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Autore: Grafiati
Pubblicato: 25 maggio 2024

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1

Han, Yuxuan, e Xiuling Cui. "Copper-Catalyzed Enantioselective Radical Heteroatomic S—O Cross-Coupling". Chinese Journal of Organic Chemistry 43, n. 3 (2023): 1201. http://dx.doi.org/10.6023/cjoc202300013.

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2

Linker, Torsten. "Addition of Heteroatom Radicals to endo-Glycals †". Chemistry 2, n. 1 (20 febbraio 2020): 80–92. http://dx.doi.org/10.3390/chemistry2010008.

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Radical reactions have found many applications in carbohydrate chemistry, especially in the construction of carbon–carbon bonds. The formation of carbon–heteroatom bonds has been less intensively studied. This mini-review will summarize the efforts to add heteroatom radicals to unsaturated carbohydrates like endo-glycals. Starting from early examples, developed more than 50 years ago, the importance of such reactions for carbohydrate chemistry and recent applications will be discussed. After a short introduction, the mini-review is divided in sub-chapters according to the heteroatoms halogen, nitrogen, phosphorus, and sulfur. The mechanisms of radical generation by chemical or photochemical processes and the subsequent reactions of the radicals at the 1-position will be discussed. This mini-review cannot cover all aspects of heteroatom-centered radicals in carbohydrate chemistry, but should provide an overview of the various strategies and future perspectives.
3

Di Vaira, Massimo, Piero Stoppioni, Stefano Midollini, Franco Laschi e Piero Zanello. "H+ addition to the heteroatomic CoP3 cluster. Synthesis of the radical CoP3+ cluster and electrochemical study". Polyhedron 10, n. 18 (gennaio 1991): 2123–29. http://dx.doi.org/10.1016/s0277-5387(00)86131-8.

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4

Rhodes, Christopher J., Harry Morris, Hikmet Agirbas, Mark Standing e Yaming Zhang. "Distonic isomerisations of imine radical cations: aspects of the reactivity of heteroatomic subunits damaged by ionising radiation". Journal of the Chemical Society, Perkin Transactions 2, n. 6 (1998): 1375–80. http://dx.doi.org/10.1039/a801066h.

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5

Taniguchi, Tsuyoshi. "Recent Advances in Reactions of Heteroatom-Centered Radicals". Synthesis 49, n. 16 (26 luglio 2017): 3511–34. http://dx.doi.org/10.1055/s-0036-1588481.

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Heteroatom-centered radicals show versatile reactivity and offer useful synthetic methods in organic chemistry. The development of new approaches for forming heteroatom-centered radicals has recently expanded the practicality of radical chemistry for synthesis. This review focuses on recent advances in reactions of representative heteroatom-centered radicals.1 Introduction2 Group 17 Elements: Chlorine and Bromine Radicals3 Group 15 and Group 16 Elements3.1 Nitrogen- and Oxygen-Centered Radicals3.2 Phosphorus- and Sulfur-Centered Radicals3.3 Other Radicals4 Group 14 Elements: Silicon-Centered Radicals5 Group 13 Elements: Boron-Centered Radicals6 Conclusion
6

Ogawa, Akiya, e Yuki Yamamoto. "Multicomponent Reactions between Heteroatom Compounds and Unsaturated Compounds in Radical Reactions". Molecules 28, n. 17 (30 agosto 2023): 6356. http://dx.doi.org/10.3390/molecules28176356.

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In this mini-review, we present our concepts for designing multicomponent reactions with reference to a series of sequential radical reactions that we have developed. Radical reactions are well suited for the design of multicomponent reactions due to their high functional group tolerance and low solvent sensitivity. We have focused on the photolysis of interelement compounds with a heteroatom–heteroatom single bond, which readily generates heteroatom-centered radicals, and have studied the photoinduced radical addition of interelement compounds to unsaturated compounds. First, the background of multicomponent radical reactions is described, and basic concepts and methodology for the construction of multicomponent reactions are explained. Next, examples of multicomponent reactions involving two interelement compounds and one unsaturated compound are presented, as well as examples of multicomponent reactions involving one interelement compound and two unsaturated compounds. Furthermore, multicomponent reactions involving intramolecular cyclization processes are described.
7

Renaud, Philippe, Alice Beauseigneur, Andrea Brecht-Forster, Barbara Becattini, Vincent Darmency, Sarkunam Kandhasamy, Florian Montermini et al. "Boron: A key element in radical reactions". Pure and Applied Chemistry 79, n. 2 (1 gennaio 2007): 223–33. http://dx.doi.org/10.1351/pac200779020223.

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Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen- and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.
8

Kawaguchi, Shin-ichi, Akiya Ogawa, Yuki Sato e Akihiro Nomoto. "Photoinduced Coupling Reaction of Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide with Interelement Compounds: Application to the Synthesis of Thio- or Selenophosphinates". Synthesis 49, n. 16 (4 luglio 2017): 3558–67. http://dx.doi.org/10.1055/s-0036-1588867.

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Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TMDPO) is a radical initiator widely used in the field of macromolecular chemistry, but not often applied in synthetic organic chemistry. We have focused­ on the use of TMDPO as a phosphorus source in reactions with different E – E compounds, where E – E represents a heteroatom–heteroatom­ bond, under photoirradiation. Interestingly, the cross-coupling reaction between TMDPO and disulfides or diselenides successfully affords thio- or selenophosphinates and thio- or selenoesters, respectively. The synthesis of series of thio- and selenophosphinates by this photoinduced cross-coupling reaction is demonstrated.
9

Guo, Weisi, Qian Wang e Jieping Zhu. "Visible light photoredox-catalysed remote C–H functionalisation enabled by 1,5-hydrogen atom transfer (1,5-HAT)". Chemical Society Reviews 50, n. 13 (2021): 7359–77. http://dx.doi.org/10.1039/d0cs00774a.

