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

• ][44][45] and systems for energy storage [46][47]. The phototautomerism of azodyes refers to the reversible isomerization process that occurs upon exposure to light, leading to exchange of a proton [48][49]. The obtained tautomeric forms have different optical and chemical properties, which make these

• , populating both KE and KK, which undergo ground-state PT to E and K, respectively. Therefore, it is crucial to have the intermediate keto tautomers KE and KK higher in energy in the ground state, comparing to the paired terminal E and K, respectively, in order to provide efficient switching. The additional

• part is flexible, the excitation of E can lead to E/Z isomerization, which competes with the initial excited-state PT process, reducing its efficiency [52]. The theoretical data, collected in Table 1, can shed light on the potential energy landscape in the ground state for the studied compounds

High-pressure activation for the solvent- and catalyst-free syntheses of heterocycles, pharmaceuticals and esters

• Kelsey Plasse,
• Valerie Wright,
• Guoshu Xie,
• R. Bernadett Vlocskó,
• Alexander Lazarev and
• Béla Török

Beilstein J. Org. Chem. 2025, 21, 1374–1387, doi:10.3762/bjoc.21.102

• generation. Using water as pressure transmitting fluid, the reaction vessel is immersed in water minimizing fire hazard during the reactions. Finally, most procedures can be carried out at ambient temperature, improving safety and energy efficiency. Energy efficiency is also supported by the nature of the

• reactions; although pressurizing the system requires energy, once the system is pressurized it does not need energy to maintain it. This can result in remarkable energy saving especially in long reactions. In order to aid the understanding of this technique a schematic design of a high hydrostatic pressure

• many reactions to proceed at ambient temperature, resulting in convenient, safe, and energy-efficient protocols; and finally, (iv) HHP instruments allow broadly tuneable procedures that include modifying pressure, temperature, reaction time, or pressure cycles to ensure easy process optimization. Based

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

• by the same research group [65][66], the Ir catalyst initially interacts through hydrogen bonds with the quinolone substrate 84, and then upon irradiation, energy transfer occurs to the unbound ketone which enantioselectively reacts with the bound quinolone. Unfortunately, investigations of the

• still runs smoothly, if the aryl is substituted for cyclohexyl. The proposed mechanism, supported by control experiments, deuterium exchange studies and energy calculations, consists of the following steps: conjugate addition of the carbene to the allenoate, regioselective addition of the resulting

• epimerisation to obtain diastereoenriched spirocycles, utilising t-BuOK/t-BuOH for the anti-diastereomer 163 and LDA/PivOH at −78 °C for the syn-diastereomer 162 (dr >10:1 in both protocols). Mechanistic and computational studies suggested the following series of steps: excitation of 159 via energy transfer

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

• molecules. On the other hand, C–H bonds exhibit low reactivity due to their relatively high bond dissociation energy (BDE) (Figure 1a). Therefore, the direct functionalization of C–H bonds is extremely challenging [1][2][3][4][5]. In recent decades, transition-metal-catalyzed C–H bond functionalization

• activation energy modulation during transition state formation. Specifically, donor/acceptor electronic configurations in the substrate could either stabilize or destabilize the transient hybrid state, thereby thermodynamically governing the energy barrier for intermolecular HAT progression. When the partial

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

• ], medicine [3], sensing [4] and energy storage [5]. Typically, bulk graphene is obtained using a top-down approach, where graphite is exfoliated using chemical or mechanical methods [6][7]. However, this method does not provide precise control over the structure of graphene and graphenoid materials, which is

• , resulting in a significant dipole moment of 1.08 D [18]. Due to its unique non-alternant topology, azulene exhibits a smaller energy gap compared to that of isomeric naphthalene and unusual emission from the S2 state (anti-Kasha’s emission), as a consequence of its non-mirror related highest occupied

• is why, in many cases, the aromaticity of the azulene moiety is discussed, particularly through the analysis of the most used variations of NICS (nucleus-independent chemical shifts) parameters [30]. Additionally, whenever possible, information on the wavelength of the lowest-energy optical

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

• energy (327 kJ/mol) and is less reactive compared to alkyl bromides or iodides. Previous methodologies predominantly relied on alkyl bromides and iodides due to their lower bond dissociation energies. By leveraging the excited-state reactivity of Pd(0) complexes under blue LED irradiation, this method

Optimized synthesis of aroyl-S,N-ketene acetals by omission of solubilizing alcohol cosolvents

• Julius Krenzer and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2025, 21, 1201–1206, doi:10.3762/bjoc.21.97

• protocol, not only does the synthesis need less energy, it can also be carried out more sustainably, making it "greener." Conclusion Changing the solvent system from 1,4-dioxane/ethanol to 1,4-dioxane and reacting the aroyl chlorides and 2-methyl-N-benzylbenzothiazolium salts at room temp for 0.5–1 h gives

