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 °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.