Polycondensation cross coupling

Heitz has performed the cross-coupling polymerization using two-step one-pot process. The first step is the reaction of 1,4-diiodobenzene 107 with 2 equiv. of 2-methyl-3-butyn-2-ol 108 at room temperature in the presence of an aqueous base to give the protected bisalkyne 109. Following polycondensation with another equivalent of dihaloarene 110 leads to the corresponding polymer 111 at 100°C (Equation (53)). The overall yield of 111 was 50-90% and the average molecular weight (M ) was 1400-48 200. 

On the other hand, Lucht showed the cross-coupling polycondensation of primary phosphine 172 with arylene dihalide to give polymer 173. (Equation (83)) The reaction takes place with a Pd(PPh3)4 catalyst in the presence of a tertiary amine base. In particular, the reaction of 1,4-diiodobenzene with isobutylphosphine proceeds at 70 °C in the presence of triethylamine to give the corresponding polymer 173a (R = Bu) in 83% yield (d/n= 1700, PDI = 1.3) 173b (d/ = 5000, PDI = 1.6). 

The application of Heck coupling polycondensation is not limited to the synthesis of poly(arylene vinylene)s via the alkenylation of haloarenes in simple monomer systems but includes a variety of self- and cross-coupling reactions involving reactants with various functionalities. For instance, the polycondensation of diiodoarene with bis(acrylamido)arene by the Pd(OOCCH3)2—P (o-C6H4—CH3)3 catalyst yields respective aromatic polycinnamamide [106] ... 

Scheme 2 Model polycondensation by cross-coupling reaction...

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. 

PPVs are accessible by polycondensation methods based on transition metal-catalyzed cross-coupling processes. Several individual reactions are known. For example, using palladium catalysts, divinylbenzene yields with diiodobenzene derivates directly from PPV derivates. Another reaction, the Suzuki coupling, uses 1,4-aryldiboron acids and 1,2-dibromo-ethene with palladium catalysts to arrive at PPV. 

Suzuki polycondensation (SPC) uses Suzuki cross-coupling (SCC), which has been described in detail including all mechanistic aspects in Part ni.2.2. It is a step-growth... 

C. POLYCONDENSATIONS USING HECK-, STILLE-, AND SONOGASHIRA/IIAGIHARA-TYPE CROSS-COUPLING REACTIONS... 

Conjugated polymers remain prime candidates for use as semiconductors in the emergent field of organic electronics [40-43]. Such materials are typically synthesized via polycondensation reactions, using a variety of aryl cross-coupling reactions. These methods are subject to problems that relate to, for example, the elimination of precursor functional groups. Unfortunately, the polymers produced via these methods often contain defects and unwanted branching, that may have deleterious effects on the conductive properties of the resultant material. 

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