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Themed collection Free Radical Chemistry special themed issue in memory of Athel Beckwith

48 items
Communication

Effects of geminal methyl groups on the tunnelling rates in the ring opening of cyclopropylcarbinyl radical at cryogenic temperature

Relative enthalpy changes for the two possible modes of ring opening of 2,2-dimethylcyclopropylcarbinyl radical. Tunnelling is indicated by wavy lines.

Graphical abstract: Effects of geminal methyl groups on the tunnelling rates in the ring opening of cyclopropylcarbinyl radical at cryogenic temperature
Communication

Iron-catalyzed sulfonyl radical formations from sulfonylhydrazides and oxidative addition to alkenes

Sulfonyl radicals generate from sulfonylhydrazides in the presence of an iron catalyst and air. Addition of resultant radicals to alkenes affords β-hydroxysulfones in good yield.

Graphical abstract: Iron-catalyzed sulfonyl radical formations from sulfonylhydrazides and oxidative addition to alkenes
Communication

Benzyl radical addition reaction through the homolytic cleavage of a benzylic C–H bond

Direct generation of a benzyl radical by C–H bond activation of toluenes and the addition reaction were developed.

Graphical abstract: Benzyl radical addition reaction through the homolytic cleavage of a benzylic C–H bond
Communication

A convenient pathway to Sm(II)-mediated chemistry in acetonitrile

Atom efficient generation of Sm(OTf)2 in acetonitrile provides a stable alternative to SmI2.

Graphical abstract: A convenient pathway to Sm(ii)-mediated chemistry in acetonitrile
Communication

Further investigations into the N-demethylation of oripavine using iron and stainless steel

Further investigations into the direct synthesis of N-nororipavine from oripavine using iron powder under non-classical Polonovski conditions have been conducted. The stoichiometry, solvents and iron oxidation rates were found to have a dramatic effect on the rate of N-demethylation as well as product yield. Herein, we also present high-yield access to the N-demethylated product simply by employing stainless steel rather than iron powder as redox catalyst.

Graphical abstract: Further investigations into the N-demethylation of oripavine using iron and stainless steel
Paper

Controlling the action of chlorine radical: from lab to environment

Stable chlorine atom complexes with lignin derivatives may mediate reaction of chlorine atom in the environment and in bleaching facilities.

Graphical abstract: Controlling the action of chlorine radical: from lab to environment
Paper

Block copolymers containing organic semiconductor segments by RAFT polymerization

Vinyl compounds can be transformed to macro-RAFT agents by RAFT single unit monomer insertion providing a route to block copolymers with a short, non-hydrolysable block linkage.

Graphical abstract: Block copolymers containing organic semiconductor segments by RAFT polymerization
Paper

Diastereoselective radical mediated alkylation of a chiral glycolic acid derivative

Radical alkylation of a chiral equivalent of glycolic acid occurs with good to high diastereoselectivity that compares favorably with the corresponding enolate alkylation.

Graphical abstract: Diastereoselective radical mediated alkylation of a chiral glycolic acid derivative
Paper

Gas-phase ion-molecule reactions using regioselectively generated radical cations to model oxidative damage and probe radical sites in peptides

Isomeric radicals of the model peptide Bz-Ala-Gly-OMe can be distinguished via gas phase ion-molecule reactions with O2 and NO2˙. The latter reagent acts as a radical trap to give nitrate esters, whose structures can be distinguished via collision induced dissociation

Graphical abstract: Gas-phase ion-molecule reactions using regioselectively generated radical cations to model oxidative damage and probe radical sites in peptides
Paper

Effect of substituents on the stabilities of multiply-substituted carbon-centered radicals

What are the factors that influence the effect of substituents on the stability of multiply substituted carbon-centered radicals? This question is addressed with the help of a variety of existing and new thermochemical quantities.

Graphical abstract: Effect of substituents on the stabilities of multiply-substituted carbon-centered radicals
Paper

Highly-controlled regiospecific free-radical copolymerization of 1,3-diene monomers with sulfur dioxide

The free-radical copolymerization of alkyl-substituted 1,3-butadienes with sulfur dioxide produced poly(diene sulfone)s consisting of a highly alternating and 1,4-regiospecific repeating structure.

Graphical abstract: Highly-controlled regiospecific free-radical copolymerization of 1,3-diene monomers with sulfur dioxide
Paper

New domino radical synthesis of aminoalcohols promoted by TiCl4–Zn/t-BuOOH system: selective hydroxyalkylation of amines in alcohol or in cyclic ether cosolvents

One-pot multicomponent domino radical synthesis of aminoalcohols under mild conditions.

