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Search for "radicals" in Full Text gives 335 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

β-Hydroxy sulfides and their syntheses

  • Mokgethwa B. Marakalala,
  • Edwin M. Mmutlane and
  • Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

Graphical Abstract
  • alkyl radicals than the corresponding diaryl disulfides and benzyl radicals, respectively, are presumed to be the reasons behind the failure of the reaction to work with aliphatic alkenes [67]. 3.3. Synthesis of masked β-hydroxy sulfides via difunctionalization of alkenes Alkenes are versatile
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Published 05 Jul 2018

Visible light-mediated difluoroalkylation of electron-deficient alkenes

  • Vyacheslav I. Supranovich,
  • Vitalij V. Levin,
  • Marina I. Struchkova,
  • Jinbo Hu and
  • Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

Graphical Abstract
  • with blue light is described. The reaction involves radical addition of 1,1-difluorinated radicals at the double bond followed by hydrogen atom transfer from sodium cyanoborohydride. Keywords: difluoroalkylation; organofluorine compounds; radical addition; visible light; Introduction Applications of
  • fluorinated alkyl radicals is typically realized either by single-electron reduction or by radical abstraction of iodine [41][42][43]. Furthermore, the carbon–iodine bond is prone to homolytic cleavage under UV irradiation [44]. In this regard, we were inspired by the work of Ryu describing the use of
  • decreased reactivity of the sulfone double bond toward fluorinated radicals. In this case, two equivalents of the alkene have to be used to achieve good yields of products 3t,u. It should also be pointed out that the reaction tolerates aromatic bromide substituents (products 3b,c,n,o), a boryl fragment
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Published 02 Jul 2018

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

  • Yuichi Yoshimura,
  • Hideaki Wakamatsu,
  • Yoshihiro Natori,
  • Yukako Saito and
  • Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

Graphical Abstract
  • out by treatment with diacetoxyiodobenzene and iodine under irradiation with visible light to give acetoxy acetals 130 and 131 in good yields with high stereoselectivities. As shown in Scheme 17, the reaction was expected to proceed via the formation of anomeric alkoxyl radicals, which underwent
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Published 28 Jun 2018

Phosphoramidite building blocks with protected nitroxides for the synthesis of spin-labeled DNA and RNA

  • Timo Weinrich,
  • Eva A. Jaumann,
  • Ute M. Scheffer,
  • Thomas F. Prisner and
  • Michael W. Göbel

Beilstein J. Org. Chem. 2018, 14, 1563–1569, doi:10.3762/bjoc.14.133

Graphical Abstract
  • could be incorporated by unmodified standard procedures into four different self-complementary DNA and two RNA oligonucleotides. After photochemical removal of the protective group, elimination of formic aldehyde and spontaneous air oxidation, the nitroxide radicals were regenerated in high yield. The
  • hydroxylamines spontaneously reacted with air to form the nitroxide radicals in high yield [43]. Although the rigid spin labels introduced by Sigurdsson [31][32][33], Hopkins [27][29] and Engels [20][21] are generally considered advantageous for EPR studies, TEMPO-modified RNAs according to structures 1 and 3
  • heating to 90 °C. This step also completes the conversion of hemiacetals into nitroxide radicals 22c–27c in all cases. It should be noted, however, that palindromic duplexes may coexist in equilibrium with monomeric hairpin structures (see below). HPLC measurements gave no evidence for the formation of
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Published 26 Jun 2018

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

  • Gwendal Grelier,
  • Benjamin Darses and
  • Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

Graphical Abstract
  • (Scheme 4b). The intermediate Cu–Bpin, then, could undergo an oxidative addition into the CF3–I bond to give 8 that, after a CF3 radical transfer, would afford the radicals 9 and 10. Radical recombination followed by reductive elimination would finally lead to the E-product and regenerate the Cu–Bpin
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Published 21 Jun 2018

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

  • Gernot A. Eller,
  • Gytė Vilkauskaitė,
  • Algirdas Šačkus,
  • Vytas Martynaitis,
  • Ashenafi Damtew Mamuye,
  • Vittorio Pace and
  • Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

Graphical Abstract
  • well documented in the literature and proceeds under different reaction conditions such as, for instance, by air oxidation [22], under O2 atmosphere using an O2 balloon [23], by organic peroxides [24], phenoxy radicals [25], by treatment with phenylhydrazine at high temperatures [26][27], by
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Published 04 Jun 2018

Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis

  • Yue Pan,
  • Kunfang Jia,
  • Yali Chen and
  • Yiyun Chen

Beilstein J. Org. Chem. 2018, 14, 1215–1221, doi:10.3762/bjoc.14.103

Graphical Abstract
  • (Scheme 4). Tertiary alcohols 6 were reported to be activated by cyclic iodine(III) reagents under photoredox conditions to generate alkoxyl radicals, and subsequently underwent β-fragmentation and alkynylation to yield 7 after eliminating the arylketone [25]. With tertiary alcohol 6a as the alkyl radical
  • ’-alkyne 3a gave a slightly lower 63% yield of 9 [21]. β-Ketone alcohols 10 were reported to be activated by cyclic iodine(III) reagents under photoredox conditions to generate alkoxyl radicals, and subsequently underwent β-fragmentation and alkynylation to yield ynone 9 [26]. The unsubstituted BI-alkyne
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Published 28 May 2018

One hundred years of benzotropone chemistry

  • Arif Dastan,
  • Haydar Kilic and
  • Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Graphical Abstract
  • Brønsted acids (Scheme 36) [142]. Bauld and Brown reported the ready generation of the first detectable dianion radicals as outlined in Scheme 36 [150]. Benzo[7]annulenide (benzotropenide) dianion radical 220 was generated in two steps from 12 via benzotropyl methyl ether 219. Holzmann’s group described
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Published 23 May 2018

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

  • Toshifumi Dohi,
  • Shohei Ueda,
  • Kosuke Iwasaki,
  • Yusuke Tsunoda,
  • Koji Morimoto and
  • Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

Graphical Abstract
  • ; C–H activation; iodine; oxygenation; radicals; Introduction The oxidative activation of a C(sp3)–H bond in organic molecules to directly install various functional groups and new carbon–carbon networks is a topic of interest for researchers engaged in modern synthetic chemistry [1][2][3][4][5][6][7
  • hypervalent iodine reagent were reported, both of which include the formation of benzyl radicals during the key initial reaction step. Togo and co-workers developed a reaction system consisting of stoichiometric amounts of PIDA with catalytic amounts of molecular iodine and p-toluenesulfonamide for the
  • subsequently decomposes by facile homolytic cleavage of the I(III)–Br bond, generating the iodanyl and bromo radicals [51][52]. It appears that these radicals can then selectively abstract the benzylic hydrogen atom of organic substrates, even in the presence of a wide variety of functional groups, such as
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Published 16 May 2018

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

  • Keshaba N. Parida,
  • Gulab K. Pathe,
  • Shimon Maksymenko and
  • Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

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  • involve the coupling of amide enolates with ketone enolates. Baran reported that stoichiometric Cu(2-ethylhexanoate)2 or Fe(acac)3 (2 equiv) are able to selectively oxidize imides, including Evan’s-type chiral imides, to the corresponding radicals. The formed radical then reacts selectively with a ketone
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Published 03 May 2018

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

  • Eirinaios I. Vrettos,
  • Gábor Mező and
  • Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

Graphical Abstract
  • tested in female BDF mice bearing estrogen independent MXT mouse mammary cancers, presenting stronger tumor inhibitory effects than their respective cytotoxic radicals up to 93%, while equimolar quantities of their respective radicals were more toxic [124]. Moreover, PDC AN-207 was significantly more
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Published 26 Apr 2018

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

  • Longcheng Hong,
  • Sebastian Ahles,
  • Andreas H. Heindl,
  • Gastelle Tiétcha,
  • Andrey Petrov,
  • Zhenpin Lu,
  • Christian Logemann and
  • Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

Graphical Abstract
  • attributed to the free vacant p-orbital of the boron atom leading to further transformations, such as decomposition via radicals (O2), reactions with nucleophiles (H2O) as well as the formations of adducts. From this perspective, a suitable Lewis base may form a Lewis complex and subsequently occupy the p
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Published 13 Mar 2018

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

  • Huangguan Chen,
  • Jianwei Han and
  • Limin Wang

Beilstein J. Org. Chem. 2018, 14, 354–363, doi:10.3762/bjoc.14.23

Graphical Abstract
  • coupling for pyrroles using a hypervalent iodine reagent and a stabilizer for pyrrolyliodonium intermediates (Scheme 1c) [9]. The reactions readily provided a variety of desired coupling products in good yields. In general, the mechanism of these arylations was postulated by generating aryl radicals with
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Published 06 Feb 2018

Recent developments in the asymmetric Reformatsky-type reaction

  • Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

Graphical Abstract
  • , the addition of ethyl iodoacetate (47) was accelerated in the presence of ZnMe2 and oxygen through a cycle in which ZnMe2 acted as a source of methyl radicals which reacted with ethyl iodoacetate giving ethyl acetate radical. The latter added to complex M to give complex N. Then complex N assisted the
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Published 02 Feb 2018

Progress in copper-catalyzed trifluoromethylation

  • Guan-bao Li,
  • Chao Zhang,
  • Chun Song and
  • Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

