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

• . The arylthiols bearing chloro and fluoro substituents gave the expected β-hydroxy sulfides in moderate yields while the much deactivated nitro-thiophenol did not lead to any product formation. The protocol allowed easy scale-up to gram quantities. The results strongly supported a free radical

• 105–109 (Scheme 40) [73]. 3.5 Other synthetic routes to β-hydroxy sulfides Incorporation of amine, silyl and sulfide functional groups into C–C multiple bonds offers an attractive route to appropriately functionalized substrates. Inter- and intramolecular thiol-ene reaction is a highly efficient, free

• -radical mediated “click” process with diverse applications in small molecule and polymer synthesis and has been reviewed [74][75][76]. The importance of the thiol-ene reaction in the synthesis of β-hydroxy sulfides is exemplified by the work of Scanlan and co-workers as shown in Scheme 41 [77][78

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

• . Furthermore, they stabilize the topoisomerase II DNA complex preventing the transcription. They may also increase quinone type free radical production, however, this plays a role rather in their cytotoxic side effects. Daunorubicin is mainly used in the treatment of leukemia [95] while doxorubicin in the cure

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

• radical. Yadav and co-workers presented a metal-free radical thiol–ene approach, using benzophenone as photoredox catalyst (Scheme 13) [43]. No sacrificial oxidant is required for this reaction as benzophenone is regenerated by hydrogen atom transfer to the anti-Markovnikov radical intermediate. Aliphatic

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

• in a sealed tube at 110 °C. Mechanistic studies by electron spin resonance were carried out in which both the CF3• and the β-CF3 alkyl radical intermediate were observed by using 2-methyl-2-nitrosopropane as a radical spin trap. A single-electron oxidative free-radical process was clearly ascertained

•  29b) [51]. A single-electron oxidative free-radical process was ascertained for the generation of CF3•. From enynes, the iodination step was realised by I2, which was formed by a multistep redox process from I2O5. The intramolecular carbotrifluoromethylations of alkenes from acrylamides and

• excellent yields. However, to achieve high yields in this trifluoromethylation, one (or more) alkoxy group(s) must be present on the arenes in order to stabilise the free-radical intermediate (see mechanism in Scheme 47). Control experiments such as the trapping of the trifluoromethyl radical with the

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Tathagata Mukherjee,
• Soumik Biswas,
• Andreas Ehnbom,
• Subrata K. Ghosh,
• Ibrahim El-Zoghbi,
• Nattamai Bhuvanesh,
• Hassan S. Bazzi and
• John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

• commercialized [4]. Many research groups have described the syntheses of other types of fluorous alkyl [5][6][7][8] and aryl [9][10][11][12] iodides [13][14][15][16][17]. The former are ubiquitous by virtue of the large number of perfluoroalkyl iodides RfnI that have been shown to undergo free radical additions

• ) dichlorides for free radical chlorinations [25]. In this regard, phenyl iodine(III) dichloride (PhICl2) is an effective free radical chlorinating agent for hydrocarbons [26][27]. Importantly, the mechanism does not involve the liberation of Cl2, followed by the textbook sequence of steps. Rather, hydrogen

• degradation under free radical chlorination conditions. However, no reactions were observed when RfnI were treated with Cl2 or NaOCl/HCl. Nonetheless, perfluoroalkyl iodides RfnI (n = 6–8, 10, 12) can be oxidized using various recipes (e.g., 80% H2O2 in trifluoroacetic acid anhydride) to the iodine(III) bis

Solid-state studies and antioxidant properties of the γ-cyclodextrin·fisetin inclusion compound

• Joana M. Pais,
• Maria João Barroca,
• Maria Paula M. Marques,
• Filipe A. Almeida Paz and
• Susana S. Braga

Beilstein J. Org. Chem. 2017, 13, 2138–2145, doi:10.3762/bjoc.13.212

• activity Developed by Blois in 1958 [40], the DPPH assay determines the antioxidant activity of a test compound by using a commercially available stable free radical, DPPH· (2,2-diphenyl-1-picrylhydrazyl) that has a strong violet color. Upon reaction with an antioxidant, DPPH· is converted into the

