Styrene-divinylbenzene copolymeric catalyst

Kureshy developed a polymer-based chiral Mn-salen complex (Figure 21). Copolymerization of styrene, divinylbenzene, and 4-vinylpyridine generated highly cross-linked (50%) porous beads loaded with pyridine ligands at 3.8 mmol g-1. Once the polymer was charged with the metal complex catalyst, enantioselective epoxidation of styrene derivatives was achieved with ee values in the range 16 46%. 79... 

Stannic chloride has been attached to monomers 21 containing ester (21a), carbazole (21b), pyrrolidone (21c), nitrile (21d) and pyridine (21d) moieties. The polymeric ligands were prepared by copolymerization of styrene, divinylbenzene and functional monomers such as methyl methacrylate, A -vinylcarbazole, Af-vinylpyrrolidone, acrylonitrile and 4-vinylpyridine [33], These polymers were treated with stannic chloride in chloroform to afford the corresponding polymer-supported stannic chloride complexes (Eq. 8). These polymeric complexes have been used as catalysts for such organic reactions including esterification, acetalization, and ketal formation. These complexes had good catalytic activity in the reactions and could be reused many times without loss of activity. Their stability was much better than that of plain polystyrene-stannic chloride complex catalyst. 

Catalyzed enantioselective Mukaiyama-aldol reactions have been developed extensively [101] and chiral polymer-supported Lewis acids are the catalysts of choice. Polymer-supported chiral A(-sulfonyloxazaborohdinones 86 and 87, prepared by copolymerization of styrene, divinylbenzene, and chiral monomers derived from L-valine and L-glutamic acid, respectively, have been used for aldol reactions [102]. The rates of reaction using the polymeric catalysts were slow and enantioselectivity was lower than was obtained by use of the low-molecular-weight counterpart (88). The best ee obtained by use of the polymeric catalyst was 90 % ee with 28 % isolated yield in the asymmetric aldol reaction of benzaldehyde with 89 (Eq. 27). 

A naphthalene supported polymer was prepared by radical copolymerization of 2-vinylnaphthalene, styrene, and divinylbenzene. This catalyst was used to mediate metallation of alkyl chlorides by lithium. The reaction was done in the presence of electrophiles to afford, after quenching, the desired addition products. 

The SAN and ABS cxjpolymers aantain approximately 25 wt% of acrylonitrile and polybutadiene rubber in amounts up to 20 wt%. Other styrene copolymers of industrial importance include styrene—maleic anhydride copolymer (SMA), styrene-divinylbenzene copolymer, acrylic—styrene-acrylonitrile terpolymer, and styrene-butadiene copolymer. Recently, metallocene catalysts have been developed to synthesize syndiotactic polystyrene (sPS). The polymerization process and process conditions have major effects on polymer properties and process economy. For styrene homopolymerization and copolymerization, various types of polymerization reactors are used commercially. 

Cornejo et al. [65] reported the first immobihzation of pyridine-bis(oxa-zoline) chiral hgands and the use of the corresponding solid ruthenium complex in the model cyclopropanation test. They synthesized vinyl-PyBOx, the vinyl functionahty being introduced in the fourth position of the pyridine ring. This monomer was further homo- or copolymerized in the presence of styrene and divinylbenzene. The corresponding ruthenium catalysts proved... 

Catalysts synthesized from crown ether monomers 61 and 62 by copolymerization with styrene and either p-divinylbenzene or p,p -divinylbiphenyl (63) are listed in Table 14 along with their relative activities for solid/solid/liquid reactions of potassium acetate with benzyl chloride (Eq. (13)) and potassium cyanide with 1,4-dichlorobutane (Eq. (14)) in acetonitrile 183). 

The catalysts used industrially in the MTBE process are sulphonated polystyrene resins of the macroreticular type. These strongly acidic materials are prepared by copolymerizing styrene and p-divinylbenzene in the presence of an organic compound that is a good solvent for the monomers but a poor swelling... 