Selective monoformylation of naphthalene-fused propellanes for methylene-alternating copolymers

• Kenichi Kato,
• Tatsuki Hiroi,
• Seina Okada,
• Shunsuke Ohtani and
• Tomoki Ogoshi

Beilstein J. Org. Chem. 2025, 21, 1183–1191, doi:10.3762/bjoc.21.95

• (HOMOs) was similarly delocalized to multiple naphthalene units, the energy for [3.3.3] (−7.23 eV) was higher than that of [4.3.3] (−7.32 eV). Upon formylation, the HOMO energies of [3.3.3] and [4.3.3] were stabilized to −7.44 eV and −7.55 eV by 0.21 eV and 0.23 eV, respectively. These values correlated

Enhancing chemical synthesis planning: automated quantum mechanics-based regioselectivity prediction for C–H activation with directing groups

• Julius Seumer,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2025, 21, 1171–1182, doi:10.3762/bjoc.21.94

• structure on the potential energy surface is located, which can be done straightforwardly using standard optimization algorithms. While the use of intermediate energies provides a computationally efficient alternative to explicit transition state searches, it rests on the assumption that there is a

• directing groups are extracted from 150 molecules, taken from Chen et al. [4], for which reaction sites are known from experiments. For each directing group, the energy of the palladacycle intermediate with H-abstraction at a specific site is calculated using B3LYP-D3/LACVP** (6-31G**, except on heavy atoms

• where effective core potential was used) in CH2Cl2, and compiled into a hierarchical list for the determination of the reaction site with the lowest energy. Using the hierarchy, the regioselectivity of C–H activations could be rationalized for the 150 molecules with remarkable accuracy. While this

A multicomponent reaction-initiated synthesis of imidazopyridine-fused isoquinolinones

• Ashutosh Nath,
• John Mark Awad and
• Wei Zhang

Beilstein J. Org. Chem. 2025, 21, 1161–1169, doi:10.3762/bjoc.21.92

• formation of 8a,h,l,m,n and 8r (68–85%), R3 = phenyl resulted in 8b,g and 8q in 78–82% yields, R3 = isopropyl and cyclopentene gave 8c,f,p and 8d in greater than 70% yields, and R3 = 2-morpholinoethyl gave 8e,i and 8s in 60–76% yields. The energy status for the transformation of compound 6a to 8a was

• calculated using the Gaussian 16 software (Figure 3) [21]. The N-acylated compound 6a has a baseline relative energy of 0 kJ/mol, while the transition state of the Diels–Alder (TS-DA) reaction presents the highest energy barrier at 1.221 kJ/mol. The DA adduct shows a little lower energy at 1.001 kJ/mol

• , indicating a smooth transition from the transition state to the product. The final dehydrative ring-opening gives products by decreasing the energy to 0.978 kJ/mol. Computational analysis indicates that the IMDA step has a high energy barrier which needs a catalyst, while the dehydrative re-aromatization

Gold extraction at the molecular level using α- and β-cyclodextrins

• Susana Santos Braga

Beilstein J. Org. Chem. 2025, 21, 1116–1125, doi:10.3762/bjoc.21.89

• , α-CD·cyanoauride. Moreover, the use of α-CD offers the benefit of a selective isolation of Au(CN)2. The path is open for the integration of the α-CD stripping method into commercial gold mining protocols, with expected reductions in costs, energy consumption, and environmental impact. Research on

Supramolecular assembly of hypervalent iodine macrocycles and alkali metals

• Krishna Pandey,
• Lucas X. Orton,
• Grayson Venus,
• Waseem A. Hussain,
• Toby Woods,
• Lichang Wang and
• Kyle N. Plunkett

Beilstein J. Org. Chem. 2025, 21, 1095–1103, doi:10.3762/bjoc.21.87

• and I. Without any metal coordination, DFT suggests conformer I is more stable than conformer II by ≈60 kJ/mol. However, upon complexation with Li+, both complexes 2 and 3 are remarkably similar in energy with the difference of less than 1 kJ/mol. This very small energy difference should be too small

• similar trend was seen in the HIM–Na+ crystals where complex 4 and complex 5 are similar in energy with a difference of less than 1.5 kJ/mol. While both Li+ and Na+ crystals were prepared in similar conditions, the difference in the resulting crystal structure (e.g., location of benzyl rings) could arise

• from a difference in the overall nucleation events of a given crystal and not necessarily from a difference in energy between conformations. DFT results of the binding energy of the two metals shows that the isolated Li+ complex 2 (1029.87 kJ/mol) is more stable than the Na+ complex (897.77 kJ/mol