• corresponding hydrazine (pale yellow in color), a reaction which can be monitored by UV–vis spectroscopy. As the kinetics of the reaction varies from sample to sample, the stabilization time for a complete reduction of the DPPH· free radical was determined. For all samples studied, the steady-state

• ’), 136.5 (C3), 125.7 (C1’), 120.9 (C6’), 114.7, 112.4 (C6, C10, C2’, C5’), 101.6 (C8). Antioxidant activity by the DPPH method. The radical-scavenging activity of fisetin and the γ-CD·fisetin inclusion compound were determined using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH·) [45]. A volume of

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• chromones via domino chromone ring construction and C(sp2)–H bond sulfenylation have been achieved under transition-metal-free conditions by using KIO3 as the only catalyst. Keywords: C–H sulfenylation; chromones; domino reaction; free-radical; transition-metal-free; Introduction The C–S bond-forming

• that a free radical intermediate has also occurred in the generation of 6 (reaction 3, Scheme 3). The reactions of 5 with 6 and 2b were both found to yield the sulfenylated chromone 3i in excellent yield, respectively (reactions 4 and 5, Scheme 3). On the other hand, the reaction of 5 and 6 in the

• presence of TEMPO, however, provides only with trace amounts of 3i, supporting that products 3 are yielded via a free radical route (reaction 6, Scheme 3). In addition, the control reaction of 1b and 2b afforded also only trace amounts of product 3i in the presence of 1 equiv TEMPO (reaction 7, Scheme 3

Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

• José Enrique Barquera-Lozada and
• Gabriel Cuevas

Beilstein J. Org. Chem. 2017, 13, 1969–1976, doi:10.3762/bjoc.13.192

• , a chair conformation due to the higher energy of the boat conformation [2][7][10][11][12][13][14][15][16][17][18][19]. In this mechanism, the electron density of the TS is delocalized into the six carbon atoms [20][21][22]. However, if the diene contains free radical stabilizing groups, this

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• the nitrooxy derivative 22, presumbaly via the corresponding benzyl-type free radical (Scheme 7). The structure of 22 was proven by single-crystal X-ray diffraction (Figure 2). According to a publication by Metz et al., a N-(4-methoxybenzyl) group can be removed from sultams by treatment with

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells

• Sadaf Hanif,
• Bernd Oschmann,
• Dmitri Spetter,
• Muhammad Nawaz Tahir,
• Wolfgang Tremel and
• Rudolf Zentel

Beilstein J. Org. Chem. 2017, 13, 1693–1701, doi:10.3762/bjoc.13.163

• are applied as catalytic membranes, thermotropic liquid crystals [12], polymer electrolytes, ionic conductive materials, CO2 absorbing materials, microwave absorbing materials and porous materials [4]. Most of these polymers were synthesized by free radical polymerization. There are just few reports

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

• reaction was facilitated at room temperature by N-hydroxyphthalimide (NHPI) and cobalt acetate (Co(OAc)2) as catalysts in acetonitrile (Scheme 20). The reaction followed a free radical mechanism as exemplified by the oxidative dehydrogenation of DHPs. The initial step involved the formation of the

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• , free radical copolymerization of a hydrophobic monomer, complexed in a host, with a stopper comonomer [24][25]. This latter has to be large enough to prevent the dissociation of the growing axis and the host, as it happens in the case of aqueous CD assisted homopolymerizations of hydrophobic monomers

• [26][27][28] including dienes [29]. This approach drastically widens the range of suitable hydrophobic polymeric axes, to all monomers being complexed in CD or hydrophilic CD derivatives. Up to now, rotaxa-polymerization was only performed via free radical reaction without control of the polymer chain

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

• Liquan Tan,
• Cui Chen and
• Weibing Liu

Beilstein J. Org. Chem. 2017, 13, 1079–1084, doi:10.3762/bjoc.13.107

• outcome. 1-(Thiophen-2-yl)ethanone (1i), which has a heteroaryl functionality, gave 2i in 83% isolated yield. A series of control experiments were performed to clarify the reaction mechanism (Scheme 3). When the reactions were performed in the presence of an excess of the free-radical scavenger 2,2,6,6

