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

• interactions to achieve directionality (E→Z), synonymous with conventional photocatalyzed isomerization processes [19], it serves as a rapid reaction probe to support sensitization via the generation of a photostationary state equilibrium. The use of Ir(ppy)3 (Table 1, entry 1), an efficient sensitizer for the

• state catalyst are not operational (see Supporting Information File 1 for full details), providing support for an EnT mechanism, while exposing the Z-isomer (Z)-1a to the model reaction conditions, led to the generation of a similar photostationary state equilibrium of isomers, characteristic of an EnT

• . Probing boron effects on reactivity (A) and confirming the generation of a photostationary state equilibrium (B). Standard reaction conditions: (E)-1 (0.1 mmol), xanthone (5 mol %), MeCN (0.03 M), rt, 16 h. Probing EnT catalysis enabled [2 + 2] cycloaddition of simple alkenylboronic esters. Establishing

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

• positively charged nitrogen atom is broken heterolytically, leading to the final pyrrolidine-2,3-dione derivatives 5a–e and 4-methoxybenzylamine (Scheme 3). Due to the higher basicity of methylamine as compared to 4-methoxybenzylamine [25], the transimination equilibrium is shifted towards product 5a–e and

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

• -hydrazones, respectively. A thermodynamic control of the reaction outcome (i.e., especially enantioselectivity) would require the possibility to approach an equilibrium between 9 and 10 (seeing the reversibility of step 9 → 10), in which case the relative energies of stereoisomeric forms of 10 determine the

• experimentally achievable ee values. Maximal theoretical ee values are 70% "S" for Z-hydrazone and 70% "R" for E-hydrazone. The relatively high racemization barriers in 9 preclude a Curtin–Hammett scenario (with fast pre-equilibrium), which would otherwise render the enantiomeric outcome (ee value) independent

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

• is flexible and the two senses of helicity – and other conformations – undergo rapid equilibrium rendering the C1 and the C1·Me6CHDA complex achiral. The centroids of the aromatic sidewall are 0.9698 Å (1.1193 Å) above and 1.3090 Å (1.4832 Å) below the mean plane of the glycoluril methine and

Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• formaldehyde and ammonia in situ by heating [83]. Under these conditions, the water present in hydrated HMTA is sufficient for this hydrothermal decomposition to occur. On the other hand, an excess of ammonia must be added to the reaction mixture to shift the equilibrium towards the imine. Using this procedure

Organocatalytic kinetic resolution of 1,5-dicarbonyl compounds through a retro-Michael reaction

• James Guevara-Pulido,
• Fernando González-Pérez,
• José M. Andrés and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2025, 21, 473–482, doi:10.3762/bjoc.21.34

• the kinetic resolution at a concentration of approximately ten millimolar (mM) to prevent the Michael retro-Michael equilibrium from affecting the process. Keywords: 1,5-dicarbonyl; equilibrium; kinetic resolution; organocatalysis; retro-Michael; Introduction For many years, enantiomers have been

• racemization when treated with inorganic bases [25], which had led us to check the equilibrium between Michael and the retro-Michael reaction (Scheme 1). These observations have prompted us to conduct further research into this reaction for potential applications in the kinetic resolution of these adducts. In

• initially promotes deracemization by rapidly reacting with the enantiomer (3R,4S) of the diastereomer anti-1. Over time, the initial equilibrium is established either because the catalyst begins to react with the syn-diastereomer or because, once the retro-Michael reaction has occurred, the catalyst

Beyond symmetric self-assembly and effective molarity: unlocking functional enzyme mimics with robust organic cages

• Keith G. Andrews

Beilstein J. Org. Chem. 2025, 21, 421–443, doi:10.3762/bjoc.21.30

• that might permit tuning of several consecutive catalytic steps [395], induced-fit binding, product release, allostery [396][397], or signaling. For the acyl transfer reaction, cage 1 is an inferior catalyst compared to cage 2, which we have postulated is due to the larger equilibrium cage height

The effect of neighbouring group participation and possible long range remote group participation in O-glycosylation

• Rituparna Das and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2025, 21, 369–406, doi:10.3762/bjoc.21.27

Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones

• Yurii A. Sayapin,
• Eugeny A. Gusakov,
• Inna O. Tupaeva,
• Alexander D. Dubonosov,
• Igor V. Dorogan,
• Valery V. Tkachev,
• Anna S. Goncharova,
• Gennady V. Shilov,
• Natalia S. Kuznetsova,
• Svetlana Y. Filippova,
• Tatyana A. Krasnikova,
• Yanis A. Boumber,
• Alexey Y. Maksimov,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26

• in the weak field at 15.2–15.8 ppm for 7a,b and 14.3–14.8 ppm for 8a,b, respectively, as a broadened singlet peak. A dynamic equilibrium of tautomeric forms 7, 8 (OH)–7, 8 (NH) exists in solution, which can be detected by the broadening of the hydroxy group proton signal in the 1H NMR spectrum

