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

• 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

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

• , 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

Isoxazole derivatives as new nitric oxide elicitors in plants

• Anca Oancea,
• Emilian Georgescu,
• Florentina Georgescu,
• Alina Nicolescu,
• Elena Iulia Oprita,
• Catalina Tudora,
• Lucian Vladulescu,
• Marius-Constantin Vladulescu,
• Florin Oancea and
• Calin Deleanu

Beilstein J. Org. Chem. 2017, 13, 659–664, doi:10.3762/bjoc.13.65

• essential role in protection of plant cells from oxidative damages at the sites of ROS and NO generation [56][57]. Measuring the ROS and NO levels in plant tissues is often difficult due to high reactivity and extremely short physiological half-life of these free radicals [58][59]. In this work, generation

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

• produces free radicals in bulk, to the formation of polylactide. Another advantage is that Lupersol is a food additive and is approved by the Food and Drug Administration (FDA). Furthermore, the authors hypothesise a mechanism by which the branching of polylactide is occurring, suggesting that the initial

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

• are probably harder to perform in a large scale as the Kolbe electrolysis. There is strong evidence that in the Kolbe electrolysis free radicals are involved in the coupling reaction. Coupling of absorbed radicals is ruled out by Eberson [43][44][45]. It was shown that the product ratio of cyanoalkyl

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

• ]. Thus, the ring shaped MLA is much more reactive in respect to the self-initiated polymerization. Calculated initial rate for the self-initiated polymerization of MLA by the use of DPPH As discussed above, the formation of free radicals is a key step for spontaneous polymerization of MLA. Accordingly

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

Cp₂TiCl/D₂O/Mn, a formidable reagent for the deuteration of organic compounds

• Antonio Rosales and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2016, 12, 1585–1589, doi:10.3762/bjoc.12.154

• -ordination of water to Cp2TiCl might weakens the strength of the O–H bond. In this way a single electron transfer from titanium to oxygen might facilitate the HAT from the titanocene aqua-complex to the free radicals. Theoretical calculations supported that the coordination of water to Cp2TiIIICl weakens the

Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• i Politècnic La Fe, Avenida de Fernando Abril Martorell 106, 46026 Valencia, Spain 10.3762/bjoc.12.115 Abstract Cholesterol (Ch) is an important lipidic building block and a target for oxidative degradation, which can be induced via free radicals or singlet oxygen (1O2). Suprofen (SP) is a

• from inflammation to cardiovascular and Alzheimer diseases [1][2]. This type of damage can be induced via free radicals or singlet oxygen (1O2) [3][4]. The former generally involves hydrogen abstraction (HA) of an allylic hydrogen and can be achieved by photosensitizing agents in combination with UVA

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• carbanions [13][14], carbocations [15][16][17][18], and free radicals [19][20][21] which has been explained by negative (nX→σ*C–Y) or positive hyperconjugation (σC–Y→π* or p). Hyperconjugation is commonly described as the interaction between electronic orbitals where one filled orbital (donor) interacts with

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas. Keywords: carboxylic acids; free radicals

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• natural ones as potential pharmaceutical and food ingredients. The present study compares the capacity of curcumin-related compounds to scavenge different free radicals and to act as chain-breaking antioxidants. Curcumin is one of the best natural antioxidants with a wide spectrum of biological activities

• [3][4][5][6]. It is known that curcumin can protect biomembranes against peroxidative damage mainly as scavenger of free radicals. Curcumin is a unique antioxidant, which contains a variety of functional groups [7]. It is generally assumed that the phenolic moieties are responsible for radical

• – ORAC, which measures the scavenging activity against peroxyl radicals generated by an azoinitiator; and model 4 – a theoretical method used for predicting the activity of the studied compounds to scavenge free radicals by H-atom abstraction and to explain the structure–activity relationship of the

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• radical initiating agent such as distannane (Scheme 6). This allows the N-acyliminium ion to react with an alkyl halide to generate the typical carbon–carbon products of the Shono oxidation [19][27][28] Examples of reactions with activated olefins have been reported using the generation of carbon free

• radicals from the cation pool method [24][25]. Indirect electrolysis methods The only indirect anodic oxidation method to perform the Shono-oxidation with a thiophenyl electroauxiliary has been reported by Fuchigami and co-workers [36]. Using a catalytic triarylamine redox mediator, anodic

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• Schemes, both FRP, CP and FRPCP can be initiated from the free radicals and cations generated. In these three situations, as a function of its structure, the PIC radical cation PIC•+ can behave as an initiating species. Reductible photoinitiator catalysts Scheme 5 shows a situation where the PIC is

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• delocalization arising by the orbital overlap, lowers the σC-Si bond dissociation energy and makes the silicon center more electropositive. Consequently, short-lived α-silyl cation radicals typically undergo fast, silophile-promoted desilylation to form the carbon centered free radicals 19 (Scheme 4). Based on

