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

• presence of H-bond acceptors [102][104][107]. The presence and the nature of the H-bond can be identified by 1H NMR spectroscopy since the N–H proton has a characteristic chemical shift depending on the H-bond acceptor [101]. Arylhydrazones based on pyridine have been intensively studied since the H-bond

Fe-catalyzed efficient synthesis of 2,4- and 4-substituted quinolines via C(sp²)–C(sp²) bond scission of styrenes

• Prafull A. Jagtap,
• Manish M. Petkar,
• Vaishnavi R. Sawant and
• Bhalchandra M. Bhanage

Beilstein J. Org. Chem. 2025, 21, 1799–1807, doi:10.3762/bjoc.21.142

• -disubstituted quinolone 3a along with 36% of 4-substituted quinolone 3a′ were observed during GC and GC–MS analysis, and the structures of both quinoline moieties were identified by 1H and 13C NMR spectroscopy. Encouraged by this result, we next examined the feasibility of the reaction with methanol as solvent

Synthesis of an aza[5]helicene-incorporated macrocyclic heteroarene via oxidation of an o-phenylene-pyrrole-thiophene icosamer

• Yusuke Matsuo,
• Aoi Nakagawa,
• Shu Seki and
• Takayuki Tanaka

Beilstein J. Org. Chem. 2025, 21, 1561–1567, doi:10.3762/bjoc.21.119

• characterized by X-ray analysis and NMR spectroscopy at elevated temperatures. Optical studies showed that compound 4 had broad absorption (up to 450 nm) and emission at 546 nm, while macrocycle 5 showed an emission peak at 528 nm, presumably as a consequence of structural relaxation and CT character. This

Facile synthesis of hydantoin/1,2,4-oxadiazoline spiro-compounds via 1,3-dipolar cycloaddition of nitrile oxides to 5-iminohydantoins

• Juliana V. Petrova,
• Varvara T. Tkachenko,
• Victor A. Tafeenko,
• Anna S. Pestretsova,
• Vadim S. Pokrovsky,
• Maxim E. Kukushkin and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2025, 21, 1552–1560, doi:10.3762/bjoc.21.118

• form two new carbon–heteroatom bonds in a 1,2,4-oxadiazoline ring through both variants of orbital overlap. It should be noted that, in this case, NMR spectroscopy is not applicable to assign the product structure due to the presence of only quaternary carbon atoms in the tetrasubstituted 1,2,4

Azide–alkyne cycloaddition (click) reaction in biomass-derived solvent Cyrene^TM under one-pot conditions

• Zoltán Medgyesi and
• László T. Mika

Beilstein J. Org. Chem. 2025, 21, 1544–1551, doi:10.3762/bjoc.21.117

• . Its purification was performed by vacuum distillation (18–20 mmHg, 114–116 °C) and stored under argon before subsequent use. The purity (>99.99%) was checked by 1H and 13C NMR spectroscopy. 1H NMR (300 MHz, CDCl3, TMS) δ 5.10 (s, 1H, CH), 4.71 (s, 1H, CH), 4.05 (d, J = 7.3 Hz, 1H, CH), 3.96 (t, J

Azobenzene protonation as a tool for temperature sensing

• Antti Siiskonen,
• Sami Vesamäki and
• Arri Priimagi

Beilstein J. Org. Chem. 2025, 21, 1528–1534, doi:10.3762/bjoc.21.115

• (≥98% purity) from Sigma-Aldrich. All of these were used as received. 4,4’-Dimethoxyazobenzene was synthesized according to the reaction depicted in Scheme S1 in Supporting Information File 1. The purity was confirmed by NMR spectroscopy (JNM-ECZR 500, JEOL). UV–vis measurements were done with a Cary

Ambident reactivity of enolizable 5-mercapto-1H-tetrazoles in trapping reactions with in situ-generated thiocarbonyl S-methanides derived from sterically crowded cycloaliphatic thioketones

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Marcin Palusiak,
• Heinz Heimgartner,
• Marta Denel-Bobrowska and
• Agnieszka B. Olejniczak

Beilstein J. Org. Chem. 2025, 21, 1508–1519, doi:10.3762/bjoc.21.113

• (ca. 13 mL N2 was collected in the nitrometer). The solvent was evaporated in vacuo and the residue was examined by 1H NMR spectroscopy. A characteristic singlet of the S–CH2 fragment was found in the region of 2.62 ppm. The pure product 8a was isolated by preparative layer chromatography. 1

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

• conditions: 2-isocyano-1,3-dimethylbenzene (0.2 mmol), iodonium salt 1 (0.2 mmol), Na2CO3 (0.34 mmol), [Ru(bpy)3](PF6)2 (0.004 mmol), MeCN (2 mL), H2O (200 μL), under irradiation by blue LED (465 nm, 20 W) for 10 h. bDetermined by 1H NMR spectroscopy after isolation as a mixture of amides or a single amide

Microwave-enhanced additive-free C–H amination of benzoxazoles catalysed by supported copper

• Andrei Paraschiv,
• Valentina Maruzzo,
• Filippo Pettazzi,
• Stefano Magliocco,
• Paolo Inaudi,
• Daria Brambilla,
• Gloria Berlier,
• Giancarlo Cravotto and
• Katia Martina

Beilstein J. Org. Chem. 2025, 21, 1462–1476, doi:10.3762/bjoc.21.108

• -formylpiperidine and aminophenol (2a-o-hydrol) (see Figure 1a). To better understand the influence of the reaction conditions on product distribution, we plotted conversion versus selectivity in Figure 1b. Crudes were analysed by 1H NMR spectroscopy, as shown in Figure S1 (Supporting Information File 1), to

• piperidine. Reaction conditions: benzoxazole (0.1 mmol), piperidine (0.15 mmol), copper catalyst, solvent (1.0 mL). Conversion was measured by NMR spectroscopy (see Figure S1 in Supporting Information File 1 for an example). Reaction rate comparison between conventional (oil bath) and MW heating. Reaction

• conditions: benzoxazole (0.1 mol), piperidine (0.15 mmol), copper catalyst 20 mol %, solvent (1.0 mL). Conversion was measured by 1H NMR spectroscopy. TGA profiles of SIPERNAT silica and Si-MonoAm and Si-DiAm. Hot filtration test for the Si-MonoAm-Cu(I)-catalysed C2-amination of benzoxazole with piperidine

Wittig reaction of cyclobisbiphenylenecarbonyl

• Taito Moribe,
• Junichiro Hirano,
• Hideaki Takano,
• Hiroshi Shinokubo and
• Norihito Fukui

Beilstein J. Org. Chem. 2025, 21, 1454–1461, doi:10.3762/bjoc.21.107

• byproduct and exhibited similar polarity as compound 5. The obtained compounds 3, 4, and 5 were identified using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) (see Supporting Information File 1) as well as single crystal X-ray diffraction analysis (vide infra). Furthermore, the

• internally functionalized DBC derivatives [22]. The dihedral angle between the mean planes of the two terminal benzene units is 83°, which is comparable to those of other derivatives. Next, products 3 and 5 were analyzed by variable temperature (VT) 1H NMR spectroscopy. The 1H NMR spectrum of bis-olefin 5 in

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

• OH functionality in compound 2 gives possibility to influence the tautomerism in this compound dynamically by protonation/deprotonation. The tautomeric and switching properties of compounds 1 and 2 have been revealed by using quantum-chemical calculations, UV–vis and NMR spectroscopy and UV

Reactions of acryl thioamides with iminoiodinanes as a one-step synthesis of N-sulfonyl-2,3-dihydro-1,2-thiazoles

• Vladimir G. Ilkin,
• Pavel S. Silaichev,
• Valeriy O. Filimonov,
• Tetyana V. Beryozkina,
• Margarita D. Likhacheva,
• Pavel A. Slepukhin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2025, 21, 1397–1403, doi:10.3762/bjoc.21.104

• larger or even commercial scale. The structures of compounds 3 were confirmed by 1H and 13C NMR spectroscopy and high-resolution mass spectrometry. The 1H NMR spectra are characterized by signals from protons of the aromatic rings in the range of 8.08–7.32 ppm, singlets for the proton at the C-3 position

N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B

• Joy E. Rajakulendran,
• Emmanuel Tope Oluwabusola,
• Michela Cerone,
• Terry K. Smith,
• Olusoji O. Adebisi,
• Adefolalu Adedotun,
• Gagan Preet,
• Sylvia Soldatou,
• Hai Deng,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2025, 21, 1388–1396, doi:10.3762/bjoc.21.103

• and LC–MS analyses (Figures S3–14), Marfey experiment (Figure S15) and the bioassay screen result (Figure S16). Acknowledgements We thank Russell Gray of the Marine Biodiscovery Centre, Aberdeen for assisting in NMR spectroscopy. Additionally, we are grateful to Blessing Akinboyo and Dr. Soji Fakoya

