Substituent effects in N-acetylated phenylazopyrazole photoswitches

• Radek Tovtik,
• Dennis Marzin,
• Pia Weigel,
• Stefano Crespi and
• Nadja A. Simeth

Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66

• the impact of substitution effects on the para position, using two types of LEDs (365 nm and 445 nm, details see Supporting Information File 1, section 3.5). The values determined are provided in Table 4. For ΦE→Z, we could observe for nearly all NAc-PAP derivatives, higher values compared to NMe-PAPs

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

• ¹H NMR spectra remained unchanged compared to the neat compounds (Figures S1, S3, and S5, Supporting Information File 1), confirming that the reaction occurs selectively in the solid state. Cl2B was also irradiated in DCM with the same 405 nm LEDs, in a quartz fluorescence cuvette. A UV–vis spectrum

• solid spread across the flask. The entire flask was then irradiated using 405 nm LEDs in the turntable chamber. Solution-phase irradiation tests For solution-phase irradiations, 10 mg of each compound was dissolved in DMSO-d6 and placed into NMR tubes. The samples were irradiated directly inside the

• using UV–vis spectroscopy, where the concentration was adjusted such that the absorbance is 2.164 at the λmax. The solution was added into a quartz fluorescence cuvette, and irradiated for 15 minutes at a time using the same 405 nm LEDs in a turntable chamber. Structures of a) the unfunctionalized

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

• surface area to light. This setup allows the reaction mixture to be irradiated efficiently using inexpensive and energy-saving light-emitting diodes (LEDs). Importantly, this apparatus can be operated in continuo, providing opportunity for limiting human intervention. Ball milling (Figure 2d) stands out

• Na2CO3 was ground in a mortar at room temperature for 3–5 min. Second, the reaction mixture was transferred into a quartz tube, heated to 50 °C (heating mantle) for 18 h, while being irradiated with blue LEDs under air-equilibrated conditions. In these conditions, product 3.3 was isolated in excellent

• exposing fresh material to light. In 2016, König and co-workers exploited rod milling to develop a photomechanochemical approach for the riboflavin tetraacetate (RFTA)-catalyzed photocatalytic oxidation of alcohols to the corresponding carbonyl compounds upon irradiation with five LEDs (λ = 455 nm) [69

Visible-light-promoted radical cyclisation of unactivated alkenes in benzimidazoles: synthesis of difluoromethyl- and aryldifluoromethyl-substituted polycyclic imidazoles

• Yujun Pang,
• Jinglan Yan,
• Nawaf Al-Maharik,
• Qian Zhang,
• Zeguo Fang and
• Dong Li

Beilstein J. Org. Chem. 2025, 21, 234–241, doi:10.3762/bjoc.21.15

• . Reaction conditions: 1 (0.2 mmol), 2 (1.4 mmol), and PIDA (0.8 mmol) in solvent (2 mL) irradiated with 72 W white LEDs at room temperature for 12 h under a N2 atmosphere. Yields refer to isolated yield. aα,α-Difluorobenzeneacetic acid (2 equiv) was used. Control experiments and plausible mechanism

Controlled oligomerization of [1.1.1]propellane through radical polarity matching: selective synthesis of SF₅- and CF₃SF₄-containing [2]staffanes

• Jón Atiba Buldt,
• Wang-Yeuk Kong,
• Yannick Kraemer,
• Masiel M. Belsuzarri,
• Ansh Hiten Patel,
• James C. Fettinger,
• Dean J. Tantillo and
• Cody Ross Pitts

Beilstein J. Org. Chem. 2024, 20, 3134–3143, doi:10.3762/bjoc.20.259

• of 1 during the screening process, we also found that irradiation with white LEDs was not necessary to boost product yields, as it was in our previously reported synthesis of 4 [36]. Both our laboratory [36] and the Qing laboratory [49] have previously observed that SF5Cl additions to 1 can proceed

