Catalyst supports crosslinked polystyrene resins

Amphiphilic resin supported ruthenium(II) complexes similar to those displayed in structure 1 were employed as recyclable catalysts for dimethylformamide production from supercritical C02 itself [96]. Tertiary phosphines were attached to crosslinked polystyrene-poly(ethyleneglycol) graft copolymers (PS-PEG resin) with amino groups to form an immobilized chelating phosphine. In this case recycling was not particularly effective as catalytic activity declined with each subsequent cycle, probably due to oxidation of the phosphines and metal leaching. 

Poly(ethylene glycol) grafted on crosslinked polystyrene (PEG-PS) resin has often been used as a polymer support for chiral catalysts of reactions performed in aqueous media. Peptides immobilized to PEG-PS resin have been developed and used as a catalyst for direct asymmetric aldol reactions in aqueous media (Scheme 3.19) [42]. When tripeptide-supported PEG-PS 67 was used as chiral catalyst in the reaction between 70 and acetone, the corresponding aldol product 69 was obtained with 73% ee. Kudo further developed the one-pot sequential reaction of acidic deacetalization and enanhoselective aldol reaction by using an Amberhte and PEG-ST-supported peptide catalyst 67 [43]. The enantioenriched aldol product 72 was obtained in 74% isolated yield from acetal 70 in a one-pot reaction (Scheme 3.20). 

Macroporous resins are generally highly (>5%, typically 20-25%) crosslinked polystyrene microbeads [9,10,21]. The term macroporous refers to their inner skeleton, which is made of a permanent porous structure even in the dry state (cf Scheme Ic). Historically, functionalised macroporous resins have mainly been used for ion exchange and separation. Nowadays, many new applications, especially in the field of polymer-supported reagents [31, 32] and catalysts [5,7], have been developed. 

The most commonly used organic support is polystyrene (crosslinked with DVB) in its microporous (1-2% crosslinking) form, although it has also been used in its macroporous and popcorn forms (Ford et al., 1982 Shan et al., 1989). Various other polymeric catalysts have also been used, such as polyvinylpyridine resins. 

In 2009, Kudo and coworkers investigated the asymmetric Michael-type addition of N-methylated and unsubstituted indoles to a,(3-unsaturated aldehydes by resin-supported polypeptides. In an initial survey of several amphiphilic polyethyleneglycol-grafted crosslinked polystyrene-supported catalysts, organocatalyst 22, which adopts a p-turn conformation aided by the polyleucine moiety under aqueous conditions, was revealed as the ideal catalyst for the preparation of a series of Michael adducts that were, in a final... 

The most commonly studied resin support is polystyrene crosslinked with divinylbenzene (DVB) (1-2% crosslinking) in its microporous form, though it has also been used in its macroporous and popcorn forms. The PT catalyst can be physically adsorbed or chemically bound on the support with or without a spacer chain between the support and the PT catalyst. These supported catalysts are active in a variety of reactions but find limited commercial applications due to lower reactivity than the soluble analogs, which is mainly due to diffusional limitations in the... 

Commercially available Amberlite IR-120 (H -form) was used as an acid catalyst this resin is a divinylbenzene-crosslinked partially sulfonated gel-type polystyrene. As a base catalyst, PEG-PS resin-supported proline was employed. The reaction was performed in water-acetone-tetrahydrofuran (1 1 1 v/v/v) at room temperature in the presence of 20 mol. % of resin-supported proline and Amberlite. After 20 h, the reaction mixture contained the starting 4-nitro-benzaldehyde dimethyl acetal, 4-nitrobenzaldehyde and the corresponding aldol product with acetone in a ratio of 4 9 87. This means that both the... 

In the laboratory, styrene can be prepared by the decarboxylation of cinnamic acid, as shown in Reaction 1, using dry distillation. However, styrene is produced commercially from ethylene and benzene, two basic ingiedienis of the petrochemical industry. With electrophilic addition of ethylene to benzene, a mixture of ethyl benzene and diethylbenzene is obtained as own in Reaction 2. The dehydrogenation of these benzene derivatives produces slyrene and divinylbenzene, respectively (Reaction 3). A detailed synthesis of styrene is described by Berthelot et al (6). As mentioned earlier, styrene is an important monomer in many industrial polymers. Additionally, divinylbenzene which is produced as a by-product is an effective crosslinker for ion-exchange resins, polystyrene-based supported reagents and catalysts, and low profile additive in a number of liquid molding resin systems. 

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