Graphical Abstract
  • ’ reagent, 1h, Scheme 22), which can generate trifluoromethyl radicals at room temperature in the presence of ambient air and moisture when combined with TBHP. Electron-neutral and -rich boronic acids proceeded smoothly to give the corresponding products in excellent yields. An addition of NaHCO3 was
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Published 17 Jan 2018

Photocatalytic formation of carbon–sulfur bonds

  • Alexander Wimmer and
  • Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

Graphical Abstract
  • . Photoredox-active metal complexes or organic dyes are used to initiate photo-induced single-electron transfer (SET) processes upon excitation with visible-light. Such photooxidations or photoreductions yield reactive organic radicals, which can undergo unique bond forming reactions, under very mild
  • diazonium salts and dimethyl disulfide (Scheme 37) [72]. They applied Eosin Y for the photoreduction of aryl diazonium salts, in order to generate the respective aryl radicals. Radical addition to the nucleophilic disulfide forms a stabilized trivalent sulfur-centred radical. Oxidation of this intermediate
  • selenosulfonates Formation of sulfone derivatives Already in 1994, the group of Barton envisioned that the photoreduction of selenosulfonates by [Ru(bpy)3]Cl2 as photoredox catalyst could lead to reactive sulfonyl radicals (Scheme 50) [87]. They were the first to report on a visible-light induced sulfonylation of
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Published 05 Jan 2018

CF3SO2X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF3SO2Na

  • Hélène Guyon,
  • Hélène Chachignon and
  • Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

Graphical Abstract
  • trifluoromethanesulfinate CF3SO2Na that are commercially available at reasonable prices, are easy-to-handle sources of trifluoromethyl radicals. Remarkably, CF3SO2Na and CF3SO2Cl are multi-purpose reagents since they not only act as CF3 donors by extrusion of SO2, but also, under certain reaction conditions, the sulfur
  • presented leading to vicinal trifluoromethyl alcohols. In 2013 Qing and Jiang described the oxytrifluoromethylation of alkenes with hydroxamic acids 32 and CF3SO2Na under Langlois’ conditions with the couple t-BuOOH/copper salt (Scheme 15) [34]. A competitive formation of two radicals, CF3• and the amidoxyl
  • persulfate by hypervalent iodine oxidants such as iodobenzene diacetate (PIDA, Scheme 28) [49], or iodobenzene bis(trifluoroacetate) (PIFA) [50]. Fu and co-workers proposed the reaction mechanism depicted in Scheme 28. PIDA reacted with CF3SO2Na under heating conditions to produce two radicals: CF3• along
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Published 19 Dec 2017

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

  • Irwan Iskandar Roslan,
  • Kian-Hong Ng,
  • Gaik-Khuan Chuah and
  • Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

Graphical Abstract
  • that in the presence of polyhalomethane CBr4, KOt-Bu undergoes a SET reaction, forming •CBr3 and t-BuO• radicals [95]. Furthermore, with other strong bases of similar strength including NaH and KOEt the reaction proceeded with significantly lower yields. This lends additional support to the hypothesis
  • •CCl3 radicals are quenched to CHCl3 via HAT [93]. The proposed catalytic cycle for the synthesis of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones is as follows. The Lewis acidic InIII metal center coordinates to the more nucleophilic benzothiazole N atom, forming an adduct A [98]. This activates the N–H
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Published 18 Dec 2017

Synthesis of naturally-derived macromolecules through simplified electrochemically mediated ATRP

  • Paweł Chmielarz,
  • Tomasz Pacześniak,
  • Katarzyna Rydel-Ciszek,
  • Izabela Zaborniak,
  • Paulina Biedka and
  • Andrzej Sobkowiak

Beilstein J. Org. Chem. 2017, 13, 2466–2472, doi:10.3762/bjoc.13.243

Graphical Abstract
  • solution to receive functionalised polymers. It is a naturally occurring flavonoid, which is abundantly found in citrus fruits, herbs, vegetables, seeds, tea, nuts, and red wine [24][25][26]. It is considered to be a strong antioxidant due to its ability to scavenge free radicals and bind transition metal
  • ions [27]. Quercetin inhibits xanthine oxidase [27][28][29], inhibits lipid peroxidation in vitro [27][28][30], and scavenges oxygen radicals [27][28][31][32][33]. There is a tremendous importance of this antioxidant in the prevention of a range of cardiovascular diseases [27][34][35], cancer [26][27
  • , Supporting Information File 1). The first of these potentials favors formation of CuI at the electrode and hence polymerization was activated, whereas the second potential, being more positive than E1/2, promotes CuII regeneration and leads to a dormant species of propagating radicals (Figure S12a
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Published 20 Nov 2017

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

  • Martina Tireli,
  • Silvija Maračić,
  • Stipe Lukin,
  • Marina Juribašić Kulcsár,
  • Dijana Žilić,
  • Mario Cetina,
  • Ivan Halasz,
  • Silvana Raić-Malić and
  • Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

