ISSN:0007-1641    

DOI:10.1002/pi.4980160402

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTechniques for the preparation of polymer supports are described. Details of suspension polymerisation reactions are given using novel resins based on poly(methacrylonitrile) as an example. The structure of supports is discussed, including both macroporous vinyl polymer based systems, and macroporous polysaccharide based species. Methods of derivatising supports are summarised with recent examples illustrating the ‘chemical modification’ approach, and the ‘functional monomer’ approach. Newer inert supports are introduced and the technique of γ‐ray irradiation grafting described as one method of achieving derivatisation of these potentially very useful

ISSN:0007-1641    

DOI:10.1002/pi.4980160403

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of the polymer‐support on the kinetics and coupling efficiency of amino acid condensations is described. Changes in the degree of swelling of the support network during peptide synthesis are also evaluated. The advantages of the solid phase method in particularly difficult amino acid sequences are highlighted. Finally, the question of site isolation and its relationship to polystyrene chain flexibility is discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980160404

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractHigh resolution and cross‐polarisation/magic angle spinning nuclear magnetic resonance spectroscopy of crosslinked polystyrene and of reagents and catalysts supported on crosslinked polystyrene and silica gel are reviewed. The materials studied include ionexchange resins, resins in solid phase peptide synthesis, organic synthetic reagents, phase transfer catalysts, transition metal catalysts, and liquid chromatography column packings.13C and31P n.m.r. spectra have been used to identify structures and to study macromolecule and micromolecule dynamics. New spectra of crosslinked polystyrenes and supported reagents are reported. Procedure to obtain qualitative and quantitative spectra are recommende

ISSN:0007-1641    

DOI:10.1002/pi.4980160405

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe present state of polymer‐supported acid catalysis is considered. Models describing the catalytic action of gel‐like and macroporous resin catalysts are presented. By chemical modification of poly (styrene‐co‐divinylbenzene) matrices, e.g. different ways of sulphonation, nitration, chlorination, fluorination and sulphoalkylation, the activity/selectivity and thermal stability of sulphonic acid resin catalysts can be improved. The synthesis of polymer‐supported Lewis acids is described. By comparison to AlCl3higher catalytic activities are obtained with the use

ISSN:0007-1641    

DOI:10.1002/pi.4980160406

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAt first glance poly(vinyl pyridine) and polystyrene appear to be very similar polymers. However, apart from obvious similarities in structure and electronic state, the two polymers have little in common as the nitrogen atom of the pyridyl ring has a profound influence on the polymer, affecting it from its cost to its chemical reactivity.

ISSN:0007-1641    

DOI:10.1002/pi.4980160407

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe technique of γ radiation grafting is shown to be of value in functionalising mechanically strong, chemically simple and chemically inert polymers such as polypropylene. The technique leads to the incorporation of several functional groups at a single site on the polymer which is of value in creating a three‐dimensional catalytically active site. Such sites enable the local environment to further enhance the natural selectivity arising from the molecular nature of a metal complex catalyst. Accordingly, supported metal complex catalysts prepared in this way have higher selectivities than their homogeneous analogues. The approach is illustrated by reference to cobalt and rhodium(I) olefin hydroformylation catalysts; in both cases the supported catalysts show greater selectivity towards the formation of normal as opposed to branched aldehydes than their homogeneous analogu

ISSN:0007-1641    

DOI:10.1002/pi.4980160408

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAsymmetric catalysis by acrylonitrile‐cinchona alkaloid copolymers (AN‐CA) in Michaeltype reactions has been studied. The copolymers having a free amino alcohol part in the alkaloid moiety gave higher optical yields than other existing polymer‐supported alkaloid catalysts. AN‐CA catalysts were easily recovered from the reaction mixture with retention of enantioselectivity, a decided advantage over monometric catalysts. In some reactions AN‐CA exhibited a distinct polymer effect which lead us to propose a new concept of stereo control: participation of C(3)‐chirality in the enantioface differentiating step (C(3)‐control). The catalytic behaviour of acrylamide‐CA copolymer in asymmetric epoxidation under phase‐transfer conditions

ISSN:0007-1641    

DOI:10.1002/pi.4980160409

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPolymer‐supported crown‐ethers9and11(4.5‐62% ring substitution) have been obtained by the reaction of 1% crosslinked chloromethylated polystyrenes with (hydroxymethyl) and (ω‐hydroxynonyl)‐18‐crown‐6, respectively. (Hydroxymethyl) and (ω‐hydroxynonyl) [2.2.2] cryptands have also been prepared and linked in a similar way to afford catalysts10and12(3‐6% ring substitution). Condensation of (aminomethyl) and (ω‐aminodecyl [2.2.2] crypands with carboxylated 1% crosslinked polystyrene gave catalysts13and14(5‐20% ring substitution). Phase‐transfer catalytic activity of polymer‐supported crown‐ethers and cryptands has been tested in anion promoted nucleophilic aliphatic substitutions, and compared with that of polymer‐supported phosphonium salts. The results indicate that catalytic activity of crown‐ethers strongly depends on the combination of three parameters: the nature of the nucleophile, the percent ring substitution, and the presence of a spacer chain. Catalytic activity of cryptands is higher than that of crown‐ethers and quaternary salts with similar percent ring substitution. It is much less dependent on the nature of the anions and on the presence of a spacer chain. As for the related quaternary salts, phase‐transfer reactions promoted by polymer‐supported crown‐ethers and cryptands follow a mechanism identical with that observed for soluble catalysts: the reactions occur in the organic shell surrounding a complexed ligand; anions are exchanged at the water‐organic solvent interface, the exchange not requiring the c

ISSN:0007-1641    

DOI:10.1002/pi.4980160410

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA concise survey of gas‐liquid phase‐transfer catalysis is reported, showing the main features of the method, and, in particular, discussing the influence of the temperature and pressure, catalyst selection and nature of the solid bed on the outcome of the reaction. Some new results concerning the malonate synthesis and the halide‐exchange on hydrocarbons are reported: the former shows that the monoalkylated ester can be selectively obtained by using the polyethyleneglycol “Carbowax 6000” as a catalyst adsorbed over potassium carbonate, whilst the latter refers to a true catalytic process, which can proceed indefinitely without renewing the catalytic bed. The influence of the catalyst percentage on the reaction equilibrium is also discussed. The advantages and the problems of gas‐liquid phase‐transfer catalysis are reviewed, together with its analogies to classic phase‐transfer catalysis and gas

ISSN:0007-1641    

DOI:10.1002/pi.4980160411

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY