Induced Radical Reaction Research Articles

Metal‐Free Synthesis of Diarylmethanes through Visible‐Light Induced Radical Reactions with Arylamines

AbstractAn efficient method for synthesis of diarylmethanes with arylamines by using a transition‐metal free photo‐induced radical Csp3‐H bond activation strategy has been achieved. This protocol proceeds under mild reaction condition and represents the first metal‐free radical strategy for synthesis of diarylmethanes with arylamines. The control experiments illustrated that the methylene radical involved in this process and play an important role in this reaction

Compatibilization of Poly(Lactic Acid) (PLA) and Bio-Based Ethylene-Propylene-Diene-Rubber (EPDM) via Reactive Extrusion with Different Coagents.

Much effort has been made to enhance the toughness of poly (lactic acid) (PLA) to broaden its possible range of usage in technical applications. In this work, the compatibility of PLA with a partly bio-based ethylene-propylene-diene-rubber (EPDM) through reactive extrusion was investigated. The concentration of EPDM in the PLA matrix was in the range of up to 20%. The reactive extrusion was carried out in a conventional twin-screw extruder. Contact angle measurements were performed to calculate the interfacial tension and thus the compatibility between the phases. The thermal and mechanical properties as well as the phase morphology of the blends were characterized. A copolymer of poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA) was used as compatibilizer, which leads to a significant reduction in the particle size of the dispersed rubber phase when compared with the blends without this copolymer. The use of EMAGMA combined with soybean oil (SBO) and a radical initiator enhances the elongation at break of the compound. The results indicate that the reduction of the particle size of the dispersed phase obtained with the compatibilizer alone is not sufficient to improve the mechanical properties of the blend system. The induced radical reactions also influenced the mechanical properties of the blend significantly.

ChemInform Abstract: Photochemical Electron and Hydrogen Transfer in Organic Synthesis: The Control of Selectivity

AbstractReview: [112 refs.

Photochemical Electron and Hydrogen Transfer in Organic Synthesis: The Control of Selectivity

Two mechanisms of hydrogen transfer are often observed in photochemical reactions. In a one-step procedure, the electron and the proton are simultaneously transferred (concerted process). In a two-step procedure, first an electron is transferred and the proton follows. Such steps are observed in photochemically induced radical reactions with α,β-unsaturated carbonyl and carboxyl compounds in which a radical species is added at either the α- or the β-position. Both mechanistic steps are also observed in photochemical reactions of imides. In Norrish­–Yang-type reactions, especially with aromatic carbonyl compounds, the spin multiplicity has an influence on the resulting cycloadditions. Such reactions are interesting tools for the synthesis of natural products and for diversity-oriented synthesis. Photochemically induced hydrogen transfer in photoredox catalytic reactions is discussed in connection with proton-coupled electron transfer. 1 Introduction 2 Two Mechanisms of Hydrogen Transfer in Competition 3 Further Reactions of Interest for Application to Synthetic Organic Chemistry 4 Photochemical Keto–Enol Tautomerization 5 Electron and Hydrogen Transfer in Photoredox Catalytic Reactions 6 Conclusion

ChemInform Abstract: Synthesis of Quinolines by Visible‐Light Induced Radical Reaction of Vinyl Azides and α‐Carbonyl Benzyl Bromides.

AbstractVisible‐light‐induced radical reaction of vinyl azides and α‐carbonyl benzyl bromides provides an efficient route to polysubstituted quinolines via a C—C and C—N bond formation sequence.

ChemInform Abstract: Photochemically Induced Radical Reactions with Furanones

AbstractReview: 119 refs.

Synthesis of Quinolines by Visible‐Light Induced Radical Reaction of Vinyl Azides and α‐Carbonyl Benzyl Bromides

AbstractA visible‐light induced radical reaction of vinyl azides and α‐carbonyl benzyl bromides was developed, which provides an efficient route to polysubstituted quinolines via a CC and CN bond formation sequence.magnified image

