A new synthesis of Tyrian purple (6,6’-dibromoindigo) and its corresponding sulfonate salts

• Holly Helmers,
• Mark Horton,
• Julie Concepcion,
• Jeffrey Bjorklund and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2026, 22, 167–174, doi:10.3762/bjoc.22.10

• unable to purchase nitric acid of this grade from a commercial source. While 3 was produced as a mixture with its regioisomer 7, this approach yielded the desired intermediate in a single step without the need for the high-energy diazonium intermediate used in other syntheses [6][7][8][9]. After having

Design and synthesis of an axially chiral platinum(II) complex and its CPL properties in PMMA matrix

• Daiki Tauchi,
• Sota Ogura,
• Misa Sakura,
• Kazunori Tsubaki and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2026, 22, 143–150, doi:10.3762/bjoc.22.7

• blue-shifted by 38 nm, and the shorter-wavelength emission peak (408 nm) was blue-shifted by 19 nm. These blue shifts are attributed to the hydrophobic environment in the PMMA matrix. In such low‐polarity surroundings, the excited state is less stabilized, resulting in a higher excited‐state energy and

Symmetrical D–π–A–π–D indanone dyes: a new design for nonlinear optics and cyanide detection

• Ergin Keleş,
• Alberto Barsella,
• Nurgül Seferoğlu,
• Zeynel Seferoğlu and
• Burcu Aydıner

Beilstein J. Org. Chem. 2026, 22, 131–142, doi:10.3762/bjoc.22.6

• indicative of a high NLO response in a typical organic NLO chromophore. Apart from the existence of donor (D) and acceptor (A) groups linked by a π-conjugation path, the NLO response is also influenced by the strength of the D and A groups in the structure. For high NLO responses, a small energy gap between

• the HOMO and the LUMO (ΔE), resulting from the presence of the strong D/A groups, is an important indicator. Based on the EFISH results, the calculations show that 2a and 2b have a small energy gap and a high β value because they have a stronger electron-donor group than 2c. Additionally, 2a and 2b

• solvents with different polarity and the calculated absorption spectra dataa. The absorption maxima (λabs), oscillator strength (f) and transitions for 2a–c and 2a–c+CN−. Experimental and calculated NLO properties and energy gap (ΔE) values for 2a–c. Td values of the dyes. Supporting Information

Highly electrophilic, gem- and spiro-activated trichloromethylnitrocyclopropanes: synthesis and structure

• Ilia A. Pilipenko,
• Mikhail V. Grigoriev,
• Olga Yu. Ozerova,
• Igor A. Litvinov,
• Darya V. Spiridonova,
• Aleksander V. Vasilyev and
• Sergey V. Makarenko

Beilstein J. Org. Chem. 2026, 22, 123–130, doi:10.3762/bjoc.22.5

• (electron) pair – the π-system of the nitro group, and bonds of the Cl···O, Cl···N, C–H···X (X = Cl, O, N) are realized, which are shown in Figures S47–S57 in Supporting Information File 1. The energy of such interactions can be comparable with the energy of “classical” hydrogen bonds [47]. Conclusion In

Advances in Zr-mediated radical transformations and applications to total synthesis

• Hiroshige Ogawa and
• Hugh Nakamura

Beilstein J. Org. Chem. 2026, 22, 71–87, doi:10.3762/bjoc.22.3

• bond dissociation energy (BDE). Although zirconium shares many characteristics with titanium as a group-congener transition metal, it is known to form stronger bonds in several cases. For example, the Ti–O BDE is reported as 115 kcal·mol−1, whereas the Zr–O BDE is 132 kcal·mol−1 [4]; likewise, Ti–Br

• transfer (XAT) mediated by zirconocene bistosylate (Scheme 7A) [22]. Alkyl chlorides are inexpensive and readily available feedstocks; however, their chemical transformation has been challenging due to the high bond dissociation energy of the C–Cl bond compared to the C–Br and C–I bonds [12]. Motivated by

• transformations of monofluoroalkyl groups have been considered difficult due to their negative reduction potentials. In contrast, the authors focused on the comparatively small bond dissociation energy (BDE) of C(sp³)–F bonds. Based on the hypothesis that this property could enable C–F bond functionalization via

Reactivity umpolung of the cycloheptatriene core in hexa(methoxycarbonyl)cycloheptatriene

• Dmitry N. Platonov,
• Alexander Yu. Belyy,
• Rinat F. Salikov,
• Kirill S. Erokhin and
• Yury V. Tomilov

Beilstein J. Org. Chem. 2026, 22, 64–70, doi:10.3762/bjoc.22.2

• the set of conformations of anion 2 and found that conformer 2', with an allyl-anionic fragment shifted to form a nucleophilic CH fragment (Figure 3), is only 9.6 kcal/mol less stable than the main conformer 2 (the energy values of other conformers are given in Supporting Information File 1). Note

