Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• presence of NHC (10 mol %) and 4CzIPN (2 mol %) and Na2HPO4 in DMSO at rt for 10–24 h. The key to success lies in the photocatalytic dual system, which combines two organocatalysts (NHC/4CzIPN) and visible light irradiation to permit a novel umpolung single-electron reduction of respective imino ester 2

• arylcyclopropanes 5 by applying NHC/ photoredox cooperative organocatalysis under visible-light irradiation. This method allows sequential C–O and C–C bond formation, leading to access to various γ-aroyloxy keto-ester derivatives 6 in good yield up to 81% and excellent functional group tolerance, including electron

• -attached ketyl radical B are generated under photoredox NHC catalysis under visible-light irradiation. The 5-exo-trig radical cyclization of the alkene-tethered iminyl radicals A furnished a dihydropyrrole-derived radical coupled with the NHC group attached ketyl radical B. This approach features readily

Effect of a photoswitchable rotaxane on membrane permeabilization across lipid compositions

• Udyogi N. K. Conthagamage,
• Lilia Lopez,
• Zuliah A. Abdulsalam and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2498–2512, doi:10.3762/bjoc.21.192

• compounds on membrane permeability over time in the absence of light irradiation, ensuring that no photoswitching occurred. LUVs containing sulforhodamine B were prepared using the lipid compositions described earlier. The release of the dye was monitored over 70 minutes after adding the studied compounds

• minutes of rotaxane insertion precludes a meaningful comparison between the two azobenzene configurations. Sulforhodamine B release from LUVs of varying lipid composition upon light irradiation We then investigated whether repeated cycles of light irradiation, and thus azobenzene photoisomerization, could

• minimal disruption of lipid packing appears to promote water accumulation in this system, and these dominant effects preclude assessing additional contributions from azobenzene isomerization. Likewise, upon light irradiation, rotaxane 2 and axle 3 induced dye release levels (65% and 54%, respectively

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

• -bisphenylene) (CBPQT4+) along the axle of rotaxanes [24]. Specifically, they used acridane as a recognition unit and stopper in a [2]rotaxane. Thus, the electron-rich acridane interacts with the electron-poor CBPQT4+, and upon light irradiation, the formation of the cationic acridinium repels the CBPQT4

• composed of a dibenzo-24-crown-8 (DB24C8) and an axle with anthracenes as stoppers on both ends [28]. Light irradiation at 365 nm triggered the dimerization of the anthracenes allowing the conversion of the [2]rotaxane into a [2]catenane. Cycloreversion and formation of the rotaxane was achieved thermally

• in-situ generation of toxic 1O2. Fumaramide Fumaramide is a bisamide photoswitch with a thermally stable trans-olefin, which, upon UV light irradiation, undergoes trans-to-cis isomerization, affording the corresponding maleamide (Figure 2). These photoswitches are distinct due to their ability to

Solar thermal fuels: azobenzene as a cyclic photon–heat transduction platform

• Jie Yan,
• Shaodong Sun,
• Minghao Wang and
• Si Wu

Beilstein J. Org. Chem. 2025, 21, 2036–2047, doi:10.3762/bjoc.21.159

• charged solar thermal fuels for deicing tests [74], showing effective ice removal capability under green light irradiation (Figure 7a). Wang et al. developed a photostimulated self-heating wristband [94] that elevates surface temperature from 29 °C to 44 °C upon blue light irradiation, protecting users

• from frostbite (Figure 7b); and Li and Wang et al. fabricated fabrics containing azobenzene-based solar thermal fuels that exhibit high energy storage density and long half-lives [95], enabling photothermal stimulation for moxibustion at acupoints upon light irradiation (Figure 7c). These examples

• irradiation (550 nm). Figure 7a was reprinted with permission from [74] Copyright © 2020 American Chemical Society. This content is not subject to CC BY 4.0. (b) Real-time infrared thermal imaging images of a charged self-heating wristband under blue light irradiation (450 nm). Figure 7b was reprinted from

