Chloromethyl polystyrene oxidation

Recently this grafting methods has been used to synthesize amphiphilic graft copolymers in which hydrophilic grafts are linked to a hydrophobic backbone. Partly chloromethylated polystyrene is used to deactivate either monofunctional "living" polyethylene oxide or monofunctional "living" polyvinylpyridine. In the latter case subsequent quaternization yields polyelectrolyte grafts. ... 

The synthesis of (S)-zearalenone began with creation of the chlo-rodibutylstannyl polystyrene resin 32, which ultimately would serve as a Stille coupling partner. Oxidation of chloromethyl polystyrene resin fol-... 

Several solid supports have been employed for the attachment of o-iodosobenzoic acid, including silica gel, titania and nylon [89]. Two polymer-supported o-iodoxybenzoic acid reagents have recently been reported. The first was obtained by attaching a carboxymethyloxy derivative of f-butyl o-iodo-benzoate to an aminopropylated silica gel and oxidation with oxone [90]. The second involved chloromethylated polystyrene which was coupled with methyl 5-hydroxy-2-iodobenzoate and eventually oxidized by Bu4NS05H/MeS03H [91]. Some of these polymeric reagents appear in Scheme 31. 

Polymers can be modified by methods similar to those described above for metal oxides. For example, chloromethylated polystyrene reacts with diphenylphosphide to yield a phosphinated polystyrene (eqnation 4). The modified polymer can then be nsed as a hgand for a variety of... 

Recently, a series of polymer-anchored tungsten carbonyl catalysts based on modified polystyrenes was prepared [86]. Polymer modification was carried out by reaction of chloromethylated polystyrene (2% cross-linked with DVB) with diphosphines, di- and triamines, pyrazine, 4,4 -bipyridine, and imidazole. The polymers were treated with W(CO)6(TEIF) and their catalytic performance was evaluated in the epoxidation of cyclooctene. Different solvents and oxidants were tested and epoxide yields up to 98% were obtained using the system CH3CN/ H2O2. A detailed catalyst recycling study was carried out and the catalyst containing 4,4 -bipyridine units kept constant activity over 10 reactions whereas other catalysts revealed deactivation. 

Polymer-supported reagent. A polymeric peracid reagent (1) has been prepared from a polystyrene resin cross-linked with 1 or 2% of divinylbenzene by chloromethylation and oxidation to give a resin substituted by carboxyl groups. The —COOH groups are then converted into —COOOH groups by treatment... 

Amine complexes. The effect of immobilization of the Cu(II) complexes of polymeric amines has been examined and reviewed by Challa et al. ( ). The polymeric ligands were varied by using the following species polymer-bound dimethylbenzylamlne (formed by treatment of chloromethylated polystyrene with dimethylamlne), the copolymer of styrene and 4-vinyl-pyridine and the copolymer of styrene and N-vinylimidazole. The reaction examined was the Cu(II) oxidative dimerization of 2,6-disubstituted phenols (Equation 1). 

In more recent developments, a qulnone ester has been bound to chloromethylated polystyrene and the entire system used or oxidations In a continuous flow mode. The redox capacity can be nionltor-ed by the color of the reactor column and such reactions as the... 

The product of a reaction of chloromethylated polystyrene and triphenylphosphine can also convert to nucleophiles. In addition, use of a phase transfer catalyst converts soluble chloromethylated polystyrenes to phosphine oxides. Reactions with dioctylphosphine can serve as an example. Sometimes, phase transfer reactions are easier to carry out than conventional ones. This is the case with a Witting reaction. Both linear and crosslinked chloromethylated polystyrenes react smoothly with triphenylphosphine to give derivatives that react with various aldehydes. Phase transfer catalysts can also be used in carrying out nucleophilic substitutions with the aid of sulfides, like tetrahydrothiophine... 

