Polymer, boronic acid-substituted

Immobilized boronic acid-substituted polymers have been used to im-... 

Recently, Fabre et al. [31] and Freund et al. [7, 8] used electro-chemically deposited, self-doped, boronic-acid-substituted, conducting polymers for saccharide and fluoride detection. Freund et al. prepared a potentiometric sensor for saccharides using self-doped PABA [7, 8]. The transduction mechanism in that system is reportedly the change in pKa of polyaniline that accompanies complexation, and the resulting change in the electrochemical potential. Sensors produced with this approach exhibit reversible responses with selectivity to various saccharides and 1,2-diols (Figure 3.22) that reflect their binding constants with phenylboronic acid observed in bulk solutions. The sensitivity... 

Finn [66] has reported that when alkenyl boronic acids are used in this process, the aminomethylphenol intermediates can undergo a further transformation to generate 2Ff-chromenes 153 (Scheme 7.20). This process can be done efficiently with catalytic amounts of dibenzylamine or the corresponding polymer-supported amine 154 to afford a variety of substituted 2H-chromenes 155-159 in one step. 

Arylmethyl(homobenzyl)ethylsulfonium salts are appropriate substrates for Suzuki-type coupling reactions. In this reaction, performed on a polymer-bound sulfonium tetrafluoroborate, the benzyl fragment on the sulfur atom was transferred to the boronic acid residue. The sulfonium salt was prepared from an al-kylthiol resin by alkylation with a substituted benzyl halide to give thioether 98 and subsequent alkylation with triethyloxonium tetrafluoroborate. Reaction with a boronic acid derivative yielded diaryl methanes 99 [94] (Scheme 6.1.22). 

From the known, differential complexing between boronic acids and polyhydroxy compounds, it follows that carbohydrate mixtures may be separated by column-chromatographic methods that exploit the differences. Nucleoside and nucleotide boronates have been separated on columns of anion-exchange resins,90 and sugars and alditols have been shown to be differentially retained on such resins in the sulfonated phenylboronic acid form,64 but perhaps the best uses of column chromatography in this connection have incorporated the resolving powers of insoluble polymers to which boronic acid groups have been covalently bonded. Such insoluble forms of boronates have been synthesized either by substitution of polysaccharide derivatives, or by polymerization of suitable arylboronic acids. 

This method is applicable to a variety of alkyl-substituted phenylene AB-type monomers [88]. The procedure was also extended to the condensation of AA and BB monomers [89]. Hereby, poly-p-phenylene polymers containing ether and carbonyl linkages in the polymer backbone are accessible. By polymerization of the AB2 monomer 3,5-dibromobenzene boronic acid in a biphasic aqueous/organic medium, Kim and Webster obtained hyperbranched polyphenylenes [90], Suzuki polycondensation in aqueous systems has proven to be a versatile method, which has been applied to the synthesis of a variety of different polymer types [91]. 

Nicolas, M., B. Fabre, G. Marchand, and J. Simonet. 2000. New boronic-acid- and boronate-substituted aromatic compounds as precursors of fluoride-responsive conjugated polymer Aims. Eur J Org Chem 1703—1710. 

Circularly polarised emission is possible from polymers containing chiral groups. Scherf and coworkers have prepared a cyclophane-substituted PPP by the Suzuki route using the dibromocyclophane 35 and the corresponding bis-boronic acid 36 (Scheme 15) [98,99]. If racemic monomers were used the resulting polymer 37 was not chiral with the cyclophanes randomly distributed on either face of the polymer (atactic). If resolved enantio-pure monomers were used, then the stereoregular isotactic 38 or syndiotactic 39 polymers could be obtained depending upon which enantiomer of each monomer was used. The isotactic polymer is chiral and both enantiomers have been prepared. 

The first water-soluble, electroactive, self-doped sulfonatoalkoxy-substituted PPP, poly[2,5-bis(3-sulfonatopropoxy)-l,4-phenylene-aZf-l,4-phenylene] (55), was synthesized from 1,4-benzenediboronic acid [4612-26-4] (56) and the disodium salt of l,4-dibromo-2,5-bis(3-sulfonatopropoxy)benzene (57) by the homogeneous Suzuki coupling method (130). The polymer purified by dialysis of an aqueous solution was composed exclusively of 1,4-linkages. The abihty to utilize a variety of bis(boronic acids) in this polymerization with sulfonate containing aiyl hahdes will lead to a high degree of structural control of the optoelectronic properties of these water-soluble poljnners. 

The incorporation of substructures into ladder polymers provides molecular properties with well-defined configuration and conformation. The difficulties, however, in synthesizing ladder-type polymers have been reported [50,51] For the synthesis of soluble ladder-type PPP, first, PPP precursor 51 with functional ketone groups was prepared by Pd-catalyzed coupling reaction of dihexyl-substituted aromatic boronic acid 29 with didecyl-substituted aryl bromide 50 in 60-80% yields. The values determined by GPC were 6100-9200 [52]. 

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