Polymer-supported TADDOL-Ti catalyst 79 prepared by chemical modification was poorly active in the Diels-Alder reaction of 3-crotonoyloxazolidinone with cyclo-pentadiene (Eq. 24) whereas polymeric TADDOL-Ti 81 prepared by copolymerization of TADDOL monomer 80 with styrene and divinylbenzene had high activity similar to that of the soluble catalyst. In the presence of 0.2 equiv. 81 (R = H, Aryl = 2-naphthyl) the Diels-Alder adduct was obtained in 92 % yield with an endolexo ratio of 87 13. The enantioseleetivity of the endo product was 56 % ee. The stability and recyclability of the catalyst were tested in a batch system. The degree of conversion, the endolexo selectivity, and the enantioseleetivity hardly changed even after nine runs. Similar polymer-supported Ti-TADDOLate 82 was prepared by the chemical modification method [99]. Although this polymer efficiently catalyzed the same reaction to give the (2R,2S) adduct as a main product, asymmetric induction was less than that obtained by use of a with similar homogeneous species. 

The miscible monomers, ethenylbenzene (styrene) and diethenylben-zene (divinylbenzene, DVB), undergo a free radical induced copolymerization reaction initiated by a benzoyl peroxide catalyst. The exothermic reaction is carried out in an aqueous suspension whereby the mixed monomers are immiscibly dispersed as spherical droplets throughout the reacting medium resulting in discreet beads of copolymer being formed. Correct reaction conditions and the use of suspension stabilizers enable the particle size distribution of the... 

Porous polymers are prepared by suspension copolymerization of a large excess of monofunctional monomer (e.g. styrene, acrylic acid derivatives or vinylpyrrolidone) with a bifunctional monomer (e.g. divinylbenzene) in a suitable solvent. The cross-linking imparts the required rigidity to the bead polymer structure and, on drying, the solvent evaporates, leaving a porous framework. The choice of reagents, the solvent, catalyst emd the reaction conditions determine bead size and porosity. 

The method of latex synthesis for thiol autoxidation catalysts was different from that used for the phenol autoxidation catalysts. Surface active quaternary ammonium ion monomers were used. Latexes were prepared by emulsion copolymerization of 96.2 mol % styrene, 1.0 mol % divinylbenzene (technical 55% active), 0.8 mol % ethylvinylbenzene, and 2.0 mol % of monomer 4, 3 5 or 6 with azo(bisisobutyronitrile) as initiator. The conductivity of an aqueous solution of 4 before polymerization was 440 x 10" ohm l cm l. Ultrafiltration of the copolymer latex gave an initial filtrate with condutivity of 20 x 10 ohm l cm l and a... 

Salen ligands can be bound to different materials. The synthesis of polymer-bound chiral Mn(III) - salen complexes was independently reported by Sivaram et al. [41, 42] and Minutolo et al. [43]. Here, the monomeric units of the Jacobsen catalyst [44] were functionalized with two vinyl groups, which were copolymerized with styrene and divinylbenzene. 

Enantioselective addition of dialkylzinc reagents to simple ketones was promoted by Ti-based catalysts prepared from chiral ligands such as trans-1-arylsulfonylamino-2-(isobornylamino)cyclohexane derivatives [70, 71]. Chiral bissulfonamide monomer (167) was prepared and copolymerized with styrene and divinylbenzene to give polymer-supported chiral ligand (168) [72]. Polymeric chiral ligands (168) were tested in the enantioselective addition of diethylzinc to acetophenone in the... 

Most investigations of polymer-supported onium ion phase transfer catalysts have used cross-linked polystyrenes. Not all of them have the same structure, even when they have the same formal degree of cross-linking with divinylbenzene. (The effect of percent cross-linking is considered in a later section). Two principal methods have been used to functionalize polystyrene for phase transfer catalysts, chloromethylation of pre-formed beads and copolymerization of chloromethylstyrene monomer with styrene and divinylbenzene. The chloromethylation route employs chloromethyl methyl ether (a cancer suspect agent), and a Lewis acid, usually stannic chloride.Substitution proceeds >90% para and is accompanied by some intrapolymer alkylation, which puts additional cross-links into the polymer... 

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