanoparticles (SWNT-PdNPs) composite has been investigated through a number of instrumental techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-vis-NIR spectroscopy, resonance Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), which disclose that the palladium nanoparticles are attached by carboxylic acid groups onto the surface of SWNTs. The SWNT-PdNPs composite has been tested as an efficient heterogeneous nanocatalytic system for copper free acyl Sonogashira reaction. A library of ynones was synthesized in high yields under mild reaction condition. The catalyst was recovered and recycled successfully up to seven times. This simple protocol was further broadened in the synthesis of trimethylsilyl-ynones (TMS-ynones) and explored in the one-pot multicomponent synthesis of 2,4-disubstituted pyrimidines.