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

Synthesis of pyrrolo[3,2-d]pyrimidine-2,4(3H)-diones by domino C–N coupling/hydroamination reactions

• Ruben Manuel Figueira de Abreu,
• Robin Tiedemann,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2025, 21, 1010–1017, doi:10.3762/bjoc.21.82

• similar absorption feature, but slightly bathochromically shifted, was observed for the thienyl-substituted derivative 4m. The strongly electron-donating N,N-dimethylaminophenyl group (products 4k,l) resulted in segmentation into two absorption bands accompanied by a strongly red-shifted lower energy

Recent total synthesis of natural products leveraging a strategy of enamide cyclization

• Chun-Yu Mi,
• Jia-Yuan Zhai and
• Xiao-Ming Zhang

Beilstein J. Org. Chem. 2025, 21, 999–1009, doi:10.3762/bjoc.21.81

• bridge cycle [36][37]. The excellent diastereoselectivity in this radical cyclization was further rationalized by DFT calculations, which suggests an energy discrepancy of the hydrogen atom transfer process from different faces of the resulting α-hydroxyl radical. Final reduction of the ketone and amide

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

• –LUMO energy gaps are identical and their respective transitions exhibit identical transition dipole moments [19][32][33]. For the |D1⟩ transition these two degenerate transitions mix in an out-of-phase fashion leading to the observed weak absorption at 544 nm (see Figure 1b and c). When looking at the

• 374 nm and 544 nm. Therefore, the higher energy for excitation to the D2 state must quickly be lost during relaxation to the relaxed D1 state, rendering the emission indistinguishable from the higher energy excitation. While for TTM and PTM there is no transient absorption data to further elucidate

• iodine should break the symmetry; however, no effect on the absorption spectra and especially on the lower energy |D1⟩ transition has been reported [45]. Interestingly, substitution of one of the para-chlorines in TTM by iodine (I-TTM) has been reported to enable Pd-catalyzed cross-coupling, allowing

Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts

• Katy Medrano-Uribe,
• Jorge Humbrías-Martín and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76

• (RAFT) polymerization [18]. Moreover, in 2022, Zysman-Colman and collaborators showed that molecule 3, initially synthesized as a TADF (thermally activated delayed fluorescence) emitter [14], can be used as a PC under electron-transfer (ET) and energy-transfer (EnT) processes (Figure 1a) [19]. All the

• experimentally in the solvatochromism study of fluorescence using solvents with diverse polarities (see Supporting Information File 1, Figure S9). Indeed, the density functional theory (DFT) calculation performed at WB97XD/Def2TZVP level of theory showed the lowest value for the HOMO–LUMO energy gap in compound

• behavior is supported by the DFT studies, which suggested a better spatial separation between the HOMO and LUMO. As expected, the HOMO–LUMO energy gap followed a trend that is dependent on the electron-donating capacity of the nitrogen heterocycles and amine present in compounds 5e (2.9 eV), 5d (3.5 eV

Recent advances in controllable/divergent synthesis

• Jilei Cao,
• Leiyang Bai and
• Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

• while regenerating the catalytic species Int-82. Comparative kinetic analysis revealed a marked preference for alkyl iodide activation, as demonstrated by its substantially lower activation energy barrier compared to alkyl bromide analogs (path b). This energetic advantage facilitates preferential

• imides and TMS-alkynes, enabling the rapid construction of S(VI)–C(sp2) or S(VI)–C(sp) bonds efficiently (Scheme 24) [55]. This linkage utilizes the high bond dissociation energy (BDE = 135 kcal/mol) of silicon–fluorine bonds, employing trifluoroborate as a fluorine transfer reagent to simultaneously

Light-enabled intramolecular [2 + 2] cycloaddition via photoactivation of simple alkenylboronic esters

• Lewis McGhie,
• Hannah M. Kortman,
• Jenna Rumpf,
• Peter H. Seeberger and
• John J. Molloy

Beilstein J. Org. Chem. 2025, 21, 854–863, doi:10.3762/bjoc.21.69

• , Germany 10.3762/bjoc.21.69 Abstract The photoactivation of organic molecules via energy transfer (EnT) catalysis is often limited to conjugated systems that have low-energy triplet excited states, with simple alkenes remaining an intractable challenge. The ability to address this limitation, using high

• energy sensitizers, would represent an attractive platform for future reaction design. Here, we disclose the photoactivation of simple alkenylboronic esters established using alkene scrambling as a rapid reaction probe to identify a suitable catalyst and boron motif. Cyclic voltammetry, UV–vis analysis

• , and control reactions support sensitization, enabling an intramolecular [2 + 2] cycloaddition to be realized accessing 3D bicyclic fragments containing a boron handle. Keywords: boron; catalysis; [2 + 2] cycloaddition; energy transfer; photochemistry; Introduction The strategic use of a photon to

