Radicals, derived from with amines

H2NO is a typical reactive intermediate endowed with short hfetime, aminoxyl radicals deriving from secondary amines may instead be stable whenever complying with the general structure 1 (R H), in which there are no hydrogens attached to the a-carbon atoms. 

Short-lived free radicals derived from aromatic amines can be generated and detected by the ETSF method. Long-lived free radicals in solution, such as tris(4-bromophenyl)amine radical cation (129), react with aromatic amines to yield short-lived radical anions (130a-d), as shown in equation 20. Solutions of 129 are generated electrolytically and... 

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. 

Due to the nucleophilicity of a-aminoaUcyl radical, it is supposed to add to electron-deficient alkenes. This assumption was first achieved by Nishibayashi [50] and Reiser [51] in early 2012 (Scheme 3.12). They reported visible-Ught-mediated addition of a-aminoalkyl radicals derived from tertiary amines to Michael acceptors (unsaturated esters and vinyl ketones). Also, radical addition to acrylate derivatives was later accomplished (Scheme 3.12) [52]. As a follow-up work, Nishibayashi et al. developed visible-light-promoted radical C(sp )-H amination of benzocyclic tertiary amines using di-terr-butyl azodicarboxylate as nitrogen source (Scheme 3.12) [53]. In 2013, Yu et al. found that AA -dimethylaniline derivatives could react with A-aryl- and A-benzyhnaleimides to give tetrahydroquinoline products with air as oxidant (Scheme 3.12) [54]. Unfortunately, the other olefins, such as furan-2,5-dione, diethyl maleate, methyl acrylate, and l-phenylprop-2-en-l-one, fail to undergo this transformation. The mechanistic... 

The oxidation of primary and secondary alcohols in the presence of 1-naphthylamine, 2-naphthylamine, or phenyl-1-naphthylamine is characterized by the high values of the inhibition coefficient / > 10 [1-7], Alkylperoxyl, a-ketoperoxyl radicals, and (3-hydroxyperoxyl radicals, like the peroxyl radicals derived from tertiary alcohols, appeared to be incapable of reducing the aminyl radicals formed from aromatic amines. For example, when the oxidation of tert-butanol is inhibited by 1-naphthylamine, the coefficient /is equal to 2, which coincides with the value found in the inhibited oxidation of alkanes [3], However, the addition of hydrogen peroxide to the tert-butanol getting oxidized helps to perform the cyclic chain termination mechanism (1-naphthylamine as the inhibitor, T = 393 K, cumyl peroxide as initiator, p02 = 98 kPa [8]). This is due to the participation of the formed hydroperoxyl radical in the chain termination ... 

Numerous reports published in recent years have focused on carbon-centered radicals derived from compounds with selected substitution patterns such as alkanes [40,43,47], halogenated alkanes [43,48,49,51-57], alkenes [19], benzene derivatives [43,47], ethers [51,58], aldehydes [48], amines [10,59], amino acids [23,60-67] etc. Particularly significant advances have been made in the theoretical treatment of radicals occurring in polymer chemistry and biological chemistry. The stabilization of radicals in all of these compounds is due to the interaction of the molecular orbital carrying the unpaired electron with energetically and spatially adjacent molecular orbitals, and four typical scenarios appear to cover all known cases [20]. 

Purines. The reactions of purines with a-hydroxyalkyl and a-alkoxyalkyl radicals have been most intensively investigated (Elad et al. 1969 Steinmaus et al. 1969, 1971 Elad and Salomon 1971 Leonov et al. 1973 Salomon and Elad 1973 Leonov and Elad 1974a,b Moorthy and Hayon 1975 Frimer et al. 1976 Aravin-dakumar et al. 1994), but the reactions of radicals derived from amino acids (Elad and Rosenthal 1969 Elad et al. 1969 Elad and Salomon 1971 Poupko et al. 1973 Salomon and Elad 1974) and amines (Elad and Salomon 1971 Salomon and Elad 1973) and of the methyl radical (Maeda et al. 1974) are also reported (for a review of the older work see Elad 1976). 

The proposed pathway is supported by the results obtained from Hg /NH3 and cyclohexane. The major amine product is the interesting tertiary amine shown. This probably results from recombination of cyclohexyl with the radical derived from hydrogen atom addition to the imine (Scheme 5). 

It was reported [231] that phenolic and aromatic aminic AO are able to form bound-in species in EPM cured with peroxides. This principle was exploited in NR doped with 2,6-di-terr-butyl-4-methylphenol and tert-butyl peroxide. Other phenolic AO bearing methyl groups may take place in a similar process too [232]. The extent of the coupling of radicals derived from phenolic antioxidants with macroalkyls is influenced by the concentration of phenols. A competitive process, autocoupling of phenol derived radicals, increases with increasing concentration of the phenolic antioxidant [17]. 