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• equiv) as the base in methanol under a nitrogen atmosphere, with 5 W LEDs irradiation for 3 days (Scheme 9). Various substituted quinone N-oxides yielded the corresponding products in satisfactory to moderate yields. Notably, electron-withdrawing groups generated higher yields compared to electron

• mechanism by adding 2 equivalents of TEMPO to the reaction mixture. The absence of the desired product indicated the involvement of a radical pathway in the process. The proposed reaction mechanism begins with the activation of eosin Y by visible light from 5 W blue LEDs, transitioning it to its excited

• corresponding heteroaryl–aryl compounds 32 in moderate to good yield. The use of blue LEDs (456 nm), nitrogen atmosphere, and HFIP/H2O 4:1 solvent mixture improved the yield of the product by up to 90%. Various substituted azauracils were used to study the reaction and it was observed that different substituted

Synthesis of spiroindolenines through a one-pot multistep process mediated by visible light

• Francesco Gambuti,
• Jacopo Pizzorno,
• Chiara Lambruschini,
• Renata Riva and
• Lisa Moni

Beilstein J. Org. Chem. 2024, 20, 2722–2731, doi:10.3762/bjoc.20.230

• of components and temperature (Table 2). We firstly irradiated with blue LEDs (451 nm) the mixture of the three components in the presence of 1.5 equiv of BrCCl3 for 18 h at room temperature under argon atmosphere (Table 2, entry 1). To our surprise, the reaction provided only traces of the expected

• , we postulated that blue light was not the optimal one. Since, the absorption spectrum of the mixture showed better absorption at higher wavelengths (see Supporting Information File 1), we repeated the synthesis by irradiating with white LEDs, succeeding in isolating product 3j in acceptable yield

• °C at 451 nm (blue LEDs) under magnetic stirring for 24 h. The reaction mixture was treated with Et3N (3 equiv, 1.44 mmol, 200 µL), concentrated and the residue was purified by column chromatography on silica gel with PE/Et2O (from 85:15 to 75:25) to give 3a (121 mg, 61%), as yellow oil; IR (ATR) ν̃

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• in the late functionalization of complex drug molecules. Due to the versatility of the azide group, the direct C(sp3)–H azidation is an extremely valuable transformation. Lei and coworkers achieved this transformation using electrochemistry upon irradiation with blue LEDs [69]. Under photoelectric

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• /alloxazine photoredox catalysis [9][14][15][16][17][18][19], 7-methoxyderivatives should also be considered due to their absorption closer to the visible light region. This allows longer wavelength LEDs with lower energy photons to be applied, potentially contributing to avoiding undesired reactions [14][15

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

• C–H insertion to produce the spiro-β-lactone was accomplished by simply exposing the diazo derivative to 440 nm blue LEDs (Kessil lamp) at 50 °C, that favored the formation of a singlet carbene that reacted selectively by insertion into the C(3)–H bond. Spiro-lactones 14 were obtained in 80% yield

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• setup for isomerization quantum yield determination is reported. The setup combines fiber-coupled LEDs, a commercially calibrated thermopile detector for measurement of the photon flux, and a fiber-coupled UV–vis spectrometer. By solving the rate equations numerically, isomerization quantum yields can

• the positive features of the aforementioned designs, which can be used to determine the forward and backward quantum yields of molecular switches without the need for actinometry, by combining fiber-coupled LEDs with a commercially calibrated thermopile detector and following the isomerization of a

• furthermore determined the quantum yields again, taking the emission spectrum of the LED into account. The emission spectra were measured using our spectrometer by connecting the LEDs to the detector (Figure S1 in Supporting Information File 1). The following input parameters were used in both methods: the

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• plate as the cathode, was electrolyzed with a cell potential of 2.3 V (corresponding to an initial anodic potential of 0.10 V versus the ferrocenium ion/ferrocene redox couple) under the irradiation of 400 nm light-emitting diodes (LEDs). Through systematic optimization, we found that the use of readily

