Synthesis of polystyrene-supported Pd(II)-NHC complex derived from theophylline as an efficient and reusable heterogeneous catalyst for the Heck-Matsuda cross-coupling reaction

• A new polystyrene-supported Pd(II)-NHC catalyst based on theophylline was synthesized.
• Heck-Matsuda arylation of olefins with arenediazonium salts performed by the catalyst.
• Desired products obtained in good to excellent yields.
• The heterogeneous catalyst was reused for seven runs.

The polystyrene-supported palladium(II)-N-heterocyclic carbene complex PS-NHC-Pd(II) was successfully synthesized from theophylline as an environmentally benign NHC precursor, using chloromethylated polystyrene resin. The PS-NHC-Pd(II) complex was characterized by various techniques including Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), thermal analysis (TGA-DTG), inductively coupled plasma (ICP), and CHN elemental analysis. The morphology of the polymer beads was also studied using scanning electron microscope. The polymer supported Pd(II)-NHC complex exhibits excellent catalytic activity and stability for the Heck-Matsuda cross-coupling reaction under mild conditions. A variety of arenediazonium tetrafluoroborate salts was coupled with the olefinic substrates in ethanol, in the presence of the 0.9 mol% of the catalyst to afford the corresponding cross-coupling adducts in high yields under aerial conditions. Moreover, the heterogeneous catalyst can be easily recovered by simple filtration and reused for seven cycles without significant loss in its activity.

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