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• optical absorption. The UV–vis absorption spectra, fluorescence properties and 1H NMR spectroscopy, indicate that 150 and 151 can be protonated to form the corresponding tropylium cation and consecutive dication under acidic conditions, with reversible protonation−deprotonation capabilities. Additionally

Silver(I) triflate-catalyzed post-Ugi synthesis of pyrazolodiazepines

• Muhammad Hasan,
• Anatoly A. Peshkov,
• Syed Anis Ali Shah,
• Andrey Belyaev,
• Chang-Keun Lim,
• Shunyi Wang and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2025, 21, 915–925, doi:10.3762/bjoc.21.74

• pyrazolo[1,5-a][1,4]diazepine core. aDetermined by 1H NMR spectroscopy analysis of crude reaction mixtures. bIsolated yield. Optimization reactions of the intramolecular post-Ugi heteroannulation.a Supporting Information Deposition Numbers 2410526 (for 16m) and 2441192 (for 17-cis) contain the

Unraveling cooperative interactions between complexed ions in dual-host strategy for cesium salt separation

• Zhihua Liu,
• Ya-Zhi Chen,
• Ji Wang,
• Qingling Nie,
• Wei Zhao and
• Biao Wu

Beilstein J. Org. Chem. 2025, 21, 845–853, doi:10.3762/bjoc.21.68

• by 1H NMR titrations in DMSO. The resulting complexes after solid–liquid extraction were also characterized by 1H NMR spectroscopy (Figure 3), showing consistent anion binding profiles. By comparing with free hexaurea receptor L, the chemical shifts of the urea units N–H in the obtained complexes are

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

• straightforward development for specific applications. In this work, we synthesized novel N-acylpyrazole-based photoswitches and conducted a comparative study with 33 phenylazopyrazoles, comparing their photoswitching properties and the impact of electronic effects. Using UV–vis and NMR spectroscopy, we

• the extent of photoisomerization, the isomer distributions of NAc-PAPs at the PSS365 and PSS445 were investigated using UV–vis and NMR spectroscopy. For the ex-situ 1H NMR irradiation experiments, we irradiated our samples in a cuvette until the PSS was reached and measured immediately afterwards the

• distribution of 98% Z by UV–vis and 96% Z by 1H NMR. EWGs, such as NAc-PAP-CF3, on the other hand, showed a lower PSD for the Z isomer of 83% by both UV–vis and 1H NMR spectroscopy. For NMe- and NAc-PAPs, we observed increased Z content to almost quantitative photoisomerization after 365 nm illumination for

4-(1-Methylamino)ethylidene-1,5-disubstituted pyrrolidine-2,3-diones: synthesis, anti-inflammatory effect and in silico approaches

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Luc Van Meervelt,
• Do Thi Thao and
• Nguyen Minh Thong

Beilstein J. Org. Chem. 2025, 21, 817–829, doi:10.3762/bjoc.21.65

• -disubstituted pyrrolidine-2,3-diones were successfully synthesized via reversible transimination reaction. The structure of all compounds was evaluated using nuclear magnetic resonance (NMR) spectroscopy and, especially, with the molecular structure of compound 5a further confirmed through single-crystal X-ray

Synthesis and photoinduced switching properties of C₇-heteroatom containing push–pull norbornadiene derivatives

• Daniel Krappmann and
• Andreas Hirsch

Beilstein J. Org. Chem. 2025, 21, 807–816, doi:10.3762/bjoc.21.64

• tools, UV–vis and NMR spectroscopy were utilized. We determined significant spectral features of the formed NBD species, including λmax and λonset values, all of which exhibit redshifts compared to their isocyclic counterparts. Additionally, the selected QC isomers were subjected to thermal and

• characterized using UV–vis and NMR spectroscopy, as well as high-resolution mass spectrometry. An overview of the synthetic and spectroscopic data for all derivatives is provided in Table 1, while the specific spectroscopic properties of the individual QC analogues can be found in Supporting Information File 1

• . Photoswitching The photoswitching of the NBDs to corresponding QCs was monitored by UV–vis and 1H NMR spectroscopy. With increasing electronegativity of the bridge-atom, a slight bathochromic shift in the absorption spectra of the parent NBD precursors O-NBD1 and N-NBD1 was found (Figure 2a and 2c). For the

Orthogonal photoswitching of heterobivalent azobenzene glycoclusters: the effect of glycoligand orientation in bacterial adhesion