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

• displays higher hydration energy than that of sulfate, and the tetrahedral shape of sulfate anion matches the pseudo-tetrahedral cavity of the folded hexaurea receptor [30]. Secondly, for Cs+ cations, two types of Cs+ binding are shown in the solid state. Two type-(I) cesium cations are found to be

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

• -art technologies ranging from energy-storage materials [6][7] to pharmacology [8][9][10][11], materials chemistry [12][13], control of peptides structure [14][15] or proteins [16], as antibacterial agents [17][18], smart coating [19], or multivalent photoresponsive systems [20][21], to name only a few

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

• necessary to elucidate the toxicological profiles of compounds 5c and 5e prior to consideration for drug development. Analysis of reactivity descriptors The primary reactivity descriptors, such as frontier molecular orbital energies (EHOMO and ELUMO), energy gap (ΔEL-H), ionization energy (IE), electron

• docking scores (DS) revealed a range of binding affinities, with values ranging from −8.55 kcal/mol (iNOS–DEX) to −9.51 kcal/mol (iNOS–5e). Notably, iNOS–5e exhibited the most favorable binding energy, suggesting it has the strongest interaction with the iNOS enzyme. Hydrogen bonding analysis demonstrated

• optimized at the M062X/6-31+G(d) level of theory using Gaussian 16 software [48]. The reactivity, stability, and electronic properties of molecules determined by key parameters such as frontier molecular orbital energies (EHOMO and ELUMO), energy gap (ΔEL-H), ionization energy (IE), electron affinity (EA

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

• catalytic back-conversion studies. Keywords: heterocycles; molecular solar thermal systems; norbornadiene; photochemistry; quadricyclane; Introduction In recent decades, the demand for renewable energy has increased tremendously [1]. A promising alternative to fossil fuels is the utilization of so-called

• molecular solar thermal (MOST) systems [2]. These systems operate on the principle of converting an energy-lean isomer into an energy-rich form by irradiating it with sunlight, effectively storing energy in the form of chemical strain energy [3]. On demand, by application of an external stimulus such as

• heat, catalysis, or an electrochemical input [4][5][6], the stored energy can be released converting the molecule back in the parent form (Figure 1). Typical MOST systems are azobenzenes (E/Z-isomerization) [7][8][9][10], the isomerization of dihydroazulenes/vinylheptafulvenes [11][12][13], conversion

Recent advances in the electrochemical synthesis of organophosphorus compounds

• Babak Kaboudin,
• Milad Behroozi,
• Sepideh Sadighi and
• Fatemeh Asgharzadeh

Beilstein J. Org. Chem. 2025, 21, 770–797, doi:10.3762/bjoc.21.61

• . Electricity can perform the oxidation and reduction process by exchanging electrons on the electrode surface in a region called the double layer (DL) [12]. Unlike traditional methods that require high temperature, pressure, and external oxidants, electrochemistry is an efficient and energy-saving approach

• Electrochemical reaction cells When a redox reaction occurs indirectly, chemical energy is transformed into electrical energy. A device that facilitates this conversion is known as an electrochemical cell. Electrochemical reaction cells are divided into two primary categories: galvanic (voltaic) and electrolytic

• . They consist of two electrodes – anode (where oxidation occurs) and cathode (where reduction occurs) – immersed in an electrolyte. Galvanic cell The redox reaction occurs spontaneously in these cells, converting chemical energy into electrical energy. The potential difference between the two electrodes

Development and mechanistic studies of calcium–BINOL phosphate-catalyzed hydrocyanation of hydrazones

• Carola Tortora,
• Christian A. Fischer,
• Sascha Kohlbauer,
• Alexandru Zamfir,
• Gerd M. Ballmann,
• Jürgen Pahl,
• Sjoerd Harder and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2025, 21, 755–765, doi:10.3762/bjoc.21.59

• ), is 0.5 kcal·mol−1 lower in energy. Substrate 1 may conceivably undergo a tautomerization towards an iminol form, 14.2 kcal·mol−1 higher in energy. Hence, amounts of this isomer are negligible in equilibrium and do not play a role also in the formation of the pre-complex 3. The competing cyanide form

• of 9 (with a collinear arrangement of Ca–C–N) was found to be a sizable 3.3 kcal·mol−1 higher in energy than the preferred isonitrile, conforming to earlier anticipations based on computations of alkaline earth metal dicyanides [54]. Similarly, it also has been recently observed that boron-catalyzed

• [1,2]H shift is orbital symmetry forbidden and has, hence, a high barrier of 39.8 kcal·mol−1, and also because a – conceivable – intermittently at carbonyl oxygen protonated species (i.e., on an iminol-type pathway) is considerably higher in energy than 10 or 11. The TMS-bound product 12, proposed in