Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• involves a formal 1,3-C shift. Keywords: Aspidosperma alkaloids; [2 + 2]-cycloaddition/retro-Mannich reaction; DFT study; photoinduced electron transfer; Introduction Photochemical reactions, which enable the construction of topologically complex architectures from simple building blocks, have attracted

• valuable strategy for synthesizing natural and unnatural products from simple building blocks [4]. Three distinct photoinitiated approaches have been established for the formation of the [2 + 2] cycloadducts: direct irradiation [5][6], energy transfer (EnT) [7], and photoinduced electron transfer (PET, or

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• peaks appeared, indicating that photoelectron transfer occurred between iodine ions and the macrocycles [27][28], and fluorescence quenching was due to the photoinduced electron transfer (PET) effect between iodine ions and acceptors, resulting in non-radiative dissipation of excited state energy rather

Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications

• Jullyane Emi Matsushima,
• Khushbu,
• Zuliah Abdulsalam,
• Udyogi Navodya Kulathilaka Conthagamage and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2345–2366, doi:10.3762/bjoc.21.179

• dithienylethene is in the closed form, caused by photoinduced electron transfer (PET) from the fluorescent pyrene stopper to the acceptor dithienylethene (Figure 15). Moreover, the efficiency of the PET is modulated by the macrocycle shuttling motion between the two recognition sites due to differences in

Thermodynamic equilibrium between locally excited and charge transfer states in perylene–phenothiazine dyads

• Issei Fukunaga,
• Shunsuke Kobashi,
• Yuki Nagai,
• Hiroki Horita,
• Hiromitsu Maeda and
• Yoichi Kobayashi

Beilstein J. Org. Chem. 2025, 21, 1577–1586, doi:10.3762/bjoc.21.121

• demonstrate that precise electronic and geometric design can enable controllable excited-state behavior in orthogonal molecular systems. Keywords: charge transfer; electron transfer; molecular dyad; transient absorption; Introduction Photoinduced electron transfer and charge separation are fundamental

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

Photocatalyzed elaboration of antibody-based bioconjugates

• Marine Le Stum,
• Eugénie Romero and
• Gary A. Molander

Beilstein J. Org. Chem. 2025, 21, 616–629, doi:10.3762/bjoc.21.49

• the light, the lamp wattage, and diverse photocatalysts or mechanisms (e.g., energy transfer, photoredox, or electron-donor/electron-acceptor photoinduced electron transfer) might all be brought to bear on controlling the DAR. In addition to the DAR, homogeneity for conjugation at specific sites using

Unraveling aromaticity: the dual worlds of pyrazole, pyrazoline, and 3D carborane

• Zahra Noori,
• Miquel Solà,
• Clara Viñas,
• Francesc Teixidor and
• Jordi Poater

Beilstein J. Org. Chem. 2025, 21, 412–420, doi:10.3762/bjoc.21.29

• photoinduced electron transfer [8][9]. Thanks to their notable photophysical properties, pyrazoles are applied in OLED technology [10]. Noticeably, in its ground state, pyrazole (C3H4N2) is an aromatic molecule that follows Hückel's rule, with two formal double bonds and a lone pair on one nitrogen generating

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

• . who employed a ruthenium(II) complex 1 activated through photoinduced electron transfer. The latter is pre-activated by the osmium complex shown in Scheme 1 after irradiation in the red region [18]. According to the mechanism proposed by the authors, the reaction is facilitated when conducted in

• plausible mechanisms: a photoinduced electron transfer (PET) between the 3MLCT state of the copper complex and DCA or a triplet–triplet energy transfer (TTET) between the 3MLCT state of the copper complex and DCA. In both of these mechanisms, the involvement of a doublet excited-state of the radical anion

• detail, and the authors have proposed that the reaction proceeds through a photoinduced electron transfer mechanism (Scheme 11). Upon red-light excitation, chlorophyll generates superoxide anion radicals (O2•−) in the presence of oxygen, which act as the active oxidant to convert organoborons 31 to

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• and a photosensitizer, facilitating photoinduced electron transfer (PET) to form the active cation radical B, and intersystem crossing (ISC) for energy transfer to generate the triplet carbene C. Radical B then reacted with biradical C, producing the new radical D, which accepted an electron from the

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures

• Yohei Haketa,
• Takuma Matsuda and
• Hiromitsu Maeda

Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215

• been widely investigated in the past decades for application as fluorescent dyes [3][4][5], chirality inducers [6][7][8], acceptors for photoinduced electron transfer (PET) [9][10], and components of supramolecular assemblies [11][12][13][14]. Owing to the stable π-electronic systems showing unique

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• agrochemical uses of pyrazoles [13] include insecticides [14], herbicides [15], and fungicides [16]. Furthermore, they are widely applied for the assembly of supramolecular ensembles [17] and molecular systems capable of photoinduced electron transfer [18]. Due to their pertinent photophysical properties [19

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical

• ), which is in good agreement with the experimental value (see Supporting Information File 1 for further information). Consequently, triplet reactivity cannot be excluded, given that photoinduced electron transfer reactions with excited singlet states or singlet radical pairs frequently suffer from low

• as the radical cation, Aza-H•+, which is in perfect agreement with our proposed photoinduced electron transfer step, while no triplet-excited Aza-H is observed (Figure 2A, blue spectrum). Since the direct ionization of Aza-H also contributes to this spectrum, we recorded a spectrum of only Aza-H in

