Polystyrene resins crosslinking

Figure 6.2.15. Result for a Py-GC/MS analysis of Wang polystyrene resin crosslinked with poly(ethylene glycol)(16) and having 0.8-1.5 mmol/g 4-benzyloxybenzyl alcohol (upper trace) and the pyrogram of polystyrene (lower trace). Pyrolysis done at 60(f C in He, with the separation on a Carbowax type column.

Lightly crosslinked resins are less robust but have greater ability to swell in appropriate solvents. Typically a 1-2% crosslinked divinyl benzene polystyrene resin is employed in organic synthesis. 

For quantitative analysis of solid supported thiol residues on free macroporous or PEG grafts, Ellman s reagent has been used [5,5 -dithio-hfr-(2-nitrobenzoic acid]. However only qualitative information can be gained using lightly crosslinked polystyrene resins [Badyal et al. Tetrahedron Lett 42 8531 2007]. 

C10Hlo)o.01 C8H8 0.57 (c8H7Br)o.42 (Bromo)polystyrene (20.00 g, 60 meq), originally prepared from commercial 1% crosslinked polystyrene resin (37), was suspended in 500 ml dry benzene under nitrogen. Into this pale orange suspension was injected 2.2 M nBuLi/hexane (60 ml,... 

The axial immobilization of chiral [Mn((S,S)-salen )j (where salen = (Si,Sj-NiN -bis(3,5-diR -salicylidene)-l,2-diRbethane-diamine R = Bu, R -R = -(CH2)4- R = Bu, R = Ph R = Pn, R R = -(CH2)4-) complexes was achieved by reaction of [Mn(salen )Cl] with sulfonic acid- or phenol-substituted crosslinked and insoluble polystyrene resins [45]. The resulting polymer-immobilized [Mn(salen )j complexes were active and enantioselective for the asymmetric epoxidation of... 

Frechet, J. M. J. and M. J. Farrall, Functionalization of Crosslinked Polystyrene Resins by Chemical Modification A Review, pp. 59-83 in Chemistry and Properties of Crosslinked Polymers, S. S. Labana, ed., Academic Press, New York, 1977. 

Likewise, in the preparation of many ion-exchange resins, suitable functional groups are introduced by secondary reactions of macromolecular substances (that are generally crosslinked see Sect. 5.2). In this context the utilization of crosslinked polystyrene resins or poly(acrylamide) gel in the solid-phase synthesis of polypeptides (Merrifield technique) or even oligonucleotides should be mentioned. After complete preparation of the desired products they are cleaved from the crosslinked substrate and can be isolated. 

The leading solid phases are the 2-chlorotrityl chloride resins. Professor K. Barlos (University of Patras, Greece) has made the single most important contribntion to the development of these resins. They consist of a polystyrene-base resin crosslinked with a small amonnt of divinylbenzene and functionalized with 2-chlorotritiyl chloride. 

Oxovanadium(V) and oxomolybdenum(VI) were incorporated into crosslinked polystyrene resins functionalized with iminodiacetic acid or diethylenetriamine derivatives 921 The polymer complexes were used as catalysts in the oxidation of olefins with f-butylhydroperoxide. Vanadium(V) complexes promote the epoxidation of allylic alcohols in a highly regioselective manner, e.g., 2,3-epoxide was obtained in 98 % selectivity from e-geraniol at 80 °C. The catalytic activity of the vanadium(V) complexes is generally higher than that of the molybdenium(VI) complexes in the oxidation of allylic alcohols, whereas an opposed trend holds for the epoxidation of cyclohexene. 

Also synthetic porphyrins were used for polymer attachment. The easiest way for synthetic porphyrins is the reaction between pyrrol and benzaldehyde to ms-tetra-phenyl-porphine (9 a). Substituted porphines (9c-e) are prepared from substituted benzaldehy-des. Porous crosslinked polystyrene resins were used in the reaction with (9c-e) as shown in Eq. 13 to get the polymers (29)-(31) containing 2-6% porphines in covalent bond ... 

Hashimoto and Otsuki [66] reported the negative-ion LC-ESI-MS analysis of all nine acids after separation on a crosslinked polystyrene resin with a mobile phase of 20% acetonitrile in water containing 3% acetic acid. Detection limits after extraction from 200 ml water was between 3 and 70 mg/1. 

Scheme 7.13. Solid-phase synthesis with Pam linker on polystyrene resin. Note that polystyrene resin is crosslinked by incorporating a small quantity of divinylbenzene.

Reichenberg, D. McCauley, D.J. Cation exchange equilibria on sulfonated polystyrene resins of varying degrees of crosslinking. J. Chem. Soc. 1955, 2741. 

Davankov and his co-workers [55, 56] first discovered these remarkable resins. They are prepared either by chemically crosslinking linear polystyrene in a post-polymerisation treatment, or similarly post-treating lightly crosslinked (with —0.3-2% divinylbenzene) polystyrene resins. Reagent quantities are chosen to allow exhaustive Friedal-Crafts alkylation of aromatic... 

Early work on the application of NMR conventional techniques to the study of solvent swollen crosslinked polymers was reported by Stenlicht and co-workers [92] and Schaefer [93]. The first detailed work on the chlorome-thylated polystyrene resins used in solid phase synthesis appears to be by Manatt and co-workers [94]. They employed a 0.095% crosslinked species supplied by the Dow Chemical Co. and chloromethylated this to varying degrees. noise decoupled C NMR spectra were recorded in the usual... 

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