• chlorine is associated with an increase in energy of the lowest unoccupied molecular orbital of halogen molecules and a decrease in their electrophilicity. Therefore, if an electrophilic mechanism takes place, iodine apparently reacts with the main conformer faster than a transition to conformer 2' may

• negative free energy changes for all the stages of this reaction. A chlorination experiment with 2,2,6,6-tetramethylpiperidinyloxyl revealed a trace amount of a trap product detected by high-resolution mass spectrometry to support the radical mechanism. However, this does not exclude the possibility of a

Sustainable electrochemical synthesis of aliphatic nitro-NNO-azoxy compounds employing ammonium dinitramide and their in vitro evaluation as potential nitric oxide donors and fungicides

• Alexander S. Budnikov,
• Nikita E. Leonov,
• Michael S. Klenov,
• Andrey A. Kulikov,
• Igor B. Krylov,
• Timofey A. Kudryashev,
• Aleksandr M. Churakov,
• Alexander O. Terent’ev and
• Vladimir A. Tartakovsky

Beilstein J. Org. Chem. 2025, 21, 2739–2754, doi:10.3762/bjoc.21.211

• most detail and attract continuing attention as perspective high-energy materials [76][77][78][79][80][81][82][83][84][85][86] and physiologically active substances [87]. At the same time, aliphatic compounds containing the nitro-NNO-azoxy group are practically unknown, with the exception of a few

• estimated, as this step requires the change in spin-state. However, unexpectedly we found that addition of higher energy singlet nitrene C-s to A is not barrierless (ΔG≠ 10.9 kcal/mol). Moreover, according to our calculations C-s can easily (ΔG≠ 5.7 kcal/mol) undergo unimolecular rearrangement to the dimer

• of 0.1 V/s at 298 K. Free energy diagram of possible interaction pathways between 1a and dinitramide-derived radical A according to ωB97X-3c [94]/CPCM(MeCN) level of theory. Free energies ΔG and activation free energies ΔG≠ are given in kcal/mol. Dashed lines correspond to spin-state-changing

Mechanistic insights into hydroxy(tosyloxy)iodobenzene-mediated ditosyloxylation of chalcones: a DFT study

• Jai Parkash,
• Sangeeta Saini,
• Vaishali Saini,
• Omkar Bains and
• Raj Kamal

Beilstein J. Org. Chem. 2025, 21, 2703–2715, doi:10.3762/bjoc.21.208

• , the detailed calculated reaction mechanism differs. Scheme 2 and Scheme 3 depicts the reaction mechanism for these two possible cases, i.e., when X is electron-donating and electron-withdrawing, respectively. Figure 1 depicts the free energy reaction profile for the chalcone with X = -SCH3. The

• corresponding reaction profile for X = -OCH3 has been discussed in our earlier study [34]. Figure 2 and Figure 3 present the free energy reaction profiles for chalcones with X = -Cl and X = -NO2, respectively. Table 1 lists the free energy and potential energy for various intermediates and transition states for

• chalcones with different substituents, X = -SCH3, -Cl, -NO2 including the data for X = -OCH3. The difference between free energies for consecutive reaction species are shown over arrows in Figures 1, 2 and 3 for substituents X = -SCH3, -Cl and -NO2, respectively. Table 1 also reports these free energy

Tandem hydrothiocyanation/cyclization of CF₃-iminopropargyl alcohols with NaSCN in the presence of AcOH

• Ruslan S. Shulgin,
• Ol’ga G. Volostnykh,
• Anton V. Stepanov,
• Igor’ A. Ushakov,
• Alexander V. Vashchenko and
• Olesya A. Shemyakina

Beilstein J. Org. Chem. 2025, 21, 2694–2702, doi:10.3762/bjoc.21.207

• , electron ionization, electron energy: 70 eV, ion source temperature 200 °C; mass range 34–650 Da. The solvent was chloroform or acetone. Column chromatography was performed on silica gel 60 (70–230 mesh, particle size 0.063–0.200 mm or 230–400 mesh, particle size 0.040–0.063 mm, Merck). Commercially

Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• , protonation of these compounds resulted in a lowering of the HOMO energy level, leading to an increase in the HOMO–LUMO gap and, consequently, greater molecular stability. In contrast, deprotonation led to an increase in the LUMO energy level, with little influence on the HOMO energy. Notably, the neutral

• operation: −x + 2, −y + 1, −z + 1. Molecular energy as a function of the torsion angle obtained from a relaxed dihedral scan at the M06-2X/def2-TZVPP level of theory. Identification of the carbon atoms used in the theoretical study of chemical shifts. In red, easily identifiable carbon atoms in the

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

• ]. The use of visible light as an energy source has significantly expanded the scope of organic molecule activation and its application in organic synthesis or medicinal chemistry [12], thereby driving the fast development of various photocatalytic transformations. Among these advances, dual catalysis