Photochemical reduction of acylimidazolium salts

• Michael Jakob,
• Nick Bechler,
• Hassan Abdelwahab,
• Fabian Weber,
• Janos Wasternack,
• Leonardo Kleebauer,
• Jan P. Götze and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2025, 21, 1973–1983, doi:10.3762/bjoc.21.153

• reactions have been developed. Employing the simple amine, DIPEA, as the terminal reductant, products resulting from overall 2-electron or 4-electron-reduction processes could be obtained using either a photocatalytic approach under blue light irradiation or directly under UV-A light irradiation without an

• appears the simple combination of the tertiary amine DIPEA and UV-A light irradiation is sufficient to effect complete reduction of the acylazolium species. Decreasing the equivalents of DIPEA did not have a significant influence on the overall amount of reduced products formed although the proportion of

• to the photocatalyzed process, testing a selection of photocatalysts in the presence of 1 equivalent of DIPEA under blue light irradiation (λmax = 440 nm). Notably, under these modified conditions, the photocatalyzed reaction with the originally test photocatalyst, [Ir(dF(CF3)ppy)2(dtbpy)]PF6

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• picoseconds to several years. The presence of heteroatoms also introduces H-bond donors and acceptors and metal coordination sites [11]. Like azobenzenes, E–Z isomerisation of azoheteroarenes can be triggered by light irradiation, while Z–E isomerisation proceeds through irradiation with a different

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• of supramolecular interactions [33][34]. Different external stimuli, including pH changes, enzymes, light irradiation, hypoxia, and multi-stimuli responses, can alter the supramolecular structure or binding affinity to activate the opening and closing of the nano-valves. In addition to the three

• employed as an external trigger for supramolecular systems. Azobenzene can regulate geometry, shape, and interfacial curvature under ultraviolet or visible light irradiation. It undergoes cis–trans isomerization, which can trigger alterations in bioactivity or assembly configurations. Methods for creating

• maintain water solubility. This assembly approach not only suppresses the fluorescence self-quenching of AnPy in the aggregated state (enhancing the yield of singlet oxygen) [115], but also boosts its photo-sensitivity – under light irradiation, the anthracene in the complex can be efficiently converted to

General method for the synthesis of enaminones via photocatalysis

• Paula Pérez-Ramos,
• Raquel G. Soengas and
• Humberto Rodríguez-Solla

Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116

• . Simultaneously, acridinium photocatalyst PC1 absorbed energy and transitioned from the ground state to excited state under visible-light irradiation. This excited state PC1* is quenched by the amine, generating the amine radical cation and PC1 radical via a single-electron transfer (SET) process. Then, the C−Br

Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides

• Nadezhda M. Metalnikova,
• Nikita S. Antonkin,
• Tuan K. Nguyen,
• Natalia S. Soldatova,
• Alexander V. Nyuchev,
• Mikhail A. Kinzhalov and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110

• synthesis of benzamides via the arylation of isonitriles with diaryliodonium salts under blue light irradiation (Scheme 1C). Results and Discussion We commenced our investigation by the optimization of the reaction conditions. During the preliminary experiments we tested different solvents and solvent-to

• ones [31][32][33] introducing the photocatalyst [Ru(bpy)3](PF6)2, which successfully initiated the reaction under blue light irradiation and afforded benzamide 2aa in 36% yield (Table 1, entry 2). In that case less than 2% of the iodonium salt 1a remained in the reaction medium according to the 1H NMR

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

• Lidia Zaharieva,
• Vera Deneva,
• Fadhil S. Kamounah,
• Nikolay Vassilev,
• Ivan Angelov,
• Michael Pittelkow and
• Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

• influenced by the structural variations and the environment (temperature, solvent properties, acidity and presence of other molecules). The E/Z isomerization of the azodyes, caused by light irradiation [12][13][14] or electrochemically [15][16], has paved the way for the development of innovative materials

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

• performing the reaction under visible light irradiation, or coupling the reaction to other light-induced processes to produce new classes of products. In 2018, Aitken and co-workers reported a synthesis of previously unknown tricyclic 4:4:4 oxetanes 73 through a photochemical triple cascade reaction starting

