72633-22-8Relevant articles and documents
Confirmation of Suzuki-Miyaura Cross-Coupling Reaction Mechanism through Synthetic Architecture of Nanocatalysts
Sun, Bo,Ning, Lulu,Zeng, Hua Chun
supporting information, p. 13823 - 13832 (2020/09/21)
Despite widespread use of heterogeneous Pd catalysts in Suzuki-Miyaura coupling reactions, detailed roles of Pd, especially the nature of its active species, are still a topic of controversial debate. While some studies showed an active surface of Pd nanoparticles or nanoclusters acting heterogeneously, others claimed soluble Pd species leached from the metallic Pd to be active species which are homogeneous in nature. Besides, within the homogeneous mechanism, how the Pd leaches and promotes the cross-coupling reaction is then another question that needs to be addressed. It could be envisioned that if the soluble Pd species and solid-phase Pd are physically separated, the mechanism of Suzuki-Miyaura coupling could then be confirmed through examining the catalytic activity in different reaction regions. Herein we use microporous St?ber silica as a membrane to separate the soluble Pd species from solid Pd and conduct size-selective reactions which allow the passage of leaching Pd species, but not of reactants or products larger than the membrane aperture. With this strategy, we have been able to differentiate the surface reaction from the solution cross-coupling. We find that the leached Pd species are the only genuine catalytic intermediate in the cross-coupling reactions. We also confirm that oxidative addition of aryl halides to the solid Pd leads to leaching of the soluble Pd species which is necessary to promote Suzuki-Miyaura reactions.
Aerobic Homocoupling of Arylboronic Acids Catalyzed by Regenerable Pd(II)@MIL-88B-NH2(Cr)
Valiente, Alejandro,Carrasco, Sergio,Sanz-Marco, Amparo,Tai, Cheuk-Wai,Bermejo Gómez, Antonio,Martín-Matute, Belén
, p. 3933 - 3940 (2019/05/22)
A fast and operationally simple method for the aerobic homocoupling of arylboronic acids is described. The process is catalyzed by Pd(II) complexes supported on the metal-organic framework MIL-88B-NH2(Cr). The benefits of this approach include the use of a benign oxidant/solvent mixture at room temperature with catalytic amounts of base, easy recovery of the catalyst, and easy isolation of the products. Very high conversions and good yields were achieved for a variety of substrates, and the process was also carried out on a larger scale with the same efficiency. The catalyst was found to suffer deactivation due to progressive reduction and agglomeration of palladium into inactive metal clusters/particles. An innovative procedure for the oxidative redispersion and regeneration of the active Pd(II)@MOF species is presented.
Pd-catalyzed chemo-selective mono-arylations and bis-arylations of functionalized 4-chlorocoumarins with triarylbismuths as threefold arylating reagents
Rao, Maddali L.N.,Kumar, Abhijeet
, p. 6995 - 7005 (2015/03/14)
Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2-4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones (3.27-3.30). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of (R)-tolterodine.
