Pd (II) Immobilized on Clinoptilolite as a Highly Active Heterogeneous Catalyst for Ullmann Coupling-type S-arylation of Thiols with Aryl Halides

Background: There are a number of protocols for Ullmann coupling–type S-arylation reactions, many of them suffer from the use of homogenous and often corrosive catalyst, cumbersome workup procedures, and long reaction times. Besides, many of these reagents are expensive and non-recoverable, leading to the generation of a large amount of toxic waste particularly when large-scale applications are considered. Objective: The aim of this study was to prepare a new Pd catalyst bonded on the surface of zeolite as a heterogeneous catalyst. Methods: A heterogeneous palladium catalyst has been prepared by immobilizing Pd ions on Clinoptilolite. This novel developed heterogeneous catalyst was thoroughly examined for Ullmann coupling–type S-arylation reaction using different bases, solvents and 0.003 mg of the catalyst. The structural and morphological characterizations of the catalyst were carried out using XRD, TGA, BET and TEM techniques. Results: Highly efficient heterogeneous palladium catalyst has been developed by immobilizing Pd ions on Clinoptilolite, as one of the most abundant naturally occurring zeolites for Ullmann Sarylation. By using this method, we provide an efficient way to a wide variety of substituted thiolic compounds. Moreover, the catalyst is easily recovered using simple filtration and reused for 5 consecutive runs. Conclusion: In this effort, we developed a new Pd catalyst bonded on the surface of zeolite as a substrate to prepare the heterogeneous catalyst. We demonstrate that this novel catalyst offers reliable and convincing data that may offer a valuable application in further developing the science and technology of Ullmann reaction protocols and allied industries. Additionally, the catalyst was reusable and kept its high activities over a number of cycles.

A heterogeneous and recoverable palladium catalyst to access the regioselective C–H alkenylation of quinoline N-oxides

Herein, we disclose the first C-2-selective C–H alkenylation of quinoline N-oxides catalyzed using a heterogeneous palladium catalyst.

Synthesis of poly(ether ketone amide)s by a heterogeneous palladium-catalyzed polycondensation of aromatic diiodides, diamines, and carbon monoxide

A series of novel aromatic poly(ether ketone amide)s (PEKAs) were synthesized by the heterogeneous palladium-catalyzed carbonylative polycondensation of aromatic diiodides with ether ketone units, aromatic diamines, and carbon monoxide in N, N-dimethylacetamide (DMAc) at 120°C using 6 mol% of a magnetic nanoparticles–supported bidentate phosphine palladium complex (Fe3O4@SiO2-2P-PdCl2) as catalyst and 1,8-diazabicyclo[5,4,0]-7-undecene as base. The PEKAs had inherent viscosities ranging from 0.61 dl g−1 to 0.75 dl g−1. All the PEKAs were soluble in strong dipolar organic solvents. These PEKAs showed glass transition temperatures between 178°C and 232°C and 10% weight loss temperatures ranging from 443°C to 496°C in nitrogen. These PEKAs could be cast into transparent, flexible, and strong films from DMAc solutions with tensile strengths of 72.8–82.6 MPa, tensile moduli of 2.19–2.84 GPa, and elongations at break of 5.4–7.5%. Importantly, the heterogeneous palladium catalyst can be conveniently recovered from the reaction mixture by simply applying an external magnet and recycled up to eight times without significant loss of activity.