Graphical abstract: New domino radical synthesis of aminoalcohols promoted by TiCl4–Zn/t-BuOOH system: selective hydroxyalkylation of amines in alcohol or in cyclic ether cosolvents
Paper

Radical carbonylation of ω-alkynylamines leading to α-methylene lactams. Synthetic scope and the mechanistic insights

Efficient methods for the synthesis of α-methylene lactams were developed based on radical carbonylation and cyclization of ω-alkynylamines.

Graphical abstract: Radical carbonylation of ω-alkynylamines leading to α-methylene lactams. Synthetic scope and the mechanistic insights
Paper

Photochemical intramolecular cyclization of o-alkynylaryl isocyanides with organic dichalcogenides leading to 2,4-bischalcogenated quinolines

The photochemical cyclization of o-alkynylaryl isocyanides with (RSe)2, (RTe)2, RSH, RSeH, R3GeH, and TTMSS provides a useful tool to access quinoline derivatives.

Graphical abstract: Photochemical intramolecular cyclization of o-alkynylaryl isocyanides with organic dichalcogenides leading to 2,4-bischalcogenated quinolines
Paper

Kinetic and thermodynamic aspects of the chain-breaking antioxidant activity of ascorbic acid derivatives in non-aqueous media

Vitamin C lipid-soluble derivatives react with peroxyl radicals at close to diffusion-controlled rate in the dissociated form which has a BDE(OH) lower by 10 kcal mol−1 than the neutral form.

Graphical abstract: Kinetic and thermodynamic aspects of the chain-breaking antioxidant activity of ascorbic acid derivatives in non-aqueous media
Paper

Radical arylation of tyrosine and its application in the synthesis of a highly selective neurotensin receptor 2 ligand

Replacement of (S)-tyrosine by a novel peptide building block led to a high subtype selectivity for the human NTS2 receptor.

Graphical abstract: Radical arylation of tyrosine and its application in the synthesis of a highly selective neurotensin receptor 2 ligand
Paper

Synthesis of the gymnodimine tetrahydrofuran core through a Ueno–Stork radical cyclization

Elaboration of the C10–C20 skeleton of gymnodimine, incorporating a tetrahydrofuran fragment, has been performed through a stereocontrolled Ueno–Stork radical cyclization.

Graphical abstract: Synthesis of the gymnodimine tetrahydrofuran core through a Ueno–Stork radical cyclization
Paper

The thermal C2–C6/[2 + 2] cyclisation of enyne-allenes: Reversible diradical formation

Experimental evidence and computational results suggest that the thermal C2–C6/[2 + 2] cyclisation of enyne-allenes follows a stepwise mechanism involving the reversible formation of the C2–C6 diradical.

Graphical abstract: The thermal C2–C6/[2 + 2] cyclisation of enyne-allenes: Reversible diradical formation
Paper

One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities

The role of structural effects on the intrinsic ET reactivities of short-lived N-oxyl radicals have been examined through a kinetic study of the one electron oxidation reactions of substituted ferrocenes

Graphical abstract: One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities
Paper

Free radical 5-exo-dig cyclization as the key step in the synthesis of bis-butyrolactone natural products: experimental and theoretical studies

Radical 5-exo-dig cyclization is used as an entry to bis-butyrolactone natural products with L-ara configuration.

Graphical abstract: Free radical 5-exo-dig cyclization as the key step in the synthesis of bis-butyrolactone natural products: experimental and theoretical studies
Paper

Synthesis and thermal decomposition of N,N-dialkoxyamides

N,N-Dialkoxyamides — unusual anomeric amides. A new PIFA mediated synthesis and studies of their radical homolysis under thermal conditions.

Graphical abstract: Synthesis and thermal decomposition of N,N-dialkoxyamides
Paper

Pyridine as proton acceptor in the concerted proton electron transfer oxidation of phenol

In the presence of pyridine, phenol oxidation occurs concertedly with proton transfer, the charge being delocalized over a primary shell of water molecules bound to the pyridinium cation.

Graphical abstract: Pyridine as proton acceptor in the concerted proton electron transfer oxidation of phenol
Paper

An important role of intramolecular free radical reactions in antimalarial activity of artemisinin and its analogs

A new mechanism of free radical reactions of artemisinin and its analogs is proposed, where the initiation of hydroxy radicals plays a key role in the antimalarial effect.

Graphical abstract: An important role of intramolecular free radical reactions in antimalarial activity of artemisinin and its analogs
Paper

Nitroxide biradicals as thread units in paramagnetic cucurbituril-based rotaxanes

The first example of paramagnetic rotaxane containing cucurbit[6]urils has been reported.

