Polystyrene resins with immobilized

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. 

Alexandratos, S. D., Trochimiczuk, A. W., Horwitz, E. P., Catrone, R. C., synthesis and characterization of a bifunctional ion exchange resin with polystyrene-immobilized diphosphonic acid ligands, J. Appl. Polymn. Sci. 61,1996,273-278. 

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... 

Aiming at easier workup conditions, immobilization of several transition metal catalysts, which show activity for the epoxidation of allylic alcohols, on polymer support has been investigated. For example, Suzuki and coworkers incorporated an oxo-vanadium ion into cross-linked polystyrene resins functionalized with iminodiacetic acid or diethylenetri-amine derivatives (Scheme 57), which afforded a heterogeneous catalyst that can promote... 

Support-bound alkylating agents have been used to N-alkylate pyridines and dihydropyridines (Entries 7 and 8, Table 15.21). Similarly, resin-bound pyridines can be N-alkylated by treatment with a-halo ketones (DMF, 45 °C, 1 h [267]) or other alkylating agents [246]. Polystyrene-bound l-[(alkoxycarbonyl)methyl]pyridinium salts can be prepared by N-alkylating pyridine with immobilized haloacetates (Entry 8, Table 15.21). These pyridinium salts react with acceptor-substituted alkenes to yield cyclopropanes (Section 5.1.3.6). Pyridinium salts have also been prepared by reaction of resin-bound primary amines with /V-(2,4-dinitrophenyl)pyridinium salts [268,269]. 

Immobilization of 6 on a commercially available aminomethylated polystyrene resin [27] was readily tracked by means of solid-phase infrared spectroscopy (IR 1660 cm-1) and yielded material with a resin loading of 0.75 mmol g 1... 

Iodophenol, immobilized on a polystyrene-Wang resin, has been treated with a series of arylboronic acids dissolved in [C imJfBFJ using Pd(PPh3)4 as the palladium source (Scheme 5).47 The catalytic system was initiated in a similar manner to that previously reported45 and the reactions conducted at 110°C for 2 h. A 1 1 mixture with DMF was required to swell the hydrophobic cross-linked polystyrene resin and when neat [C4mim][BF4] was used no biaryl products were isolated. 

Recycling of the catalyst has been investigated by using Ru complexes with a chiral water-soluble ligand [286, 287], a dendritic ligand [288], or a TsDPEN immobilized on a polystyrene resin [289, 290],... 

Boehm [363] has described for the first time the synthesis of oxygen-bridged tetrahydropyridones by a three-component condensation among coumarin-3-carboxylic acid, ketones, and primary amines. A solid-phase version of this reaction has recently been reported [364]. 1,3-Propylenediamine was immobilized onto chloro-trityl polystyrene resin (loading of 0.65 mmol g ). The supported amine (470) was then treated with coumarin-3-carboxylic acid and 8 different ketones in NMP/THF... 

Figure 16.5 shows the comparison of the IR-spectrum of an aryl ether immobilized on polystyrene resin using the KBr pellet method with a spectrum taken with the ATR method [29]. With regard to the resolution of the spectrometer, the absolute positions of the absorptions are identical. 

A series of aryl radical cyclizations were reported by a group at Novartis [10], and some of these processes were also compared with bond formation by Pd-mediated Heck cyclization of the same substrates. The tributyltin hydride-mediated reaction of iodo alkenes 7 (Scheme 3), immobilized on polystyrene resin through a linker, gave dihydrobenzofurans 8 [11]. It was also possible to perform a tandem cyclization using allyltributyltin to give the allylated product 9, although the yields were less satisfactory. The radical cyclization onto enol ethers was demonstrated [12] by the conversion of 10 to 11. For best results, the tributyltin hydride and AIBN were added portionwise every 5-8 h. The impressive 95% yield was in fact higher than that for the solid-phase Heck cyclization of 10. Similarly, cyclization of anilide 12 afforded the phenanthridine 13. 

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