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The generation of heteroatom-centred radicals followed by intramolecular 1,5-HAT and functionalisation of the translocated carbon-centred radical is an efficient way to functionalize chemo- and regio-selectively the remote unactivated C(sp3)–H bond.
10

Kubo, Takashi. "Synthesis, Physical Properties, and Reactivity of Stable, π-Conjugated, Carbon-Centered Radicals". Molecules 24, n. 4 (13 febbraio 2019): 665. http://dx.doi.org/10.3390/molecules24040665.

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Recently, long-lived, organic radical species have attracted much attention from chemists and material scientists because of their unique electronic properties derived from their magnetic spin and singly occupied molecular orbitals. Most stable and persistent organic radicals are heteroatom-centered radicals, whereas carbon-centered radicals are generally very reactive and therefore have had limited applications. Because the physical properties of carbon-centered radicals depend predominantly on the topology of the π-electron array, the development of new carbon-centered radicals is key to new basic molecular skeletons that promise novel and diverse applications of spin materials. This account summarizes our recent studies on the development of novel carbon-centered radicals, including phenalenyl, fluorenyl, and triarylmethyl radicals.
11

Xiao, Tiebo, Lei Zhou, Hongtai Huang e Devireddy Anand. "Iminyl-Radical-Triggered C–C Bond Cleavage of Cycloketone Oxime Derivatives: Generation of Distal Cyano-Substituted Alkyl Radicals and Their Functionalization". Synthesis 52, n. 11 (5 marzo 2020): 1585–601. http://dx.doi.org/10.1055/s-0039-1690844.

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Alkyl nitriles are versatile building blocks in organic synthesis because the cyano group can be easily converted into other functional groups. Iminyl-radical-triggered C–C bond cleavage of cycloketone oxime­ derivatives provides a practical route to access distal cyano-substituted alkyl radicals, which has given chemists a new radical reaction platform for the synthesis of diverse alkyl nitriles. This review provides an overview of various types of radical cyanoalkylation via ring opening of cycloketone oxime derivatives.1 Introduction2 C–C Bond Formation2.1 Alkenes as Radical Acceptors2.2 Aromatic Rings as Radical Acceptors2.3 Organometallic Reagents as Radical Acceptors2.4 Cyanoalkyl-Radical-Triggered Cyclization Reactions2.5 Miscellaneous3 C–Heteroatom Bond Formation3.1 C–O Bond Formation3.2 C–N Bond Formation3.3 C–S Bond Formation3.4 C–Halogen Bond Formation3.5 C–B Bond Formation4 Conclusion
12

Paick, Jihun, Seunghee Hong, Jy-Young Jyoung, Eun-Sook Lee e Doohwan Lee. "Comparative Studies on Effects of Metal Cation (La) and Non-Metal Anion (N) Doping on CeO2 Nanoparticles for Regenerative Scavenging of Reactive Oxygen Radicals". Catalysts 13, n. 3 (11 marzo 2023): 572. http://dx.doi.org/10.3390/catal13030572.

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The intrinsic effects of metal cation (La) and non-metallic anion (N) doping of CeO2 nanoparticles (NPs) for regenerative scavenging of reactive oxygen radicals were studied. La-doped CeO2 NPs were prepared by the conventional impregnation method at various La doping levels. N-doped CeO2 NPs were prepared by urea thermolysis with two different methods: (i) direct thermolysis of urea after physical mixing with CeO2 NPs and (ii) wet impregnation of CeO2 NPs with urea followed by thermolysis under inert N2 atmosphere. Physicochemical properties of samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 sorption measurement. Radical scavenging properties of the samples were characterized by applying Fenton’s reaction. Results indicated that atomic N doping on CeO2 NPs significantly enhanced radical scavenging properties of CeO2 NPs, resulting in an activity of N-doped CeO2 about 3.6 times greater than the pristine CeO2 NPs and 1.6 times higher than the La-doped CeO2 NPs. This result suggests that anionic N doping of CeO2 NPs is highly effective in enhancing radical scavenging properties of CeO2 NPs, whereas such modifications have been typically practiced by hetero-metal doping with rare earth metal elements. A collective structure–property correlation analysis suggested that enhancement of radical scavenging properties of heteroatom-doped CeO2 NPs was largely attributed to an increase in surface oxygen vacancies on CeO2 NPs due to heteroatom doping.
13

Yamamoto, Yuki, Qiqi Chen e Akiya Ogawa. "Diphenyl Diselenide-Assisted Radical Addition Reaction of Diphenyl Disulfide to Unsaturated Bonds upon Photoirradiation". Molecules 28, n. 6 (7 marzo 2023): 2450. http://dx.doi.org/10.3390/molecules28062450.

