Poly-Suzuki coupling

The dibromo- (and diiodo-) stilbenes ate potentially useful monomers tor the synthesis of poly(p-phenylenevinylenes) via poly-Heck or poly-Suzuki coupling reactions. ... 

At about die same time, die application of the Suzuki coupling, the crosscoupling of boronic acids widi aryl-alkenyl halides in die presence of a base and a catalytic amount of palladium catalyst (Scheme 9.12),16 for step-growth polymerization also appeared. Schliiter et al. reported die synthesis of soluble poly(para-phenylene)s by using the Suzuki coupling condition in 1989 (Scheme 9.13).17 Because aryl-alkenyl boronic acids are readily available and moisture stable, the Suzuki coupling became one of die most commonly used mediods for die synthesis of a variety of polymers.18... 

Similar Suzuki couplings have been performed by Hu and coworkers utilizing a poly(dicyclohexylcarbodiimide)/palladium nanoparticle composite [152]. This PDHC-Pd catalyst showed remarkable activity and stability under microwave irradiation. Near quantitative conversion (95% isolated yield) was obtained after 40 min of microwave heating of a mixture of iodobenzene with phenylboronic acid in dioxane. Re-using the immobilized catalyzed showed no significant loss of efficiency, as the fifth cycle still furnished a 90% isolated yield of the desired biphenyl. 

J. Terao, A. Tang, J.J. Michels, A. Krivokapic, and H.L. Anderson, Synthesis of poly(p-phenylene vinylene) rotaxanes by aqueous Suzuki coupling, Chem. Commun. 56-57, 2004. 

S. Guillerez and G. Bidan, New convenient synthesis of highly regioregular poly(3-octylthiophene) based on the Suzuki coupling reaction, Synth. Met., 93 123-126, 1998. 

Over the past decade, literally dozens of new AB2-type monomers have been reported leading to an enormously diverse array of hyperbranched structures. Some general types include poly(phenylenes) obtained by Suzuki-coupling [54, 55], poly(phenylacetylenes prepared by Heck-reaction [58], polycarbosilanes, polycarbosiloxanes [59], and polysiloxysilanes by hydrosilylation [60], poly(ether ketones) by nucleophilic aromatic substitution [61] and polyesters [62] or polyethers by polycondensations [63] or by ring opening [64]. 

Ruthenium-catalysed Ring-Opening Metathesis Polymerization (ROMP) 29 526 529 (Equation 10) and Pd(tppms)3-catalysed synthesis of water soluble poly-(p-phenylene) derivatives (Equation ll).530 The latter is a special example of a Suzuki coupling (see earlier). 

Water-soluble poly(p-phenylene) 24, shown in Scheme 29, was prepared by the introduction of carboxylic acid pendant substituents along the p-phenylene chains [102]. In initial work in this area, a dicarboxy-substituted dibromobiphe-nyl was polymerized with 4,4f-biphenyl bis-boronic acid via Suzuki coupling... 

Terao J et al (2004) Synthesis of poly(para-phenylenevinylene) rotaxanes by aqueous Suzuki coupling. Chem Commun 56-57. 

As was shown earlier with the Suzuki coupling reactions, organopalladium intermediates can show good stability to water and other protic sources. This stability has been exploited in the synthesis of polyacetylene under air- and moisture-stable conditions. It was found that simple palladium(II) salts (PdCl2, Pd(CH3C02)2, etc.) can be used to initiate the 1,2-insertion polymerization of strained cyclic alkenes in water (eq. (8)) [31]. Once formed, poly-8 can be converted to polyacetylene through a retro-Diels-Alder reaction. 

Suzuki coupling. Synthesis of temperature in the presence of the W reusable polymer-supported (Ph,P Rd c arylboronic acids with poly(ethylcnc j... 

Scheme 7.12 Synthesis of functionalized poly(p-phenylene) via AA/BB Suzuki coupling in an aqueous biphasic system.

Poly p-phenylene (104) was expected to have good thermal and oxidative stability as well as electrical conductivity in the oxidized or reduced states. Rehahn et al. reported the first cross-coupling reaction of dihaloarenes 100 and aryldiboronic acids (101) to provide poly (p-phenylenes) (104) [160]. Homologation was achieved via repeating the following sequence of reactions lithiation, boration, and Suzuki coupling [160]. 

A somewhat similar technique was discovered by Bergbreiter etal. [123]. He found that biphasic solvent systems exhibit an increase in phase miscibility at elevated temperature if special soluble polymers are added (cf. also Section 7.6). An elegant option is to fix the catalyst on this soluble polymer. For example, he used poly(N-isopropylacryl amide) derivatives which are able to bound phosphine ligands coordinated to a Pd catalyst. High yields in Heck- and Suzuki-couplings can be obtained and the catalyst can be recycled (cf. also Section 6.6). 

The use of Suzuki coupling for the synthesis of polyphenylene polymers was introduced by Rehahn, Schluter, and Wegner (Eq. 8) [87]. Poly(p-2,5-di-n-hexylpheny-lene) was prepared in a biphasic mixture of benzene and water as a reaction medium, using sodium carbonate as a water-soluble base. This AB-type polymerization afforded polymers containing an average of about 28 phenylene units. 

Finally, conjugated materials 40 based on poly(phenylene thiophene) and poly (fluorene thiophene) main chain polymers functionalized with pendant trithiocyanato ruthenium terpyridine complexes were synthesized by the Suzuki coupling reaction. Heterojunction photovoltaic cells with the simple structure ITO/polymer/C-60/Al were fabricated. Under simulated AM1.5 solar light illumination, the short circuit currents, open circuit voltages, and power conversion efficiencies of the photovoltaic cells were measured to be 1.53-2.58 mAcm 2, 0.12-0.24 V, and 0.084-0.12%, respectively [77]. 

FIGURE 9.17 Syntheses of poly(2,7-carbazole)s by Yamamoto and Suzuki couplings from 2,7-difunctional carbazoles. 

Semihydrogenation. Alkynes are hydrogenated to (Z)-alkenes with Pd on pumice. C—C Bond couplings. Different supported Pd catalysts have been tried. For example, Suzuki coupling based on Pd-thiourea resin" and nanosize Pd on poly(Af-... 

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