Cyclodextrins tethered with oligolactides – green synthesis and structural assessment

• Cristian Peptu,
• Mihaela Balan-Porcarasu,
• Alena Šišková,
• Ľudovít Škultéty and
• Jaroslav Mosnáček

Beilstein J. Org. Chem. 2017, 13, 779–792, doi:10.3762/bjoc.13.77

• available as commercial products, the modification with polymers is still under development [4][5]. So far, several polymerization reactions were used for CD modification, including free radical polymerization, reversible-deactivation radical polymerizations [5] as well as ring opening polymerizations (ROP

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• ; Introduction The selection of suitable monomers is a critical step for any free-radical polymerization approach. Particularly for (in situ) photo-induced polymerizations, monomers should comprise sufficient solubility in a given matrix, moderate viscosity, matching refractive indices as well as an optimized

• ]. Yet, acrylamides are particularly affected by the solvent regarding propagation reaction in free radical polymerization, even more so, if water is present [21]. Factors such as hydrogen bonding, hydrogen abstraction and the overall electronic characteristics are crucial in the design of improved

• this type of crosslinkers highly attractive for a broad range of free radical (photo)polymerization applications, for example in the constantly growing medical device sector. Experimental Materials. Chemicals and reagents were purchased from Acros, Carl Roth, ChemPUR, Sigma-Aldrich, TCI or ABCR or have

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• , the most common transformation, involves the constant growth of a polymer chain where the ability to terminate the reaction is removed [14]. Again, there are several types of transformation including ionic polymerisation, ring opening metathesis, free radical and growth polycondensations [15]. All of

• . It must be noted, however, that the reaction reported by Höcker involves the use of s-BuLi, making the process more difficult, but still a greater throughput rate is obtained than that predicted by Meyer [20]. Free radical polymerisation involving deactivation polymerisation, iniferter polymerisation

• and reversible addition fragmentation chain transfer (RAFT) polymerisation, amongst others [21], has been studied extensively by extrusion to produce, for example, branched polypropylene, polyethylene and polylactide polymers. The process involves the production of a free radical at the end of an

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• ]. This finding points to a free radical or its reversible adsorption at the electrode. However, the latter pathway was ruled out by experiments of Utley et al. [48][49], when comparing the coupling of unsaturated and saturated carboxylic acids and the effect of adsorption. Ester 30a has been cleaved with

Synthesis and evaluation of anti-oxidant and cytotoxic activities of novel 10-undecenoic acid methyl ester based lipoconjugates of phenolic acids

• Naganna Narra,
• Shiva Shanker Kaki,
• Rachapudi Badari Narayana Prasad,
• Sunil Misra,
• Koude Dhevendar,
• Venkateshwarlu Kontham and
• Padmaja V. Korlipara

Beilstein J. Org. Chem. 2017, 13, 26–32, doi:10.3762/bjoc.13.4

• of the prepared derivatives were studied by the well-established DPPH radical scavenging assay and also by studying the oxidation of linoleic acid using DSC. The DPPH radical is a commercially available stable free radical which is widely used to preliminarily determine the radical scavenging

• cinnamic acid derivative 3a. This could be due to the absence of a phenolic hydroxy group which is responsible for the anti-oxidant activity of most of the natural phytochemicals. Among all compounds, 3c was found to be the most efficient free radical scavenger which showed a value closest to the standard

• anti-oxidant, α-TP. Compounds 3d and 3e also showed free radical scavenging activity (FRSA) of 68% and 67%, respectively, whereas compound 3b showed only moderate activity with 30% FRSA. In another study, the ability of the prepared derivatives in inhibiting the oxidation of linoleic acid was studied