Photochemically induced radical reactions with furanones

AbstractRadicals are easily generatedviahydrogen transfer form secondary alcohols or tertiary amines using photochemical sensitization with ketones. They can subsequently add to the electron deficient double bond of furanones. The addition of the alcohols is particularly efficient. Therefore, this reaction was used to characterize and to compare the efficiency of different photochemical continuous flow microreactors. A range of micro-structured reactors were tested and their performances evaluated. The enclosed microchip enabled high space-time-yields but its microscopic dimensions limited its productivity. In contrast, the open microcapillary model showed a greater potential for scale-up and reactor optimization. A 10-microcapillary reactor was therefore constructed and utilized for typical R&D applications. Compared to the corresponding batch processes, the microreactor systems gave faster conversions, improved product qualities and higher yields. Similar reactions have also been carried out with electronically excited furanones and other α,β-unsaturated ketones. In this case, hydrogen is transferred directly to the excited olefin. This reaction part may occur either in one step, i.e., electron and proton are transferred simultaneously, or it may occur in two steps, i.e., the electron is transferred first and the proton follows. In the first case, a C–C bond is formed in the α position of the α,β-unsaturated carbonyl compound and in the second case this bond is formed in the β position. For the first reaction, the influence of stereochemical elements of the substrate on the regioselectivity of the hydrogen abstraction on the side chain has been studied.

Free radical cyclization reactions of allylsulfonyl substituted N-aryl amide derivatives

p-Toluenesulfonyl radical can be generated by the manganese(III) acetate oxidation of sodium p-toluenesulfinate. The corresponding alkyl radicals could be produced effectively by the p-toluenesulfonyl radical induced radical reaction of allylsulfonyl substituted N-aryl amides. These alkyl radicals undergo 5-exo-trig, 6-endo-trig, or 6-exo-trig cyclization onto the aromatic ring effectively. The product distribution is highly dependent on the substituent of aromatic ring and the stability of radical intermediate. This p-toluenesulfonyl radical induced reaction provides a synthetically useful method for the synthesis of dihydroquinolinones, azaspirocyclic cyclohexadienes, and spirodihydroquinolinones.

Highly dispersed Pd nanoparticles on covalent functional MWNT surfaces for methanol oxidation in alkaline solution

4-Aminobenzoic acid (4-ABA) was covalently grafted on to the surface of multiwalled carbon nanotubes (MWNTs) via a novel amine-cation induced radical reaction. Then, Pd nanoparticles were deposited on functional 4-ABA group-grafted MWNTs (F-MWNTs) by NaBH 4 reduction method. The structure and nature of the resulting product were characterized by Fourier transform infrared (FT-IR) spectrometry, transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements. The electrocatalytic properties of the Pd/F-MWNTs catalyst for methanol oxidation have been investigated by cyclic voltammetry, linear sweep voltammetry and chronomperometry methods. In contrast to the unfunctionalized counterpart, the electrochemical results demonstrate that Pd/F-MWNTs exhibit better electrocatalytic activities and stability, mainly due to the uniform dispersion and small particle size of Pd nanoparticles on the F-MWNT supports. The results imply that the Pd/F-MWNTs catalyst shows the better electrocatalytic performances and has a promising application potential in fuel cells.

Triethylborane Induced Radical Reaction of Gallium Enolates with α‐Halo Esters.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Triethylborane Induced Radical Reaction of Gallium Enolates with α -Halo Esters

Abstract Treatment of silyl enolates with methyllithium followed by an addition of gallium trichloride afforded the corresponding gallium enolates. The reaction of the resulting gallium enolates with α-halo carbonyl compounds in the presence of triethylborane as a radical initiator provided 1,4-dicarbonyl compounds in good yields.

Free radical reaction of ω-allylsulfonylalkyl substituted aromatic derivatives

Benzenesulfonyl radical can be generated from sodium benzenesulfinate in aqueous acetic acid or formic acid. A benzenesulfonyl radical induced radical reaction of ω-allylsulfonylalkyl substituted aromatic and heteroaromatic derivatives is described. Alkyl radicals can be generated efficiently from allylsulfones. This sulfonyl radical induced reaction provides a synthetically useful method for the synthesis of polycyclic aromatic and heteroaromatic derivatives.

Free Radical Reaction of 1-(4-Allylsulfonylbutyl)indoles

A benzenesulfonyl radical induced radical reaction of 1-(4-allylsulfonylbutyl)indoles is described. Piperidino[1,2-a]indoles were obtained via free radical cyclization of 4-(1-indolyl)butyl radical. © 1997 Elsevier Science Ltd.