• , in an undivided cell, at 2.3 V cell potential, 400 nm LEDs, for 12 hours. a2,4,6-Collidine (1.0 equiv) was used instead of BTMG. bPhen was used instead of BPhen. cDMF/CH3CN (1:15 v/v) was used as solvent. dReactions were run with 0.4 mmol LiClO4 instead of TBABF4. Mechanistic studies and proposed

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• in DMF solvent and requires ca. 18 h to finish upon irradiation with blue LEDs. The catecholboronic esters produced at first are transesterified into pinacol borane by addition of pinacol and triethylamine. The reaction proved to be useful for a wide variety of substrates, such as borneol, menthol

• -based activator. The deoxyalkylation was performed by initially stirring the alcohol substrate with NHC and pyridine in MTBE for 15 min. After that, Michael acceptor, sodium acetate, 1,1,3,3-tetramethylguanidine, and [Ir(III)] photocatalyst in MTBE/DMA were added to the mixture. Then, blue LEDs were

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

• hydroarylation of alkenes with aryl halides. Substrate scope. Reaction conditions for 1 (X = Cl, Br): 1 (1.0 mmol), 2 (3.5 mmol), 1,3-DCB (5 mol %), H2O (5.0 mmol), Et4NCl (0.1 mmol), MeCN (6 mL), Al(+)-Pt(−), 7.5 mA/cm2, 3.5 F/mol, 0 °C, blue LEDs; reaction conditions for 1 (X = I): 1 (1.0 mmol), 2 (5.0 mmol

• ), 1,3-DCB (50 mol %), H2O (5.0 mmol), Et4NCl (0.1 mmol), MeCN (3 mL), Al(+)-Pt(−), 7.5 mA/cm2, 4.5 F/mol, 0 °C, blue LEDs. a4.5 F/mol. b2 (5 equiv). cMeCN (3 mL). d5 F/mol. 1,3-DCB, 1,3-dicyanobenzene. Gram-scale reaction and control experiments. Plausible mechanism. Evaluation of reaction conditions.a

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

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

• . The acridinium ion 161 now takes on the additional role of a phase-transfer catalyst, facilitating the transport of the chloride ion into the lipophilic alkene phase. Subsequently, under irradiation with blue LEDs, the acridinium cation 161 and the chloride anion engage in a single-electron-transfer

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• source such as green LEDs or a compact fluorescent lamp (CFL) were used only a small decrease in yield could be observed, although 4 hours of irradiation were needed to reach full conversion using CFL (Table 5, entries 8 and 9). The concentration, a factor expected to play an important role in a three

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• (LEDs) have plenty of advantages including long life span (up to 100 000 h), robustness, compact size, and high energy efficiency, which make LEDs very attractive as a light source for photocatalytic hydrogen generation studies [29]. In this work, a loop photoreactor for scaling up the photocatalytic

• hydrogen generation is designed and equipped with 365 nm LEDs. Fluid dynamics in the loop photoreactor are characterized using a color tracer mixing experiment and image analysis. Photonic characterization is performed with the ferrioxalate actinometer. Finally, the photocatalytic hydrogen evolution with

• . Photonic characterization The loop photoreactor using 6 LEDs was photonically characterized by chemical actinometry. Figure 6 shows the actinometer conversions and calculated photon fluxes at different irradiation times. The reasonable linear fits of the conversion (see Figure 6a) prove the applicability

Thienothiophene-based organic light-emitting diode: synthesis, photophysical properties and application

• Recep Isci and
• Turan Ozturk

Beilstein J. Org. Chem. 2023, 19, 1849–1857, doi:10.3762/bjoc.19.137

• many applications such as OLEDs, micro-LEDs, LCDs, lasers, and photodiodes by applying thin film methods and solution processes [5][6][7][8]. The performance of organic electronics is based on the active layer composition as well as the fabrication methods and processing parameters. The organic active

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

• approach. Importantly, the demonstration of the exceptional compatibility between blue LEDs and diazirine compounds also held the promise of inspiring further exploration and development of novel synthetic strategies in this field. Enamides are commonly found in medicinal compounds and physiologically

