Silica-supported Schiff-based palladium nanocatalyzed cross-coupling reactions and its applications in the synthesis of antiplatelet and fungicidal

Abstract

The readily available silica gel was converted into an amino functionalized silica by refluxing with 3-aminopropylthiethoxy silane. The amino functionalized silica was transformed into the respective Schiff-based ligand by the incorporation of [2,2′-bithiophene]-5,5′-dicarbaldehyde. The Pd(0) nanocatalyst on the silica gel support was developed by further processing the Schiff-based ligand with ammonium tetrachloropalladate and hydrazine. The Schiff-based Pd(0) nanocatalyst was extensively characterized using a range of spectroscopic techniques, including Raman, SEM, EDX, TEM, XRD, ICP, and XPS. Raman spectroscopy was used to confirm that the organic moieties have been successfully incorporated, and XPS, XRD, and EDX analyses supported the existence of palladium species on the silica surface. According to the TEM analysis, Pd-nanocomplex with a size distribution of 5.3 ± 0.6 nm was found to be evenly distributed on the silica surface. Palladium was incorporated into the silica surface at a rate of 1.9 w%, according to ICP and EDX analysis. The Mizoroki-Heck and Suzuki-Miyaura coupling reactions were successfully catalyzed by the Schiff-based Pd(0) catalyst using a diverse range of aryl halides, olefines, and organoboronic acids. High yields were achieved in each example in the case for the coupling products. Despite being recovered from the reaction medium and used multiple times, the catalyst still maintained the majority of its catalytic activity. Furthermore, this Schiff-based Pd(0) catalyst was used to produce biologically active molecules of Ozagrel, an antiplatelet agent and fungicidal Boscalid with high yield.

Keywords

• Silica gel
• Bithiophene-5,5′-dicarboxaldehyde
• Palladium
• Schiff-base
• Heck reaction
• Suzuki reaction