Novel Dialkyl (.beta.-Halotetrafluoroethyl)phosphonates: Facile Synthesis via Thermally and Photochemically Induced Radical Reactions. A Unique Photochemical Transformation of BrCF2CF2I

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNovel Dialkyl (.beta.-Halotetrafluoroethyl)phosphonates: Facile Synthesis via Thermally and Photochemically Induced Radical Reactions. A Unique Photochemical Transformation of BrCF2CF2IH. K. Nair and D. J. BurtonCite this: J. Am. Chem. Soc. 1994, 116, 13, 6041–6042Publication Date (Print):June 1, 1994Publication History Published online1 May 2002Published inissue 1 June 1994https://doi.org/10.1021/ja00092a094RIGHTS & PERMISSIONSArticle Views128Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (289 KB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Two-step synthesis of (.gamma.,.gamma.-difluoroallyl)carbonyl compounds via addition of 1,1,2-trichloro-2,2-difluoroethyl radical to silyl enol ethers followed by reductive dechlorination

Ru(II)- or Cu(I)-induced radical reaction of CF 2 ClCCl 2 . radical (2), regioselectively derived from CF 2 ClCCl 3 , to trimethylsilyl enol ethers and a ketene silyl acetal yields (β,β,γ-trichloro-γ,γ-difluoropropyl)carbonyl compounds 5 as the intermediates. Spontaneous dehydrochlorination affords [β-chloro-β-(chlorodifluoromethyl)vinyl]carbonyl compounds 4. Reductive dechlorination of 4 with zinc gave γ,γ-difluoroallyl ketones 7a-e and an ester 7f. In some cases, Ni(O)-catalyzed reduction with zinc is superior than the simple hydrodechlorination

Triethylborane Induced Radical Reaction of Ketene Silyl Acetals with Polyhalomethanes

Abstract The treatment of ketene silyl acetal with tetrahalomethane or trihalomethane at room temperature in the presence of a catalytic amount of Et3B provides 3,3-dihaloacrylate or (E)-3-haloacrylate, respectively. On the other hand, a reaction at −23 °C mainly gives 3,3,3-trihalopropanoate or 3,3-dihalopropanoate.

Photodegradation of hyaluronic acid: EPR and size exclusion chromatography study.

Photochemically induced radical reactions involving the lateral sequences and the end macromolecular chain groups of hyaluronic acid in aqueous solutions at 293K were studied by EPR spin trapping technique with DMPO (5,5-dimethylpyrroline-1-oxide). In the first 1-10 minutes of irradiation EPR indicates spin adducts of two carbon centered radicals with the splitting constants of aN = 1.60 mT, aH = 2.51 mT and aN = 1.56 mT, aH = 2.28 mT. After longer irradiation time (over 10 minutes) dominate two further DMPO adducts of radicals centered on hetero-atoms with splitting constants of aN = 1.44 mT, aH = 1.60 mT and of aN = 1.49 mT, aH = 1.49 mT. Simultaneously, molecular weight followed by SEC decreases, suggesting that UV irradiation leads to the breaking of interglycosidic bonds of hyaluronic acid main macromolecular chain.

Triethylborane Induced Radical Reaction of Ketene Silyl Acetals with Polyhalomethanes. Synthesis of 3,3-Dihalo- and 3-Haloacrylates

Abstract Treatment of ketene octyl t-butyldimethylsilyl acetal with tetrabromomethane or tribromomethane in the presence of a catalytic amount of triethylborane gave octyl 3,3-dibromoacrylate or octyl (E)-3-bromoacrylate, respectively.

Luminescence of Zinc Oxide Crystals Controlled by Electrode Potential and Electrochemical Reactions

The voltage dependence of the green luminescence of ZnO crystals used as electrodes in an electrochemical cell was investigated and compared with the voltage dependence of the photocurrent. When the exciting light is of shorter wavelength than the band edge of ZnO, this luminescence can be varied from its maximal value to complete extinction by applying small positive voltages. The luminescence resulting from excitation within the long wavelength tail of absorption, however, cannot be influenced. The potential dependence of the luminescence has been investigated with differently doped crystals under various conditions. The addition of formic acid to the electrolyte causes an increase of luminescence; this is found to be a consequence of photoelectrochemically induced radical reaction by which electrons are injected into the conduction band of the electrode. The potential dependence of the green luminescence is explained by a mechanism in which the trapping of the holes in recombination centers competes with their extraction, which leads to the generation of the photocurrent. The average concentration of photogenerated holes in the crystal is therefore rate limiting for the intensity of luminescence, provided that an excess of electrons is available for recombination. At sufficiently large positive potentials, however, when electrons are being depleted in the space charge layer, their concentration also becomes limiting, and electron injection can stimulate luminescence. The experimentally observed potential dependence of luminescence and photocurrent, as well as their interrelation, is shown to be consistent with results which were derived from a theoretical treatment of these effects. It is suggested that this green luminescence may be used as a probe for the study of the space charge layer and of electrochemical reactions.