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  1. NA (Ed.)
    The advancement of metal-catalyzed carbon-carbon bond forming reactions represents one of the most significant contributions to contemporary organic synthesis. Innovations in the area of palladium catalyzed homogeneous cross-coupling catalysis have dominated this area of chem. and are playing an increasingly important role in the area of pharmaceutical drug discovery and development. However, the use of these catalysts under homogeneous conditions has limited their com. viability due to product contamination as a direct result of inability to effectively sep. the catalyst from the reaction product. Ligand-free heterogeneous catalysis presents a promising option to address this problem as evidenced by the significant increase in research activity in this area. We have recently developed a simple, one-step method for the preparation of bimetallic nickel-palladium nanoparticles supported on multi-walled carbon nanotubes (Ni-Pd/MWCNTs) under mech. shaking in a ball- mill. The preparation method is very fast and straightforward which does not require any chems., solvents, or addnl. ligands. Notably, the concentration of palladium can be lowered to a min. amount of 1% and replaced by more abundant and less expensive nickel nanoparticles while effectively catalyzing the reaction. The as-prepared nanoparticles demonstrated remarkable catalytic activities in cross-coupling catalysis such as Suzuki and Sonoga shira reactions with functionalized substrates in batch with high turnover number in a single catalytic reaction. Batch operations have several inherent limitations that include reproducibility, scalability, and reactor productivity. Continuous flow chem. has been considered as an alternative approach in academic and industrial processes due to its efficient and innovative synthetic design. The low palladium loading and excellent recyclability of the catalyst make this an affordable and clean option for cross-coupling catalysis under continuous flow conditions, a feature that enables the large-scale industrial and pharmaceutical applications of this method in the future. 
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    Free, publicly-accessible full text available March 20, 2025
  2. NA (Ed.)
    Buchwald-Hartwig amination is a cross-coupling reaction between aryl halides or pseudohalides and primary or secondary amines to produce aryl amines. The reaction has become a fundamental tool in organic synthesis for the formation of carbon-nitrogen bonds in a variety of biologically active molecules, natural products, pharmaceuticals, and material science. These reactions usually employ a palladium complex in homogeneous form along with a ligand to stabilize the metal center. In this regard, there are many disadvantages for using homogeneous catalysis including the potential contamination of the metal in the final product and lack of recyclability of the catalyst. Heterogeneous catalysis is an alternative attractive approach to construct carbon-nitrogen bonds in which the metal is fixed on variety of solid supports such as zeolites, polymers, mesoporous silica, and carbon materials. This would allow for ease of separation of the catalyst from the reaction and reusability for the subsequent runs. In this presentation, we will introduce the synthesis of amine-functionalized carbon nanotubes (CNTs) supported Pd nanoparticles (Pd/MWCNTs-NH2) via simple dry mixing of the corresponding palladium salts and amine-functionalized CNTs using the mechanical energy of a ball-mill mixer. The method is very straightforward and rapid and does not require any solvent or reducing agents, a feature that allows for large-scale preparation of these materials. The as-prepared catalyst demonstrated excellent catalytic activity for the Buchwald-Hartwig carbon–nitrogen cross-coupling reactions of variety of aryl halides and functionalized amines under microwave irradiation conditions and short reaction time. The Pd/MWCNTs-NH2 nanoparticles prepared by this simple, solventless, and inexpensive preparation provide a more direct, cost-efficient, and streamlined means to accomplish often-challenging Buchwald-Hartwig amination reactions. 
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