• studied compounds. The difference in the energy characteristics of the (NH) and (OH) tautomeric forms of compounds 7a, 7b, 8a, and 8b in the polar solvent and the gas phase is small (2.0–3.8 kcal/mol), and probably the nature of the solvent can influence the shift of the equilibrium towards one of the

• large Stokes shift values (Table 2, Figure 5). This is consistent with the above conclusion about the existence of tautomeric equilibrium 7,8 (OH)–7,8 (NH) in solutions based on NMR data and DFT quantum chemical calculations (Scheme 2). The emission with a larger Stokes shift appears to correspond to

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

• therapeutic methods [78][79][80]. Such reactions can be performed at particular locations such as DNA or tubulin, when the photocatalyst is placed via a tethered ligand (Scheme 17) [81]. In the present case, the triarylmethine dye 67 was used as sensitizer. It is in equilibrium with the lactone form 68 and

Three-component reactions of conjugated dienes, CH acids and formaldehyde under diffusion mixing conditions

• Dmitry E. Shybanov,
• Maxim E. Kukushkin,
• Eugene V. Babaev,
• Nikolai V. Zyk and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2025, 21, 262–269, doi:10.3762/bjoc.21.18

• 9 in toluene for 7 h led to the formation of an equilibrium mixture of these compounds in a ratio of ≈2:1 (Scheme 5). We propose that the reversible transformation of 8 to 9 proceeded via the intermediate formation of zwitterion 21, in which the charges were stabilized by mesomeric effects under

Heteroannulations of cyanoacetamide-based MCR scaffolds utilizing formamide

• Marios Zingiridis,
• Danae Papachristodoulou,
• Despoina Menegaki,
• Konstantinos G. Froudas and
• Constantinos G. Neochoritis

Beilstein J. Org. Chem. 2025, 21, 217–225, doi:10.3762/bjoc.21.13

• Goals (SDGs), wherein the 7th goal focuses on ensuring access to affordable, renewable and clean energy [1]. Moreover, the European Union has committed to ambitious environmental targets as part of the European Green Deal [2]. Advancements in C1 chemistry are pivotal to achieving this equilibrium. As

Nickel-catalyzed cross-coupling of 2-fluorobenzofurans with arylboronic acids via aromatic C–F bond activation

• Takeshi Fujita,
• Haruna Yabuki,
• Ryutaro Morioka,
• Kohei Fuchibe and
• Junji Ichikawa

Beilstein J. Org. Chem. 2025, 21, 146–154, doi:10.3762/bjoc.21.8

• findings suggest that nickelacyclopropanes E and 2-fluorobenzofurans 1 are in equilibrium (see Scheme 5). Consequently, in the absence of arylboronic acids 2, the consumption of 1 was suppressed. Upon adding phenylboronic acid (2a, 1.0 equiv) to the above reaction mixture, the coupling proceeded, producing

Direct trifluoroethylation of carbonyl sulfoxonium ylides using hypervalent iodine compounds

• Radell Echemendía,
• Carlee A. Montgomery,
• Fabio Cuzzucoli,
• Antonio C. B. Burtoloso and
• Graham K. Murphy

Beilstein J. Org. Chem. 2024, 20, 3182–3190, doi:10.3762/bjoc.20.263

• reductive elimination (path 1) [37][38][39]. This pathway initiates by formation of a halogen bond complex between 1a and the trifuoroethyl(mesityl)iodonium ion 2a’, where adduct XB-1 is presumably in equilibrium with isomeric XB-2. Reductive elimination of the iodoarene from XB-2 would furnish B, whose

• was found at a relative energy of 10.1 kcal/mol, where the C–I–C bond angle is 178° with C–I bond lengths of 2.2 Å (I–CH2CF3) and 2.9 Å. The reaction coordinate diagram for path 1 showed a near barrierless equilibrium between halogen bond adducts XB-1 and XB-2, where XB-2 has a C–I–C bond angle of 86

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

• reported the pseudorotaxane equilibrium observed by mixing α-CD and the axle molecules bearing methylpyridinium moieties on their ends, where the bigger rim of CD (the head side) was likely to include the dumbbell (Figure 8A) [71][72]. Concurrently, Komiyama and co-workers performed the kinetic analysis of

Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety

• Anastasia I. Ershova,
• Sergey V. Fedoseev,
• Konstantin V. Lipin,
• Mikhail Yu. Ievlev,
• Oleg E. Nasakin and
• Oleg V. Ershov

Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251

• group, a strong blue shift occurred down to 394 nm. The only exception was a solution of 1i in acetic acid, where two peaks were observed. Apparently, the weaker acetic acid caused just a partial protonation of the amino group, and the equilibrium shown in Scheme 2 was observed. This was evidenced by