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The addition reaction of interelement compounds with heteroatom–heteroatom single bonds to unsaturated bonds under photoirradiation is an important method for the efficient and atom-economical construction of carbon–heteroatom bonds. However, in practice, the desired addition reaction is sometimes unable to proceed as expected due to the low efficiency of the desired addition reactions or the preferential polymerization of unsaturated compounds. In this study, by combining an interelement compound with homologous heteroatom compounds as a catalyst, we succeeded in suppressing the polymerization of the unsaturated compounds and in attaining a highly selective carbon–heteroatom bond formation through the desired addition reaction. In this paper, we have examined in detail whether such a “catalytic radical reaction” proceeds for unsaturated compounds and found that the dithiolation of some unsaturated compounds (i.e., vinylic ethers, styrenes, and isocyanides) could proceed with the assistance of (PhSe)2 under light. The developed methods in this study are expected to have strong implications in the fields of radical chemistry, heteroatom chemistry, synthetic organic chemistry, and catalyst chemistry as atom-economical methods for carbon–heteroatom bond formation.
14

Mozafari, Mina, Lalangi Chandrasena, Iain McKenzie, Kerim Samedov e Paul W. Percival. "Characterization of free radicals in clathrate hydrates of pyrrole, thiophene, and isoxazole by muon spin spectroscopy". Canadian Journal of Chemistry 96, n. 2 (febbraio 2018): 217–25. http://dx.doi.org/10.1139/cjc-2017-0313.

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Gas hydrates have long been of interest to the petrochemical industry, but there has been growing interest in potential applications for carbon dioxide sequestration and hydrogen storage. This has prompted many fundamental studies of structure and host–guest interactions, but there has been relatively little investigation of chemical reactions of the guest molecules. In previous work, we have shown that it is possible to use muon spin spectroscopy to characterize H atom like muonium and muoniated free radicals formed in clathrate hydrates. Muonium (Mu) forms in clathrate hydrates of cyclopentane and tetrahydrofuran, whereas furan and its dihydro derivatives form radicals. The current work extends studies to clathrates hydrates of other five-membered heterocycles: thiophene, pyrrole, and isoxazole. All form structure II hydrates. In addition to the clathrates, pure liquid samples of the heterocycles were studied to aid in the assignment of radical signals and for comparison with the enclathrated radicals. Similar to furan, two distinct radicals are formed when Mu reacts with thiophene and pyrrole. However, only one muoniated radical was detected from isoxazole. Muon, proton, and nitrogen hyperfine constants were determined and compared with values predicted by DFT calculations to aid the structure assignments. The results show that Mu adds preferentially to the carbon adjacent to the heteroatom in thiophene and pyrrole and to the carbon adjacent to oxygen in isoxazole. The same radicals are formed in clathrates, but the spectra have broader signals, suggesting slower tumbling. Furthermore, additional signals in the avoided level-crossing spectra indicate anisotropy consistent with restricted motion of the radicals in the clathrate cages.
15

Katritzky, Alan R., Baozhen Yang e Naresh S. Dalal. "Novel Heteroatom-Linked Analogues of Trityl Radicals: Diaryl(benzotriazol-1-yl)methyl Radical Dimers". Journal of Organic Chemistry 63, n. 5 (marzo 1998): 1467–72. http://dx.doi.org/10.1021/jo9715229.

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16

Kaur, Rupinder preet, Damanjit Kaur e Ritika Sharma. "Substituent effect on N–H bond dissociation enthalpies of carbamates: a theoretical study". Canadian Journal of Chemistry 93, n. 3 (marzo 2015): 279–88. http://dx.doi.org/10.1139/cjc-2014-0326.

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The present investigation deals with the study of the N–H bond dissociation enthalpies (BDEs) of the Y-substituted (NH2-C(=X)Y-R) and N-substituted ((R)(H)NC(=X)YH) carbamates (X, Y = O, S, Se; R = H, CH3, F, Cl, NH2), which have been evaluated using ab initio and density functional methods. The variations in N−H BDEs of these Y-substituted and N-substituted carbamates as the effect of substituent have been understood in terms of molecule stabilization energy (ME) and radical stabilization energy (RE), which have been calculated using the isodesmic reactions. The natural bond orbital analysis indicated that the electrodelocalization of the lone pairs of heteroatoms in the molecules and radicals affect the ME and RE values depending upon the type and site of substitution (whether N- or Y-). The variations in N−H BDEs depend upon the combined effect of molecule stabilization and radical stabilization by the various substituents.
17

Wan, Zhonghao, Yuqing Sun, Daniel C. W. Tsang, Iris K. M. Yu, Jiajun Fan, James H. Clark, Yaoyu Zhou, Xinde Cao, Bin Gao e Yong Sik Ok. "A sustainable biochar catalyst synergized with copper heteroatoms and CO2 for singlet oxygenation and electron transfer routes". Green Chemistry 21, n. 17 (2019): 4800–4814. http://dx.doi.org/10.1039/c9gc01843c.

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18

SCHUCHMANN, H. P., e C. VON SONNTAG. "ChemInform Abstract: Heteroatom Peroxyl Radicals". ChemInform 29, n. 22 (22 giugno 2010): no. http://dx.doi.org/10.1002/chin.199822209.

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19

Zhang, Kai, Benjamin B. Noble, Adam C. Mater, Michael J. Monteiro, Michelle L. Coote e Zhongfan Jia. "Effect of heteroatom and functionality substitution on the oxidation potential of cyclic nitroxide radicals: role of electrostatics in electrochemistry". Physical Chemistry Chemical Physics 20, n. 4 (2018): 2606–14. http://dx.doi.org/10.1039/c7cp07444a.