• . Photochemical reaction pathways of N-alkylphthalimides. Photoreactions of N-methylnaphthalimides 8 and 12 with allylsilane 9. Regioselective generation of carbon-centered free radicals through sequential SET-desilylation processes. Mechanistic pathway of photochemical reactions of α-silyl n-electron donor

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• sphere of the metal”. Indeed, the present radicals led to less side-reactions – in particular, oligomerization in the case of alkenes as substrates –, which shows that they exhibit “restricted reactivity” in comparison with “that of free radicals initiated by peroxides or diazo compounds and by

Damage of polyesters by the atmospheric free radical oxidant NO₃^•: a product study involving model systems

• Catrin Goeschen and
• Uta Wille

Beilstein J. Org. Chem. 2013, 9, 1907–1916, doi:10.3762/bjoc.9.225

• well as products of these reactions are potentially capable of promoting further degradation processes in polyesters under environmental conditions. Keywords: environmental oxidants; free radicals; nitrate radicals; polyester degradation; product studies; reaction mechanisms; Introduction Polymers

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• has been studied before using the G3-(MP2)-RAD protocol and a value of 7.6 × 104 s−1 was reported for the rate constant at 21 °C [57]. This high-level composite method was designed to yield accurate gas-phase thermochemical data for free radicals [58]. Nevertheless this protocol does not include

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

• Martin Goez and
• Martin Vogtherr

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

• solvent reorganization. Keywords: CIDNP; electron transfer; free radicals; kinetics; photochemistry; pyrylium salts; self-exchange; sulfides; Introduction Single-electron transfer is probably the simplest chemical process of an organic molecule, because usually no full bonds are broken or formed. For

• ], The fast component k0 in Equation 4 is the decay rate of the excited state whereas the slow component κ, comprises the effects of self-exchange (rate constant, kex; donor concentration, D0) and nuclear spin relaxation in the free radicals (relaxation time, T1). The latter spoils a perfect cancelation

• of geminate and escape polarizations, so is responsible for the residual magnetization at long times after the flash. Bimolecular recombination of the free radicals, which would lead to an additional term in Equation 5 [17], usually is of marginal importance only [19], and was neglected in our

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• proposed. Keywords: copper(II) salt; cyclopropanol; electron transfer; free radical; radical ion probe; Introduction Radical ions are key intermediates in electron-transfer (ET) reactions of organic molecules [1][2][3][4][5] and they often undergo fragmentations to yield free radicals and ions [6][7][8

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• the O2-mediated selective oxidation of organic compounds and looking for environmentally safe alternatives to metal catalysis. Keywords: autoxidation; free-radicals; metal-free; molecular oxygen; N-hydroxyphthalimide; Introduction The development of efficient and cheap catalytic systems for the

A study on electrospray mass spectrometry of fullerenol C₆₀(OH)₂₄

• Mihaela Silion,
• Andrei Dascalu,
• Mariana Pinteala,
• Bogdan C. Simionescu and
• Cezar Ungurenasu

Beilstein J. Org. Chem. 2013, 9, 1285–1295, doi:10.3762/bjoc.9.145

• bonds to form fullerenyl radicals, which can capture free electrons to generate negative charges, while fullerenoxyl radicals produced by O−H bond cleavage are much more stable against the free radicals. In addition to simple bond cleavages, fullerenol ions containing at least eight fullerenyl radicals

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

• Roy T. McBurney and
• John C. Walton

Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120

• DFT computations, which gave insights into factors influencing the two cyclisation modes. Keywords: cyclisation; EPR spectroscopy; free radicals; heterocycles; oxime carbonates; Introduction Radical cyclisations onto aromatic acceptors take place readily, even though disruption of the 6π-electron

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• Chimie Radicalaire, UMR 7273, F-13397 Marseille, France ENSCMu-UHA, 3 rue Alfred Werner, F-68093 Mulhouse Cedex, France 10.3762/bjoc.9.101 Abstract Eleven di- and trifunctional compounds based on a core-pyrene π structure (Co_Py) were synthesized and investigated for the formation of free radicals. The

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• agreement between experimental and calculated values of ∆G‡298. Keywords: amines; CIDNP; electron transfer; free radicals; hydrogen transfer; ketones; kinetics; photochemistry; self-exchange; Introduction Sensitized hydrogen abstractions from tertiary aliphatic amines present a mechanistic spectrum with a

• , which leads to opposite polarizations in the products of the two radicals of a pair with each other (geminate products) and the products of subsequent free radicals (escape products), and thus yields information about the entry and exit channels of the radical pairs. The spin sorting is driven by

• pulsed laser triggers a photoreaction; after a short delay, the polarizations of the products are probed with an NMR pulse; variation of the delay yields the kinetics. The method is very well suited to study bimolecular reactions of the free radicals, because typical NMR pulses are of microsecond