Suzuki reactions poly phenylene

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]. 

Many poly(p-phenylenes) have since been synthesized by such Suzuki reactions [137]. 

Discoveries made in the late 1970s of electrical conductivity in conjugated polymers spawned a monumental interest in the study of these materials, which are ideally suited for synthesis via cross-coupling reactions. Yamamoto was the first to realize this possibility with a regiochemicahy defined synthesis of poly(/ -phenylene) formed via the Kumada-Corriu protocol. Since then, various cross-coupling reactions have been applied in condensation polymerization reactions,with the Suzuki and Sonogashira protocols gaining the most widespread use. 

Later, the same methodology was applied by Wallow and Novak for the synthesis of water-soluble poly(p-phenylene) derivatives via the poly-Suzuki reaction of 4,4 -biphenylylene bis(boronic acid) with 4,4 -dibromodiphenic acid in aqueous di-methylformamide [26]. These aromatic, rigid-chain polymers exhibit outstanding thermal stability (decomposition above 500 °C) and play an important role in high-performance engineering materials [27] conducting polymers [28] and nonlinear optical materials [29]. 

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]. 

With the first method, Schluter [180,181] utilized the Suzuki reaction to produce a poly(p-phenylene)-type backbone possessing reactive ort/to-hydroxy-methyl substituents. These substituents were subsequently used to couple a variety of Frechet-type monodendrons along the backbone as described in Figure 26. In general, the lower generations (i.e., G = 1) coupled with... 

As for poly(p-phenylene), there are two important methods the Ni-catalyzed coupling of Yamamoto and Colon, on the one hand, and the Suzuki reaction based on the coupling of aromatic boronic acids with halogenated aromatic compounds in the presence of a Pd(0) catalyst, on the other. Besides these two main methods, a series of other metal-catalyzed couplings have been explored. 

Over the past two decades, Suzuki polycondensation has become one of the most efficient methods for the synthesis of conjugated polymers. As another important cross-coupling protocol, the Suzuki-Miyaura cross-coupling reaction was invented by Suzuki and co-workers in 1979 The scope of the Suzuki reaction for synthetic applications has been surveyed in several excellent reviews by Kotha, Lahiri, Kashinath, Miyaura and Fu. The Suzuki-Miyaura cross-coupling reaction provided deeper insights into how to connect two specific sp -hybridized C-atoms more efficiently and under milder conditions. The Suzuki-Miyaura cross-coupling reaction was first used by Schlueter et al. to prepare poly(para-phenylene)s. ... 

The side reaction responsible for the coupling of phenyl groups from triphenylphosphine with the organic electrophile (see 148) has also been identified as being capable of incorporating phosphorous into poly(p-phenylene)s synthesized by the Suzuki reaction (249). 

Interfacial adhesion and, thereby, compatibility can be enhanced by the selective crosslinking reaction in polymer blends. Inoue and Suzuki [26] reported the properties of blends dynamically crosslinked PP-EPDM blends. The crosslinking agent was yV,N -/w-phenylene-bismaleimide - poly(2,2,4 - trimethyl - 1,2-dihydroquino -line) system. Increase in interfacial adhesion leads to... 

Scherf and Mullen prepared (Scheme 47) the ladder-type polyphenylene (LPPP, 5) with methine bridges [126-129], via a poly(diacylphenylene-co-phenylene) precursor copolymer 103 obtained by an AA-BB type Suzuki polycondensation. The key step is the polymer analogous Friedel-Crafts ringclosing reaction on the polyalcohol 104, obtained by the reduction of 103. This was found to proceed quickly and smoothly upon addition of boron-trifluoride to a solution of 104 in dichloromethane. The reaction appeared to be complete by both NMR and MALDI-TOF analysis, indicating the presence of less than 1% of defects due to incomplete ring closure. LPPPs with num-... 

The use of Suzuki couphng for the synthesis of polyphenylene polymers was introduced by Rehahn, Schlueter and Wegner [Eq. (9)] [230]. Poly(p-2,5-di-n-hexylphe-nylene) 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 polymerizahon afforded polymers containing, e.g., an average of about 28 phenylene units. 

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]. 

FIGURE 9.10 Syntheses of poly(2,5-substituted-phenylene)s by Yamamoto (A) and Suzuki (B) coupling reactions. 

Goodson et al. [246] reported formation of soluble derivatives of poly(p-phenylene) of high molecular weight via Suzuki coupling reactions catalyzed by palladium (0) precursors in the presence of either triphenylphosphine or tri(o-tolyl)phosphine. Use of triphenylphosphine, however, apparently resulted in incorporation of the phosphine [246],... 

Izumi and coworkers carried out similar preparations of conjugated polymers with azobenzenes in the main chain [212, 213]. Application of various palladium-catalyzed coupling methods such as the Suzuki coupling and the Heck reactions allowed formation of poly(p-phenylene)- and poly(phenyl vinylene)-based polymers ... 

For the Suzuki coupling reactions, see (a) Miyaura, N., Yanagi, T, and Suzuki, A., The palladium-catalyzed cross-coupling reaction of phenylboronic acid with haloarenes in the presence of bases, Synth. Comm., //, 513 (1981) (b) Suzuki, A., Organoborates in new synthetic reactions, Acc. Chem. Res., 15, 178-184 (1982) (c) Huber, J., and Scherf, U., A soluble poly(para-phenylene) composed of cyclophane units poly(2,5-(oxydecanoxy)-l,4-phenylene] Macromol. Rapid Commun., 15, 897 (1994). 

The synthesis of alltyl-bridged poly(p-phenylene)s is based on typical poly(p-phenylene) chemistry, followed by a second reaction in which the rigidifying bridge is created. Scherf et al. [314, 315,704,705] used Suzuki coupling to create a ketone-substituted poly(p-phenylene). In a next step, the ketone functions in this polymer were reduced and, finally, the ladder polymer was obtained by Friedel-Crafts alkylation (Fig. 43). 

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