• , and advanced optical and energy materials. Review Visible-light-driven NHC/4CzIPN-catalyzed reactions Recently, Shu and co-workers developed a direct and innovative preparation of highly functionalized aryl amide derivatives 3 from aryl aldehydes 1 and substituted imines 2 under mild conditions in the

Rapid access to the core of malayamycin A by intramolecular dipolar cycloaddition

• Yilin Liu,
• Yuchen Yang,
• Chen Yang,
• Sha-Hua Huang,
• Jian Jin and
• Ran Hong

Beilstein J. Org. Chem. 2025, 21, 2542–2547, doi:10.3762/bjoc.21.196

• Yilin Liu Yuchen Yang Chen Yang Sha-Hua Huang Jian Jin Ran Hong Faculty of Chemical Engineering and Energy Technology, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418, P.R. China State Key Laboratory of Chemical Biology, Shanghai Institute of Organic Chemistry, Chinese Academy

Pentacyclic aromatic heterocycles from Pd-catalyzed annulation of 1,5-diaryl-1,2,3-triazoles

• Kaylen D. Lathrum,
• Emily M. Hanneken,
• Katelyn R. Grzelak and
• James T. Fletcher

Beilstein J. Org. Chem. 2025, 21, 2524–2534, doi:10.3762/bjoc.21.194

• the pentacyclic series itself, minor differences in emission energy were observed as the naphthalene, quinolone, and isoquinoline subunits were varied, and compounds 31–36 with N1-triazole subunit connectivity displayed generally sharper emission signals than their C5-triazole subunit connected

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

• the axle occurs in rotaxane 1, the dominant absorption of the azobenzene units ensures that most of the light energy is directed toward azobenzene photoisomerization. Additionally, their different release kinetics provide more insights: rotaxane 1 causes gradual, stepwise release beginning from the

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

• 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

• formation of intermediate L is challenging because its ring-strain energy (Figure 1e, 52.1 kcal/mol) is higher than that of its counterpart, i.e. the bicyclo[3.2.0]heptane motif (28.3 kcal/mol) in H [24]. Herein, we report our recent results on the development of a novel strategy for the stereoselective

• formation of IN1. The radical cation IN1 served as the reference point for DFT investigations. As illustrated in Figure 2a, facilitated by a favorable radical cation–π interaction [31], IN1 proceeds to the first radical addition transition state (TS1), with an energy barrier of 8.3 kcal/mol. This leads to

The intramolecular stabilizing effects of O-benzoyl substituents as a driving force of the acid-promoted pyranoside-into-furanoside rearrangement

• Alexey G. Gerbst,
• Sofya P. Nikogosova,
• Darya A. Rastrepaeva,
• Dmitry A. Argunov,
• Vadim B. Krylov and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2025, 21, 2456–2464, doi:10.3762/bjoc.21.187

• , we turned to computational studies to elucidate the driving force of this pyranoside-into-furanoside isomerisation. The DFT B3LYP-D3 approach was employed for this task with additional validation of its results at DLPNO-CCSD(T) level for the lowest energy conformers. The results demonstrate that the

• ° correspondingly, after which the starting structures were fully optimized. Quite expectedly for galactose, the gt conformer was found to have the lowest energy. Supporting Information File 1, Table S1 contains the energies obtained for the three conformers and Figure 4C provides graphical representation of the

• +60° there were produced some conformers with the energy of the furanoside substantially lower than that of the pyranoside form. The energies are provided in Supporting Information File 1, Table S2 and the graphical representation is given in Figure 4C, bars 2-a and 2-b, and Figure 4B. The Altona

Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds

• Natalya Akhmetdinova,
• Ilgiz Biktagirov and
• Liliya Kh. Faizullina

Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185

• simple building blocks [72]. The main feature of light-induced transformations is the involvement of electronically excited states that occur during photon absorption, leading to the formation of reactive intermediates causing significant changes in chemical compound reactivity. As a result, light energy

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• but not limited to methyl laurate, has found application in a variety of direct and indirect food additive applications [94]. The Hansen solubility parameter is a numerical expression that quantifies a molecule's cohesive energy density from non-polar, polar, and hydrogen-bonding interactions. It is a

• . As well-known the Hildebrand solubility parameter (HSP, δT) has been defined as a measure of the cohesive energy density of a material, thus facilitating prediction of the solubility of a solute in a solvent [96]. Methyl laurate has been found to have HSPs that are in close proximity to those that

• approximately ≈ 6.57 MPa1/2. The radius of interaction (Ro) for a typical small organic molecule, such as the nitrone, is estimated to be approximately 7.5 MPa1/2 which value is usually determined for solute molecules [97][99]. The relationship between Ra and Ro is denoted by the term relative energy difference