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20

Mieden, Oliver J., e Clemens von Sonntag. "Peptide Free-Radicals: The Reactions of OH Radicals with Glycine Anhydride and its Methyl Derivatives Sarcosine and Alanine Anhydride. A Pulse Radiolysis and Product Study". Zeitschrift für Naturforschung B 44, n. 8 (1 agosto 1989): 959–74. http://dx.doi.org/10.1515/znb-1989-0818.

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The reactions of radiolytically generated OH radicals and H atoms with the cyclic dipeptides of glycine, alanine and sarcosine in deoxygenated aqueous solutions and the subsequent reactions of the transient peptide radicals were studied in the absence and presence of K3Fe(CN)6 as oxidant by pulse radiolysis and product analysis.Hydroxyl radicals and H atoms react with glycine anhydride and alanine anhydride by abstracting an H atom bound at C-3; there is no evidence for any other site of attack at these two peptides. The resulting radicals have pKa values of 9.8 and 10.6, respectively.In the absence of an oxidant the radicals decay by second order (2k = 7.0×108 dm3 mol-1 s-1 and 2k = 4.4×108 dm3 mol-1 s-1, resp.), the main fraction (94% of the glycine anhydride-derived radicals, 90% of the alanine anhydride-derived radicals) yielding dehydrodimers (G = 0.58 μmol J-1 and 0.56 µmol J-1 (in monomer units), resp.). A small portion however disproportionates via abstraction of a C-6-bound Η atom followed by isomerization to 2,5-dihydroxypyrazines (pKa values of the parent 2,5-dihydroxypyrazine at about 7.9 and 10.1) and subsequent addition of water to 2,5-diketo-3-hydroxypiperazines, thus indicating that the transfer of a carbon-bound hydrogen atom is prefered to the transfer of a nitrogen-bound hydrogen atom.No disproportionation products but three different dehydrodimers (G = 0.36, 0.18 and 0.04 µmol J-1 (in monomer units)) were found after irradiation of sarcosine anhydride. In this case a dose rate and solute concentration dependence of dehydrodimer formation indicates a radical-solute reaction converting part of the N-methyl radicals (21% of ‘initial’ attack) into the C-3-yl radicals. A rate constant of k = 600 ± 50 dm3 mol-1 s-1 was obtained for this reaction by measuring and computing the dehydrodimer yields as a function of dose rate and solute concentration. Thus the observed transient spectrum accounts only for about 79% of the radicals from the ‘initial’ attack at C-3.The rate of oxidation of the glycine anhydride-derived radicals by Fe(CN)63- reflects the pKa of the transient radical. The rate constant for oxidation of the (protonated) radical derived from glycine anhydride is: k = 1.0x 108 dm3 mol-1, the corresponding radical anion is oxidized with k = 3.1 × 108 dm3 mol-1 s-1. No change with pH was observed in the case of the alanine anhydridederived radicals (k = 7.9x 108 dm3 mol-1 s-1). In contrast to the disproportionation, oxidation by Fe(CN)63- leads to the removal of a proton from the heteroatom, a carbocation being the intermediate. The resulting dehydropiperazines rapidly add water to yield the corresponding 2,5-diketo-3-hydroxypiperazines (G = 0.61 μmol J-1 after oxidation of the glycine anhydride-derived radicals, G = 0.58 µmol J-1 after oxidation of the alanine anhydride-derived radicals). The radicals derived from sarcosine anhydride are readily oxidized with k = 4.0×108 dm3 mol-1 s-1, independent of pH.1H and 13C{1H} NMR-spectroscopic and mass-spectroscopic data of the products are given.
21

Ross, Philip L., Scott E. Van Bramer e Murray V. Johnston. "Ultraviolet Photodissociation of Gas-Phase Alcohols, Amines, and Nitroalkanes". Applied Spectroscopy 50, n. 5 (maggio 1996): 608–13. http://dx.doi.org/10.1366/0003702963905862.

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The 193-nm photochemistry of alcohols, amines, and nitroalkanes in the C3-C6 size range is presented. The photolysis products are photoionized with coherent vacuum ultraviolet radiation and analyzed by time-of-flight mass spectrometry. For alcohols and amines, C-C bond dissociation competes with dissociations involving the heteroatom (C-O, O-H, C-N, N-H). Dissociation of the α(C-C) bond is preferred over other locations. Dissociation of a C-C bond is suppressed when a methyl radical would be produced. This behavior is similar to that observed for other substituted alkanes. Nitroalkanes exhibit both C-N and N-O bond dissociation pathways. Their low bond energies cause a substantial amount of internal energy to be partitioned among the primary photodissociation products. Under collision-free conditions, the alkyl radicals produced from these molecules undergo extensive secondary fragmentation. If the photodissociation step is performed in a free jet expansion, collisional cooling stabilizes the primary products and allows large species, such as intact pentyl and hexyl radicals, to be detected.
22

de la Vega-Hernández, Karen, Elise Romain, Anais Coffinet, Kajetan Bijouard, Geoffrey Gontard, Fabrice Chemla, Franck Ferreira, Olivier Jackowski e Alejandro Perez-Luna. "Radical Germylzincation of α-Heteroatom-Substituted Alkynes". Journal of the American Chemical Society 140, n. 50 (29 novembre 2018): 17632–42. http://dx.doi.org/10.1021/jacs.8b09851.

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23

Zhi, Sanjun, Hongjun Yao e Wei Zhang. "Difunctionalization of Dienes, Enynes and Related Compounds via Sequential Radical Addition and Cyclization Reactions". Molecules 28, n. 3 (23 gennaio 2023): 1145. http://dx.doi.org/10.3390/molecules28031145.