• solutions of compounds 1a–i in toluene (top) and DMSO (bottom) taken under a 365 nm UV lamp. Normalized solid-state emission spectra of compounds 1a–i (bottom) and photos of powders taken under a 365 nm UV lamp (top). Synthesis of donor–acceptor 1-pyrindane derivatives 1. Plausible equilibrium of compounds

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

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

• upon binding of the enolate molecule to iodine either through a carbon–iodine or an oxygen–iodine bond. Both intermediates, I and II, are in rapid equilibrium with each other and further undergo two different types of reactions: [1,2]-ligand coupling and [2,3]-rearrangement (Scheme 2). Either of these

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• -glycosyl aniline β-22b which was formylated to give 22c in 74% yield (Scheme 16) [24]. Product 22c resides as a mixture of α- and β-anomers, because an anomeric equilibrium was activated during the acid-mediated formylation. The cyclization of 22c with oxalyl chloride, carried out under forcing conditions

• (TiCl4, chlorobenzene, 85 °C), afforded anomerically pure β-configured isatin-N-glucoside β-23a in 80% yield. The product was formed as the pure β-anomer, because the anomeric equilibrium was again active in the presence of the Lewis acid and the β-anomer is thermodynamically favored because of the

• in case of the oxoindirubins 41 seems to decrease this unfavorable dipol situation in case of the E-configured isomers. It is likely, that an E/Z isomerization takes place under acidic conditions. The barrier of this equilibrium is most likely lowered by the presence of the ring oxygen as it

Synthesis of tricarbonylated propargylamine and conversion to 2,5-disubstituted oxazole-4-carboxylates

• Kento Iwai,
• Akari Hikasa,
• Kotaro Yoshioka,
• Shinki Tani,
• Kazuto Umezu and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2024, 20, 2827–2833, doi:10.3762/bjoc.20.238

• hydrated product 9. The less acidic ammonium acetate was effective for the ring closure of 4a (Table 4). When a solution of 4a and ammonium acetate was heated for 15 h, a 28% yield of 5a was obtained (Table 4, entry 1). Ammonium acetate dissociates into ammonia and acetic acid in an equilibrium upon

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• preparation of biologically active compounds [15]. The synthesis was achieved via a sulfonyl group rearrangement driven by the azide–tetrazole equilibrium in quinazolines. The researchers utilized two synthetic pathways to prepare the target compounds. The first pathway involved a nucleophilic aromatic

Computational design for enantioselective CO₂ capture: asymmetric frustrated Lewis pairs in epoxide transformations

• Maxime Ferrer,
• Iñigo Iribarren,
• Tim Renningholtz,
• Ibon Alkorta and
• Cristina Trujillo

Beilstein J. Org. Chem. 2024, 20, 2668–2681, doi:10.3762/bjoc.20.224

• K) suggest a kinetically controlled reaction. To further shift the chemical equilibrium toward CO2 capture, increasing steric hindrance at the epoxide was explored by introducing bulky substituents into the scaffold. This resulted in an increase in activation barriers for adduct formation. Including

Photoredox-catalyzed intramolecular nucleophilic amidation of alkenes with β-lactams

• Valentina Giraldi,
• Giandomenico Magagnano,
• Daria Giacomini,
• Pier Giorgio Cozzi and
• Andrea Gualandi

Beilstein J. Org. Chem. 2024, 20, 2461–2468, doi:10.3762/bjoc.20.210

• as final product, characterized by significant ring strain [59]. Under light irradiation, PhSSPh is in equilibrium with the corresponding thiyl radical, which is subsequently reduced to thiophenolate by PC•, originating from the reduction of *PC+. The reduction potential of PhS−/PhS• (Epred = +0.45 V

Phenylseleno trifluoromethoxylation of alkenes

• Clément Delobel,
• Armen Panossian,
• Gilles Hanquet,
• Frédéric R. Leroux,
• Fabien Toulgoat and
• Thierry Billard

Beilstein J. Org. Chem. 2024, 20, 2434–2441, doi:10.3762/bjoc.20.207

• ’) decreases with time in favor of the thermodynamic Markovnikov regioisomer (2e, 2i). This phenomenon cannot occur for products 2g and 2h because the kinetic and thermodynamic products are the same. This observation confirms the existence of an equilibrium between the episelenonium and the final products 2

Evaluating the halogen bonding strength of a iodoloisoxazolium(III) salt

• Dominik L. Reinhard,
• Anna Schmidt,
• Marc Sons,
• Julian Wolf,
• Elric Engelage and
• Stefan M. Huber

Beilstein J. Org. Chem. 2024, 20, 2401–2407, doi:10.3762/bjoc.20.204

• reaction) were considered, as such a coarse approximation cannot be applied after reaching the plateau due to equilibrium processes (see Supporting Information File 1 for further details). The determined TOF of tetrafluoroiodolium salt 2BArF reaches a value of 80 h−1, almost 1.7 times as high as the TOF of