Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Metal-catalyzed couplings thiophene

As outlined earlier, three methods of polymerization have been established for the preparation of thiophenes, viz. electrochemical polymerization [189, 190], oxidative chemical polymerization using Lewis acid catalysts such as FeCl3 [191,192], and step-growth condensation polymerization using transition metal-catalyzed coupling reactions [lj]. [Pg.97]

Much effort has been devoted to studies of thiophene oligomers and polymers, in particular in connection with development of new organic materials for electronic applications. Many of the synthetic approaches towards oligothiophenes rely on well-established methodology, such as metalations, halogen-metal exchange reactions, and transition metal catalyzed couplings. [Pg.106]

The synthesis of conjugated polymers is highly dependent on the effective carbon-carbon single bond generation between unsaturated carbons in aromatic molecules. Aromatic units in conjugated polymers can be benzene, aniline, pyrrole, thiophene, carbazole, naphthalenediimide, perylenediimide (PDI), or their derivatives, etc. Although monomers are various, their synthetic methods can be mainly classified into chemical and electrochemical polymerizations. Chemical polymerization includes chemical oxidative polymerization and metal-catalyzed coupling condensation. [Pg.14]

Polymerization of thiophenes can be carried out in many different ways and the most commonly used methods can be generalized into three categories (i) electropolymerization, (ii) metal-catalyzed coupling reactions and (iii) chemical oxidative polymerization. Electropolymerization is a widely used method to prepare insoluble films of PTs and represents a simple and efficient way to study the optical and electronic properties of PTs [4], although it is rarely used in the preparation of electroluminescent materials. In 1980, Yamamoto et al. reported the Ni-catalyzed polycondensation of 2,5-dibromothiophene 1. The latter was allowed to react with Mg in THF, affording 2-magnesiobromo-5-bromothiophene 2, which in the presence of Ni(bipy)Cl2 (bipy = 2,2 -bipyridyl) produced PT 3 (Scheme 19.2) [15], In the same year, Lin and Dudek described another example of a metal-catalyzed route to unsubstituted PT 3, exploiting acetylacetonates of Ni, Pd, Co and Fe as catalysts [16]. [Pg.697]

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). [Pg.37]

The last method for the preparation of 2-quinolones described in this chapter relies on a intramolecular Heck cyclization starting from heteroaryl-amides (Table 2) [57]. These are synthesized either from commercially available pyrrole- and thiophene-2-carboxylic acids (a, Table 2) or thiophene-and furan-3-carboxylic acids (b, Table 2) in three steps. The Heck cyclization is conventionally performed with W,Ar-dimethylacetamide (DMA) as solvent, KOAc as base and Pd(PPh3)4 as catalyst for 24 h at 120 °C resulting in the coupled products in 56-89% yields. As discussed in Sect. 3.4, transition metal-catalyzed reactions often benefit from microwave irradiation [58-61], and so is the case also for this intramolecular reaction. In fact, derivatives with an aryl iodide were successfully coupled by conventional methods, whereas the heteroarylbromides 18 and 19, shown in Table 2, could only be coupled in satisfying yields by using MAOS (Table 2). [Pg.320]

Much work has been directed towards the synthesis of thiophene oligomers and polymers. This is due to the current interest in research on conducting polymers and molecular electronics (92CRV711). Two main approaches have been used for making such polymers (i) chemical (e.g. FeCl3) or electrochemical oxidation of monomeric thiophenes and (ii) transition metal-catalyzed cross-coupling reactions. [Pg.363]

Transition metal-catalyzed cross-coupling reactions of thiophenes have been extensively covered in CHEC-II(1996). These include ... [Pg.766]

Transition metal catalyzed processes are useful tools for the synthesis of functionalized thiophenes. Thus for instance, a phosphine-free, palladium catalyzed coupling protocol for the synthesis of 2-arylbenzo[d]thiophenes from various 3-substituted benzo[6]thiophenes and aryl bromides or iodides has been reported <04T3221>. Likewise, 2,2 -bithiophenes have been 5,5 -diarylated directly with aryl bromides in the presence of Pd(OAc)2, bulky phosphine ligands and CS2CO3 <04T6757>. A series of electron-deficient and relatively electron-rich benzo[6]thienyl bromides have been shown to participate in palladium catalyzed amination reactions, as exemplified by the interesting conversion of 63 to the tetracyclic system 64 upon reaction with 2-aminopyridine 65 <04EJO3679>. [Pg.90]


See other pages where Metal-catalyzed couplings thiophene is mentioned: [Pg.117]    [Pg.119]    [Pg.185]    [Pg.100]    [Pg.117]    [Pg.119]    [Pg.76]    [Pg.131]    [Pg.256]    [Pg.118]    [Pg.152]    [Pg.154]    [Pg.78]    [Pg.128]    [Pg.124]    [Pg.175]    [Pg.330]    [Pg.128]    [Pg.175]    [Pg.130]    [Pg.203]    [Pg.86]    [Pg.600]    [Pg.96]    [Pg.158]    [Pg.35]    [Pg.123]    [Pg.105]    [Pg.179]    [Pg.301]    [Pg.3]    [Pg.45]    [Pg.119]   
See also in sourсe #XX -- [ Pg.102 , Pg.103 , Pg.104 , Pg.105 , Pg.106 , Pg.107 ]




SEARCH



Metal catalyzed coupling

Metalation thiophenes

Thiophenes metallation

© 2024 chempedia.info