Carbethoxyallylation using radical chemistry

Radicals derived from the esters of $\text{N}$-hydroxy-2-thiopyridone react smoothly in a concerted reaction with 2-carbethoxy-3-$\text{t}$-butylhioprop-1-ene to give the corresponding 2-carbethoxyallyl derivatives with shift of the double bond.     

Redox-active ligands and organic radical chemistry

Knowledge about bonding in diiminepyridine (L) halide, alkyl, and dinitrogen complexes of the metals iron, cobalt, and nickel is summarized, and two new examples are added to the set: L(1)Ni(Me) and L(1)Ni(N(2)). Reactivity of these types of complexes is discussed in terms of organic radical chemistry. New C-C couplings with L(2)CoAr complexes are described and proposed to involve halide abstraction and radical coupling. Calculations support the high tendency of the diiminepyridine ligand to accept an electron coming from a metal-carbon bond and so facilitate loss of a radical.     

Strained heterocycles in radical chemistry

Over the last few decades the use of radicals in synthesis has witnessed an explosive growth through introduction of efficient chain and electron-transfer reactions. Strained heterocycles, in particular, have emerged as a highly versatile and readily available class of radical precursors. The generation of carbinyl radicals of heterocycles has resulted in many elegant applications of heteroatom-centered radicals, such as beta fragmentations, cyclizations, and intramolecular hydrogen atom abstractions. Direct electron transfer to strained heterocycles has been realized through the use of arene radical anions. The method combines the virtues of radical and organometallic chemistry to yield useful functionalized organolithium compounds. Epoxides have been opened with high regioselectivity by titanocene(III) reagents in either stoichiometric or catalytic quantities to yield beta-titanoxy radicals. This development has resulted in many new applications in natural product synthesis.     

Microwave-assisted free radical chemistry using the persistent radical effect

Environmentally benign radical carboaminoxylations of various nonactivated olefins and difficult radical cyclization reactions are performed in good to excellent yields and with short reaction times under microwave irradiation.     

Nighttime peroxy radicals chemistry at Rishiri Island during the campaign RISFEX 2003

Peroxy radicals (ROx) concentrations were measured by Peroxy Radical Chemical Amplifier (PERCA) technique during the field campaign RISFEX 2003 (RiShiri Fall Experiment 2003), which was performed in September 2003 at Rishiri island (45.07 N, 141.12 E, and 35 m asl) in the sea of Japan. The concentrations of nighttime ROx radicals had temporal variations around an average of 7.9±5.8 (1σ) pptv and showed a positive correlation with the summed mixing ratio of four monoterpene species. Model calculations suggested that local nighttime ROx radicals were dominated by the reactions of monoterpene with ozone (O 3 ) and nitrate radical (NO 3 ), contributing ca. 76% and 19%, respectively. The comparisons between the observed ROx and ones modeled had implied that the current model may be overestimated the yields of peroxy radicals from the reactions of monoterpenes with ozone and an important source of peroxy radicals was possibly missed. Abnormal high concentrations of observed ROx radicals were found during high relative humidity (RH) period (especially > 95%), and the possible explanation was that the humidity correction of ROx radicals under high RH conditions may be inaccurate and overestimates ROx concentrations.     

Polymers for catalytic cation radical chemistry

Cation radical polymers which have cation radical functions at up to 5% of the poly(styrene) monomer sites have been prepared, and their effectiveness in catalyzing the cation radical Diels-Alder reaction is demonstrated.     

Gas-phase radical chemistry in the troposphere

Atmospheric free radicals are low concentration, relatively fast reacting species whose influence is felt throughout the atmosphere. Reactive radicals have a key role in maintaining a balanced atmospheric composition through their central function in controlling the oxidative capacity of the atmosphere. In this tutorial review, the chemistry of three main groups of atmospheric radicals HO(x), NO(x) and XO(x)(X = Cl, Br, I) are examined in terms of their sources, interconversions and sinks. Key examples of the chemistry are given for each group of radicals in their atmospheric context.     

