Hollow Mesoporous Organic Polymeric Nanospheres (HMOPNs)‐Supported Carbene Rovis Catalyst: Mesopore and Morphology‐Dependent Catalytic Performances in Asymmetric Organocascade

Abstract

In view of the vital functions of mesopore and hydrophobicity of organic polymer in the mass transfer of reactants and enantioselectivity in heterogeneous asymmetric organocatalysis, a novel type of well‐shaped hollow mesoporous organic polymeric nanospheres (HMOPNs)‐supported triazolium carbene Rovis catalyst was developed for the first time by the copolymerization of styrene and vinylated triazoline on the surface of polystyrene nanosphere (PS), etching of PS template by THF and then trityl cation‐mediated oxidation. The as‐fabricated well‐shaped HMOPNs with mesoporous shell and thin shell thickness was proven to be highly active in asymmetric Michael/Stetter cascade with the higher yields and enantioselectivities than mesopore‐deficient polystyrene‐supported triazolium carbene Rovis catalyst (PS‐7), and achieve the same enantioselectivities as corresponding homogeneous triazolium carbene Rovis catalyst. The as‐fabricated mesopores in the shell of HMOPNs played an important role in enantioselectivity on the basis of the calculated transition state of Breslow intermediate. Moreover, the HMOPNs‐supported Rovis catalyst displayed good reusability and mechanical stability in batch repeated experiments.

Ligand Free Heterogeneous Sonogashira Cross-Coupling Reaction over an in Situ Organoiodine Capsulized Palladium Anchored to a Perovskite Catalyst

“…The reported hydrophobicity for Co based perovskites was also found to be higher than those of Fe based ones, previously used for cross-coupling reactions. , This hydrophobicity can improve the interaction of the surface of this catalyst with the precursors for Sonogashira cross-coupling reactions. According to reports, surface pore hydrophobicity reduces mass transfer limitations of organic reactions in aqueous or semiaqueous media, thus, enhancing the interaction of the introduced organic substrates with the active sites and, hence, giving a greater reaction activity . Also, the hydrophobicity enhances the stability of the catalysts toward decomposition with water .…”

“…According to reports, surface pore hydrophobicity reduces mass transfer limitations of organic reactions in aqueous or semiaqueous media, thus, enhancing the interaction of the introduced organic substrates with the active sites and, hence, giving a greater reaction activity. 66 Also, the hydrophobicity enhances the stability of the catalysts toward decomposition with water. 67 Consequently, less leaching is expected.…”

Cross-Linked Porous Polymers as Heterogeneous Organocatalysts for Task-Specific Applications in Biomass Transformations, CO2 Fixation, and Asymmetric Reactions

“…Preparation of mesoporous N -heterocyclic carbine Rovis catalyst. [Reproduced with permission from ref . Copyright 2018, John Wiley and Sons.…”

“…Triazoliumcarbene-containing mesoporous hollow support was prepared by Ma and others through 2,2′-azobis(2methyl-propionamidine)dihydrochloride (AIBA) initiated polymerization of vinyl monomers (Figure 14). 84 The authors showed that thin mesoporous shell containing carbene is an effective catalyst for asymmetric Michael−Stetter cascade reaction, producing higher enantioselectivities than nonporous polystyrene-supported carbene. The authors showed that mesopores (3−10 nm) have a great impact on high Besides, in a flow reaction system, the authors showed that this COF executes 100% conversion, 44% ee, and 65/35 dr values for a continuous 48 h of reaction (see Figure 15).…”

Hollow Mesoporous Organic Polymeric Nanobowls and Nanospheres: Shell Thickness and Mesopore-Dependent Catalytic Performance in Sulfonation, Immobilization of Organocatalyst, and Enantioselective Organocascade

“…In the past two decades, the size, − morphology, and hollow structure − dependent catalytic performances, closely related to effectiveness factor (η), have mainly focused on metal catalysis owing to the spectacular advances in the well-controlled syntheses of nanosized metals and oxides. However, the investigation of polymer-based heterogeneous organocatalysts with well-controlled size, pore structure, and morphology is in its infancy due to the difficulty in well-controlled synthesis. , With those as the motivations, there is an overwhelming desire for the synthesis of nanosized, mesopore-abundant, and well-shaped polymer-supported organocatalyst with high void fraction (θ) and short sphere radius ( R ) to improve the effectiveness factor (η) of organocatalyst, especially to satisfy the spatial demand for severe mass transfer of bulky reactants in complex heterogeneous multicomponent/multicatalytic enantioselective organocascade.…”