Amino radical generation

Organosamariums also add to enones in is present. a-Amino radicals generated fro alkenyljbenzotriazoles on exposure to SmI ... 

Organosamariums also add to enones in the Michael fashion when a copper salt is present. o-Amino radicals generated from cleavage of Al-[l-()V, Al -dialkylamino)-alkenyl]benzotriazoles on exposure to Sml2 may add to the electron-deficient double... 

A very important tactic for a-amino radical generation involves translocation via hydrogen abstraction by an aromatic free radical generated from a halogen five bonds away. Thus chain extension at the a-position of an amide or amine can be accomplished with great success. 

There is a very wide range of aromatic compounds present in living systems, e.g. the amino acids phenylalanine and tyrosine, and catecholamines such as norepinephrine. Although these speciesi are very useful for in vitro investigations of OH radical generation, their applicability as suitable aromatic detector molecules for OH radical in vivo largely depends on their concentration (i.e. their ability to compete with alternative... 

The addition of perfluoroalkyl iodides to simple olefins has been quite successful under aqueous conditions to synthesize fluorinated hydrocarbons.119 In addition to carbon-based radicals, other radicals such as sulfur-based radicals, generated from RSH-type precursors (R = alkyl, acyl) with AIBN, also smoothly add to a-allylglycines protected at none, one, or both of the amino acid functions (NH2 and/or CO2H). Optimal results were obtained when both the unsaturated amino... 

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... 

Fig. 4 Trapping of free radicals generated in photodegradation of fenvalerate (9). 3-AP 3-amino 2,2,5,5-tetramethyl-l-pyrrolidinyloxy free radical, FL fluorescamine...

In the presence of hydroxy or perhydroxy radicals generated from Fenton s reagent, atrazine undergoes oxidative dealkylation in aqueous solutions (Kaufman and Kearney, 1970). Major products identified by GC/MS included deisopropylatrazine (2-chloro-4-ethylamino-6-amino-s-triazine), 2-chloro-4-amino-6-isopropylamino-5-triazine, and a dealkylated dealkylatrazine (2-chloro-4,6-diamino-s-triazine) (Kaufman and Kearney, 1970). 

Nitrogen oxides. Nitric oxide (NO) itself, has been shown to be a poor nitrosating agent (28), probably because it is unable to abstract an amino-H atom to generate the dialkyl-amino radical, which might then combine with further NO. However, the presence of even a small amount of air results in complete conversion, presumably via oxidation of NO to NO2. Nitrosation by NO is catalyzed by metal salts, such as Znl2, CuCl, and CUSO4. The metal catalyzed reaction is inhibited in acid or aqueous media (29). 

The stability of the semireduced Eosin radical produced by reduction with triethanolamine is similar to that reported for the radical in aqueous solution [209], Our results indicate that the lifetime is substantially shorter when it is generated by reduction with triphenylamine. We attribute this difference to the ability of the triethanolamine radical cation to form the a-amino radical by loss of a proton, as shown below, thus preventing the reaction of the radical by reverse electron transfer (Eq. 18). 

A potential method for the preparation of novel amino acids via the highly selective addition of radicals to the glyoxylic oxime derivative of Oppolzer s camphor sultam (88) has been reported.181 Both Lewis acid and non-Lewis acid-mediated reaction conditions for the addition of alkyl radicals generated from alkyl iodides and Et3B/Bu3SnH were examined. A new chiral auxiliary based upon (R,R)-2,5-diphenylpyiTolidine has been used in the addition of phenylthiyl radicals to unsaturated methacrylamides. The selectivity was found to be better than that reported for the structurally related 2,5-dimethylpyrrolidine derivative.182... 

Neutral aminyl radicals generated from tin hydride-mediated reactions of sulfenamides (Section II,F) have been shown to undergo cyclizations when energetically favored by addition to a strained alkene or by formation of a stabilized intermediate benzylic radical. In both cases, the reverse reaction, cleavage of the /3-amino radical, apparently did not occur (92TL4993). 

Sequential SET desilylation has been used to generate a-amino radicals. The mechanistic and synthetic aspects of the reaction have been briefly surveyed.283 Thus irradiation of A, N- d i e t h y 11 r i m e t h y I si I yl meth y I a m i n e with acenaphthenequinone in acetonitrile or methanol produces 2-hydroxy-2-[(diethylamino)methyl]acenaphthylen-1-one.284... 

Fig. 4.6.5. Assay for spectroscopic investigation of how aromatic amino acids modulate DNA-mediated HT. The peptide radicals generated by DNA-mediated HT have different...

Hydroaminomethylation reactions can be accomplished by addition of nucleophilic a-amino alkyl radicals (generated from amines) onto electron-deficient alkenes [7, 21], Amines have a low oxidation potential, and are easily oxidized by excited aromatic ketones bearing electron-donating substituents (e.g., Michler s ketone) or... 

Pandey, G. and Devi Reddy, G. (1992) Stereoselectivity in the cyclisation of photoinduced electron transfer (PET) generated cyclic a-amino radicals first general stereoselective entry to 1-azabicyclo (m n o) alkane systems. Tetrahedron Letters, 33, 6533-6536. 

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