Subject polystyrene supports

The group of Botta demonstrated the feasibility of their microwave-assisted iodi-nation protocol (see Scheme 6.143 d) toward a polymer-supported substrate [68], An appropriate pyrimidinone attached to conventional Merrifield polystyrene resin was suspended in N,N-dimethylformamide, treated with 2 equivalents of N-iodosuccini-mide (NIS), and subjected to microwave irradiation for 3 min. Treatment of the polymer-bound intermediate with OXONE released the desired 5-iodouracil in almost quantitative yield (Scheme 7.57). 

One point which can be settled qualitatively, however, is whether singlet exciton migration does in fact occur in the aryl vinyl polymers. It will be shown that available evidence supports energy migration as an important feature of the photophysics of polystyrene (PS), poly(l-vinyl naphthalene) (P1VN), and poly(2-vinyl naphthalene) (P2VN), the homopolymers which are the subject of the majority of the review. 

A general scheme for the production of such functionalized polymers can be presented as follows The polymer support (polyethylene (PE), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene (FIFE), ethylene-propylene copolymers (CEP), etc.) are subjected to mechanical, chemical, radiation-chemical ( -irradiation or with accelerated electrons) or high-frequency (HF), UV-irradiation treatment with a subsequent grafting of the appropriate monomers ... 

The interpretation of diffraction data on amorphous polymers is currently a subject of debate. Ovchinnikov et al. (31,34) interpreted their electron diffraction data to show considerable order in the bulk amorphous state, even for polyethylene. Miller and co-workers (3536) found that spacings increase with the size of the side groups, supporting the idea of local order in amorphous polymers. Fischer et al. (32), on the other hand, found that little or no order fits their data best. Schubach et al. (37) take an intermediate position, finding that they were able to characterize first- and second-neighbor spacings for polystyrene and polycarbonate, but no further. 

Bidentate ligands were used by Alper and coworkers. The bis(diphenylphospino-methyl)amine ligands were prepared on primary amine-terminated PAMAM dendrons on silica as well as polyamido dendrons on polystyrene via the double Mannich-like reaction with formaldehyde and diphenylphosphine (Scheme 15.36a). " Subsequently, Alper and coworkers subjected the dendronized ligand-decorated supports to complexation with rhodium and palladium precursors in order to prepare active catalysts for a number of important chemical transformations (Scheme 15.36b). Initially, the dendronized rhodium catalysts were tested in the hydroformylation reaction and carbonylative ring expansion of... 

To initiate the first step of the repetitive synthesis, the trityl chloride derivative of polystyrene was subjected to reaction with thymidine in pyridine (Scheme 6). It is note-worthy that unreacted trityl chloride groups were blocked as methyl ethers by addition of methanol [41], The thymidine content was found to be 60-340 jumol g" after polymer-analogous cleavage from the support. This capacity corresponds to a degree of functionalization of 15-85% and points to steric problems of this attachment to the polymer. 

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