Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• same team further proposed various infrared-mediated reactions catalyzed by 40 as presented in Figure 7. It has to be noted that other squaraine derivatives have also been explored as innovative photoinitiators and photosensitizers for initiating the free radical polymerization (FRP) of methacrylates

Synthesis of disulfides and 3-sulfenylchromones from sodium sulfinates catalyzed by TBAI

• Zhenlei Zhang,
• Ying Wang,
• Xingxing Pan,
• Manqi Zhang,
• Wei Zhao,
• Meng Li and
• Hao Zhang

Beilstein J. Org. Chem. 2025, 21, 253–261, doi:10.3762/bjoc.21.17

• whether the reaction proceeded through a free radical mechanism, different free radical inhibitors were added to the reaction (reaction 7, Scheme 5). The addition of TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) resulted in complete inhibition of the reaction, while BHT (2,6-di-tert-butyl-4-methylphenol

• ) exhibited a lesser effect. Considering that TEMPO, as an oxidizing agent, affected the reaction, it could be concluded that the reaction did not proceed through a free radical mechanism. Based on the results of the control experiments and the related literature [26][30][41][52], a possible mechanism for the

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• units are easily modified by acylation, the hydrophilicity of the rotaxane crosslinker (RC) could be tuned in this manner. This [3]rotaxane crosslinker RC was added 0.5 mol % on the standard free radical polymerization of vinyl monomers to afford rotaxane-crosslinked polymer (RCP) (Figure 15B). Similar

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• reaction mechanism was proposed as an anchored ionic type pathway, rather than the free radical one. First, the Togni reagent forms complex A with the dinuclear paddle-wheel copper nodes of Cu3(BTC)2. Complex A then adds to styrene 175 to form iodonium cation B, which is converted to intermediate D by

Transition-metal-free synthesis of arylboronates via thermal generation of aryl radicals from triarylbismuthines in air

• Yuki Yamamoto,
• Yuki Konakazawa,
• Kohsuke Fujiwara and
• Akiya Ogawa

Beilstein J. Org. Chem. 2024, 20, 2577–2584, doi:10.3762/bjoc.20.216

• obtained with almost complete consumption of 1a. The results clearly indicate that air can play an important role in the thermal activation of triarylbismuthines to generate aryl radicals. Furthermore, the yield of 3a was dramatically reduced in the presence of 2,2,6,6-tetramethylpiperidine 1-oxyl free

• radical (TEMPO) as a radical scavenger, strongly suggesting that a radical pathway is involved in the key step of the arylboronate synthesis (Scheme 4a). In addition, the reaction of triphenylbismuthine 1a (0.07 mmol) and TEMPO (0.4 mmol) under air resulted in the formation of 4 in 10% yield, which was

Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

• Daria A. Burmistrova,
• Andrey Galustyan,
• Nadezhda P. Pomortseva,
• Kristina D. Pashaeva,
• Maxim V. Arsenyev,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202

• neuroprotective, antihypoxic effects, act as antiparkinsonian agents [3][4][5], exhibit antitumor and antibacterial activity [6][7][8], possess antioxidant properties for regulating free radical processes [9][10][11]. The functionalization of polyphenolic compounds by introducing various substituents or

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

• moderate DPPH free radical-scavenging activities (IC50: 18.7 µM) [232], exhibited COX-2 inhibitory activity (IC50: 9.5 µM) [242], and proved to be antiparasitic against Trypanosoma brucei rhodesiense and Leishmania donovani (IC50 values of 8.3 and 21.5 µM, respectively) [159]. Altenusin B (51), the methyl

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• yields (82–85%) (Scheme 28). The authors proposed a free radical mechanism facilitated by hydrogen peroxide, generating a primary radical at the terminal nitrogen atom -CO-HN• which then adds to the carbon atom of the imino group. The reaction mechanism was substantiated by theoretical calculations

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• detailed metal-free radical C(sp3)–H fluorinations suitable for benzylic substrates. These typically involve the generation of a HAT reagent that is selective for benzylic C–H bonds and facilitates the generation of a benzylic radical. Subsequent FAT, from a fluorinating reagent, yields the desired benzyl

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• by preventing overreduction [39]. While the metal-catalyst-free radical cyclization of alkene-tethered aryl halides has been well documented in the literature [40][41][42][43], the efficient intermolecular hydroarylation of alkenes still relies on the use of transition-metal catalysts, including Pd

A new analog of dihydroxybenzoic acid from Saccharopolyspora sp. KR21-0001

• Rattiya Janthanom,
• Yuta Kikuchi,
• Hiroki Kanto,
• Tomoyasu Hirose,
• Arisu Tahara,
• Takahiro Ishii,
• Arinthip Thamchaipenet and
• Yuki Inahashi

