Polycondensation palladium-catalyzed

The observed stoichiometrically imbalanced polymerization behavior is rationalized by involvement of olefin-Pd(O) complex 14, which leads to cascade bidirectional allylation. Thus, after the first allylation of 13, 14 selectively forms the allylpalladium(II) complex at the other allylic terminal. Therefore, the polymer end groups are always the malonic ester moiety even in the presence of excess 13, which would not terminate the polycondensation by the attack on both polymer end groups. This behavior is dependent on the ligand of the Pd(0) catalyst bis(diphenylphosphino)butane (dppb) is indispensable, and use of PPh3 results in low molecular weight polymer as expected by Carothers and Flory s basic principle [1-3]. 

The Pd-catalyzed nonstoichiometric polycondensations of other monomers, in which an olefin-Pd(O) complex after the first allylic substitution exchanges the olefin ligand with the remote double bond, was also reported [258]. The dependence of nonstoichiometric polycondensation behavior on a catalyst is interesting in comparison to the polycondensation mentioned above, where that behavior only stems from the structure of the monomers. 

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Several phosphines, such as 2,4,4-trimethylpentylphosphine and phenylphosphine, give similarly the corresponding polymers. Several phosphorous-containing polyanilines are also prepared in a similar manner by the palladium-catalyzed polycondensation reaction. 

We recently presented the synthesis of polymer 1 via the palladium-catalyzed polycondensation of ( 7 -arene)Cr (00)3 and organostannane monomers (eq 7) [11]. This polycondensation technique is based on previous work... 

Poly(silylenealkynylenearylene)s. The first poly(silylenealkynylene arylene) to be reported was poly(dimethylsilyleneethynylene-p-phenyleneethynylene), (Si(CH3)2C=CC6H4C=C)rc, which was prepared by polycondensation of the disodium salts ofp-diethynylbenzene with dimethyldichlorosi-lane (83). A more efficient method was reported, which is a palladium-catalyzed polycondensation of dihaloaromatics and diethynyldiphenylsilanes (eq. 13). 

Palladium-catalyzed polycondensation of zinc organometaUic reagents with aryl bromides... 

Poly(9-hexyl-3,6-carbazolyleneethynylene) (32c) has been prepared by palladium catalyzed polycondensation of 3,6-diiodo-9-hexylcarbazole (32a) and 3,6-diethynyl-9-hexyl-carbazole (32b) [172]. The polymer has a number average molecular weight of 3000. By fractionation a polymer with of 6400 has been obtained. 

The same spacer has also been used to interrupt the conjugation between oligothiophenes [125,126]. In this case, the insertion of the dialkylsilyl group occurs via a Wurtz coupling or a palladium-catalyzed polycondensation. The general structure of the obtained polymers is depicted in Scheme (46) where R represents an alkyl chain. 

The synthesis of polymer 141 was reported by Rehahn and coworkers via the palladium-catalyzed polycondensation reaction of monomers 139 and 140." This methodology shown in Scheme 37 allowed for the synthesis of soluble poly(l,l -ferrocenylene-o/l-p-oUgophenylenes) that were isolated with high molecular weights. 

Rabani G and Kraft A (2002) S5mthesis of poly(ether-esteramide) elastomers by a palladium-catalyzed polycondensation of aromatic diiodides with terechelic diamines and carbon monoxide, Macromol Chem Rapid Commun, 23 375-379. 

A.-D. Schliiter and G. Wegner, Palladium and nickel catalyzed polycondensation — the key to structurally defined polyarene and other aromatic polymers, Acta Polym., 44 59-69, 1993. 

The palladium-catalyzed amination reaction with a monofunctional primary amine 167 effects i / -diarylation to afford the tertiary amine polymers 168. Hence, polycondensation of 167 with bifunctional arylene dihalides leads to 168 (Equation (81)). Polycondensation of a primary amine bearing an azobenzene moiety with dibromides in the presence of Pd2(dba)3 (2.5mol%)- Bu3P (P/Pd = 3 l) and NaO Bu at 100°G for 24h in toluene gives 168 in 81-93% yields, as reported by Kanbara. 

