Relative kinetics of the homolytic addition of 2-phenyl-1,3-dioxolane to unsaturated compounds

The CH₂ = CHX olefins form a series relative to their reactivity in reactions with 2-phenyl-1,3-dioxolan-2-yl radicals, which qualitatively correlates with the electron-withdrawing capacity of substituent X: CN CO₂Me >> SiMe₃ C₄H₉. This behavior indicates that the dioxolanyl radical is nucleophilic.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1663–1666, July, 1992.     

Conversion of a trans-syn-trans to a cis-syn-trans perhydrobenz[e]indenone triggered by intramolecular 1,5-hydrogen transfer

The conversion of a trans-syn-trans perhydroiodomethyltrimethylbenz[e]indenone to the corresponding cis-syn-trans perhydrobenz[e]indenone occurred during the reduction of the iodomethyl to a methyl group under radical conditions.     

Stabilisation of Methylene Radicals by Cob(II)alamin in Coenzyme B12 Dependent Mutases

Coenzyme B₁₂ initiates radical chemistry in two types of enzymatic reactions, the irreversible eliminases (e.g., diol dehydratases) and the reversible mutases (e.g., methylmalonyl‐CoA mutase). Whereas eliminases that use radical generators other than coenzyme B₁₂ are known, no alternative coenzyme B₁₂ independent mutases have been detected for substrates in which a methyl group is reversibly converted to a methylene radical. We predict that such mutases do not exist. However, coenzyme B₁₂ independent pathways have been detected that circumvent the need for glutamate, β‐lysine or methylmalonyl‐CoA mutases by proceeding via different intermediates. In humans the methylcitrate cycle, which is ostensibly an alternative to the coenzyme B₁₂ dependent methylmalonyl‐CoA pathway for propionate oxidation, is not used because it would interfere with the Krebs cycle and thereby compromise the high‐energy requirement of the nervous system. In the diol dehydratases the 5′‐deoxyadenosyl radical generated by homolysis of the carbon–cobalt bond of coenzyme B₁₂ moves about 10 Å away from the cobalt atom in cob(II )alamin. The substrate and product radicals are generated at a similar distance from cob(II )alamin, which acts solely as spectator of the catalysis. In glutamate and methylmalonyl‐CoA mutases the 5′‐deoxyadenosyl radical remains within 3–4 Å of the cobalt atom, with the substrate and product radicals approximately 3 Å further away. It is suggested that cob(II )alamin acts as a conductor by stabilising both the 5′‐deoxyadenosyl radical and the product‐related methylene radicals.     

Free-Radical Gossypol Derivatives for Cotton Verticillium Wilt

The ability to bind reversibly molecular oxygen was established for a free-radical product of gossypol oxidation. Conversion of dianhydrogossypol into the stable biradical dioxodianhydrogossypol was viewed as the reason for interruption of the gossypol redox conversion cycle in the extracellular milieu of cotton steles.     

辣根过氧化物酶对心肌线粒体过氧化损伤的保护作用

以黄嘌呤氧化酶／次黄嘌呤自由基诱生系统建立了稳定的离体心肌线粒体的损伤模型，并应用此模型研究辣根过氧化物酶对心肌线粒体自由基氧化损伤的保护作用，结果表明，辣根过氧化物酶能抑制心肌线粒体中氧自由基的形成，降低膜脂的过氧水平，保护了线粒体膜酶活性，有效地防止自由基对线粒体结构和功能的损伤。     

Esters of 4,5-dihydro-1H-imidazole-1-oxyl-3-oxide-carboximidic acid

Esters of 4,5-dihydro-1H-imidazole-1-oxyl-3-oxide-carboximidic acid were synthesized. Their structures and magnetic properties were investigated.     

Synthesis and inhibitory activity of alkyl(hydroxyaryl)amines

The reaction of ω-(4-hydroxyaryl)haloalkanes with various nitrogen-containing agents afforded primary, secondary, and tertiary amino derivatives of 2,6-dialkylphenols. For the compounds synthesized, the reaction rate constants with peroxide radicals were measured for cumene and methyl oleate oxidation. The total inhibitory activity in the model reactions of thermal autooxidation of lard and hexadecane was studied. The rate constants of alkyl(hydroxylaryl)amines are the same as those of the corresponding alkylphenols, whereas the total inhibitory activity of some alkyl(hydroxylaryl)amines exceeds substantially that for alkylphenols. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1107–1112, June, 2007.     

Crystal Structure of Cu(hfac)2 Complexes with Organomercury Binitroxide

The organomercury biradical HgL₂ (L is deprotonated 4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl) is capable of performing the bridging function for design of multinuclear heterospin systems. This paper describes synthesis and crystal structure of HgL₂ and the first multinuclear complexes of Cu(hfac)₂ with HgL₂.     

Amides as precursors of imidoyl radicals in cyclisation reactions

Amides have been successfully used as precursors of imidoyl radicals for radical cyclisation. The amides have been converted to imidoyl selanides via reaction with phosgene to yield imidoyl chlorides followed by reaction with potassium phenylselanide. Imidoyl selanides were reacted with tributyltin hydride (Bu₃SnH) as the radical mediator with triethylborane or AIBN as initiators to yield imidoyl radicals for cyclisation reactions. Imidoyl radicals have been cyclised onto alkenes to yield 2,3-substituted-indoles and -quinolines and also onto pyrroles and indoles to give bi- and tricyclic heteroarenes.     

Probing electrochemical properties of pi-conjugated thienylenevinylenes/fullerene C(60) adducts by ESI/MS: evidence for dimerized cation-radicals

Oligothienylenevinylenes/C(60) dyads n-C and triads n-C(2) are studied by electrospray mass spectrometry. A clear correlation is observed between the nature of the charged species detected by mass spectrometry, i.e. protonated molecule [M + H], (+) cation radical M(+.) and dication M(++), and the oxidation potentials of the molecules. Moreover, under defined solubility conditions, mass spectrometry provides conclusive evidences for the reversible dimerization of cation-radicals of n-C(2) compounds.