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Radical reactions are powerful in creating carbon–carbon and carbon–heteroatom bonds. Designing one-pot radical reactions with cascade transformations to assemble the cyclic skeletons with two new functional groups is both synthetically and operationally efficient. Summarized in this paper is the recent development of reactions involving radical addition and cyclization of dienes, diynes, enynes, as well as arene-bridged and arene-terminated compounds for the preparation of difunctionalization cyclic compounds. Reactions carried out with radical initiators, transition metal-catalysis, photoredox, and electrochemical conditions are included.
24

Huang, Min-Hua, Wen-Juan Hao, Guigen Li, Shu-Jiang Tu e Bo Jiang. "Recent advances in radical transformations of internal alkynes". Chemical Communications 54, n. 77 (2018): 10791–811. http://dx.doi.org/10.1039/c8cc04618b.

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This review highlights the recent progress in the radical transformation of internal alkynes and focuses on the reaction mechanisms by carbon/heteroatom-centered triggered additions, and offers a comprehensive overview on the existing procedures and employed methodologies.
25

Yateem, Ali Hussain. "Rotational Barrier and Bond Dissociation Energy and Enthalpy: Computational Study of the Substituent Effects in <i>Para</i>-Substituted Anilines and Phenols". Indonesian Journal of Chemistry 22, n. 1 (8 gennaio 2022): 179. http://dx.doi.org/10.22146/ijc.68687.

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This report presents the N–H and O–H bond dissociation energies (BDEs) and enthalpies (BDEts) of 27 para-substituted anilines and phenols using Density Functional Theory (DFT) with functional wB97X-D and basis set 6-31G**. The computed BDEs/ BDEts show a strong correlation with the calculated rotational barrier (RB) around phenyl–NH2 and phenyl–OH bonds of the parent neutral molecules. Electron-withdrawing (EW) substituents increased RB and BDEs/BDEts, while electron-donating (ED) substituents caused opposite behavior. Geometric, atomic, molecular, and spectroscopic properties of NH2 and OH groups in neutral anilinic and phenolic molecules exhibited excellent correlations with RB and BDEs/BDEts. The geometry around heteroatoms of the radicals displayed constant geometrical changes for all substituents. Spin density maps confirmed that the unpaired electrons in radicals are delocalized in heteroatoms and phenyl rings for all the para-substituents. Spin delocalization in both types of radicals was further enhanced in the presence of para-ED substituents. The increase in electronic density around heteroatoms of radicals with the strength of ED substituents was found proportional to that in neutral molecules. Therefore, the N–H and O–H BDE/BDEt are mainly governed by the stabilization/destabilization of the neutral molecules and, to a significantly lower extent, the stabilization of radicals in the case of strong ED groups.
26

Demay-Drouhard, Paul, H. Y. Vincent Ching, Christophe Decroos, Régis Guillot, Yun Li, Leandro C. Tabares, Clotilde Policar, Helene C. Bertrand e Sun Un. "Understanding the g-tensors of perchlorotriphenylmethyl and Finland-type trityl radicals". Physical Chemistry Chemical Physics 22, n. 36 (2020): 20792–800. http://dx.doi.org/10.1039/d0cp03626a.

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Mukhopadhyay, Anamika, Lilit Jacob e Sugumar Venkataramani. "Dehydro-oxazole, thiazole and imidazole radicals: insights into the electronic structure, stability and reactivity aspects". Physical Chemistry Chemical Physics 19, n. 1 (2017): 394–407. http://dx.doi.org/10.1039/c6cp05677f.

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28

Yorimitsu, Hideki. "Homolytic substitution at phosphorus for C–P bond formation in organic synthesis". Beilstein Journal of Organic Chemistry 9 (28 giugno 2013): 1269–77. http://dx.doi.org/10.3762/bjoc.9.143.

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Organophosphorus compounds are important in organic chemistry. This review article covers emerging, powerful synthetic approaches to organophosphorus compounds by homolytic substitution at phosphorus with a carbon-centered radical. Phosphination reagents include diphosphines, chalcogenophosphines and stannylphosphines, which bear a weak P–heteroatom bond for homolysis. This article deals with two transformations, radical phosphination by addition across unsaturated C–C bonds and substitution of organic halides.
29

Dénès, Fabrice. "Intermolecular Radical C–H Bond Activation: A Powerful Tool for Late Stage Functionalization". CHIMIA International Journal for Chemistry 74, n. 1 (26 febbraio 2020): 23–32. http://dx.doi.org/10.2533/chimia.2020.23.

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The synthesis of complex molecules via radical reactions involving carbon–carbon and carbon–heteroatom bonds has become a very successful approach. Radical chemistry has long been dominated by the use of tin-based reagents. Those strongly contributed to the development of the field, allowing one to achieve spectacular transformations, most of which being difficult or impossible to achieve under ionic conditions, and giving access to invaluable kinetics data that paved the way for the development of improved protocols and the design of new synthetic strategies. However, tin reagents and tin byproducts are often toxic and they proved to make purification steps sometimes tedious. In this context, tin-free methods have progressively gained in interest. This short review aims at providing the reader with alternative methods employing C–H bonds in place of the classical alkyl halides to generate, via an intermolecular hydrogen atom transfer (HAT), the radical species. Examples of carbon–carbon and carbon–heteroatom bond formation using this type of C–H bond activation approach will be provided, from early reports to the more recent developments.
30

Naito, Takeaki. "Heteroatom Radical Addition-Cyclization and Its Synthetic Application". HETEROCYCLES 50, n. 1 (1999): 505. http://dx.doi.org/10.3987/rev-98-sr(h)2.