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

• synergistic binding mechanism driven by cavity complementarity, and the energy of the PBG–iodide complex is lower than that of the WDG–iodide complex, it indicates that PBG forms a thermodynamically more stable complex with iodide ions compared to WDG. This stability difference arises from the distinct

• conformational behaviors of the two macrocycles. PBG's flexible benzene ring allows for induced-fit binding, where the macrocycle dynamically adjusts its cavity to optimize interactions with iodide, minimizing energy through conformational adaptability. WDG's rigid fluorene backbone relies on a preorganized

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

• increasingly require rethinking and developing new structural designs that incorporate more efficient and advanced photoswitches to fully realize their potential. Keywords: macrocycle; photoisomerization; photoswitches; rotaxanes; shuttling; Introduction Harnessing light energy to control intra- and

• , spirobenzopyran, stilbene and stiff-stilbene (Figure 2). Systems whose photoinduced behavior primarily depends on photoredox or energy-transfer mechanisms fall outside the scope of this review. Review Rotaxanes featuring photoswitches on the axle Rotaxanes that incorporate photoswitchable units into the axle are

• . Although no shuttling or energy transfer process was observed, both rotaxanes presented good photoisomerization behavior. Remarkably, the use of cucurbit[6]uril macrocycles enhanced the photoisomerization. Later, Liu and co-workers designed a symmetric [3]rotaxane where the pH-responsive shuttling motion

Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis

• Peng-Xi Luo,
• Jin-Xuan Yang,
• Shao-Min Fu and
• Bo Liu

Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177

• key late-stage step in this total synthesis, the Norrish–Yang photocyclization exhibits high chemoselectivity and efficiency. It regulates selectivity through C–H bond dissociation energy and restricted bond rotation, constructing a 6/6/4 fused ring system with three contiguous quaternary carbons

• : reactive substrates exhibited λmax < 460 nm (yellow-orange), whereas unreactive ones showed λmax > 460 nm (dark red-purple). This suggests insufficient excitation energy for Norrish type-II hydrogen abstraction in the latter. Such chromophore-dependent reactivity provides critical insights for designing

• cyclization of the saturated C5–C6; c) calculated Gibbs free energy difference (ΔΔG‡) for 1,5-HAT processes of 22 and 30. Total synthesis of avarane-type meroterpenoids. Total synthesis of gracilisoid A. Divergent total synthesis of gracilisoids B–I. Mechanism of the late-stage biomimetic photooxidation

Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

• Suvenika Perera,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176

• ], and non-conventional adsorbents [14]. Although activated carbon is widely used, its ability to capture polar compounds is limited and the regeneration process is complex and energy-intensive [15]. In work that stimulated supramolecular chemists to enter the game, Dichtel and co-workers demonstrated

Enantioselective radical chemistry: a bright future ahead

• Anna C. Renner,
• Sagar S. Thorat,
• Hariharaputhiran Subramanian and
• Mukund P. Sibi

Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174

• preparation of chiral β-aminoalcohols [63]. Chiral copper(I) complexes convert imidate radicals, formed transiently through energy-transfer catalysis, to oxazolines. The transformation includes a regioselective and enantioselective HAT process. Upon blue LED irradiation, oxime imidates (derived from alcohols

Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates

• Gyöngyvér Pusztai,
• László Poszávácz,
• Anna Vincze,
• András Marton,
• Ahmed Qasim Abdulhussein,
• Judit Halász,
• András Dancsó,
• Gyula Simig,
• György Tibor Balogh and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169

• calibration was performed using leucine enkephalin as the reference compound (m/z 556.2771), introduced at 15 µL/min. Data acquisition was performed in MSE mode with alternating low collision energy (6 eV) and ramped high-energy collision dissociation (20–40 eV). The mass range was set from 50 to 1200 Da

A m-quaterphenyl probe for absolute configurational assignments of primary and secondary amines

• Yuka Takeuchi,
• Mutsumi Kobayashi,
• Yuuka Gotoh,
• Mari Ikeda,
• Yoichi Habata,
• Tomohiko Shirai and
• Shunsuke Kuwahara

Beilstein J. Org. Chem. 2025, 21, 2211–2219, doi:10.3762/bjoc.21.168

• of all local minima employing DFT at the B3LYP/6-31G* level of theory [47]. Four low-energy conformers of (S)-3a were identified within 10.0 kJ/mol (Figure 3). Among them, conformers A and D exhibited an M twist between the long axes of the biphenyl chromophores, whereas conformers B and C displayed

• )-3a–g and (R)-3h using MMFF. All local minimum conformers were then optimized with DFT using the B3LYP/6-31G* model [47]. The lower energy conformers with relative energies ranging from 0.0 to 10.0 kJ/mol were selected. By the Bolzmann distribution based on the energy difference of the conformers at