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  • and acetic acid added) showed that there are no copper(II) cations present in the final mixture (Figure 4). The ESR spectrum reveals only the presence of free radicals, characterized by sharp signal with g-value g ≈ 2.01. Milling the azide and alkyne with copper(I) catalytic system (CuI/DIPEA/acetic
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Published 06 Nov 2017

Difunctionalization of alkenes with iodine and tert-butyl hydroperoxide (TBHP) at room temperature for the synthesis of 1-(tert-butylperoxy)-2-iodoethanes

  • Hao Wang,
  • Cui Chen,
  • Weibing Liu and
  • Zhibo Zhu

Beilstein J. Org. Chem. 2017, 13, 2023–2027, doi:10.3762/bjoc.13.200

Graphical Abstract
  • [40]. The subsequent iodination reaction could proceed via a homolytic attack involving t-BuOI and HOI to generate intermediate 3, tert-butoxyl radicals and hydroxyl radicals[41]. In the presence of TBHP, a fast reaction between tert-butoxyl radicals and TBHP take place, leading to the formation of
  • tert-butylperoxyl radicals and tertiary butanol [41][42]. Subsequently, the radical 3 can be further oxidized into cation 4 with I2 [24][43][44]. The iodide ion is then reoxidized with TBHP to regenerate I2 and tert-butoxyl radicals [24][45]. Finally, cation 4 can be attacked by TBHP to give the final
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Published 28 Sep 2017

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

  • Santanu Hati,
  • Ulrike Holzgrabe and
  • Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

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  • quinazolinones. A putative mechanism involved the homolysis of DTBP to generate tert-butoxide radicals, which in turn abstracts a proton radical from the methyl(hetero)arene to facilitate the formation of a benzylic radical. The benzylic radical couples with o-aminobenzylamide to generate H. It then interacts
  • compounds 90 and 91 were obtained in excellent yields (Scheme 32) [92]. Two mechanisms were proposed for this conversion. In one the tert-butyl peroxy radicals were generated by the interaction of Cu salts with TBHP. This radical abstracts the C4 hydrogen of the dihydropyrimidine to generate P, which would
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Published 15 Aug 2017

Detection of therapeutic radiation in three-dimensions

  • John A. Adamovics

Beilstein J. Org. Chem. 2017, 13, 1325–1331, doi:10.3762/bjoc.13.129

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  • the first chemical approach to quantifying ionizing radiation [6]. During irradiation water is decomposed to reactive HO· and H· radicals which further react with oxygen to produce the hydroperoxy radical which oxidizes the ferrous ions (Scheme 1) [7][8]. The ferric ion generates a blue color that is
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Published 05 Jul 2017

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen

  • Naoki Doi,
  • Yasushi Sasai,
  • Yukinori Yamauchi,
  • Tetsuo Adachi,
  • Masayuki Kuzuya and
  • Shin-ichi Kondo

Beilstein J. Org. Chem. 2017, 13, 1174–1183, doi:10.3762/bjoc.13.116

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  • , Japan 10.3762/bjoc.13.116 Abstract A detailed electron spin resonance (ESR) analysis of mechanically induced free radicals (mechanoradicals) formation of glucose-based polysaccharides, dextran (Dx) and glycogen (Gly) was performed in comparison with amylose mechanoradicals. The ESR spectra of the
  • reaching the each maximum value of radical concentration, after that the molecular weight or the particle diameter slowly decreased. These results suggested that Dx and Gly mechanoradicals might be more unstable than amylose radicals possessing an intramolecular helical structure due to the branched
  • structure. Keywords: dextran; electron spin resonance (ESR); glycogen; mechanoradical; polysaccharide; Introduction There are many reports on the mechanolysis of synthetic and natural polymers. It is well-known that mechanically induced radicals, so-called mechanoradicals, are produced by the mechanolysis
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Published 19 Jun 2017

Chemoselective synthesis of diaryl disulfides via a visible light-mediated coupling of arenediazonium tetrafluoroborates and CS2

  • Jing Leng,
  • Shi-Meng Wang and
  • Hua-Li Qin

Beilstein J. Org. Chem. 2017, 13, 903–909, doi:10.3762/bjoc.13.91

Graphical Abstract
  • and to minimize the formation of the byproducts was conducted. As recently surveyed, photoredox catalysts are widely employed for the generation of radicals for diverse radical reactions [19]. Further, the application of aryl radicals generated from aryldiazonium salts under visible light irradiation
  • byproduct 4. Finally, radical III can react with various equivalents of CS2 with release of carbon sulfide to generate aryl-polythio radicals IV and V. The combination of the latter intermediates with radical I then finally affords polysulfides 5. To demonstrate the scope of the reaction, a series of
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Published 15 May 2017
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