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31

Coote, Michelle L., Ching Yeh Lin e Andreas A. Zavitsas. "Inherent and transferable stabilization energies of carbon- and heteroatom-centred radicals on the same relative scale and their applications". Phys. Chem. Chem. Phys. 16, n. 18 (2014): 8686–96. http://dx.doi.org/10.1039/c4cp00537f.

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32

Yu, Jing-Miao, e Chun Cai. "Iodine(iii)-mediated intramolecular sulfeno- and selenofunctionalization of β,γ-unsaturated tosyl hydrazones and oximes". Organic & Biomolecular Chemistry 16, n. 3 (2018): 490–98. http://dx.doi.org/10.1039/c7ob02892j.

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Abstract (sommario):
A cascade radical cyclization/sulfenylation or selenylation of β,γ-unsaturated hydrazones and oximes was realized under mild conditions with phenyliodine(iii) diacetate (PIDA) as the sole oxidant, leading to the construction of diversely functionalized heteroatom-containing pyrazoline and isoxazoline derivatives.
33

Kirchhoff, Dirk, Hans-Friedrich Grützmacher e Hansjörg Grützmacher. "Trends in the Periodic System: The Mass Spectrum of Dimethylphenyl Phosphane and a Comparison of the Gas Phase Reactivity of Dimethylphenyl Pnictogene Radical Cations C6H5E(CH3)2•+, (E = N, P, As)". European Journal of Mass Spectrometry 15, n. 2 (aprile 2009): 131–44. http://dx.doi.org/10.1255/ejms.940.

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Abstract (sommario):
The mass spectrometric reactions of dimethylphenyl phosphane, 1, under electron impact have been studied by methods of tandem mass spectrometry and by using labeling with deuterium. The results are compared to those for the previously investigated dimethylaniline, 2, and dimethylphenyl arsane, 3, to examine the effects of heavy main group heteroatoms on the reactions of radical cations of the pnictogen derivatives C6H5E(CH3)2. Decomposition of the radical cation 1•+ gives rise to large peaks in the 70 eV electron impact (EI) mass spectrum for loss of a radical, •CH3, which is followed by abundant loss of a molecule, H2, and formation of ion C7H7+, and the 70 eV EI mass spectrum of the deuterated derivative 1d3 shows that excessive positional hydrogen/deuterium (H/D) exchange accompanies all fragmentation reactions. This is confirmed by the mass analyzed kinetic energy (MIKE) spectrum of the molecular ion 1d6•+ which displays a group of signals for the loss of all isotopomers, •C(H/D)3, and three signals for formation of ions C7H5D2+, C7H4D3+ and C7H3D4+. The intensity distribution within this latter group of ions corresponds to a statistical positional exchange (“scrambling”) of all six D atoms of the methyl substituents with only two H atoms of the phenyl group. In contrast, the intensity distribution of the signals for loss of •C(H/D)3 uncovers a bimodal reaction. About 39% of metastable molecular ions 1•+ eliminate •CH3 after scrambling of the six H atoms of the methyl substituents with two H atoms of the phenyl group, while the remaining 61% of metastable 1•+ lose specifically a CH3 substituent without positional H exchange. Further, the metastable ion [M – CH3]+ eliminates, almost exclusively, a molecule H2, which is preceded by excessive positional H/D exchange in the case of metastable ion [M – CD3]+. The formation of ion C7H7+ from metastable ion [M – CH3]+ is not observed and this is a minor process, even under the high energy condition of collision-induced dissociation (CID). The mechanisms of these fragmentation and exchange reactions have been modeled by theoretical calculations using the DFT functionals at the level UHBLY/6-311+G(2d,p)//UHBLYP/6-31+G(d). The key feature is a rearrangement of molecular ion 1•+ to an α-distonic isomer 1dist1•+ by a 1,2-H shift from the CH3 substituent to the P atom in competition with a direct loss of a CH3 substituent. The distonic ion 1dist1•+ performs positional H exchange between H atoms of both CH3 substituents and H atoms at the ortho-positions of the phenyl group and rearranges readily to the (conventional) isomer benzylmethyl phosphane radical cation 1bzl•+. The ion 1bzl•+ undergoes further positional H exchange before decomposition to ion C7H7+ and a radical CH3P•H or by loss of a radical •CH3. Finally, ions [M – CH3]+ of methylphenyl phosphenium structure 1a+ and benzyl phosphenium structure 1b+ interconvert easily parallel to positional H exchange involving all H atoms of the ions. Eventually, a molecule H2 is lost by a 1,1-elimination from the PH2 group of the protomer 1b–H+ of 1b+. The trends observed in the gas phase chemistry of the pnictogen radical cations dimethylaniline 2•+, dimethylphenyl phosphane 1•+ and dimethylphenyl arsane 3•+ can be comprehended by considering the variation of the energetic requirements of three competing reaction: (i) α-cleavage by loss of •H from a methyl substituent, (ii) rearrangement of the molecular ion to an α-distonic isomer by a 1,2-H shift and (iii) loss of •CH3 by cleavage of the C-heteroatom bond. 2•+ exhibits a strong N–C bond and a high activation barrier for 1,2-H shift and fragments far more predominantly by α-cleavage. Both 1•+ and 3•+ eliminate •CH3 by cleavage of the weak C-heteroatom bond. The barrier for a 1,2-H shift is also distinctly smaller than for 2•+ and, for the P-derivative 1•+, the generation of the α-distonic ion is able to compete with loss of •CH3.
34

Blank, Lena, Maurizio Fagnoni, Stefano Protti e Magnus Rueping. "Visible Light-Promoted Formation of C–B and C–S Bonds under Metal- and Photocatalyst-Free Conditions". Synthesis 51, n. 05 (6 febbraio 2019): 1243–52. http://dx.doi.org/10.1055/s-0037-1611648.