Beilstein J. Org. Chem. 2024, 20, 497–503, doi:10.3762/bjoc.20.44

• [16]. KR21-0001A (1) is a new analog of 2,3-DHBA connected to N-acetylcysteine (Figure 2b). 1 has a stronger antioxidant activity than trolox, which is a water-soluble analog of the free radical scavenger α-tocopherol [17][18]. 1 shows no antimicrobial activity against bacteria and fungi. Conclusion

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• indicated that both the acylamino and quinoline N motifs played a significant role. On the other hand, the stoichiometric amount of free radical inhibitors, including TEMPO and BHT, could not comprehensively suppress the reaction. Based on these experimental results and previous works [30][31][32], a

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• , numerous remarkable breakthroughs and notable progresses have been achieved in the realm of photoredox catalysis [1][2][3]. This domain has profoundly transformed modern organic synthesis, resulting in a considerable surge in research efforts centered on free radical reactions [4]. Presently, photoredox

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• glycoprotein (≈1–2%), laccase (≈0.2%), and stellacyanin (≈0.02%) [6][7]. Urushiol is the main active coating-forming ingredient of the resin. A typical urushiol is shown in Scheme 2. In a humid and warm environment, urushiol absorbs oxygen from air and is oxidized to a phenolic oxygen free radical under the

• an initiator molecule; M represents a monomer molecule; Pi represents a polymer chain with i repeating units; S represents a solvent molecule; and a dot indicates free radical species. These reactions are classified into four elementary steps: initiation, propagation, termination, and transfer. The

• negative free energy of polymerization and the latter an adequate reactivity of the monomer, stability of the derived free radical, and a low proportion of side reactions. A slow rate of chain initiation, a fast rate of chain propagation, and a rapid rate of chain termination are key features of

C–H bond functionalization: recent discoveries and future directions

• Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

• well as famous Noble-prize-winning cross-couplings, therefore approaching another step up towards sustainability. Likewise, a free-radical process is also a classical way to functionalize nonactivated C−H bonds in which site selectivity arises either from the relative strength of the C−H bonds or from

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• that the reaction is not a free radical reaction. Based on the control experiments and previous literature [21], we propose the following possible mechanism, which is shown in Scheme 5. Aluminum trichloride reacts with sodium nitrite to form an intermediate aluminum complex A, which is further

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• alkylidenemalonates [9][10][11]. These reactions follow a free-radical chain process wherein alkyl radicals (R•) add across the C–C double bond of the 1,4-acceptor, activated by complexation with the dialkylzinc, to deliver an enoxyl radical that undergoes homolytic substitution at zinc (SH2) to produce a zinc

• neither in the β-fragmentation (Scheme 4) nor in the addition across the carbonyl bonds. Overall, the mechanistic investigations support the scenario depicted in Scheme 9. Oxygen (in air) triggers a free-radical chain reaction between α-(aminomethyl)acrylates and dialkylzinc reagents that entails 1,4

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• challenging-to-generate “uncontrollable” species prone to side reactions to versatile reactive intermediates enabling construction of myriad C–C and C–X bonds. This maturation of free radical chemistry has been enabled by several advances, including the proliferation of efficient radical generation methods

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

• donor were all essential for product formation. A diminished yield of 19% under aerobic conditions indicates the involvement of a triplet excited state. Addition of i) 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) as a free-radical quencher or ii) 1,4-dinitrobenzene as an electron trap inhibited product

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• -formation processes (Scheme 12) [82][83]. These recently obtained results indicate that a sulfur-stabilized carbon radical derived from 1,4-dithiane (1) is a viable reaction intermediate, opening up the use of 1,4-dithianes in various free radical-type cross-couplings. 5 Synthetic equivalents of the allyl

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• , requiring only two purification steps [77]. FGI of 146 led to (−)-enantiomer 147, which serves as the radical point od divergence of this plan. HAT-initiated transannular free-radical cyclization of (−)-enantiomer 147 according to Baran’s protocols [78] provided the benzyl-protected (−)-pseudocopsinine 148

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• , organocatalysis by the modulation of redox properties of reagents has much in common with redox-neutral organocatalysis. With the exception of free-radical processes, the distinguishing feature of these organocatalyzed oxidations frequently lies in the involvement of peroxides as O-nucleophiles or O-electrophiles

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• chilled tube containing PRP (1), appeared to undergo free-radical polymerization when increasing the temperature to 25 °C. Despite this failed experiment, in general, PRP (1) has established itself as a highly reactive 1,3-dipole towards cyclopropene dipolarophiles 2. In this study, we did not confine

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• reaction mechanisms: free radical autoxidation, cation radical autoxidation, and thermal intersystem crossing (ISC), using 18O2 labeling, spin-trapping, spectroscopic, mass spectrometric, kinetic, and computational techniques. After several experiments, the obtained results have demonstrated that the 2

• 24–75% yields (Scheme 28). Alkylation and acylation by free radicals One of the largest groups of reactions that use menadione (10) as substrate comprises free radical alkylation and acylation reactions. The most useful alkylation approach is the Kochi–Anderson method [76] or (Jacobsen–Torssell