• depicted in Scheme 16. Initially, a photoactive EDA complex II was transiently formed through the combined action of NaI, PPh3, and the γ,σ-unsaturated phthalimide 33a. Upon irradiation with blue LEDs, the alkyl radical A was generated through a single-electron transfer from the iodide anion to the γ,σ

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• under the irradiation of purple LEDs afforded the desired coupling product 3a in 50% yield (Table 1, entry 1). Further screening of other activators (Table 1, entries 2–5) indicated that pivalic anhydride (A3) was optimal, delivering 3a in 56% yield. The yield of 3a was increased to 74% when 3.0 equiv

• LEDs (λmax = 399 nm) for 7 h. After the reaction was complete, the reaction mixture was poured into water and extracted with EtOAc. The combined organic phase was separated and washed with brine, dried over Na2SO4, and concentrated under vacuum. The resulting residue was purified by silica gel flash

• mmol), NiBr2(dtbbpy) (0.04 mmol), Hantzsch ester (0.6 mmol), Piv2O (0.6 mmol) and H2O (1.2 mmol) in DMAc (4.0 mL) was irradiated by purple LEDs for 7 h. Isolated yields are presented. aThe reaction was performed in a 1.0 mmol scale. Optimization of the reaction conditions.a Supporting Information

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• source played a key role, with lower yields or no product obtained when the reaction was performed without water or under other light source conditions such as 19 W CFL or irradiation with blue or green LEDs. This method is applicable to various heteroatom-containing compounds such as quinolines

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

• ) wavelength LEDs that complicate the setup. The simpler reaction setups and lack of a heterogeneous surface (electrodes) can make the mechanistic investigation more accessible. While quantum parameters (quantum yield, quadratic relationships with light intensity, etc) have been touched upon for a

• qualitative description is used as per the report in question (e.g., ‘blue LEDs’). The König group first reported a photocatalytic approach to C(sp2)–X activation harnessing multiple photon energies in their seminal work on perylene diimide (PDI) catalysts [15]. In their proposed consecutive photoinduced

• radical. This is strongly supported by a single turnover experiment, where exclusive excitation of [FeII(btz)3]2+ with 700 nm LEDs after in situ generation and substrate addition in the dark generated 5% of product even with only 0.5 mol % of catalyst present. In its ground state, [FeII(btz)3]2+ is not

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• compound 5 in hand, the required radical–radical coupling was investigated next, and some of the representative results are shown in Table S1 (see Supporting Information File 1). Irradiation from blue light-emitting diodes (LEDs) in the presence of 2 mol % of the photocatalyst [Ir(dF(CF3)ppy)2(dtbpy)]PF6

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• reaction was carried out between 1a and 2a in dry CH3CN as solvent under N2 atmosphere using 4CzIPN as the photocatalyst. Irradiating the reaction mixture for 10 h under blue LEDs (450 nm) led to the isolation of products 5 (54%) and 6 (28%) (Table 1, entry 1). However, the same reaction, under aerobic

• photocatalyst 10-phenylphenothiazine (PTH) under violet LEDs which uplifted the yield up to 52% (Table 1, entry 7). Now with the optimal catalyst in hand, we screened some common solvents, out of which 1,2-DCE positively impacted the yield (Table 1, entries 8–11). However, the best result was obtained when 3.0

• functionalizations of IPs and present work. Substrate scope. Conditions: unless otherwise noted, all reactions were carried out with 1 (0.2 mmol), 2 (0.4 mmol), PTH (5 mol %), Zn(OAc)2 (0.6 mmol), dry 1,2-DCE (2 mL), irradiation with LEDs (λmax = 390 nm), under air for 10 h. Mechanistic investigations. Plausible

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• Discussion Key elements of reaction optimization are summarized in Table 1. With NaI (20 mol %) and PPh3 (20 mol %), acrylamide 1a and redox-active ester 2a were used as model substrates to react for 36 h in acetonitrile (MeCN) under blue LEDs irradiation and N2 atmosphere, delivering the desired oxindole