Graphical abstract: Nitroxide biradicals as thread units in paramagnetic cucurbituril-based rotaxanes
Paper

Structural effects on the photodissociation of alkoxyamines

The search for photosensitive alkoxyamines remains a challenge. We investigate the effect of alkoxyamine structure on the photodissociation process.

Graphical abstract: Structural effects on the photodissociation of alkoxyamines
Paper

Intramolecular homolytic substitution of sulfinates and sulfinamides – a computational study

BHandHLYP/6-311++G(d,p) calculations predict that intramolecular homolytic substitution by aryl radicals at the sulfur atom in phenylsulfinates and sulfinamides competes with intramolecular addition to the phenyl ring.

Graphical abstract: Intramolecular homolytic substitution of sulfinates and sulfinamides – a computational study
Paper

Radical-based alkylation of guanine derivatives in aqueous medium

The addition of α-hydroxyalkyl radicals to 8-bromoguanine derivatives results in the efficient formation of intermolecular C–C bonds in aqueous media.

Graphical abstract: Radical-based alkylation of guanine derivatives in aqueous medium
Paper

Characterization of 2′-deoxyguanosine oxidation products observed in the Fenton-like system Cu(II)/H2O2/reductant in nucleoside and oligodeoxynucleotide contexts

Copper-mediated Fenton oxidation of 2′-deoxyguanosine leads to predominant formation of 5-carboxamido-5-formamido-2-iminohydantoin (d2Ih) via C5 hydroxylation.

Graphical abstract: Characterization of 2′-deoxyguanosine oxidation products observed in the Fenton-like system Cu(ii)/H2O2/reductant in nucleoside and oligodeoxynucleotide contexts
Paper

Enantioselective radical cyclisation reactions of 4-substituted quinolones mediated by a chiral template

Upon association of quinolones to template (+)-1 the chirality information is provided for the enantioselectivity determining cyclisation step.

Graphical abstract: Enantioselective radical cyclisation reactions of 4-substituted quinolones mediated by a chiral template
Paper

Linoleic acid peroxidation vs. isomerization: a biomimetic model of free radical reactivity in the presence of thiols

A biomimetic model offers for the first time the parallel estimation of peroxidation and isomerization as results of oxidative free radical conditions in the presence of thiols.

Graphical abstract: Linoleic acid peroxidation vs. isomerization: a biomimetic model of free radical reactivity in the presence of thiols
Paper

The mechanism of radical-trapping antioxidant activity of plant-derived thiosulfinates

The ease with which plant-derived thiosulfinates undergo Cope elimination to form the corresponding sulfenic acids accounts for their differences in antioxidant activity.

Graphical abstract: The mechanism of radical-trapping antioxidant activity of plant-derived thiosulfinates
Paper

Ring-opening radical clock reactions: many density functionals have difficulty keeping time

Many density-functional theory methods provide poor agreement to experimental rate constants for the ring opening of radical clock species.

Graphical abstract: Ring-opening radical clock reactions: many density functionals have difficulty keeping time
Paper

Fragmentations observed in the reactions of α-methoxy-γ-alkoxyalkyl iodide substrates with super-electron-donors derived from 4-DMAP and N-methylbenzimidazole

Interception of alkyl radicals leads to fragmentation, detected by release of alcohols.

Graphical abstract: Fragmentations observed in the reactions of α-methoxy-γ-alkoxyalkyl iodide substrates with super-electron-donors derived from 4-DMAP and N-methylbenzimidazole
Paper

Radical-based grafting of GMA on sutures of different nature

The formation of radicals upon high energy irradiation of sutures allows their easy GMA-derivatization.

Graphical abstract: Radical-based grafting of GMA on sutures of different nature
Paper

An ab initio and DFT study of radical addition reactions of imidoyl and thioyl radicals to methanimine

Imidoyl and thioyl radicals add to the nitrogen of methanimine through simultaneous multi-orbital interactions between the radicals and the imine.

Graphical abstract: An ab initio and DFT study of radical addition reactions of imidoyl and thioyl radicals to methanimine
Paper

A flexible, unified radical-based approach to polycyclic structures

Cis- and trans-decalins, trans-perhydroazulenes, and [5.3.1]bicyclo-undecanone scaffolds can be readily constructed starting from unsaturated ketones and using the degenerative xanthate transfer technology to accomplish unusual and otherwise difficult radical cyclisations

Graphical abstract: A flexible, unified radical-based approach to polycyclic structures
Paper

Damage of aromatic amino acids by the atmospheric free radical oxidant NO3˙ in the presence of NO2˙, N2O4, O3 and O2

Damage of aromatic amino acids by the most important atmospheric free-radical oxidant, NO3˙, was studied under simulated environmental conditions.

