Knoevenagel condensation of 4,5- and 1,8-diazafluorenes

• Darya S. Cheshkina,
• Christina S. Becker,
• Alina A. Sonina and
• Maxim S. Kazantsev

Beilstein J. Org. Chem. 2026, 22, 803–812, doi:10.3762/bjoc.22.62

• additionally due to C–H···π intramolecular interactions: φ1 = 106.8(2)° (N3–C13–C12–C5) and φ2 = 99.6(2)° (N4–C18–C12–C5) (Figure 2a). The molecules of 4,5-DPDAF are packed into stacks due to π-stacking interactions between diazafluorenes which are stabilized by C–H···N interactions between pyridine and

• -DPDAF) where Zn is four-coordinated to the nitrogens of the diazafluorene and pyridine rings forming a positively charged cyclic dimer (Figure 2d). The dimers are arranged in a herringbone-type structure via C–H···π, C–Cl···π and π-stacking interactions between diazafluorene and pyridine (Figure 2f

• CH2Cl2 solution and b) optical absorption spectra of 4,5-DPDAF and 1,8-DPDAF in THF. Molecular structure, atom and cycle numbering of 4,5-DPDAF (a) and Zn-4,5-DPDAF (d) with anisotropic displacement ellipsoids drawn at a 50% probability level; crystal structure fragments of 4,5-DPDAF with π-stacking (b

Halogenated azobenzene acrylates: from efficient solution photoswitching to stable solid-state photochromic materials

• Martina Vachtlová,
• Michaela Fecková,
• Vítězslav Zima,
• Jan Podlesný,
• Milan Klikar,
• Oldřich Pytela,
• Patrik Pařík,
• Jakub Opršal,
• Eliška Juhaňáková,
• Veronika Chrtová and
• Filip Bureš

Beilstein J. Org. Chem. 2026, 22, 782–794, doi:10.3762/bjoc.22.60

• crystallization process simultaneously suppressing the counter-effect of the long aliphatic pendant. On the other hand, when a bulky bromine atom is involved, π-stacking is probably much less efficient and only amorphous solidification dominates upon cooling. Whereas the dichloro derivative 1d is a liquid under

Design, synthesis, and biological evaluation of FXR/ASK1 dual-target modulators

• Xi Zhang,
• Jingyan Wang,
• Ziqiang Zhao,
• Caiyi Wang,
• Zenghui Ye,
• Wei-Yuan Ma,
• Jian-Xing Xu and
• Fengzhi Zhang

Beilstein J. Org. Chem. 2026, 22, 771–781, doi:10.3762/bjoc.22.59

• hydrophobic pocket formed by Phe 284, Leu 287, Trp 454, and Phe 461; the dichlorophenyl moiety engages in π–π stacking with Phe 329; and the meta-positioned carboxy group forms a strong electrostatic interaction with Arg 331. The modification strategies for GW4064 are as follows: The stilbene moiety can be

Synthesis and biological evaluation of new brassinosteroid analogs with C-22 benzoate function

• María Núñez,
• Camila Escobar,
• Mario Párraga,
• Mauricio Soto,
• Luis Espinoza-Catalán,
• Katy Díaz and
• Andrés F. Olea

Beilstein J. Org. Chem. 2026, 22, 753–762, doi:10.3762/bjoc.22.57

• compound 19 generates two π–π stacking interactions with Trp564 and Tyr597. Finally, there are also van der Waals interactions with residues Phe60, Phe681, Ile682, Ile706, Tyr642, Tyr599, Pro648, Ile540, Ile563, and Trp564 (Figure 4). The calculated binding energies suggest the following order of activity

• = steroidal skeleton of the structure. Binding modes of compound 19 into BRI1–BAK1 heterodimer. Hydrogen bonds are represented in green segmented lines. π–π stacking is represented by dark pink segmented lines. Hydrophobic interactions are represented by pink segmented lines. Synthesis of compounds 23–28 and

Configuration–packing synergy enabling integrated crystalline-state RTP and amorphous-state TADF

• Ruiyan Wang and
• Yunan Wu

Beilstein J. Org. Chem. 2026, 22, 224–236, doi:10.3762/bjoc.22.16

• activated delayed fluorescence (TADF). Correlating temperature-dependent lifetimes with phase characterization indicate that, in amorphous environments lacking ordered π–π stacking and rigid confinement, the small ΔEST promotes reverse intersystem crossing, yielding delayed fluorescence; whereas in powder

