An Eco-friendly Approach to C-H Bond Activation through Microwave Irradiation Employing Synthesized Palladium-PEPPSI-NHC Complexes

The formation of carbon-carbon bonds constitutes one of the most fundamental synthetic operations in organic chemistry. Arylation of heteroarenes through C-H bond activation using Pd-PEPPSI complexes as catalysts was widely performed using the classical heating method. However, the use of this heating method is associated with an unfavorable environmental profile, as they generally use a high reaction temperature, a high catalyst load, and a long reaction time. Herein, we disclose the synthesis of new Pd-PEPPSI-NHC complexes bearing NHC ligands, which were tested as a catalyst in the arylation of 2-acethylfuran and 2-acethylthiophene with different aryl bromides using microwave irradiation. This novel method provides access to the biaryl scaffolds in good yields using 0.5 mol % as catalyst loading and at 110 degrees C. The structure of the five palladium(II) complexes has been elucidated through NMR 1H, 13C, and FT-IR spectroscopy. Furthermore, the square-planar geometry of the organometallic ion was confirmed by single-crystal X-ray diffraction carried out on complexes 3b and 3e.