In situ green biosynthesis of palladium nanoparticles by using Ginger/Pectin as plant mixture: investigation of its catalytic efficiency in the Sonogashira cross coupling reaction

Among the wide range of reactions in synthetic organic chemistry, the C-C coupling reactions are protagonist. Different reactions under this category such as Suzuki-Miyaura, Heck, Sonogashira, Hiyama, Kumada, Negishi, Stille and Fukuyama coupling are utilized as powerful tools towards thesynthesis of different synthetic intermediates, heterocycles, polymers, drugs, ligands and dendrimers (Shahriari M. et al 2022).The Sonogashira coupling reaction of terminal alkynes and aryl or alkenyl halides provides an efficient method to the synthesis of aryl alkynes. This reaction is performed in the presence of catalytic amounts of a palladium complex and copper (I) iodide in the presence of a base. Using copper iodide as the co-catalyst sometimes lead to the homo-coupling reaction of terminal alkynes (Khazaei A., et al. 2013). The ginger has a powerful fragrance and is used globally as a spice, flavoring, or fragrance in foods, beverages, soaps, cosmetics, and more prominently as medicine, including Coronavirus disease. It has antioxidant and antibacterial properties and is used for stomach ache, cough and exclusively reduces the severity of acute chemotherapy-induced nausea in adult cancer patients (Mehata M.S. 2021). Pectin is a polysaccharide that is found extensively in all plant primary cells. It is a natural polymer which extensively employed in food industry, as a thickener or stabilizing agent. Pectin is a linear chain of 1,4-linked α-D-galacturonic acid residues in which some of the carboxyl groups are methyl esterified (Figure 1). Eye-catching properties of pectin, such as flexibility, biodegradability, non-toxicity, low price and carrying freely available hydroxyl groups make it suitable and ideal candidate for many practices in different areas of science (Ridley B.L. et al. 2001). Pectin contains free carboxyl groups on its backbone which can form complexes with Pd(II) ions in solution and reduce them to Pd(0) without using any extra reducing agent such as NaBH4, hydrazine or molecular hydrogen. This slow rate in situ reduction of Pd(II) to Pd(0) causes the formation of small size and well distributed palladium nanoparticles on the surface of mixture ginger and pectin (Khazaei A., et al. 2013). Here, we report on ginger/pectin mixture mediated green biosynthesis of PdNPs. The effects of different environmental parameters like temperature, extract concentration, and time interval in the fabrication of palladium nanoparticles were monitored. Various characterization techniques were used to investigate the shapes, sizes, and morphology of ginger/pectin capped PdNPs (Fig. 1)