Graphical abstract: Damage of aromatic amino acids by the atmospheric free radical oxidant NO3˙ in the presence of NO2˙, N2O4, O3 and O2
Paper

Radical reductions of alkyl halides bearing electron withdrawing groups with N-heterocyclic carbene boranes

Stable, readily available, low molecular weight N-hetereocyclic carbene boranes reduce halides bearing electron withdrawing substituents. Product isolation is convenient.

Graphical abstract: Radical reductions of alkyl halides bearing electron withdrawing groups with N-heterocyclic carbene boranes
Paper

Aggregation behaviour of peptidepolymer conjugates containing linear peptide backbones and multiple polymer side chains prepared by nitroxide-mediated radical polymerization

The synthesis, characterization and studies on aggregation behavior by DLS and AFM of various peptide–polymer conjugates synthesized by NMP are described.

Graphical abstract: Aggregation behaviour of peptide–polymer conjugates containing linear peptide backbones and multiple polymer side chains prepared by nitroxide-mediated radical polymerization
Paper

In search of a new class of stable nitroxide: synthesis and reactivity of a peri-substituted N,N-bissulfonylhydroxylamine

Cyclic, peri- and benzo-fused N,N-bissulfonylnitroxides undergo hydrogen atom abstraction in preference to fragmentation.

Graphical abstract: In search of a new class of stable nitroxide: synthesis and reactivity of a peri-substituted N,N-bissulfonylhydroxylamine
Paper

A stereoselective, Sm(II)-mediated approach to decorated cis-hydrindanes: synthetic studies on faurinone and pleuromutilin

A route to cis–hydrindanes, featuring SmI2-mediated cyclisations, has been used in an RCM approach to analogues of the antibacterial pleuromutilin.

Graphical abstract: A stereoselective, Sm(ii)-mediated approach to decorated cis-hydrindanes: synthetic studies on faurinone and pleuromutilin
Paper

DEPMPO: an efficient tool for the coupled ESR-spin trapping of alkylperoxyl radicals in water

Spin trapping of peroxyl radicals using DEPMPO as the spin trap

Graphical abstract: DEPMPO: an efficient tool for the coupled ESR-spin trapping of alkylperoxyl radicals in water
Paper

Treasures from the Free Radical Renaissance Period – Miscellaneous hexenyl radical kinetic data

Rate constant data and Arrhenius parameters have been determined for a series of substituted hexenyl radicals of differing electronic and steric demand. Rate constants (kcis + ktrans) were found to lie in the range 0.4–2.1 × 105 s−1 at 25°. Cis/trans and kc/kH ratios were found to be solvent dependent.

Graphical abstract: Treasures from the Free Radical Renaissance Period – Miscellaneous hexenyl radical kinetic data
Paper

Kinetic studies of retinol addition radicals

The dynamics of β-elimination for retinol thiyl addition radicals and their reactions with oxygen were examined for the first time.

Graphical abstract: Kinetic studies of retinol addition radicals
Paper

Revising the mechanism of polymer autooxidation

The propagation step of Bolland and Gee's basic autooxidation scheme is not actually thermodynamically favoured for many polymers and biopolymers.

Graphical abstract: Revising the mechanism of polymer autooxidation
Paper

Rate constants for cyclizations of α-hydroxy radical clocks

Rate constants for 5-exo and 6-exo cyclizations of α-hydroxy radicals were measured.

Graphical abstract: Rate constants for cyclizations of α-hydroxy radical clocks
Paper

Tandem free-radical addition/substitution chemistry and its application to the preparation of novel AT1 receptor antagonists

Homolytic addition/substitution chemistry has been used to prepare benzoselenophene analogues of the antihypertensive compounds milfasartan and eprosartan. Benzothiophenes were also prepared.

Graphical abstract: Tandem free-radical addition/substitution chemistry and its application to the preparation of novel AT1 receptor antagonists
Paper

Switching from (R)- to (S)-selective chemoenzymatic DKR of amines involving sulfanyl radical-mediated racemization

Chemoenzymatic dynamic kinetic resolution of amines involving sulfanyl radical-induced racemization happened to be the very first switchable DKR process allowing the synthesis of either (R)- or (S)-amides.

Graphical abstract: Switching from (R)- to (S)-selective chemoenzymatic DKR of amines involving sulfanyl radical-mediated racemization
48 items

About this collection

Organic & Biomolecular Chemistry and Carl Schiesser are delighted to publish this very special themed issue on free radical chemistry in memory of Athel Beckwith: a scientific treasure, a gentleman and a wonderful person.

For an introduction to this web themed issue by Carl Schiesser, Guest Editor of this issue see OBC Blog.

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