• Leon M. Friedrich and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2025, 21, 736–748, doi:10.3762/bjoc.21.57

• thermodynamically stable EE isomer was followed over time starting from the PSS@365 nm. The kinetic traces of the relaxation process were recorded by 1H NMR spectroscopy at 37 °C (Supporting Information File 1, Figure S2) and the population of the EE, ZE, EZ, and ZZ isomers were plotted against time. Using a

• glycocluster 1 [24] and the homobivalent azobenzene glycocluster 6αMan3αMan 2 and the glycoazobenzene-functionalized individual antennas 6αMan 3, 6βGlc 4, and 3αMan 5. The PSS was reached after irradiation with light of the denoted wavelength for 5 min and determined by NMR spectroscopy. Rate constants (k

Acyclic cucurbit[n]uril bearing alkyl sulfate ionic groups

• Christian Akakpo,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 717–726, doi:10.3762/bjoc.21.55

• according to the results of 1H NMR dilution experiments. The molecular recognition behavior of the hosts C1 and M1 toward a panel of seven ammonium ions was explored by 1H NMR spectroscopy and isothermal titration calorimetry (ITC). We find that C1 generally binds slightly more tightly than M1 toward a

• ). Qualitative study of C1·guest recognition properties by 1H NMR spectroscopy Next, we decided to perform a qualitative investigation of the host–guest properties of C1 by 1H NMR spectroscopy. Figure 3 shows the chemical structures of a panel of guests that were studied and the complexation-induced changes in

• -association in phosphate-buffered saline (PBS) which might impinge on guest binding and complicate the determination of C1·guest binding constants. For this purpose, we performed dilution experiments monitored by 1H NMR spectroscopy. We prepared a series of NMR samples of C1 in D2O (from 4 mM to 125 μM) and

Photochemically assisted synthesis of phenacenes fluorinated at the terminal benzene rings and their electronic spectra

• Yuuki Ishii,
• Minoru Yamaji,
• Fumito Tani,
• Kenta Goto,
• Yoshihiro Kubozono and
• Hideki Okamoto

Beilstein J. Org. Chem. 2025, 21, 670–679, doi:10.3762/bjoc.21.53

• Scheme 1 and Scheme 2. The newly synthesized compounds were characterized by NMR spectroscopy as well as elemental analysis or high-resolution mass spectrometry. The experimental details and compound data are provided in Supporting Information File 1. Aldehyde 4, in which one of the formyl groups in

Study of the interaction of 2H-furo[3,2-b]pyran-2-ones with nitrogen-containing nucleophiles

• Constantine V. Milyutin,
• Andrey N. Komogortsev and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2025, 21, 556–563, doi:10.3762/bjoc.21.44

• , 13C NMR spectroscopy and high-resolution MS. 1H NMR spectra of obtained products contain characteristic signals of the protons of the methyl group in the region δ 1.72–2.16 ppm and proton of pyranone fragment in the region δ 5.98–6.62 ppm. Besides that, the key structures of synthesized products were

Asymmetric synthesis of β-amino cyanoesters with contiguous tetrasubstituted carbon centers by halogen-bonding catalysis with chiral halonium salt

• Yasushi Yoshida,
• Maho Aono,
• Takashi Mino and
• Masami Sakamoto

Beilstein J. Org. Chem. 2025, 21, 547–555, doi:10.3762/bjoc.21.43

• for the construction of contiguous tetrasubstituted carbon centers via the Mannich reaction and this work. Plausible reaction mechanism. Catalyst screening for the asymmetric Mannich reaction. All yields were determined by 1H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. N

• -Protecting group optimization for the asymmetric Mannich reaction. All yields were determined by 1H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. aReaction conducted for 24 h. Catalyst screening using 7b as a substrate. All yields were determined by 1H NMR spectroscopy using 1,3,5

Deep-blue emitting 9,10-bis(perfluorobenzyl)anthracene

• Long K. San,
• Sebastian Balser,
• Brian J. Reeves,
• Tyler T. Clikeman,
• Yu-Sheng Chen,
• Steven H. Strauss and
• Olga V. Boltalina

Beilstein J. Org. Chem. 2025, 21, 515–525, doi:10.3762/bjoc.21.39

• photochemical reaction. Its structure was elucidated by NMR spectroscopy and single crystal X-ray diffractometry. The latter revealed no π–π interaction between neighboring ANTH cores. A combination of high photoluminescence quantum yield (PLQY) of 0.85 for 9,10-ANTH(BnF)2, its significantly improved