Silica-Immobilized Pd-Amine Catalysts for Suzuki-Miyaura Coupling with Catalytic Amounts of Base

Suzuki-Miyaura coupling is a robust method for constructing C-C bonds. Typically, stoichiometric amounts of a base are required. However, high pH conditions can lead to the protodeboronation of several substrates and generate stoichiometric waste salt from the additive base. Here, we present a Pd-amine co-immobilized catalyst enabling SMC with a catalytic amount of base; the amount of cross-coupling product was 18 times higher than that of co-immobilized amines. Furthermore, the use of a co-immobilized amine with a hydrophobic alkyl chain and a water-based solvent effectively removed acid byproducts from the Pd active species on the support surface, resulting in a high coupling product yield. The immobilized catalyst was characterized by elemental analysis, solid-state NMR, and X-ray absorption fine structure spectroscopy. Additionally, X-ray photoelectron spectroscopy, powder X-ray diffractometry, and transmission electron microscopy measurements revealed the in situ formation of Pd nanoparticles as the active species. Crucially, this system facilitates reactions even in the presence of aryl halides with acidic substituents.