Some interesting observations in chlorine oxyflouride chemistry

A new synthesis of FOC10₃ was discovered involving the fluorination of ClO₄^? with ClF₆⁺. An unexpected oxygen abstraction from ClF₄O^? was observed when CsClF₄O was reacted with FOSO₂F.     

Special issue on organic free radical chemistry

<正>The discipline of organic free radical chemistry dates back over 110 years since the discovery of triphenylmethyl radical by Moses Gomberg in 1900. Organic radical reactions became a thriving field in synthetic organic chemistry for a decade or so starting from the mid 1980s. Nevertheless, the significance of radicals in organic synthesis somehow remained hidden for a long period of time. The 1990s saw a     

Iron-sulfur proteins as initiators of radical chemistry

Iron-sulfur proteins are very versatile biological entities for which many new functions are continuously being unravelled. This review focus on their role in the initiation of radical chemistry, with special emphasis on radical-SAM enzymes, since several members of the family catalyse key steps in the biosynthetic pathways of cofactors such as biotin, lipoate, thiamine, heme and the molybdenum cofactor. It will also include other examples to show the chemical logic which is emerging from the presently available data on this family of enzymes. The common step in all the (quite different) reactions described here is the monoelectronic reductive cleavage of SAM by a reduced [4Fe-4S](1+) cluster, producing methionine and a highly oxidising deoxyadenosyl radical, which can initiate chemically difficult reactions. This set of enzymes, which represent a means to perform oxidation under reductive conditions, are often present in anaerobic organisms. Some other, non-SAM-dependent, radical reactions obeying the same chemical logic are also covered.     

Study of the radical chemistry promoted by tributylborane

The structures of radicals generated in the oxidation process of trialkylborane were detected based on ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC/Q-ToF MS) combined with the spin trapping method. Structural identification of the spin adducts produced by 5,5-dimethyl-1-pyrroline-1-oxide with radicals could be carried out unambiguously by combining the data obtained by UPLC/Q-ToF MS analyses. Then the oxidation mechanism was described. To specify the inter-relationships between the oxidation process of trialkylborane and the concomitant radical chemistry, four kinds of alkanes providing different H-abstraction reactivity to alkoxy radical were chosen as radical capturers. The final oxidation products of trialkylborane were characterized by GC?CMS and ¹¹B-NMR. The results indicted that the radical content was not only affected by the oxidation degree of trialkylborane, but also done by the activity of alkane. Especially the hydrogen atom abstraction by n-butoxy radical played an important role in the oxidation process of tributylborane, which would promote the oxidizability of tributylborane and deepen the oxidation degree of tributylborane.     

Unimolecular chemistry of metastable dimethyl isophthalate radical cations

The MS/MS spectrum of the metastable molecular ions of dimethyl isophthalate 1 differs from that of the isomeric dimethyl terephthalate 2 by the observation of, inter alia, a quite intense loss of C,H₂,O ascribed to formaldehyde. Results obtained using a combination of mass spectrometry techniques suggest that this process could consist of an isomerization reaction of the molecular ion into an ion–neutral complex (INC) linking a benzoyl radical and neutral formaldehyde to a proton [ArCOHOCH₂]⁺. Within the complex, a proton transfer catalyzed by formaldehyde occurs resulting in the production of an ionized cyclohexadienylidene methanone (ketene) structure.     

Tin-free radical chemistry using the persistent radical effect: alkoxyamine isomerization, addition reactions and polymerizations

In this tutorial review applications of alkoxyamines as C-radical precursors for the conduction of tin-free radical reactions are presented. These processes are controlled by the Persistent Radical Effect. A brief introduction on the Persistent Radical Effect is provided. In addition, the use of microwave irradiation to conduct thermal radical reactions is discussed. Finally, the use of alkoxyamines as initiators/mediators for the controlled/living radical polymerization is highlighted.     

Early contributions to the chemistry of organic radical ions

The correct chemical composition and the true nature of organic radical ions were not recognized until well into the 20th century. Yet, the earliest observation of such a species as a colored transient dates back at least 150 years. Some pioneering reactions involving radical ions are discussed, and contributions to their understanding are reviewed.