Aromatic amines reactions with carbonate radical

Accordingly, many reactions can be performed on the sidewalls of the CNTs, such as halogenation, hydrogenation, radical, electrophilic and nucleophilic additions, and so on [25, 37, 39, 42-44]. Exhaustively explored examples are the nitrene cycloaddition, the 1,3-dipolar cycloaddition reaction (with azomethinylides), radical additions using diazonium salts or radical addition of aromatic/phenyl primary amines. The aryl diazonium reduction can be performed by electrochemical means by forming a phenyl radical (by the extrusion of N2) that couples to a double bond [44]. Similarly, electrochemical oxidation of aromatic or aliphatic primary amines yields an amine radical that can be added to the double bond on the carbon surface. The direct covalent attachment of functional moieties to the sidewalls strongly enhances the solubility of the nanotubes in solvents and can also be tailored for different... 

The photoreactions of aliphatic amines with aromatic hydrocarbons have also been reported by several groups. With tertiary amines, deprotonation occurs from the radical cations of amines at the a-carbon to generate carbon radicals which react with the radical anion of aromatic hydrocarbons. With secondary amines, deprotonation from the radical cations of amines occurs both at the a-carbon and at the nitrogen atom, so that the reaction becomes complicated [64-65]. 

All substitutions at this nitrogen atom result from nucleophilic attack by the amine on electrophilic centres in positively charged or neutral species. The only exception is condensation of free radicals derived from aromatic amines by hydrogen abstraction, reactions which are not considered in detail in this review. Amines are such powerful nucleophiles that they will react readily with even feebly electrophilic centres such as that in carbon dioxide. 

The electrochemical mechanism has been investigated [386] for amines with an a-methylene group, but not for aromatic amines. It involves the one electron formation of a radical cation that deprotonates to a carbon radical after tautomerization. The resulting aminyl radical binds to the surface (Figure 3.58). It was also shown that the reaction of secondary amines was more limited and that tertiary amines did not react [364]. 

Secondary aromatic amines and, in part, aromatic diamines are very efficient hydrogen donors (H donors). The reaction products can react further with the radicals, similar to phenols. The use of amine stabilizers can lead to discoloration of the plastic due to the formation of azo compounds (chinonimines). Therefore, the use of aromatic amines is limited to carbon-black filled elastomers as well as other substrates where discoloration is not an issue. 

Vinyl-functional alkylene carbonates can also be prepared from the corresponding epoxides in a manner similar to the commercial manufacture of ethylene and PCs via CO2 insertion. The most notable examples of this technology are the syntheses of 4-vinyl-1,3-dioxolan-2-one (vinyl ethylene carbonate, VEC) (5, Scheme 24) from 3,4-epoxy-1-butene or 4-phenyl-5-vinyl-l,3-dioxolan-2-one (6, Scheme 24) from analogous aromatic derivative l-phenyl-2-vinyl oxirane. Although the homopolymerization of both vinyl monomers produced polymers in relatively low yield, copolymerizations effectively provided cyclic carbonate-containing copolymers. It was found that VEC can be copolymerized with readily available vinyl monomers, such as styrene, alkyl acrylates and methacrylates, and vinyl esters.With the exception of styrene, the authors found that VEC will undergo free-radical solution or emulsion copolymerization to produce polymeric species with a pendant five-membered alkylene carbonate functionality that can be further cross-linked by reaction with amines. Polymerizations of 4-phenyl-5-vinyl-l,3-dioxolan-2-one also provided cyclic carbonate-containing copolymers. 

The one-electron oxidation of a secondary amine results in the formation of a secondary aminium ion which on deprotonation gives an aminyl radical (Scheme 1). The nature of the final products derived from these intermediates dqiends very much on the structure of the substrate and the reaction conditions. If the amine has a hydrogen atom on the a-carbon atom the major products usually result from deprotonation at this a-position. With aromatic secondary amines, products can result from coupling of the delocalized radicals at a ring carbon atom. The formal dimerization of aminyl radicals shown in Scheme 21 is therefore not often a useful method of preparation of hydrazines. Nickel peroxide has been used to oxidize diphenylamine to tetraphenylhydrazine in moderate yield, and other secondary arylamines also give... 

Takuwa and his coworkers have demonstrated that the irradiation of the aromatic carbonyl compounds (120) in the presence of the stannanes (121) affords the unsaturated alcohols (122) as the principal products. An electron transfer mechanism is proposed. Electron transfer is also involved in the reaction of amines with alkenes such as the phenylethylenes (123). The electron transfer in this instance affords an alkenyl radical anion the presence of which has been demonstrated by a variety of techniques. A further reaction has been uncovered in the photoreaction of, for example, the alkene (123a) with iV, AT-diethylani lino in the presence of carbon dioxide. This treatment affords the three carboxylated derivatives (124), (125), and (126) by trapping of the radical anion by carbon dioxide. Similar carboxylation was demonstrated for (123b) and biphenyleno. The influence of the amine on the yield of product was studied. ... 

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