Benzenes with anions

The reaction pathway of 0-, N-, and S-containing l, 2-bifunctional benzenes with fluoroolefins depended on the relative abilities of the heteroatom to stabilize an adjacent anionic center, e.g., (17) and (18) [87-JCS(P1)763]. 

Packer et al. (1981) found that y-irradiation reduces arenediazonium tetrafluoro-borates to aryl radicals. Packer and Taylor (1985) investigated the y-irradiation of 4-chlorobenzenediazonium tetrafluoroborate by a 60Co source in the presence of 1 alone or I- +13 . The major product in the presence of iodide was 4,4 -dichloroazo-benzene. With I- + 1 ", however, it was 4-chloroiodobenzene. Two other investigations of the reactivity of aryl radicals with iodine-containing species are important for the understanding of the chain process of iodo-de-diazoniation that starts after formation of the aryl radical. Kryger et al. (1977) showed that, in the thermal decomposition of phenylazotriphenylmethane, the rate of iodine abstraction from I2 is extremely fast (see also Ando, 1978, p. 341). Furthermore, evidence for the formation of the radical anion V2 was reported by Beckwith and Meijs (1987) and by Abey-wickrema and Beckwith (1987) (see Sec. 10.11). 

Another type of interaction is the association of radical ions with the parent compounds. Recently (118), a theoretical study was reported on the interaction of butadiene ions with butadiene. Assuming a sandwich structure for the complex, the potential curve based on an extended Hiickel calculation for two approaching butadienes (B + B) revealed only repulsion, as expected, while the curves for B + and B + B" interactions exhibit shallow minima (.068 and. 048 eV) at an interplanar distance of about 3.4 A. From CNDO/2 calculations, adopting the parameter set of Wiberg (161), the dimer cation radical, BJ, appears to be. 132 eV more stable than the separate B and B species, whereas the separate B and B species are favored by. 116eV over the dimer anion radical, BJ. This finding is consistent with experimental results formation of the dimer cation radical was proved in a convincing manner (162) while the attempts to detect the dimer anion radical have been unsuccessful. With other hydrocarbons, the reported formation of benzene dimer anion radical (163) represents an exceptional case, while the dimeric cation radical was observed... 

A very attractive anionic/anionic/pericyclic/anionic fourfold domino sequence was developed by Kuehne s group, as illustrated in Scheme 2.147 [336]. Herein, on treatment of the enantiopure tryptophane-derived diester 2-644 with a, 3-unsatu-rated aldehydes 2-645 at 70 °C in benzene with benzoic acid and freshly activated... 

In order to avoid the SET process, we chose diphenylmethylsilyl anions (PI MeSiM 8a, M = K 8b, M = Na 8c, M = Li) as initiators for 7 instead of alkyllithium and benzene as a solvent. The polymerization did not take place in benzene with silyl anions alone. However, in the presence of an equimolar amount of suitable cryptands, the silyl anions initiated the polymerization. The results are summarized in Table 2. The molecular weights of polysilylenes thus obtained were in good agreement with the calculated values within experimental error. 

In moderately acidic solutions bromocriptine mesilate readily forms ion pairs with anionic dyes such as picric acid, bromothymol blue, methyl orange, which are extractable with an organic solvent. A procedure has been developed both for direct assay and for assay following chromatographic separation from the impurities. Therein bromocriptine mesilate is allowed to react with bromothymol blue at pH 2.5. The resulting ion pair is then extracted with benzene and its concentration determined at 410 nm (25). ... 

Scheme 3.37 describes gas-phase generation of m-benzyne anion (the distonic anion-biradical) from m-bis(trimethylsilyl) benzene (Wenthold et al. 1994, 1996 Wenthold and Squires 1998). The same anion-biradical is formed from isophthalic acid under the same conditions (Reed et al. 2000). Particularly, the reaction of m-bis(trimethylsilyl) benzene with fluoride ion, followed by treatment of the formed trimethylsilyl phenyl anion with fluorine in helium, produces the anion-biradical mentioned. The latter is transformed into the corresponding nitro benzoate anion through the addition of CO2 and NO2 (Scheme 3.37). 