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• permeation chromatography (GPC). The polymerization of DMA and AA mediated by α-CD-CTA gave polymers with similar molecular weights (12.8 and 14.8 kDa) and narrow distributions in good yields (85–88%) (Table 1, entries 2 and 5). In contrast, in the absence of α-CD-CTA, free radical polymerization with VA-044

• inhibiting the molecular recognition of α-CD, the inclusion complexation ratio between the monomer and α-CD-CTA was decreased, which lead to lower yields and higher molecular weight of the resulting polymers due to preceding free radical polymerization. In the reaction of AAm monomer, which has a low

• reaction, some of the polymer chains (Pn•) form dead chains through termination or irreversible chain transfer. However, the Mw/Mn of the polymer mediated by α-CD-CTA agents that the termination reaction is suppressed by α-CD-CTA compared to free radical polymerization. Conclusion We studied the radical

A new protocol for the synthesis of 4,7,12,15-tetrachloro[2.2]paracyclophane

• Donghui Pan,
• Yanbin Wang and
• Guomin Xiao

Beilstein J. Org. Chem. 2016, 12, 2443–2449, doi:10.3762/bjoc.12.237

• bromides from substituted (4-methylbenzyl)bromides. Bromination of 2,5-dichloro-p-xylene (1) with H2O2–HBr. Visible-light induced free-radical bromination of substituted p-xylenes with H2O2–HBr. Synthesis of 4,7,12,15-tetrachloro[2.2]paracyclophane 16 from 11. Synthesis of substituted [2.2]paracyclophanes

Methylenelactide: vinyl polymerization and spatial reactivity effects

• Judita Britner and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 2378–2389, doi:10.3762/bjoc.12.232

• Judita Britner Helmut Ritter Institute of Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University, Universitätsstraße 1, 40225 Düsseldorf, Germany 10.3762/bjoc.12.232 Abstract The first detailed study on free-radical polymerization, copolymerization and controlled radical

• employing MLA as dienophile was described [3][4][5][6]. In a recent NMR study we demonstrated that, poly(MLA) prepared via free radical polymerization contains mainly isotactic units. Furthermore, we found that the polymer attached lactide rings react like activated esters and thus readily undergo

• -Michael additions on MLA were reported [11][12]. In this paper, we wish to present a kinetic study of free radical and controlled/living radical polymerization of MLA. The latter reactions were conducted via a reversible addition fragmentation chain transfer (RAFT) mechanism. We also investigated the

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• epidermidis, Escherichia coli, Klebsiella pneumoniae, and Bacillus subtilis. None of the compounds was active at a concentration of 50 μg/mL. In the free radical scavenging assay using 2,2-diphenyl-1-picrylhydrazyl (DPPH), only compounds 1 and 3 exhibited weak activity with EC50 values of 125 and 130 μM

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• agents and initiators for free-radical reactions both in industry and in laboratory. These compounds are produced and involved in various natural and biological processes and were explored extensively as antimalarial agents, anthelmintics, and anticancer drugs. Organic peroxides, such as alkyl

• Baeyer−Villiger oxidation and it is one of the methods for the synthesis of commercially important caprolactone from cyclohexanone with peracetic acid [55][56]. Autoxidation processes with formation of hydroperoxides and their subsequent free-radical transformations with generation of carbon- and oxygen

• ][109][110][111][112][113]. Organic peroxides are widely used as oxidants in oxidative coupling processes [114][115][116][117][118][119][120]. Industrial-scale production of readily available and efficient initiators of free radical polymerization and effective biologically active compounds promotes the

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• equiv of NaOt-Bu [38][39]. In the same year, Taylor and co-workers independently reported synthesis of 2-oxindoles in the presence of Cu(OAc)2·H2O as oxidant (Scheme 1) [40][41][42][43][44]. Experimental evidence suggests involvement of a free-radical process in the addition of α-carbonylalkyl radicals

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• traditional Suzuki–Miyaura coupling. It is used to control a range of plant pathogens in broadacre and horticultural crops (Scheme 6) [207]. Felpin and co-workers have reported its synthesis starting from aryldiazonium salts [208], while the Heinrich group has employed a free-radical biaryl cross-coupling of