Aryl dihalide

More attention has been devoted to aromatic and heteroaromatic substrates since first reported in 1983 [40]. The results are shown in Table 2 [25, 41-51]. All these reactions were run with nickel complexes associated with a phosphane or bpy ligand. Depending on the experimental conditions, the polymers were either precipitated during the electrolysis or deposited as films at the surface of the electrode. The method is also convenient to prepare copolymers from a mixture of two aryl dihalides. A mechanistic investigation on the nickel-bpy catalyzed polymerisation has been reported very recently [52]. 

Organic Electroreductive Coupling Reactions using Transition Metal Complexes as Catalysts Table 2. Reductive electropolymerisation of aryl dihalides using nickel catalysts... 

Kraft et al., 1998 Lowen and Van Dyke, 1990 Wei and Tian, 1993], Reactions other than oxidative polymerization are also being studied for producing polyaniline and polythiophene [Kraft et al., 1998 Loewe et al., 2001]. An example is the Pd-catalyzed dehydrohalogenation between aryl dihalides and aryl primary diamines to synthesize polyanilines [Kanbara et al.,... 

Tomita and Endo have shown that three-component coupling of bisallene 163, aryl dihalide, and a malonate nucleophile takes place with a palladium catalyst. Arylpalladium species derived from the halide attacks the central carbon of allene to form a Tt-allylpalladium intermediate, which is then attacked by the malonate anion to form C-C... 

An elegant synthesis method which is specific to sulfone polymers containing phenyl—phenyl linkages (such as PPSF) is the nickel-catalyzed coupling of aryl dihalides. The scheme for this synthesis involves a two-step process. First, an aromatic dihalide intermediate is formed which carries the backbone features of the desired polymer. This aromatic dihalide intermediate is then self-coupled in the presence of zero-valent nickel, triphenylphosphine, and excess zinc to form the biphenyl- or terphenyl-containing polymer. Application of this two-step scheme to PPSF can be depicted as follows ... 

Scheme 17. An intramolecular aryl dihalide tandem cyclization via the Stille reaction...

The sulfide polymers covered in this chapter are those based on the polysulfides derived from the reaction of dihalides and sodium di- or polysulfides polyphenylene sulfides generated from aryl dihalides and sodium sulfide polyalkylene sulfides generated from ethylene episulfide or dimercaptan-olefin or diolefin-diketone reactions, all of which are outlined in Scheme 1. 

Recently, Vidaurri [120] reported a batch process for increasing the production capacity of the poly(phenylene sulfide) wherein incremental quantities of the aryl dihalide are added to an alkali metal sulfide in the presence of a polar organic compound (A/ -methyl-2-pyrrolidone). These conditions allow the reaction to be carried out with good control of the temperature and without excessive build-up of pressure in a closed reactor system. Vidaurri prefers the use of sodium sulfide monohydrate [120]. 

Yu and coworkers describe a technique to retain stability and maximize the electrooptic response. They preformed the imide structure with an aryl dihalide monomer and incorporated highly efficient chromophore groups before polymerization. This highly functionalized monomer was subjected to a Pd-catalyzed coupling reaction with 2,5-bis(tributyltin)thiophene to give the polymer... 

The arylation of olefins by the treatment with an arylpalladium reagent (known as the Heck reaction [71]), which can be generated in situ from palladium acetate and an aryl dihalide, in the presence of a base, has been applied to the synthesis of many PPVs, some of which are shown in Scheme 12 [72-74]. Ethylene is the most reactive olefin, but a variety of functional groups, attached to the double bond, such as CO2R, OR, and CN can be... 

The Rosenmund-von Braun reaction involves the treatment of aryl halides with Cu CN or a 2 1-mixture of K CN/Cul in pyridine, quinoline or an appropriate aprotic polar solvent such as A-methylpyrrolidine (NMP), DMF, DMAC, HMPA at temperatures ranging from 150-250°C". This reaction has been postulated to proceed via organocopper intermediates. The reactivity of aryl-halogen bonds is in the order I > Br > Cl F. The difference in reactivity between Ar-Br and Ar Cl is normally sufficient to permit selective cyanation of the Ar—Br bonds (for example, compounds 2 and 3 ) (Figure 7.2). Discrimination between Ar—Br and Ar—1 bonds, however, is more difficult to accomplish, and therefore mixtures of iodo- and bromo-substituted aryl [ C]nitriles can be expected whenever iodo, bromo aryl dihalides are employed The selechve replacement of iodine... 

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