Unraveling aromaticity: the dual worlds of pyrazole, pyrazoline, and 3D carborane

• Zahra Noori,
• Miquel Solà,
• Clara Viñas,
• Francesc Teixidor and
• Jordi Poater

Beilstein J. Org. Chem. 2025, 21, 412–420, doi:10.3762/bjoc.21.29

• carborane and the π-aromaticity of the heterocycle are orthogonal, making a true 3D/2D aromatic system unachievable. The carborane is highly aromatic, generating highly negative NICS values (−25 to −30 ppm). We have observed that these high NICS values extend to fused rings, leading to incorrect estimations

Oxidation of [3]naphthylenes to cations and dications converts local paratropicity into global diatropicity

• Abel Cárdenas,
• Zexin Jin,
• Yong Ni,
• Jishan Wu,
• Yan Xia,
• Francisco Javier Ramírez and
• Juan Casado

Beilstein J. Org. Chem. 2025, 21, 277–285, doi:10.3762/bjoc.21.20

• ], including [3]naphthylenes 1 and 2 in Figure 1 [18]. They are endowed by three aromatic naphthalenoid (NAP) moieties, fused by two antiaromatic CBD ones in two different topologies. Structurally, these polycyclic π-conjugated hydrocarbons consist of eight fused rings and thirty π-electrons. In this work, we

• electronic delocalization. In order to figure out the driving force that leads the stabilization of the oxidized species of 1 and 2, we calculated the NICS values of all fused rings in the neutral and cationic species of m-1 and m-2 (Figure 7), in order to obtain a precise and comparable measurement of the

• sequence of fused rings, from the aromaticity viewpoint, in which we can stand out the following facts: i) the external/internal NAPs evolve from largely/slightly aromatic to slightly/more aromatic, and ii) the CBDs change from antiaromatic to slightly aromatic. This picture is quantitatively reflected by

The charge transport properties of dicyanomethylene-functionalised violanthrone derivatives

• Sondos A. J. Almahmoud,
• Joseph Cameron,
• Dylan Wilkinson,
• Michele Cariello,
• Claire Wilson,
• Alan A. Wiles,
• Peter J. Skabara and
• Graeme Cooke

Beilstein J. Org. Chem. 2024, 20, 2921–2930, doi:10.3762/bjoc.20.244

• using the B3LYP functional with the 6-311G (d,p) basis set. The geometry of the two molecules was found to be nearly identical to the ones previously reported, with the nine fused rings of compound 2 almost planar, compared to the more twisted geometry of compound 3. This could possibly result in weak π

• the energies of the frontier molecular orbitals of molecules 2 and 3. In both cases, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are uniformly delocalised throughout the nine fused rings, indicating that the two molecules could benefit from a

Generation of multimillion chemical space based on the parallel Groebke–Blackburn–Bienaymé reaction

• Evgen V. Govor,
• Vasyl Naumchyk,
• Ihor Nestorak,
• Dmytro S. Radchenko,
• Dmytro Dudenko,
• Yurii S. Moroz,
• Olexiy D. Kachkovsky and
• Oleksandr O. Grygorenko

Beilstein J. Org. Chem. 2024, 20, 1604–1613, doi:10.3762/bjoc.20.143

• showed biological activity according to the ChEMBL database. Keywords: fused rings; heterocycles; imidazoles; isonitrile; multicomponent reactions; Introduction Multicomponent reactions are widely recognized as a powerful source of biologically active compounds, in particular, for drug discovery

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• several cases the reaction does not work. Application of the Houk's distortion model to those reactions suggested that the observed lack of reactivity for reactions involving the formation of medium-size fused rings is mainly due to the negative effect of the tethers consisting of allowing a more stable

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• backbone with 8 fused rings, a unique [7-8] bicyclic motif, an oxa-bridge over the cyclooctane ring, and the presence of 12 stereogenic centers [36]. The strategy proposed by the authors was to carry out a RCM reaction to elaborate the cyclooctene ring from functionalized intermediate 66, prepared as a

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• all the sulfur atoms of the DTT core and the electron-withdrawing [20] keto groups. The LUMO is presented strongly in the seven fused rings, but is poorly represented in the outer ethylhexylthiophenes, which are electron-rich and twisted out of plane. The LUMO is strongly localised at the electron

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• ring-closure step have been routinely employed for the construction of diverse arene- and heteroarene-fused rings (Scheme 1A) [1][2][3]. In most of these approaches, the new CAr–C bond is formed ortho to the tether/directing functionality on an aromatic or a heteroaromatic ring, as the geometrical

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• in natural product synthesis reported from 2011–2020 (inclusive). The intermolecular all-carbon [3 + 2] cycloaddition offers a facile approach to install functionalized five-carbon carbocycles, including fused-rings (e.g., longeracinphyllin A (10)) and/or spiro-ring (e.g., marcfortine B (8)), at

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• coupled with C–H bond insertion offers the potential to build both the bridged bicycle and additional fused rings in a single reaction (see Figure 2). The foundation of this strategy was laid by Hoye and Padwa [77][78][79][80][81][82][83][84][85]. Some substrates with a well-defined C–H bond insertion as

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• only low tendencies of boronic ester formation [23]. Therefore, we turned to cis-dihydroxylated 5, which exhibited a unique reactivity towards boronic acids because it forms two anellated cis-fused rings. 5 shows 86% esterification after drying in a 1:1 mixture with the arylboronic acid 6, a single

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• on pyridoacridine-related metabolites as one biologically interesting group of alkaloids identified from marine sources. They are produced by marine sponges, ascidians and tunicates, and they are structurally comprised of four to eight fused rings including heterocycles. Acridine, acridone

• comprised of four to eight fused rings including heterocycles [34][35][36][37][38][39]. Acridine, acridone, dihydroacridine, and quinolone cores [33][40] are features regularly found in these alkaloid skeletons. The high conjugation of their structure induces a strong electron delocalization, leading to

• with compact, and fused rings do not undergo fragmentation and only their corresponding ion peak is observed [47]. However, those containing a side chain show a few ion peaks corresponding to the sequential fragmentation of the latter. This observation is supported by the mass spectrometry data of

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• spectra, and in one case, from an X-ray crystal structure. Assorted bicyclic and tricyclic imines were formed with both spiro-rings and fused-rings and with varying ring sizes and substituents. Extending this work, we have studied radical cyclizations of several ene-sulfonamides and N-sulfonylindoles. The

Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Ongolu Ravikumar

Beilstein J. Org. Chem. 2015, 11, 1259–1264, doi:10.3762/bjoc.11.140

• reaction and RRM as key steps. Here, we generated polycyclic compounds with 10 stereocenters involving six fused rings in four steps starting with readily available starting materials such as 1,3-cyclopentadiene, 1,3-cyclohexadiene and 1,4-benzoquinone. Further studies to expand the scope of this strategy

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• restricted rotation about C–N bonds conferred by the fused rings of 10. By using the method of Williams [42], the quantum yields of 9 and 10 were determined relative to rhodamine B (5) and rhodamine 6G (7, Figure 3, panels A and B), and the extinction coefficients of these compounds were quantified (Figure 3

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• presence of an additional dihydro ring. In all derivatives, the core of the fused rings is conformationally constrained, and for most of them, even the introduced substituents do not provide high conformational freedom. The O–CAlkyl bond of alkoxy groups lies in the plane of the adjacent aromatic ring; for