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A green, efficient, photoinduced synthesis of arylboronic esters and aryl sulfides has been developed. Bench stable arylazo sulfones were used as radical precursors for a photocatalyst- and additive-free carbon–heteroatom bond formation under visible light. The protocols are applicable to a wide range of substrates, providing products in good yields.
35

Hendon, Christopher H., David R. Carbery e Aron Walsh. "Three-electron two-centred bonds and the stabilisation of cationic sulfur radicals". Chem. Sci. 5, n. 4 (2014): 1390–95. http://dx.doi.org/10.1039/c3sc53432d.

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36

Schier, Jan E. S., David Cohen-Sacal e Robin A. Hutchinson. "Hydrogen bonding in radical solution copolymerization kinetics of acrylates and methacrylates: a comparison of hydroxy- and methoxy-functionality". Polymer Chemistry 8, n. 12 (2017): 1943–52. http://dx.doi.org/10.1039/c7py00185a.

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37

Russell, Glen A., Preecha Ngoviwatchai, Hasan I. Tashtoush, Anna Pla-Dalmau e Rajive K. Khanna. "Reactions of alkylmercurials with heteroatom-centered acceptor radicals". Journal of the American Chemical Society 110, n. 11 (maggio 1988): 3530–38. http://dx.doi.org/10.1021/ja00219a030.

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38

RANAUD, P. "ChemInform Abstract: Heteroatom-Substituted Radicals: 1,2-Asymmetric Induction". ChemInform 27, n. 40 (4 agosto 2010): no. http://dx.doi.org/10.1002/chin.199640268.

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39

Serwinski, Paul R., Burak Esat, Paul M. Lahti, Yi Liao, Richard Walton e Jiang Lan. "Photolysis and Oxidation of Azidophenyl-Substituted Radicals: Delocalization in Heteroatom-Based Radicals". Journal of Organic Chemistry 69, n. 16 (agosto 2004): 5247–60. http://dx.doi.org/10.1021/jo049500r.

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40

Miyabe, Hideto, e Yoshiji Takemoto. "Cascade radical reactions via carbon-carbon/heteroatom bond-forming process". Universal Organic Chemistry 2, n. 1 (2014): 1. http://dx.doi.org/10.7243/2053-7670-2-1.

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41

Naito, Takeaki. "ChemInform Abstract: Heteroatom Radical Addition-Cyclization and Its Synthetic Application". ChemInform 30, n. 20 (15 giugno 2010): no. http://dx.doi.org/10.1002/chin.199920279.

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42

Erfan, Abeer, Emad Yousif, Ahmed Neama Alshanon, Dina Saadi Ahmed, Muna Bufaroosha e Gamal El-Hiti. "Organotin(IV) Complexes as Promising Potential Drug Candidates in the Field of Cancer Chemotherapy: A Narrative Review". Al-Rafidain Journal of Medical Sciences ( ISSN 2789-3219 ) 5 (15 luglio 2023): 48–56. http://dx.doi.org/10.54133/ajms.v5i.146.

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Abstract (sommario):
Organotin(IV) complexes have a wide range of different applications. They are highly involved in pharmaceutical applications and have shown anticancer activity against various cancer cell lines. They act as antioxidants and can scavenge free radical species. The biological activity of organotin complexes depends on the organic moiety, type of substituents, number, type, and content of heteroatoms, and their geometry. The current review aimed to discuss using organotin complexes against different cancer cells.
43

Buntinx, G., e O. Poizat. "Time-Resolved Resonance Raman Spectroscopy of Photochemical Reactive Intermediates: Radical Cation of Fluorene and Triplet State of Fluorene, Dibenzofuran and Dibenzothiophen". Laser Chemistry 10, n. 5-6 (1 gennaio 1990): 333–47. http://dx.doi.org/10.1155/1990/28350.

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Abstract (sommario):
The time-resolved Raman spectra of the first triplet state–in resonance with the Tn←T1 absorption at 370 nm–and of the radical cation transient–in resonance with the R+⋅∗←R+⋅ absorptions at 370 nm and in the 560-600 nm range-are reported for fluorene. The triplet state Raman spectra of dibenzofuran and dibenzothiophen are also given. The vibrational assignments, resonance Raman activity and intensity enhancement effects are studied. On this basis, the structures and electronic configurations of the triplet state and radical cation transients and the nature of the resonant Tn←T1 and R+⋅∗←R+⋅ transitions are discussed. It turns out from this investigation that the title molecules present close analogies with biphenyl. The insertion of a methylene group or a heteroatom does not disturb markedly the electronic properties of the ground state, the first triplet state and the radical cation transient of biphenyl.
44

Pyszka, Ilona, e Beata Jędrzejewska. "Acenaphthoquinoxaline Derivatives as Dental Photoinitiators of Acrylates Polymerization". Materials 14, n. 17 (27 agosto 2021): 4881. http://dx.doi.org/10.3390/ma14174881.

