Recent Advances in Pd/C-Catalyzed Coupling Reactions

Abstract

A practical approach to multifunctional compounds through palladium on activated carbon (Pd/C)-catalyzed coupling reactions is described. A close correlation of the properties of the Pd/C with reaction efficiency has been observed and depends largely upon the type of reaction. A critical role of the activated carbon is to help palladium disperse sufficiently on the solid support to form the active palladium complex without aggregating to inactive palladium black. The use of Pd/C avoids contamination of the product with palladium and expedites recovery of the metal. The reactions are practical and have been applied to cost-effective largescale production of multifunctional compounds for drug synthesis. 4 Reaction Mechanism 5 Conclusion

A Practical Synthesis of Multifunctional Ketones through the Fukuyama Coupling Reaction

“…[9][10][11] Screening of the Pd/C in the reaction of 1a with 2a has been conducted as shown in Figure 1. Among the Pd/C forms tested, oxidic Pd/C D1, D2 and D3, whose reduction degree [relative amount of Pd(0) species on the total amount of Pd] is from 0 to 25 %, are more active than the reduced counterpart Pd/C D4 whose reduction degree is from 25 to 99 %.…”

“…[9][10][11] In eggshell Pd/C, Pd distributes in close proximity within 50 to 150 nm from the surface. In uniform Pd/C, in contrast, Pd distributes uniformly in the catalyst.…”

“…A diffusion issue, i.e., access of the substrate to the Pd surface located in the charcoal matrix will arise, depending on the size of the substrate. [9,10] When a molecule of relatively larger size is employed as the substrate, Pd/C whose Pd locates closer to the surface should perform better: eggshell > thickshell > uniform. The selection of the Pd/C thus partly depends on the nature of the substrate.…”

High Catalytic Activity of Palladium(II)‐Exchanged Mesoporous Sodalite and NaA Zeolite for Bulky Aryl Coupling Reactions: Reusability under Aerobic Conditions

“…Such heterogeneous catalysts can be prepared by grafting ligated Pd complexes onto polymer resins and metal oxides. [4] Alternatively, ligand-free catalysts can be prepared by supporting Pd 0 nanoparticles or Pd 2+ ions on porous solid materials, such as carbon, [5] zeolites, [6][7][8][9] mesoporous silica, [9,10] and metal oxides. [11][12][13] The ligand-free system is preferable in heterogeneous catalysis, owing to economic preparation and high stability in air.…”

New Electrochemically Generated Polymeric Pd Complexes as Heterogeneous Catalysts for Suzuki Cross‐Coupling Reactions

“…[4] Immobilization of these catalysts onto solid inert supports is a green alternative to homogeneous systems as it enables the facile removal of the catalytically active species from the reaction solution, thus avoiding time-consuming and expensive workup processes that require additional separation steps and larger volumes of hazardous materials. [5,6] To date, two main strategies have been used to immobilize catalysts onto inert matrices, namely, (i) binding palladium centres by van der Waals interactions to solid supports such as charcoal, [7] metal oxides, [8] zeolites/molecular sieves, [9] organic polymers [10] or polymer capsules; [11] or (ii) covalently binding palladium complexes to solid supports such as silica [12] or organic polymers. [13] Unfortunately, catalyst poisoning, limited accessibility to sterically encumbered active sites, and poor anchoring linkages are drawbacks that prevent these heterogeneous catalytic systems from being widely used on industrial scales.…”