Cobalt(III) complexes are reduced readily to Co(II) by radiation-generated reducing radicals" including aliphatic radicals derived from alcohols, acids, amines, and aldehydes". However, the rate constant for the reaction of a-hydroxyalkyl radicals with Co(NH3)jP is pH-dependent (high in neutral solution, low in acidic solution) indicating an inner-sphere mechanism" the yield of Co follows the same pH dependence. ... 

Work carried out in our laboratories over the past three years and in conjunction with the research group of Daktemieks at Deakin University has been directed toward the development of novel enantiomerically pure stannanes for use in free-radical reduction chemistry. To that end Dunn prepared a series of menthyl-substituted stannanes 18 -20 and some others derived from aromatic amines (eg. 21, 22).Perchyonok tested these reagents against a series of substrates while Henry modelled the reactions in question through the use of ab initio molecular orbital theory. 

As shown in Table I, these stable radicals showed strikingly higher light stabilization activity in polypropylene than that of the UV absorber tested. We felt that their activity was related to their radical scavenging ability. This hypothesis is supported by the observation that the coupled products (32) and (33) were obtained by the reaction of the nitroxyl radicals (2) and (27), respectively, with a C-radical derived from AIBN (10). The radical scavenging ability of the stable nitroxyl radicals is now well known to play a major role in the mechanism of light stabilization by hindered amine compounds (13). 

Polycyclic borazines (55) X = 0, NH, or NMe, n = 2 or 3) result from the reaction of a trisalkylthioborane with hydroxyamines or amines. Their i.r. and mass spectra, with possible mechanisms of formation, were reported. Photochemical reactions of borazine in the presence of (photochemically generated) radicals derived from hexafluoroacetone have led to the formation of B-(2H-hexafluoro-2-propoxy- and B-(perfluoro-butoxy)-borazine. ... 

In the same sense that a-alkoxy radicals derived from carbohydrates can be generated and utilized in intramolecular addition reactions, a-amino radicals can be employed by the reduction of A-(a-benzotriazolylalkyl)alkenylamines in syntheses of amino-substituted carbocycles and C-substituted pyrrolidines [20]. In the carbo-cycle synthesis, cu-unsaturated aldehydes are condensed with benzotriazole and secondary amines to provide (a-benzotriazolylalkyl)alkenylamines (Scheme 1). These intermediates rapidly ionize in solution to the corresponding iminium ions... 

Captodative alkenes 67 can be dialkylated, for example, by addition of iso-butyronitrile radical derived from thermal decomposition of AIBN under the same conditions as those which lead to polymerization of other acrylic alkenes. For example, a-morpholino-acrylonitrile (67, c = CN, d = N(CH2CH2)20) leads to 69, in 71% yield (Scheme 12) [4a]. With a-/-butylthio-acrylonitrile (67, c = CN, d = SC(CHj)3), the same process leads to 70 in 88% yield [7]. The adduct radical 68 is highly stabilized, and is in equilibrium with dimer 70. The reaction is quite general, and has been applied to other captodative alkenes (c = CN, COR, CO2R and d = NR2, OR, SR) together with various sorts of radical partners, derived from alkanes, alcohols, thiols, thioethers, amines, amides, ketones, aldehydes, acetals and thioacetals [44, 45]. 

Electron transfer from the amine nitrogen to CIO2, with production of chlorite and the radical cation derived from the amine (Ozawa and Kwan, 1984), appears to predominate over hydrogen abstraction from the carbon adjacent to the amino... 

There have been several papers dealing with the oxidation reactions of nitrogen and sulfur-based compounds. Hindered amines, such as substituted 2,2,6,6-tetramethylpiperidines, are easily oxidized by electron-transfer reactions to the corresponding cation, by the sulfate radical anion, and by sensitized electron transfer to carbonyl triplets. Radicals derived from tertiary piperidines were observed directly by optical spectroscopy and deprotonated to a-alkylamine radicals. The amine radical cation derived from secondary piperidines deprotonated to give aminyl radicals. In the presence of oxygen, both classes were oxidized to give nitroxyl radicals, but by different proposed mechanisms. Both oxidation and fragmentation pathways have been observed in the photochemical reaction of alkyl phenyl sulfides with tetranitromethane. The oxidation of various A-(arylthio)-4-substituted-2,6-diarylanilines (18) with PbOa yielded, in most cases, persistent radicals that could... 

Bertrand and coworkers have reported that quaternization of the nitrogen center upon coordination with BH3, provides a significant increase in the selectivity of the 5-exo radical cyclization of 3-aza-5-hexenyl radicals derived from substrates equipped with a terminal double bond (Equation 28) [30]. Coordination of BH3 to the nitrogen of the parent amine creates strong steric interactions, which disfavor the trans product. 

Hasegawa, E., Ishiyama, K., Horaguchi, T., and Shimizu, T., Exploratory study on photoinduced single electron transfer reactions of a,P-epoxy ketones with amines, /. Org. Chem., 56,1631, 1991. Hasegawa, E., Ishiyama, K., Horaguchi, T., and Shimizu, T., Free radical trapping of a-keto radicals derived from a,P-epoxy ketones via photoinduced single electron transfer process. Tetrahedron... 

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