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• state thereof, denoted with an asterisk, possessing a reduction potential of 2.0 V versus SCE (saturated calomel electrode). Subsequently, this excited state undergoes quenching through photoinduced electron transfer (PET) with styrene 5. The resulting vinyl radical cation exhibits electrophilicity at

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• (Scheme 6A). Stern–Volmer analysis revealed that quenching of the photocatalyst’s excited state by the NHPI ester occurred only in presence of a hydrogen bond donor such as water (H2O) or methanol (MeOH). This supported the hypothesis that activation of NHPI esters towards photoinduced electron transfer

• photoactive catalysts can be achieved by combining simple transition metal (TM) salts with suitable ligands. These TM catalysts are fundamentally distinct from traditional Ru- and Ir-based photoredox catalysts, as they play a dual role, by engaging in photoinduced electron transfer processes with the

• [80] (Scheme 22A). The study showed that a photoexcited Pd0 species formed upon blue-light irradiation of Pd(Ph3)4, was able to promote the activation of NHPI esters via SET (Scheme 22B). The photoinduced electron transfer process between the Pd-photocatalyst and RAE 58 was proposed to form a hybrid

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• physicochemical properties of the family of these compounds that have been investigated is provided to clarify their potential for future applications. Keywords: click chemistry; donor–acceptor conjugate; intramolecular charge transfer; photoluminescence; photoinduced electron transfer; Introduction Push–pull

• lifetime of 71 ps in toluene. Meanwhile, the absorption at 640 nm, corresponding to the ZnP radical cation, was not observed. The results obtained from Rehm–Weller’s equation [146] suggested that photoinduced electron transfer was thermodynamically permitted in 86. However, ultrafast energy transfer from

• spacers [147][148]. Comprehensive analyses and characterizations of the photoinduced electron-transfer processes in these conjugates were conducted. In these molecular designs, the center-to-center distances of the electron donor and acceptor ranged from 13.9 Å to 25.1 Å. Marcus curves were obtained by

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• efficient fluorescence quenching (Figure 5), which is commonly observed with this class of cationic ligands [3][70], mainly as a result of a photoinduced electron transfer from the excited, DNA-bound ligand with the DNA bases [71]. The binding isotherms obtained from the titration data were used to

• intermediates (Scheme 4). Under anaerobic conditions, the DNA damage is similar to the one observed with the isomeric benzo[c]quinolizinium ions [35]. In the latter case, it has been shown that frank DNA-strand breaks are induced by hydroxyl radicals, supposedly formed by photoinduced electron transfer (PET

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• binding different alkali and transition metal cations with intramolecular photoinduced electron transfer [48][80]. Further applications of crown ether-appended porphyrins acting as multitopic receptors, catalytically active species, and ligands were also investigated [81][82][83][84][85][86][87][88][89

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

• , excellent alternative conditions are available to overcome these limitations, harvesting two different but correlated concepts: the use of multi-photon processes such as consecutive photoinduced electron transfer (conPET) and the combination of photo- and electrochemistry in synthetic photoelectrochemistry

• 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

• process at photosystem II (PSII) via an electron transfer chain to photosystem I (PSI) where a second photoexcitation occurs [13][14]. Mimicry of this “Z-scheme” led to a seminal disclosure the concept of consecutive photoinduced electron transfer (conPET) by König and co-workers in 2014 for the

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• a photophysical investigation, a weak interaction was observed between two subunits at ground state in porphyrin-ferrocene dyads. Also, the fluorescence of porphyrin was significantly quenched in porphyrin-ferrocene conjugates due to photoinduced electron transfer from ferrocene to porphyrin

• -triazole linker significantly influences the charge separation, charge recombination, and photoinduced electron transfer processes. Since, the through-bond distance is approximately the same for all the synthesized ZnP-Tri-C60 conjugates, therefore, the variation in charge separation and charge

• . Some of these porphyrin complexes have shown significant electron and/or energy transfer between the porphyrin and the accompanying chromophore, and the 1,2,3-triazole bridge affects charge-separation and photoinduced electron transfer processes between connecting molecules. Various combinations of

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

• radical to circumvent the unsuccessful Friedel–Crafts reaction. Prior reports implicated β-keto radical formation in the ring opening of siloxycyclopropanes with photoinduced electron transfer (PET) to 1,4-dicyanonaphthalene [65]. Inspired by reports on dual photoredox and Ni-catalytic cross-coupling

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

• Ashish Kumar Mazumdar,
• Gyana Prakash Nanda,
• Nisha Yadav,
• Upasana Deori,
• Upasha Acharyya,
• Bahadur Sk and
• Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

• developed mainly by focusing on photophysical processes, such as photoinduced electron transfer (PET), excited-state intramolecular proton transfer (ESIPT), fluorescence resonance energy transfer (FRET), etc. [21][22][24][25]. Several literature reports have also demonstrated the switching of fluorescence

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• reaction with Alk-4 gave higher yields with both light sources. In the light of previous studies, a photoinduced electron transfer mechanism presented in Scheme 1 can be proposed. Upon the light irradiation, BPNs absorb the light and generate a single electron which was transferred from the conduction band

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• reaction rate-determining step in a radical mechanism in which the alkane participates in both the initiation and propagation steps of the radical chain (Scheme 37C). Photoinduced electron transfer Under photoinduced electron transfer (PET) conditions, olefins generate cation radical species that are

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ultrahigh molecular weight (≈106 g⋅mol−1) and a reasonably low dispersity (Đ ≥ 1.33) by using various monomers. Triethanolamine (TEOA) was used as an electron donor to initiate the photoinduced electron transfer to the PDI–CB[7] system, and thus to start the polymerization reaction. In addition, the rate of