Poly substitution process

Reactions of perfluorinated alkenes, such as hexafluoropropene, with fluoride ion give perfluoroalkylcarbanions which can act as nucleophiles in S Ar reactions with perfluoroheteroaromatic systems (Fig. 8.13). These reactions are another example of mirror-image chemistry and reflect well-known Friedel-Crafts reactions of hydrocarbon systems that proceed by reaction of the corresponding electrophile and carbocationic intermediates. Poly substitution processes are possible and, indeed, all five fluorine atoms may be replaced upon reaction with an excess of tetrafluoroethylene and fluoride ion. ... 

The problem of the thermally induced polymerization reaction of partially or completely substituted cyclophosphazenes has been considered in the past by several authors [355-357], and more recently by H. R. AUcock [358]. This is because of the ease of synthesizing these substrates, the possibihty of preparing structurally regulated poly(organophosphazenes), and the lack of any additional nucleophilic substitution processes on the poly(organophosphazenes) obtained by the ROP process of fully saturated trimers. 

Since the initial disclosure by Allcock, workers have sought to answer various questions 1) What is the nature of the polymerization process (mechanism) 2) What is the structure of poly(dichlorophosphazene) that distinguishes it from the insoluble "inorganic rubber (III) 3) The substitution process gives a seemingly endless variety of products. What are the limitations or... 

Ill. N. Naz, T. H. Al-Tel, Y. Al-Abed, and W. Voelter, Palladium-cobalt-mediated double annulation process a new strategy to chiral and poly substituted bis-cyclopentanoids on carbohydrate precursors, J. Org. Chem., 61 (1996) 3250-3255. 

Beller and coworkers recently reported a new strategy for the synthesis of poly-substituted anilines based on a three-component-coupling reaction and a domino deprotec-tion/aromatization reaction (equation l)44. A mixture of O-benzyl carbamate, p-toluene-sulfonic acid, aldehyde, AC2O and dienophile in /V-rnclhy I pyrrol idone was allowed to react for 24 h at 120 °C, followed by Pd/C catalyzed dehydrogenation in triglyme at 140 °C. A variety of tri-, tetra- and penta-substituted anilines were efficiently created by this domino process. 

Elsenbaumer, R. L., Jen, K.Y., Miller, G. G., Eckhardt, H., Shacklette, L. W., and Jow, R., 1987. Poly [alkyl thiophenes] and poly (substituted heteroaromatic vinylenes] versatile, highly conductive, processible polymers with tunable properties, in Electronic Properties of Conjugated Poiymers, Kuzmany, H., Mehring, M., and Roth, S. [Eds.], Springer, Berlin. ISBN 0-387-18582-8. 

Metal-free iodine-promoted oxidative cyclization domino process was successfully utilized by Jiang et al. [15] to synthesize poly substituted oxazoles. Similarly, very efficient iodine-promoted oxidative cyclization domino process was reported by Wu et al. [16] for the synthesis of 2-acylbenzothiazoles 38 via a sp C-H functionalization (Scheme 9.8). 

Obviously, the first example of poly(substituted methylene) synthesis (PSMS) is polymerization of diazoalkanes and aryldiazomethanes, which was extensively studied in 1950-1970 [9-11] and whose importance as an alternative method for polyolefin synthesis was well recognized. In that period, in spite of the high explosiveness of the diazo compounds, many researchers were engaged in the polymerization and some unique and important characteristics for the process were revealed. Although some reviews of the polymerization were published [9-11], it is worthwhile to mention briefly some of the representative results, which are closely related to the contents of the later sections of this review. In addition, the unique character of surface-catalyzed polymerization of diazomethane has been utilized for surface modification recently, which is also described in this section. The efficient synthesis of nanometer-scale polymethylene thin films from diazomethane is quite remarkable, compared to the difficulty of polyethylene thin film formation because of the low solubility of the polymer. 

The alkylation process is the addition of an alkene to benzene, usually over an acidic catalyst to give the alkyl benzene. The reaction is non-selective, and polyalkyl benzenes are regular impurities in the cmde product stream. The degree of poly substitution is usually Umited by controlling the ratio of reactants. 

Barbe G, Charette A. Total synthesis of (+)-lepadin B stereoselective synthesis of nonracemic poly substituted hydroquinolines using an RC-ROM process. J. Am. Chem. Soc. 2008 130(42) 13873-13875. 

In addition to providing fully alkyl/aryl-substituted polyphosphasenes, the versatility of the process in Figure 2 has allowed the preparation of various functionalized polymers and copolymers. Thus the monomer (10) can be derivatized via deprotonation—substitution, when a P-methyl (or P—CH2—) group is present, to provide new phosphoranimines some of which, in turn, serve as precursors to new polymers (64). In the same vein, polymers containing a P—CH group, for example, poly(methylphenylphosphazene), can also be derivatized by deprotonation—substitution reactions without chain scission. This has produced a number of functionalized polymers (64,71—73), including water-soluble carboxylate salts (11), as well as graft copolymers with styrene (74) and with dimethylsiloxane (12) (75). 

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

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