• states, intermolecular interactions enhance spin–orbit coupling and crystallinity suppresses nonradiative decay, thereby activating RTP. This work achieves an integrated “crystalline-state RTP–amorphous-state TADF” regulation within a single molecule. Keywords: imide; π–π stacking; room-temperature

• reasonably inferred that, in the amorphous state, intermolecular π–π stacking interactions are significantly suppressed. This suppression of π–π interactions, along with a more disordered molecular conformation and microenvironment, makes it difficult to establish effective rigid constraints necessary for

Improved synthesis and physicochemical characterization of the selective serotonin 2A receptor agonist 25CN-NBOH

• Adrian G. Rossebø,
• Hannah G. Kolberg,
• Anders E. Tønder,
• Louise Kjaerulff,
• Poul Erik Hansen,
• Karla A. Frydenvang,
• Jesper Østergaard and
• Jesper L. Kristensen

Beilstein J. Org. Chem. 2026, 22, 175–184, doi:10.3762/bjoc.22.11

• two different chloride ions, and the phenol OH moiety interacts with another chloride ion. The triclinic crystal packing (Figure 2b) reveals alternating layers, a polar layer with the observed hydrogen bonds, and a hydrophobic layer with van-der-Waals interactions and π–π-stacking (distance 4 Å

• , oxygen atoms red, and chloride ion green. b) The crystal packing reveals alternating layers, a polar layer with hydrogen bonds (black dashed lines), and a hydrophobic layer with π–π-stacking (grey dashed lines). SCXRD and XRPD spectra of different preparations of 1·HCl. Blue: SCXRD spectrum of 1·HCl. Red

Assembly strategy for thieno[3,2-b]thiophenes via a disulfide intermediate derived from 3-nitrothiophene-2,5-dicarboxylate

• Roman A. Irgashev

Beilstein J. Org. Chem. 2025, 21, 2489–2497, doi:10.3762/bjoc.21.191

• ) derivatives are a valuable class of fused heteroaromatic compounds characterized by rigid planar π-conjugated backbones that provide narrow band gaps, high charge carrier mobility, and intermolecular π–π stacking interactions, making them particularly attractive for the design of organic materials. Indeed

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

• predominance of the trans isomer can be attributed to the stabilizing of secondary orbital interactions in the endo transition state, which results in the formation of this product, in contrast to the exo transition state [53][108]. In this case, the most significant factor is the π–π interaction (π–π stacking

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

• reflects π–π stacking on the external face of G2W1 in the solid. In contrast, the bulkier and non-planar dyes (e.g., rhodamine 6G and methyl violet 6B) are less complementary to the cavity and external faces of glycoluril dimer-based receptors. Accordingly, we decided to conduct a detailed investigation

• walls within the initial dimer are co-planar with each other and the distance between the mean planes of the triphenylene sidewalls is 3.4975 Å (marked with @) which is somewhat longer than the commonly accepted π-stacking distance of 3.4 Å. The mean planes of the external triphenylene walls between the

Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• of ortho-cyclized products 80, enabled by coordination to both the directing group and alkyne (Scheme 17, path a). However, the rigid electron-rich XPhos ligand (L2) promoted para-cyclization due to steric constraints and π–π stacking to yield dihydroquinoline derivatives 82 (Scheme 17, path b). This

Discovery of cytotoxic indolo[1,2-c]quinazoline derivatives through scaffold-based design

• Daniil V. Khabarov,
• Valeria A. Litvinova,
• Lyubov G. Dezhenkova,
• Dmitry N. Kaluzhny,
• Alexander S. Tikhomirov and
• Andrey E. Shchekotikhin

Beilstein J. Org. Chem. 2025, 21, 2062–2071, doi:10.3762/bjoc.21.161

• . Such compounds can intercalate into nucleic acids, primarily through π–π stacking interactions with nitrogenous bases. The introduction of side chains with terminal amino groups enhances binding to oligonucleotides via additional ionic interactions and hydrogen bonds. The indolo[1,2-c]quinazolin-6(5H

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• ortho-positions. The dual hydrogen-bonding interactions were critical for this reaction, ensuring that the reaction proceeded within the chiral pocket of the CPA catalyst. Moreover, the authors proposed that the extended π-substituents at the ortho-positions of CPA could engage in π–π-stacking

Systematic pore lipophilization to enhance the efficiency of an amine-based MOF catalyst in the solvent-free Knoevenagel reaction

