Amino methyl radical

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

The authors of primary Reference 80 present their own and selected literature values for the R—NO bond enthalpies for the hydrocarbyl cases of Me, Et, t-Bu, allyl and benzyl, as well as mixed fluorinated, chlorinated methyl radicals. We now wish to compare nitroso species with the corresponding amino and nitro compounds. Choosing what we consider the most reliable and relevant nitroso compound data, and accompanying them with the corresponding radical data, we derive enthalpies of formation of gaseous nitrosomethane, 2-methyl-2-nitrosopropane and o -nitrosotoluene81 to be 65 2, —29 4 and 174 7 kJmol-1. (By comparison, the earlier values recommended8 for nitrosomethane and 2-methyl-2-nitrosopropane were 70 and —42 kJmol-1 respectively.)... 

An alternative route for the synthesis of TV-methyl amino acids without racemization is shown in Scheme 8.[98 This method includes the use of TBPB in the presence of copper(I) octanoate. The proposed mechanism of this free radical reaction is given in Scheme 8. Electron transfer from copper(I) to TBPB affords the copper(II), benzoate, and tBuO radical 4, which undergoes (3-scission to acetone and methyl radical 5. In turn, electron transfer from the urethane to the copper(II) ion, followed by proton transfer, affords the corresponding urethane radical 6, which reacts with the methyl radical 5 to give the desired product in overall yields of 54% (Z derivative) or 57% (Boc derivative), respectively. 

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 quinolones depicted in Fig. 14.10 represent a combination of 3-amino-methyl- and 3-hydroxy-l-pyrrolidinyl quinolones [108], of which those containing less bulky radicals display improved in vitro activity over those containing bulky substituents. The inadequate in vivo properties, however, prevented any further development. 

The addition of a radical to the C=C bond of enamines generates an a-amino radical, stabilized via spin delocalization onto the nitrogen atom15. The extent of this stabilization as compared to the unsubstituted methyl radical has been determined by theoretical calculations16 and experimental studies17 to be about 9-10 kcal mol-1. However, the contribution of this stability effect to the reactivity in radical addition to enamines is important only if the addition process has a late transition state, which is usually not the case for radical addition to alkenes. 

Transient intermediates arising by radical additions to the amide bond have been studied recently in an effort to explain the complex processes occurring in electron-capture dissociation of multiply charged peptide and protein cations [192]. The amino(hydroxy)methyl radical, HC(OH)NH2 (64), is a prototypical species that represents the simplest model for radical additions to peptide bonds. Radical 64 was generated from cation 64+ which in turn was prepared by... 

Free radical species that are capable of initiating vinyl polymerization reactions have been identified as Cu -co-ordinated amino-acid radicals, and these are produced in the primary photoreactions of the complex. An examination of the quantum yield and photodecomposition stoicheiometry of Cu (H2Aib)3 (H2Ajb= a-aminoisobutyric acid) as a function of irradiation wavelength and medium conditions has shown that 7r-copper -amidyl radicals are the primary photoproducts. The behaviour of other Cu -peptide complexes suggests that these photochemical parameters are dependent on the peptide chain-length and the number of a-carbon methyl substituents. ... 

Decomposition. Just as alkyl and alkyloxy radicals can decompose to give a stable double-bonded molecule and either a hydrogen atom or methyl radical— Reactions 23 and 24—so we would expect decomposition of alkyl-substituted amino radicals to take place. 

However, this is probably an oversimplification, as the disproportionation reaction is surface-catalyzed and the two reactions must have different energies of activation. This behavior of dimethylamino radicals is in marked contrast to the iso-electronic isopropyl radicals, the disproportionation-combination ratio of which is unaltered by temperature and siuface (2, 30). The surface-promoted radical decomposition is also in marked contrast to the absence of such effects in the isopropyl radical reactions (2) and must be attributed to the presence of the nitrogen atom. Amino radicals also undergo surface reactions (28). The occurrence of TMA suggests the participation of methyl radicals in the reactions, and a possible route is provided by Reactions 28 and 34. 

Although the hot aniline molecules undergo the aryl-amino C—N bond cleavage (Scheme 2), this reaction is inefficient for anilines in the excited states. In contrast, the anilino-alkyl C—N bond homolysis has been observed for several aniline derivatives. For example, methyl radical (Me") and anilino radical (PhN Me) have been detected as the products of the photoirradiation of tetramethylphenylenediamine (25) and N,N-dimethylaniline (lb), respectively, in 3-methylpentane at 77 K124,125. 

In the case of cyclic amino alcohols where nitrogen enters into the composition of the cycle, the optimal anticholinergic effect is produced not by the N-ethyl, iV-isopropyl, or N-allyl, but by N-methyl radical, as is apparent from a comparison of the esters of tropine (Tables 4-6). It may be that the elements of the cyclic structure occupy a sufficiently large space besides the nitrogen atom. 

Photooxidation rates of propan-2-ol in aqueous Ti02 suspensions are reported to be increased by ultrasound radiation, an observation which has been rationalised in terms of mass transport of the substrate and activation of the solid catalyst. The value of the newly described photochemical rearrangement of 2-phenylthio-l,3-cyclohexanediols such as (69) to deoxysugars (70) which are in equilibrium with the closed form (71) has been illustrated by its application to the synthesis of (+)-m-rose oxide (72), and the same authors have also described the regioselective photorearrangement of 2-phenylthio-3-aminocyclohexanols (73) to deoxyazasugars (74) this has proved to be useful in the synthesis of various piperidines (75), amino-sulfones, -sulfoxides and -acids. Hydroxy(alkoxy)methyl radicals have been generated by photo-induced electron transfer. ... 

ESR studies of the amino acids in glasses confirm the formation of the disulfide anion (20), which is especially stable, and the methyl radical (20). Similar reactions may be expected to occur directly or indirectly on peptides. 

In this way a nitro group is introduced into the ring in a position meta to the methyl radical. In order to obtain nitro-toluene from the nitrotoluidine formed in this way, the amino group present in the latter must be removed. This is accomplished by converting the amine into a diazo compound (513), and boiling the latter with alcohol, when the diazo group is replaced by hydrogen —... 

Fig. 3 Energy diagram of strongly doped n-Si/Si02 electrode in contact with aqueous electrolyte solution. The diagram contains the formal redox potentials of the primary radicals and combined redox and luminescence properties of Ru(bpy)3, and 2,6-bisPM,N-bis(carboxymethyl)amino-methyl]-4-benzoylphenol (ligand L). The diagram demonstrates clearly that on thermodynamical basis, both of these luminopbores could be excited even to their singlet excited states in the simultaneous presence of hydrated electrons and sulfate radicals via both ox-red and red-ox pathways. However, in practice the ox-red pathway seems to be dominant in both cases. E-type electron centers in silica fully correspond to F and F electron centers in alumina [36]...

In this case, the benzoyl radical and a methyl radical produced through the fragmentation of a,a-dimethoxy benzyl radical both initiate pol5unerization. Other families include benzoin ethers, acetophenone derivatives, amino ketones, and phosphine oxide derivatives (1 ) (3,11). 

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