• . published a light-induced cross-selective [2 + 2] cycloaddition between 3-(arylmethylidene)oxetanes 159 and electron-deficient alkenes 160 (Scheme 40) [91]. The methodology used a commercially available iridium-based photosensitiser and blue-light irradiation at a slightly elevated temperature. The

• acids under blue-light irradiation, and the Giese adducts were obtained in moderate to high yields. As demonstrated by the authors, this protocol is also suitable for synthesising oxetane-containing dipeptides, and opens the door for exploring a novel oxetane-spirocycle motif if the γ-aminoester product

Recent advances in amidyl radical-mediated photocatalytic direct intermolecular hydrogen atom transfer

• Hao-Sen Wang,
• Lin Li,
• Xin Chen,
• Jian-Li Wu,
• Kai Sun,
• Xiao-Lan Chen,
• Ling-Bo Qu and
• Bing Yu

Beilstein J. Org. Chem. 2025, 21, 1306–1323, doi:10.3762/bjoc.21.100

• ambient temperature and visible-light irradiation, achieving site-selective bromination (products 94–96) in 51–99% yields across electronically differentiated positions. The system's operational mildness and functional group tolerance highlight its suitability for late-stage functionalization of complex

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

• ), the process involves the homolytic cleavage of Umemoto's reagent 39 under visible light irradiation, releasing a trifluoromethyl radical 42. The radical then adds to the double bond of N-arylacrylamide, forming intermediate radical 43. Subsequently, this intermediate undergoes intramolecular

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

Biobased carbon dots as photoreductants – an investigation by using triarylsulfonium salts

• Valentina Benazzi,
• Arianna Bini,
• Ilaria Bertuol,
• Mariangela Novello,
• Federica Baldi,
• Matteo Hoch,
• Alvise Perosa and
• Stefano Protti

Beilstein J. Org. Chem. 2025, 21, 1024–1030, doi:10.3762/bjoc.21.84

• biocompatibility. The electrochemical properties of such materials have been then evaluated by cyclic voltammetry (CV). For all the properties mentioned above, CDs emerged as low-cost and sustainable photocatalysts. Indeed, upon visible-light irradiation, the generated excited state CD* can operate as either

On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals

• Daniel Straub,
• Markus Gross,
• Mona E. Arnold,
• Julia Zolg and
• Alexander J. C. Kuehne

Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80

• such diradicals and we group the molecules in accordance with their type of conjugation. Kekulé-conjugated diradicals Trityl radicals and trityl-derived diradicals have been reported to be instable especially under light irradiation and in the presence of oxygen. As for the monoradicals, also

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

• ) that can form covalent bonds when exposed to UV or visible light. These photoaffinity tags or crosslinkers are designed to bind to specific biomolecules, such as proteins, nucleic acids, or lipids, in a highly selective manner. The light irradiation triggers a chemical reaction, such as a bond

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

• Metodej Dvoracek,
• Brendan Twamley,
• Mathias O. Senge and
• Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

• light irradiation, undergoing rearrangement and photodegradation, so there may be a risk of degradation if irradiation using UV light is tried. Alternatively, the lack of a [2 + 2] cycloaddition of Me2B, may be due to its photophysical properties not allowing for a reaction to occur, rather than the

Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• , since in a control experiment without RFTA the mixture was found to liquefy. This was due to the heat generated by LEDs and not by the grinding action. Thus, light irradiation fulfils a double function: the excitation of the photocatalyst and melting of the substrate, inducing mobility of the molecules

• oxidation of 1,2-diphenylethyne to benzil [71]. Thus, when a 1:2 mixture of 7.1 and 4-chlorothiophenol (7.2) was ground in the presence of eosin Y as the photocatalyst and anhydrous Na2SO4 as a bulking agent, benzil (7.3) was obtained in 43% GC yield under blue light irradiation (LED, 14.5 W). Isolation led

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

• , making it particularly suited for large-scale applications. Recent advances highlight the unique advantages of both metal-based and metal-free catalysts under red-light irradiation, broadening the range of possible reactions, from selective oxidations to complex polymerizations. In biological contexts

• organic photocatalysts. Unlike metal-based systems, organic photocatalysts such as phthalocyanins, squaraines and cyanins, offer effective electron and energy transfer under red-light irradiation without relying on transition metals. This shift towards organic catalysts opens new possibilities for