• Pricilla Matseketsa,
• Margret Kumbirayi Ruwimbo Pagare and
• Tendai Gadzikwa

Beilstein J. Org. Chem. 2025, 21, 1854–1863, doi:10.3762/bjoc.21.144

• enhance covalent and/or acid–base catalysis via any combination of non-covalent interactions (hydrogen bonding, π–π stacking, lipophilic interactions, etc) [4][5][6]. Inspired by enzymes, Nature's most efficient catalysts, chemists have long endeavored to synthesize catalytic materials in which multiple

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• CAs to selectively bind drugs of different sizes through hydrophobic and π–π stacking interactions and undergo targeted modifications to enhance their affinity for various guest molecules, such as choline [54], quaternary ammonium salts [55], drug molecules [56], etc. Although they generally have poor

• π–π stacking interactions [86]. Their amphiphilic nature enables these systems to enter cells efficiently through endocytosis, providing a new drug delivery approach and holding great potential in precision medicine due to their programmable and stimulus-responsive features. Additionally, PAs can be

• neutral environment (pH 7.4), deprotonated WP6 can rebind with the guest molecules. The molecular recognition mechanism of this system is based on the synergistic effect of multiple non-covalent interactions, including electrostatic attraction, hydrophobic interactions, and π–π stacking. Researchers have

General method for the synthesis of enaminones via photocatalysis

• Paula Pérez-Ramos,
• Raquel G. Soengas and
• Humberto Rodríguez-Solla

Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116

• , pseudo-octahedral Ni(II) complex [44] involving the carbonyl groups of PS1 and 7a, which is further activated on aggregation of the pyridinium salt and the chromone aromatic ring through π−π stacking. Then, PC1 was submitted to Stern–Volmer quenching experiments. Whereas no interaction occurred between

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

• go beyond common organic functional materials composed of rigid π-conjugated planes and flexible peripheral substituents. Because larger π-conjugated planes mostly display low solubility and dense packing due to the π–π stacking and CH–π interactions, surrounding alkyl and other flexible moieties are

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

• devices or therapeutics [1], drug delivery [2], supramolecular sensing [3], purification [4], and separation [5][6]. The interactions in supramolecular assemblies are driven by well-known hydrogen-bonding, hydrophobic interactions, electrostatic interactions and π–π stacking [7][8]. The supramolecular

Salen–scandium(III) complex-catalyzed asymmetric (3 + 2) annulation of aziridines and aldehydes

• Linqiang Wang and
• Jiaxi Xu

Beilstein J. Org. Chem. 2025, 21, 1087–1094, doi:10.3762/bjoc.21.86

• of the catalyst for the next catalytic cycle. The electron-deficient aromatic aldehydes exhibit excellent stereoselectivity due to the π-stacking interaction between their aryl group and the electron-rich malonate group. Similar π-stacking interaction-controlled stereoselectivities were observed in

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

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

• offers unique features, including twisted structures, reduced π–π stacking, and enhanced reverse intersystem crossing rates, becoming a better donor compared to fully planar compounds as carbazole (c). Similarly, 5H-dibenz[b,f]azepine (IMD, b) has been incorporated into D–A–D structures, showing

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

• π–π stacking is observed in the crystal packing of the complexes, but only C–H···π interactions are present. Two C–H···O hydrogen bonds complete the interactions stabilizing the crystal packing (Figure S1 and Table S2 in Supporting Information File 1). Inhibitory activity of NO production It is

Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

• Gianpaolo Gallo and
• Bartosz Lewandowski

Beilstein J. Org. Chem. 2025, 21, 541–546, doi:10.3762/bjoc.21.42

• protons of 1 shifted downfield and a marginal downfield shift of several crown ether protons as well as H-1 and H-3 of the glucopyranose was also observed. These observations suggest that the main interaction between 1 and H-Trp-OH is the π–π stacking between the naphthalene unit of 1 and the indole

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

• ANTH and the –C6F5 group might provide the desired spatial isolation of the ANTH (and other PAH) cores, and result in enhanced photoluminescence by disrupting close π–π stacking in the solid state. In addition, air- and photostability might also be improved due to the steric and electronic properties

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

• compounds used thus far is likely due to reliance on their ability to undergo π-stacking interactions, which facilitate face-to-face packing. Therefore, the discovery of a new type of structure capable of undergoing this reaction, as reported here, represents a significant advancement, enabling the

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

• involving π–π-stacking [75]. The resulting radical anion releases NO also yielding the anion 63. Electron transfer to the radical cation of the photocatalyst regenerates it. In this step, the neutral radical 64 is also formed. Hydrogen abstraction (hydrogen atom transfer, HAT) yields compound 65. NO and the