Cross polymeric catalysts

Derivative Formation. Hydrogen peroxide is an important reagent in the manufacture of organic peroxides, including tert-huty hydroperoxide, benzoyl peroxide, peroxyacetic acid, esters such as tert-huty peroxyacetate, and ketone derivatives such as methyl ethyl ketone peroxide. These are used as polymerization catalysts, cross-linking agents, and oxidants (see Peroxides and peroxide compounds). 

Polymerization. Chloroprene is normally polymerized with free-radical catalysts in aqueous emulsion, limiting the conversion of monomer to avoid formation of cross-linked insoluble polymer. At a typical temperature of 40°C, the polymer is largely head-to-taH in orientation and trans in configuration, but modest amounts of head-to-head, cis, 1,2, and 3,4 addition units can also be detected. A much more regular and highly crystalline polymer can be made at low temperature (11). Chloroprene can also be polymerized with cationic polymerization catalysts, giving a polymer with... 

The 3,3 -cross-linked polymeric binaphthol ligand 238 in combination with A1Mc3 is also a highly selective catalyst for the 1,3-dipolar cycloaddition reaction in Scheme 12.69 (345). The only observable diastereomer resulting from the reactions was exo-233, which was obtained with an enantioselectivity of up to 99% ee using the aluminium catalyst of 238 (20 mol%). One of the advances of using a polymeric catalyst is the easy removal and recovery of the ligand from the... 

In the second method, activated zinc is employed for the synthesis of regioreg-ular P3ATs [241-244]. This procedure is illustrated in Scheme 58 and revolves around the selectivity of Reike zinc addition followed by Ni(0)- or Pd(0)-catalyzed cross-coupling polymerization. Catalyst selection has been shown to play a major role in this coupling scheme. For example, Pd(PPh3)4 was determined to be the most effective catalyst for the coupling of iodozinc compounds, whereas Ni(dppe)Cl2 proved superior in conjunction with bromozinc monomers. 

Scheme 70 Polymer-bonded lanthanide-based diene polymerization catalysts. PS = DVB-cross-linked polystyrene (2% divinylbenzene), PE = polyethylene (adopted from [293])...

Use Chemical intermediates, primers for adhesion promotion in extrusion coating, dispersants, scratch-resistant finishes on glass, masonry water repellents, cross-linking agents, esterification and olefin polymerization catalyst. 

Choice of Support. The most commonly used organic support is polystyrene (cross-linked with DVB) in its microp-orous (1-2% cross-linking) form, although it has also been used in its macroporous and popcorn form (Ford et al, 1982 Shan et al.,1989). Various other polymeric catalysts have been used like polyvinylpyridine resins, commercial ion-exchange resins (Arrad and Sasson, 1989), modified dextran anion exchangers (Kise et al, 1981), and macroporous glycidyl methacrylate-ethylene dimethacrylate resins (Hradil and Svec,... 

Cross-coupling reactions have also been examined in water using amphiphilic PS-PEG resin-supported palladium complexes. Palladium-catalyzed coupling of aryl halides with aryl(or alkenyl)boronic acids (the so-called Suzuki-Miyaura coupling) took place in aqueous alkaline solution in the presence of polymeric catalyst 59 at 25 °C to give the biaryls in excellent yields [90,... 

At attempt has been made to use gels as phase transfer catalysts [190]. A considerable difference was observed between the effects of cross-linked and linear polymeric catalysts. 

PMMA cross-linked by ethylene dimethacrylate with immobilized side oligooxy-ethylene chains were used as interfacial transfer catalysts [80]. Also studied was the formation of benzyl acetate, benzyl bromide and alkali metal acetates in boiling chloroform and of n-octylphenyl ester from n-octyl iodide and K or Na phenoxide in toluene at 100 °C in the presence of a catalytic polymer amount. The product yield increased with an increase in the reaction time and the catalyst/acetate or catalyst/ phenoxide molar ratio. The conversion of benzyl bromide increased according to the following sequence of acetates Napolymeric catalyst could be regenerated and used many times. 

The dimraization-alkoxylation of butadioie (Equation 24) is catalyzed by soluble Pd(PPh3)4 and by the analogous 1% cross-linked polystyryldiphenylphosphine catalyst (991. At similar P/Pd ratios die rates per Pd are higher with the polymeric catalysts, and the polyirm retards the agglomoation and precipitation of the catalyst observed in solution. 

---