Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• the most appropriate for a given reaction, scale and purpose of a project. Keywords: consecutive photoinduced electron transfer; electro-activated photoredox catalysis; photoelectrochemistry; photoredox catalysis; radical ions; Review 1 Introduction Owing to the unique reactivity patterns of free

• especially in the case of excited radical ions which oftentimes exhibit unusual wavelength dependencies on catalytic efficiency. Light source wavelengths/input powers (radiant flux is rarely reported) are quoted if available, readers are directed to the report in question for details. When not available, the

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• ; spiro ring system; Introduction Single-electron transfer is one of the simplest modes for small molecule activation, employing a polarity inversion to generate radical ions which have proven to be unique reactive intermediates in the field of synthetic organic chemistry. A radical cation Diels–Alder

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• electron transfer and forming a pair of radical ions trapped in the solvent cage. The pair of radical ions escapes the solvent cage by diffusion to give radical ions, which could initiate chemical reactions or reverse electron transfer (Scheme 1) [6]. The continuously increasing demand for sustainable

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• -hydroxyphthalimide (NHPI, OD22, similar to the benzophenone photocatalysts OD9 and OD10) can abstract an H atom from the aldehyde substrate 20.1. The resulting acyl radical adds to the (E)-β-nitrostyrene 20.2, and the following denitrosylation affords the chalcones 20.3. Alkenyl and aryl radical ions (radical

• cations and radical anions) Recently, the exploitation of alkenyl and aryl radical ions has emerged as a platform for the functionalization of small molecules. They appear as attractive intermediates for a direct alkene difunctionalization or arene C–H functionalization. In particular, radical cations are

• class of substrates that usually undergo a protonation to form C(sp3) radicals. Alkenyl or aryl radical ions are generally accessed through SET. The presence of electron-donating groups facilitates the oxidation of the precursor to the radical cations, while electron-poor alkynes and arenes can undergo

Cyclobutane dication, (CH₂)₄²⁺: a model for a two-electron four-center (2e-4c) Woodward–Hoffmann frozen transition state

• G. K. Surya Prakash and
• Golam Rasul

Beilstein J. Org. Chem. 2019, 15, 1475–1479, doi:10.3762/bjoc.15.148

• ethylene radical ions, (C2H4)2·+, culminating in the formation of a 2e-4c bond involving four carbon atoms. The planar rectangular shaped structure 2 with a 2e-4c bond was found to be not a minimum. CCSD(T)/cc-pVTZ (MP2/cc-pVTZ) optimized structures and relative energies [in kcal/mol] of 1–4. (a) Total

Investigating radical cation chain processes in the electrocatalytic Diels–Alder reaction

• Yasushi Imada,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 642–647, doi:10.3762/bjoc.14.51

• Recently, radical ion reactivity has received great attention in the field of synthetic organic chemistry. The single electron transfer (SET) strategy is the key to generating radical ions, which provide powerful intermediates for bond formations. Photo- [1][2][3][4][5][6] and electrochemistry [7][8][9][10

• ][11][12] are the most straightforward approaches to induce SET processes. Since the pioneering work by Ledwith [13][14][15][16][17], a chain process involving radical ions has constituted a unique mechanism for this class of reactions, which also has the potential for contributing to effective

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• photodegradation of methylene blue [24], and CD-functionalized Fe3O4/TiO2 was efficient catalyst in photodecomposition of endocrine disrupting compounds, such as bisphenol A and dibutyl phthalate [30]. Producing strong oxidizing radicals (hydroxyl and superoxide radical ions) titanium dioxide is a widely used

A new approach to ferrocene derived alkenes via copper-catalyzed olefination

• Vasily M. Muzalevskiy,
• Aleksei V. Shastin,
• Alexandra D. Demidovich,
• Namiq G. Shikhaliev,
• Abel M. Magerramov,
• Victor N. Khrustalev,
• Rustem D. Rakhimov,
• Sergey Z. Vatsadze and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2015, 11, 2072–2078, doi:10.3762/bjoc.11.223

• we assume that the radical-ions formed after the first electron transfer would enter the intramolecular cyclization reaction involving the second adjacent double bond with subsequent electropolymerization. The latter is confirmed by a pronounced decrease in current values (3–4 times) as compared to

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

• photoredox catalysts (PRCs), have been exploited that enable visible and UVA radiation to be put to use without directly breaking chemical bonds. Typically, PRCs when photoexcited mediate electron transfer between suitable precursor substrates thus generating radical ions and thereby launching fresh

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• of odd-electron intermediates such as radicals and radical ions under exceptionally mild reaction conditions. A large number of transition metal chromophores with well-characterized photophysical and electrochemical properties are known, and the influence of ligand modification on the photoredox

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• the semiconductor valence band hole, the other from the substrate radical anion that is formed from reduction by the semiconductor conduction band electron. Mostly, one of these steps consumes a sacrificial electron/hole donor. In type B photocatalysis, combination of the radical ions leads to a new

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

• reagents are low [11][12][13][14][15][16][17][18][19]. When radical intermediates and ions derived from their precursor radical ions undergo different rearrangement reactions, it is often possible to distinguish respective reaction pathways of radicals and ions by examining the product distributions of the

• , 1547, 1449, 1298, 1229, 912, 731; HRMS–ESI (m/z): [M + Na]+ calcd for C18H23NO2, 308.1621; found, 308.1622. Radical anion and cation probe substances I and II, possessing 5-hexenyl structures. Comparison of fragmentation reaction pathways of organic radical ions generated under the redox-reagent

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• began early. Ipso substitution was one of the paths with secondary amines and the only reaction with tetrabutylstannane. The results fully support the previously proposed mechanism for electron transfer (ET) mediated photochemical alkylation of aromatic acceptors via radical ions and radical

• under mild conditions, avoiding the use of aggressive inorganic reagents otherwise required. Photoinduced electron transfer indeed offers an advantageous access to radical ions as well as the possibility to control the ensuing chemistry, in a way hardly attained through electrochemical or chemical

• methods [1][2][3][4][5][6]. A radical ion formed at a cathode/anode finds itself in an environment where electrons/holes are abundant. Likewise, reducing/oxidizing chemicals must be used at a sufficiently high concentration to be active, and again the radical ions are formed in an environment where a

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

• proportionality between the magnitude of CIDNP and the inverse square root of ∆g [11]. For the pair of radical ions, ∆g is about three times larger with XA than with AQ (see above). This would predict correspondingly smaller polarizations, yet quite the opposite is observed: CIDNP is more than an order of

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• enthalpy of the radical ion pair formation, ΔEexcit = excitation energy of the chromophore, ΔEcoul = coulomb interaction energy of the radical ions and = half wave potential of donor and acceptor. If electron transfer pathways dominate, substitution reactions are found to prevail. However, if the electron

Synthesis of bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine oxide – a tailor-made photoinitiator for dental adhesives

• Norbert Moszner,
• Iris Lamparth,
• Jörg Angermann,
• Urs Karl Fischer,
• Frank Zeuner,
• Thorsten Bock,
• Robert Liska and
• Volker Rheinberger

Beilstein J. Org. Chem. 2010, 6, No. 26, doi:10.3762/bjoc.6.26

• significantly impair the formation of initiating radicals. Moreover, especially in the aqueous medium, the polar radical ions are well solvated by the surrounding medium, thus inhibiting the proton transfer. If proton transfer occurs, both non-ionic and therefore rather hydrophobic species are kept in the