Polymerization Grignard coupling

In particular, H-H PIBs with molecular weights in the range of 3-10 k Dalton were prepared by the Grignard coupling polymerization of 2,2,3,3-tetramethyl-l,4-dibromobutane with copper(I) tris-(triphenylphosphino)bromide as catalyst (20). This catalyst is also referred to as the Yamamoto catalyst (21). The reaction is sketched out in Figure 6.2. 

Figure 6.2 Grignard Coupling Polymerization (19) Table 6.2 End Chain Functionalization...

Arylation, olefins, 187, 190 Arylketimines, iridium hydrogenation, 83 Arylpropanoic acid, Grignard coupling, 190 Aspartame, 8, 27 Asymmetric catalysis characteristics, 11 chiral metal complexes, 122 covalently bound intermediates, 323 electrochemistry, 342 hydrogen-bonded associates, 328 industrial applications, 8, 357 optically active compounds, 2 phase-transfer reactions, 333 photochemistry, 341 polymerization, 174, 332 purely organic compounds, 323 see also specific complexes Asymmetric induction, 71, 155 Attractive interaction, 196, 216 Autoinduction, 330 Axial chirality, 18 Aza-Diels-Alder reaction, 220 Azetidinone, 44, 80 Aziridination, olefins, 207... 

Polythiophene, as obtained from Grignard-coupling polymerization from dibromothiophene, was vacuum deposited on various substrates and studied by electron diffraction by Yamamoto el al. [51]. They report diffraction patterns obtained from a single crystalline region, showing 44 distinct reflections of hkO-type. The indexing is in accordance with the a and 6-axes values obtained by Mo el al. Curiously the crystal is oriented with its c-axis perpendicular to the substrate, and the c-axis parameter could not be determined. The crystal is reported to deteriorate under the electron beam. 

Relatively little is known of aryl Grignard reagents or aryllithium reagents, for example, produced from bromostyrene, but the former seems to have a tendency to polymerize during coupling [8]. On the other hand, the corresponding reagents prepared from vinylbenzyl chloride may in principle be used to couple a variety of functionalities to the styrene moiety. 

When one considers how synthetic chemistry has impacted the development of conjugated polymers, there is no better example than the poly(3-alkylthio-phenes) (P3ATs, 4). Early work focused on oxidative polymerization methods as a means of preparing soluble forms of this polymer. Subsequently, Grignard coupling reactions were able to prepare the polymer directly in the... 

The polymerization is thought to proceed via cationic processes. PPP prepared by this method essentially has a linear structure and DP of about 50 this DP is comparable to that of PPP prepared via Grignard coupling. Dehydro electrochemical oxidative polymerization of benzene has also been reported. ... 

Many of the simple monomers can be purchased commercially. Facile Grignard coupling alfords the 3-substitued thiophene derivatives, which can be purified by distillation procedures. The more complex monomers or hahde derivatives are synthesized via various techniques dependent upon the type of synthetic method and are usually noted in the polymerization reaction schemes. The most common polymerization techniques involve anhydrous solvents, with stable catalysts. THF is the most commonly used solvent for both substituted and nonsubstituted polythiophenes. 

E electrochemical polymerization, G Grignard coupling, Fe polymerization with FeClj, Zn regioregular polymerization by Rieke zinc, RG regioregular polymerization by Grignard coupling. 

The alkylthiophenes were first reacted with I2 in the presence of concentrated nitric acid to give the diiodoalkylthiophenes which were subsequently converted to their Grignards after reaction with Mg in 2-methyl THF. The Grignard monomers were then polymerized by coupling which was catalyzed by nickel-phosphine complex 1,2-bis-diphenylphosphino-propane-nickel(II) bromide [NiBr2(dppp)]. 

The synthetic methods used to polymerize the 3-alkyl thiophene do not differ substantially from these employed for thiophene. The good choice of the solvent is important to ensure a complete dissolution of the monomer and the electrolyte in the electrosynthesis case. Chemically polymerization is based on the Grignard coupling method used by Yamamoto et al. [71] and later revised by Kobayashi et al. [72]. Some polymerizations carried out with chemical oxidants are also known with poly(3-alkyl-thiophene) [73]. 

PATs can be prepared by electropolymerization [66,70], by nickel-catalyzed Grignard coupling of 2,5-dihalogenated thiophenes [72], and by oxidative polymerization using ferric chloride (Scheme 1) [17,74]. 

The wide variety of coupling methods adapted from organic synthesis to condensation polymerization of just one CP can be appreciated from Fig. 5-12. for poly(pheny-lene). Typical condensations and eliminations adapted to syntheses of such CPs as poly(phenylene) and poly(phenylene vinylene) (P(PV)) are illustrated in Fig. 5-13. Fig. 5-14 shows the variety of precursor routes available to P(PV). More recently, the Yu group [86] has demonstrated application of Pd-catalyzed Stille and Heck reactions to the synthesis of poly(thiophene) (P(T)) derivatives (cf. Fig. 5-15. Besides the Grignard couplings such as shown in Eq. 1.6, Chapter 1, P(T) s can also be prepared via a variety of other procedures, such as Friedel-Crafts alkylation [87], and direct oxidation with FeClj as for P(Py) above. 

The synthesis involves the nickel-catalyzed coupling of the mono-Grignard reagent derived from 3-alkyl-2,5-diiodothiophene (82,83). Also in that year, transition-metal hahdes, ie, FeCl, MoCl, and RuCl, were used for the chemical oxidative polymerization of 3-substituted thiophenes (84). Substantial decreases in conductivity were noted when branched side chains were present in the polymer stmcture (85). 

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