Palladium complex grafted onto SBA-16: as a heterogeneous catalyst for the Suzuki-Miyaura cross-coupling reaction in deep eutectic solvents

The palladium-catalyzed Suzuki-Miyaura cross-coupling reaction has become arguably one of the most important and versatile transformations for the formation of biaryl subunits, which play an important role as intermediate building blocks in the field of herbicides, natural products, conducting polymers, and pharmaceuticals [1,2]. Recently, designing heterogenized palladium complex catalysts for this reaction has been of great attention from economic and environmental considerations [3]. In this work, a new heterogeneous palladium catalyst for the Suzuki reaction was prepared. First, SBA-16 was covalently modified with 3-aminopropyltriethoxysilane and thiophene-2-carbaldehyde to achieve SBA-16 supported bidentate Schiff base ligand. Then, reaction of the supported ligand with palladium acetate produced heterogeneous palladium catalyst. Several instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were carried out to characterize the structure and composition of the catalyst. The prepared catalyst exhibited excellent activity in the Suzuki reactions of aryl halides with phenylboronic acid in the deep eutectic solvent (DES) choline chloride/glycerol (1:2) as a sustainable and environmentally responsible medium. Moreover, the catalyst was easily and successfully recycled.

Keywords:

SBA-16 , Palladium , Suzuki , Deep eutectic solvent