The resulting 6-(methylthio)hexanoic acid is easily separable by aqueous extraction or by filtration through silica gel and can be reoxidized to 1873 with sodium metaperiodate in 97% yield. Low temperature (—60 °C) NMR spectrometry has been used to examine the intermediates of this Swem process. The results indicate that any residual unoxidized alcohol is generated during Pummerer elimination of the alkoxysulfonium intermediate and can be minimized by prolonged exposure to triethylamine at —40 °C. Reaction of the potassium salt of 1873 with cross-linked chloromethyl polystyrene affords a polymer-bound reagent that quantitatively oxidizes bomeol to camphor when used in two-fold excess [1394]. 

In the case of sodium periodate as oxidant, manganese(III) complexes with a bis(salicylaldehyde)-4-methyl-l,2-phenyl-enediimine (BSMP) [249b] or tetrapyridylporphyrin supported on chloromethylated polystyrene (TPyP)-CMP [249a] have proven as the catalysts of choice (Scheme 13.143). 

The application of the nucleophilic properties oS Bender s salts to the displacement of reactive halides on polymer substrates has been thoroughly evaluated by Daly and Lee (72). Polymers containing halomethyl hinctional groups such as chloromethylated polystyrene, poly(epichlorohydrin), copoly(epichlorohydrin-ethylene oxide), poly(2,6-feis-bromomethylphenylene oxi ) and poly vinyl chloride) were utilized as substrates with varying degrees of success. 

Although phase transfer catalysis is certainly an important and extremely versatile tool for the chemical modification of chloromethyl polystyrene, it is not necessarily always the best method as excellent results can also be obtained for some nucleophilic displacements when DMF or even DMSO (at low temperature to avoid oxidation to the carboxaldehyde polymer) are used as solvent for the nucleophile. For example, we prefer to use a solution of sodium cyanide in DMF to prepare cyanomethyl polystyrene from I rather than using a different solvent and phase transfer conditions, and we routinely prepare iodomethyl polystyrene from I by reaction with sodium or potassium iodide in acetone rather than under the conditions of Gozdz (Ref. 25). Recent work by Bied-Charreton et al. (Ref. 32) has also shown that excellent results could be obtained even under classical conditions in the transformation of I into its malononitrile derivative if the chloromethylated polymer is first transformed into the more reactive iodomethyl derivative this is in sharp contrast with earlier data from the same laboratory (Ref. 33). 

CHEMICAL MODIFICATION OF CHLOROMETHYLATED POLYSTYRENE WITH PHOSPHINE OXIDES USING PHASE-TRANSFER CATALYSIS... 

Graft polystyrene/poly(ethylene oxide), poly(styrene-g-ethylene oxide) (174), has been prepared by making chloromethylated polystyrene and condensing this product with living potassium-poly(ethylene oxide). The chloromethylpolystyrene can be prepared by chloromethylating polystyrene (175) or by copolymerization. 

The reaction of living poly(ethylene oxide) onto partially chloromethylated polystyrene is also quite straightforward, being an early example of the preparation of amphiphilic graft copolymers (Scheme 18). ... 

Polystyrene-g-poly(ethylene oxide) was synthesized by the copolymerization of styrene and styrenic PEO with CpTiCb/MAO catalyst [190]. In this case the macromonomer was prepared by first reacting the sodium salt of PEO-OH with NaH and then with a 5-fold amount of p-chloromethyl styrene. 

The principles needed to design a polymer of low flammability are reasonably well understood and have been systematized by Van Krevelen (5). A number of methods have been found for modifying the structure of an inherently flammable polymer to make it respond better to conventional flame retardant systems. For example, extensive work by Pearce et al. at Polytechnic (38, 39) has demonstrated that incorporation of certain ring systems such as phthalide or fluorenone structures into a polymer can greatly increase char and thus flame resistance. Pearce, et al. also showed that increased char formation from polystyrene could be achieved by the introduction of chloromethyl groups on the aromatic rings, along with the addition of antimony oxide or zinc oxide to provide a latent Friedel-Crafts catalyst. 

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