Polystyrene-Cross-Linking Triphenylphosphine on a Porous Monolith: Enhanced Catalytic Activity for Aryl Chloride Cross-Coupling in Biphasic Flow

Abstract

Immobilized transition metals for continuous-flow catalyses are greatly in demand to achieve automation, scaleup, facile separation, regeneration, and energy-saving production with high level of sustainability and efficiency. Here, we report a tertiary phosphine immobilized on a macroporous monolith (M-PS-TPP) for challenging Pd-catalyzed cross-coupling reaction of aryl chloride in continuous-flow system. The monolithic and macroporous structure of M-PS-TPP was fabricated by bulk polymerization in the presence of high internal phase emulsion (HIPE) template. Owing to the large pore size and high porosity, the M-PS-TPP showed high permeability against continuous flow of mobile phase. Continuous-flow Suzuki-Miyaura cross-coupling reaction was realized by permeation of organic/aqueous media containing inorganic salt through Pdloaded monolith (M-PS-TPP-Pd) column without serious clogging. Controlling coordination chemistry and hydrodynamics of M-PS-TPP-Pd boosted highly active phosphine-metal complex forming and fast mass transfer of reactants. Indeed, the M-PS-TPP-Pd column showed surprisingly higher yields (~93%) and turnover numbers (2704) in continuous-flow conditions than those in batch conditions (~6%).

Surface and Interface Coordination Chemistry Learned from Model Heterogeneous Metal Nanocatalysts: From Atomically Dispersed Catalysts to Atomically Precise Clusters

“…On the contrary, soft bases should have strong affinity with soft acids. Due to the soft nature of P atoms, P-doped materials have been extensively exploited as supports for stabilizing single-site metal catalysts. − For example, a new type of polystyrene (PS)–phosphane covalently bound hybrid was prepared via radical emulsion copolymerization of styrene, divinylbenzene, and a tris­( p -vinylphenyl) phosphane 3-fold cross-linker as an effective support for anchoring different catalytic metal centers (e.g., Pd, Rh, Ir) through mono-P-ligation (Figure a). While the as-prepared Pd catalysts were highly active for the C–C/C–N couplings (e.g., Suzuki–Miyaura coupling and Buchwald–Hartwig amination), the Ir and Rh catalyst systems were applicable for catalyzing C­(sp 3 )–H borylation .…”

Novel porous organic polymers functionalized by metalloporphyrin and phosphonium salts for the efficient synergistic catalysis of CO2 conversion under mild conditions

“…Ph 2 PSt was synthesized according to previous reports. [33][34][35] Typically, magnesite powders (1.41 g, 58.6 mmol, 2 eq.) were added into a 250 mL round-bottom flask equipped with a magnetic stirring bar.…”

Continuous‐Flow Suzuki‐Miyaura Coupling in Water and Organic Solvents Promoted by Blends of Stabilized Convoluted Polymeric Palladium Catalysts and Polymeric Auxiliary Materials

“…developed a polymeric palladium catalyst with a phosphine ligand on a chloromethyl polystyrene resin and argued that the high σ‐donation ability of this ligand stabilized the palladium species and thus improved catalyst durability. Matsumoto et al [8e] . used the copolymerization of tris(4‐vinylphenyl)phosphane, 4‐ tert ‐butylstyrene (4tBS), and divinylbenzene to synthesize a polystyrene monolith containing a crosslinked triphenylphosphine structure and employed this material as an efficient support to prepare a palladium catalyst efficiently promoting the continuous cross‐coupling of 4‐chlorotoluene with phenylboronic acid.…”