• hemoglobin, and silicon by selectively irradiating a specific area of the reaction medium with red light (660 nm) or blue light (456 nm), respectively (Scheme 2). The authors have demonstrated that this polymerization reaction proceeded much more efficiently under red light irradiation. Indeed, red light can

Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory

• Misato Suganuma,
• Daichi Kitagawa,
• Shota Hamatani and
• Seiya Kobatake

Beilstein J. Org. Chem. 2025, 21, 242–252, doi:10.3762/bjoc.21.16

• Information File 1. The photochromic properties of N3, N4, and I1–I4 were investigated in n-hexane. Figure 1a,b and Figure S1 in Supporting Information File 1 show the absorption spectral changes of N3, N4, and I1–I4 in n-hexane upon UV light irradiation. Compounds N3(o), N4(o), and I1(o)–I4(o) have

• absorption band in the visible region disappeared and returned to the initial one by stopping UV light irradiation. These results indicate that all molecules exhibit T-type photochromic reactions based on 6π aza-electrocyclic reaction. The absorption bands of compounds I1(c)–I4(c) are blue-shifted compared

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• and sulfur dioxide afforded vinyl sulfones with excellent regio- and stereoselectivity (Scheme 9) [22]. The authors used DABCO(SO2)2 to generate sulfur dioxide, and visible light irradiation and the mandatory presence of a photocatalyst for this transformation suggested a radical mechanism. The

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

• initiated the reaction pathway. The authors proposed that under light irradiation, the porphyrin transitioned to its excited state, generating a phenyl radical through photoinduced single-electron transfer (Figure 15c). This phenyl radical then added to the furan (heteroarene), forming an aryl radical

• of enol acetates with aryldiazonium salts [93]. The excitation of the porphyrin macrocycles by light irradiation initiated the catalytic cycle, generating aryl radicals from the diazonium salts, similar to findings by Gryko and co-workers. They explored both batch and continuous-flow photocatalysis

• light irradiation. There are a few reports on red light-mediated transformations using other pyrrolic macrocycles, such as thiaporphyrin [94], phthalocyanine [95], and subphthalocyanine [96]. Porphyrin macrocycles can also absorb red light (Q bands at 518, 553, 592, and 648 nm with extinction

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

• visible-light irradiation or heating, CD was moved back to the azobenzene moiety, and the entire process was reversible. This system was further developed in 2005 by introducing bipyridinium moieties to implement the selective transfer of the wheel via heating or light irradiation (Figure 5B) [57]. During

• α-CD-based rotaxane comprising a stilbene axle that was synthesized by the Suzuki coupling reaction to light irradiation (Figure 6, right) [58]. In this structure, α-CD was first located on the trans-stilbene moiety, after which it moved to the benzene ring moiety via the cis-isomerization of the

• stilbene framework by 335 nm light irradiation before returning to the stilbene moiety via trans-isomerization induced by the 280 nm light irradiation; this system is also reversible. The change in the local position of CD is significantly reflected in the ICD behavior of this system. Kodaka and co-workers

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

• photocatalytic system under visible light irradiation (443 nm) [56]. Peroxidation of β-ketoesters, cyanoacetic esters, and malonic esters 37 was performed using the TBAI/TBHP system (Scheme 15) [57]. The highest product yields in the TBAI-catalyzed peroxidation were achieved with malonic acid esters, in contrast

• recombination of radicals F and D leads to the product 67. Photochemical peroxidation of isochromans and other benzylic C(sp3)–H substrates 68 with TBHP was developed using Ir(ppy)3 as the photocatalyst and Bronsted acid as an additive (Scheme 25) [68]. Visible light irradiation of [IrIII(ppy)3] to give the

• –peroxidation of alkenes 155 with TBHP and aldehydes 156 through visible-light photocatalysis was developed using fac-Ir(ppy)3 as the photoredox catalyst (Scheme 49) [113]. Under visible light irradiation, the excited state Ir(III)* is generated, and the single electron transfer of Ir(III)* with TBHP results in