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A series of dyes based on the acenaphthoquinoxaline skeleton was synthesized. Their structure was modified by introducing electron-withdrawing and electron-donating groups, increasing the number of conjugated double bonds and the number and position of nitrogen atoms, as well as the arrangement of aromatic rings (linear or angular). The dyes were investigated as a component in the photoinitiating systems of radical polymerization for a potential application in dentistry. They acted as the primary absorber of visible light and the acceptor of an electron, which was generated from a second component being an electron donor. Thus, the radicals were generated by the photoinduced intermolecular electron transfer (PET) process. Electron donors used differed in the type of heteroatom, i.e., O, S and N and the number and position of methoxy substituents. To test the ability to initiate the polymerization reaction by photoinduced hydrogen atom transfer, we used 2-mercaptobenzoxazole as a co-initiator. The effectiveness of the photoinitiating systems clearly depends on both the modified acenaphthoquinocaline structure and the type of co-initiator. The lower amount of heat released during the chain reaction and the polymerization rate comparable to this achieved for the photoinitiator traditionally used in dentistry (camphorquinone) indicates that the studied dyes may be valuable in this field.
45

Kamijo, Shin, Kaori Kamijo e Toshihiro Murafuji. "Aryl Ketone Mediated Photoinduced Radical Coupling for the Alkylation­ of Benzazoles Employing Saturated Heterocyclic Compounds­". Synthesis 51, n. 20 (31 luglio 2019): 3859–64. http://dx.doi.org/10.1055/s-0037-1611895.

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An aryl ketone mediated synthesis of 2-alkylated benzazoles was achieved via radical coupling under photoirradiation starting from saturated heterocycles and 2-sulfonylated benzazoles, such as benzothiazoles, benzoxazole, and benzimidazole. Heterocyclic compounds, including a cyclic ether, azacycles, and tetrahydrothiophene, were applicable, and the benzazole unit was site-selectively installed at the carbon center proximal to the heteroatom. The present transformation takes place at ambient temperature under neutral reaction conditions without the aid of any metallic catalysts or reagents.
46

Katritzky, Alan R., Baozhen Yang e David P. M. Pleynet. "Novel Heteroatom-Substituted Trityl Radical Analogues: Preparation and Properties of Diaryl(benzotriazol-2-yl)methyl Radical Dimers‡". Journal of Organic Chemistry 63, n. 26 (dicembre 1998): 9992–94. http://dx.doi.org/10.1021/jo980618f.

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47

Li, Ping, Boon Chong Lee, Ming Joo Koh e Xiaoxiang Zhang. "Base-Mediated Site-Selective Hydroamination of Alkenes". Synthesis 54, n. 06 (28 ottobre 2021): 1566–76. http://dx.doi.org/10.1055/a-1681-4720.

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AbstractWe present a base-mediated hydroamination protocol, using substoichiometric amounts of a hydrosilane and potassium tert-butoxide­, that operates under mild conditions at 30 °C. Many aryl- and heteroatom-substituted olefins as well as arylamines are tolerated, affording the desired products with complete regioselectivity. Preliminary mechanistic investigations reveal a non-radical pathway for hydroamination. A sequential remote hydroamination strategy involving an initial Fe-catalysed olefin isomerisation followed by our base-mediated hydroamination was also developed to directly access β-arylamines from terminal aliphatic alkenes.
48

Schiesser, Carl H., e Lisa M. Wild. "Free-radical homolytic substitution: New methods for formation of bonds to heteroatoms". Tetrahedron 52, n. 42 (ottobre 1996): 13265–314. http://dx.doi.org/10.1016/0040-4020(96)00809-5.

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49

Sonawane, Amol D., Rohini A. Sonawane, Masayuki Ninomiya e Mamoru Koketsu. "Synthesis of Seleno‐Heterocycles via Electrophilic/Radical Cyclization of Alkyne Containing Heteroatoms". Advanced Synthesis & Catalysis 362, n. 17 (9 luglio 2020): 3485–515. http://dx.doi.org/10.1002/adsc.202000490.

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50

Ogawa, Akiya, Taichi Tamai, Takenori Mitamura e Akihiro Nomoto. "Highly selective introduction of heteroatom groups to isocyanides and its application to electrocyclic reactions". Pure and Applied Chemistry 85, n. 4 (7 dicembre 2012): 785–99. http://dx.doi.org/10.1351/pac-con-12-07-01.

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Photoinduced cyclization of o-alkenylaryl isocyanides with (PhS)2 in the presence of (PhTe)2 affords the corresponding bisthiolated indene derivatives in good yields via radical cyclization process by thio radical. The procedure can be applied to the construction of tetracyclic systems by using bis(o-aminophenyl) disulfides in place of (PhS)2. In sharp contrast, when o-alkynylaryl isocyanides are employed as the substrates, novel electrocyclic reactions take place upon photoirradiation or heating at 40~80 °C to generate quinoline 2,4-biradical species, which are trapped with organic diselenides, ditellurides, and molecular iodine to give the corresponding 2,4-diseleno-, ditelluro-, and diiodo-quinoline derivatives, respectively, in good yields. The obtained quinoline derivatives are useful synthetic intermediates; for example, cross-coupling reactions using 2,4-diiodoquinolines lead to the preparation of functionalized quinoline derivatives.

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