Recently, a number of studies have been aimed at expanding the scope of palladium- and nickel-catalyzed polycondensation reactions through new twists on established routes or the advent of entirely new reaction pathways. The Ni(0)-catalyzed homo-coupling polymerization of triflate-substituted benzenes 17, as shown in Scheme 22, was utilized to synthesize a number of PPP derivatives [74-76]. Structural characterization indicated that these polymers are para-linked,... 

Regioselective polycondensations with transition-metal catalysts were also reported. Nomura et al. developed palladium-catalyzed allylation polycondensation, in which nucleophile predominantly reacted with jt-allyl palladium at the terminal allylic carbon to give fi-linear products [122,123]. On the other hand, polymerization with an iridium catalyst selectively proceeded at the internal allylic carbon to yield branched polymers with pendant vinyl groups (Scheme 30). These polycondensations demonstrate that polymers having different structures can be synthesized from the same monomers by changing the catalyst [124],... 

Nomura, N., Tsurugi, K., Okada, M. Mechanistic rationale of a palladium-catalyzed allylic substitution polymerization-carbon-carbon bondforming polycondensation out of stoichiometric control by cascade bidirectional allylation. Angew. Chem., Int. Ed. Engl. 2001,40, 1932-1935. 

We recently developed efficient synthetic routes to the required 1,3- and -1,4 - dichlorobenzene Cr( CO) 3 (2) complexes for the preparation of pol3rmers such as 1 [13]. Complex 2 can be further modified by photolysis in the presence of tributylphosphine to produce the new monomer 3 (Scheme I). A relative rate study between 2 and 3 showed the latter complex to be less reactive in the palladium-catalyzed cross-coupling reaction with 1-(trimethylstannyl)-2-phenylethyne. The palladiiun-catalyzed polycondensation of monomers 3 and 4 resulted in high yields of polymer 5 (>90%). A reaction temperature of 65 °C and the use Of THF as solvent proved to be the optimum polymerization conditions. Lower temperatures or a solvent change to toluene afforded little if any polymer after several hours of reaction. 

Wang, Q., Takita, R., Kikuzaki, Y., Ozawa, E, 2010. Palladium-catalyzed dehydrohalogenative polycondensation of 2-bromo-3-hexylthiophene an efficient approach to head-to-tail poly(3-hexylthiophene). J.Am. Chem. Soc 132,11420-11421. 

Carbonylation was applied in oligomerizations and polycondensations as well, even though most of the previous work focused on monocarbonylation reactions. Chaudhari and colleagues reported a palladium-catalyzed carbonylation-polycon-densation reaction of aromatic diiodides and aminohydroxy compounds [117]. With their methodology, alternating polyesteramides were prepared in chlorobenzene with l,8-diaza-bicyclo[5.4.0]undec-7-ene (DBU) as a base under 3 bar of carbon monoxide at 120 °C (Scheme 2.8). 

Kanhara, T. Oshima, M. Imayasu, T. Hasegawa, K. Preparation of new polymers containing an azohenzene group in the side chain by palladium-catalyzed polymer reaction and polycondensation and characterization of the polymers. Macromolecules 1998, 31, 8725-8730. 

New Palladium- and Nickel-Catalyzed Polycondensations for Synthesis of Carbon-Carbon Chain Polymers, Polyamides, and Related Condensation Polymers. 

Palladium and Nickel Catalyzed Polycondensation—The Key to Structurally Defined Polyarylenes and Other Aromatic Polymers. 

Applications of these C-H activation processes in polymerization reactions have also been reported in the literature. For example, a palladium-catalyzed C-H arylation polycondensation was carried out between a thiophene unsubstituted at the 2- and 5- positions and its 2,5-dibromo derivative. The transformation was effected in the presence of palladium acetate, a phosphine, and cesium carbonate in DMF at 100 °C for 48 h (eq 23). A survey of different phosphines showed that similar yields, molecular weights (Mn), and polydispersity indexes (PDI) could be obtained using di-tert-butyl(methyl)phosphonium tetrafluoroborate or tri-cyclohexylphosphonium tetrafluoroborate as the ligand. ... 

Yamamoto, T, K. Osakada, T. Wakabayashi, and A. Yamamoto Nickel and Palladium Catalyzed Dehalogenating Polycondensation of Dihaloaromatic Compounds with Zinc. A New Route to Poly(2,5-thienylene) and Poly(l,4-phenylene). Makromol. Chem., Rapid Commun. 6, 671 (1985). 

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