Pinson and Saveant 1978, Swartz and Stenzel 1984). On electrochemical initiation (Hg cathode), 4-bromobenzophenone gives rise to 4-(phenylthio)benzophenone in the 80% yield, whereas bromoben-zene yields diphenyldisulfide with the yield of only 10% and unsubstituted benzene with the yield of more than 95%. In the bromobenzene case, this means that the substitution is a minor reaction, whereas the main ronte is ordinary debromination. According to Swartz and Stenzel (1984), the substrate anion-radicals are initially formed in the preelectrode space. Stability of these anion-radicals are different. The less stable anion-radicals of bromobenzene do not have enough time to go into the catholyte pool. They give rise to the phenyl radicals in the vicinity of the cathode. The phenyl radicals are instantly reduced into the phenyl anions. They tear protons from the solvent and yield benzene. 

However, different experimental conditions were used in the case of (rc/7-butylsulfmyl-methyl)benzene, the anion was made with butyllithium at 78 °C and quenched after one hour at — 78 C49, while in the case of (methylsulfmylmethyl)benzene the anion was made with methyllithium at — 60 °C and quenched after one minute45. 

The quenching of [lithio(methylsulfinyl)methyl]benzene with iodomethane produced [l-(methyl-sulfinyl)ethyl]benzene in a 15 1 diastereomer ratio (with predominant inversion) independent of the origin of methyllithium used to generate the anion. However, the stereochemistry of the methylation of [lithio(methylsulfinyl)methyl]benzene is dependent on the nature of the methylating agent52 (Table 1). 

Mixed dimerization also affects the kinetics of anionic copolymerization of styrene and para-methyl styrene, a system studied by O Driscoll(24). The reaction was performed in benzene with lithium counter-ions and the plots of In.[styrene] or In(para-methyl styrene] vs. time were both linear. Their slopes,... 

Oxidation of Anionic Polymers In the Solid State The ability of the macroradical and of the macroions to diffuse In the mixture, and to interreact Is responsible for the secondary products formation coupling reaction and alcoholate synthesis. To prevent the diffusion phenomenon, we have carried out the deactivation In the solid state. The living polymers have been prepared In benzene, with or without a solvating agent (THF or TMEDA) and the solution has been freeze dried before the oxygen introduction. The experimental results are collected in Table VII. 

Arylsilane radical anions undergo cleavage and coupling reactions, usually under conditions where excess reducing agent is available. Reduction of phenylsilane, diphenylsilane, or triphenylsilane with sodium-potassium alloy under preparative conditions gives high yields of tetraphenylsilane (7). In the reduction of phenylsilanes, the appearance of 1,4-bis(silyl)benzene radical anions is frequently observed (135, 35, 86, 97, 75, 120, 100). Typical results are shown in Table II. 

The carbonation of polymeric anions using carbon dioxide is one of the most useful and widely used functionalization reactions. However, there are special problems associated with the carbonation of polymeric organolithium compounds317 . For example, Wyman, Allen and Altares318) reported that the carbonation of poly-(styryl)lithium in benzene with gaseous carbon dioxide produced only a 60% yield of carboxylic acid the acid was contaminated with significant amounts of the corresponding ketone(dimer) and tertiary alcohol(trimer) as shown in Eq. (70). 

Atlox 3470, a product of ICI Ltd. is classed as an anionic/ non-ionic surfactant comprised mainly of dodecyl benzene sulfonate (anionic) and a nonylphenol ethoxylate of polyethylene glycol (non-ionic emulsifyer). Recent evidence strongly suggests that the active agent in the viral enhancement coincident with Reye s syndrome is a polyethylene glycol derived from the polyethylene moiety of the parent emulsifyer when the number of repeating ethoxy units in the polymer approaches 9 or 10 (12). 

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