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

• mixture collected from the reaction medium after five minutes. Figure 13e presents the spectrum of the isolated product 3a. As demonstrated in Figure 13c and 13d, the signal attributed to the C=N stretching of starting nitrone 1a, observed at 1548 cm−1, disappears. This finding suggests that the nitrone

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

• are reported in cm−1. Mass spectrometry was performed using a JEOL AccuTOF electrospray instrument (ESI). The dye uptake was quantified by UV–vis spectroscopy (Cary 100 Bio UV–visible spectrophotometer) at 25 °C. Incubation of hosts with dyes was performed using an Eppendorf ThermoMixer™ C in 1.5 mL

• ), 4.22 (d, J = 15.8 Hz, 2H), 4.03 (s, 12H), 3.72 (s, 12H), 3.37 (s, 12H), 1.78 (s, 6H), 1.72 (s, 6H); 13C NMR (100 MHz, CDCl3) δ 154.2, 151.4, 148.9, 148.1, 128.5, 124.8, 123.9, 122.2, 108.8, 103.6, 77.4, 75.6, 61.2, 56.1, 55.9, 43.7, 36.1, 17.5, 17.4; IR (ATR, cm−1): 2935 (w), 2833 (w), 1714 (w), 1614

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

• permeability (Pe) results were considered good above 10 × 10−6 cm/s, moderate under 10 × 10−6 cm/s and low, when no substance was detected on the acceptor side. Compounds with low kinetic solubility were not measured in the permeability assay. As a result, four compounds presented good permeability: (E)-7a, (E

• on a Bruker ALPHA FT-IR spectrometer in KBr pellets, ν̃ was reported in cm−1. NMR spectra were recorded at 295 K on a Bruker Avance III HD 600 (600 and 150 MHz for 1H and 13C NMR spectra, respectively) spectrometer equipped with a Prodigy cryo-probe head. Full 1H and 13C assignments were achieved

• , 20.5; IR (KBr) ν̃: 3407, 3360, 1477, 1302, 1151, 1106 cm−1; HREIMS (m/z): [M•]+ calcd for C9H12N4O2S, 240.0675; found, 240.0677. 8-Hydrazino-2-methyl-4-phenyl-2H-1,2,3-benzothiadiazine 1,1-dioxide (5b). To a mixture of 4b (4.00 g, 13.0 mmol) and pyridine (36 mL), hydrazine monohydrate (6.30 mL, 6.50 g

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

• polarized along the long axes of the methoxybiphenyl chromophores. The CD spectrum of (S)-2a shows Cotton effects arising from exciton-coupling between the two methoxybiphenyl chromophores; λext = 278 nm (Δε1 = −0.6 dm3 mol−1 cm−1) and λext = 258 nm (Δε2 = +1.7 dm3 mol−1 cm−1). The amplitude of exciton

• -coupled CD (ACD value) [7], defined as ACD = Δε1 (first Cotton effect) − Δε2 (second Cotton effect), is measured to be −2.3 dm3 mol−1 cm−1. The direction of the twist of the two chromophores in biaryl compounds can be determined by the sign of the Cotton effect of the exciton-coupled CD. Maison [44

• , 1038, 822 cm−1; FABMS (matrix DTT/TG = 1:1) m/z: 465 [M]+ (100%); Anal. calcd for C31H31NO3: C, 79.97; H, 6.71; N, 3.01; found: C, 79.73; H, 6.75; N, 2.98. Theoretical calculations To obtain the population between M and P conformers, preliminary conformational searches were run on the structures of (S

Enantioselective desymmetrization strategy of prochiral 1,3-diols in natural product synthesis

• Lihua Wei,
• Rui Yang,
• Zhifeng Shi and
• Zhiqiang Ma

Beilstein J. Org. Chem. 2025, 21, 1932–1963, doi:10.3762/bjoc.21.151

• intramolecular cyclization of 16 generated benzofuran 17 in 83% yield. After protecting the phenolic hydroxy group of 17, cross-metathesis (CM) with allylic alcohol 18 catalyzed by 13 furnished intermediate 19. Desilylation of 19 produced heliannuol G (20) and heliannuol H (21), with the structure of 21

Synthesis, biological and electrochemical evaluation of glycidyl esters of phosphorus acids as potential anticancer drugs

• Almaz A. Zagidullin,
• Emil R. Bulatov,
• Mikhail N. Khrizanforov,
• Damir R. Davletshin,
• Elvina M. Gilyazova,
• Ivan A. Strelkov and
• Vasily A. Miluykov

Beilstein J. Org. Chem. 2025, 21, 1909–1916, doi:10.3762/bjoc.21.148

• –3.69 (m, 2H, OCH2), 4.07–4.09 (m, 2H, OCH2); 31P{1H} NMR (CDCl3, δ, ppm, J, Hz) 32.04 (s); IR (liquid, cm−1): 762 (m, oxirane), 858 (m,oxirane), 927 (m, oxirane), 1019 (m), 1139 (w), 1166 (w, P=O), 1240 (m, oxirane), 1316 (m, R-P(O)OR), 1349 (s, P=O), 1425 (w), 1455 (m), 1647 (m), 2932 (m), 3004 (m

• ), 3.75–3.84 (m, 2H, OCH2), 4.13–4.23 (m, 2H, OCH2); 31P{1H} NMR (CDCl3, δ, ppm, J, Hz) −0.1 (s); IR (liquid, cm−1): 598 (w), 763 (m, oxirane), 865 (m, oxirane), 921 (m, oxirane), 1021 (m, P(O)(OR)2), 1140 (w, P(O)(OR)2), 1168 (s, P(O)(OR)2), 1185 (w), 1261 (m), 1350 (m, P=O), 1430 (w), 1455 (m), 1644 (w

• -oxirane), 3.14–3.24 (m, 3H, CH-oxirane), 3.84–3.95 (m, 3H, OCH2), 4.22–4.36 (m, 3H, OCH2); 31P{1H} NMR (CDCl3, δ, ppm, J, Hz) −1.2 (s); IR (liquid, cm−1): 599 (w), 700 (w), 763 (m, oxirane), 797 (m, oxirane), 869 (m, oxirane), 918 (m, oxirane), 1024 (m), 1139 (w, P=O), 1166 (s, P=O), 1259 (m), 1349 (m, P

Preparation of spirocyclic oxindoles by cyclisation of an oxime to a nitrone and dipolar cycloaddition

• Beth L. Ritchie,
• Alexandra Longcake and
• Iain Coldham

Beilstein J. Org. Chem. 2025, 21, 1890–1896, doi:10.3762/bjoc.21.146

• EtOAc/petrol 1:4, to give the tosylate 3 (1.30 g, 79%) as an amorphous solid; Rf 0.57 (EtOAc/petrol 1:1); IR (film, cm−1) νmax: 2943, 1708, 1647, 1611, 1599, 1494, 1468, 1455, 1425, 1359, 1314, 1292, 1258, 1178, 1119, 1023, 976, 936, 885, 831, 816, 776, 752; 1H NMR (400 MHz, CDCl3) δ 7.66–7.59 (m, 2H

• aldehyde 4 (562 mg, 41%) as needles; mp 94–96 °C; Rf 0.35 (EtOAc/petrol 1:1); IR (film, cm−1) νmax: 2942, 1712, 1614, 1581, 1495, 1472, 1260, 1190, 1177, 1122, 1096, 1064, 1019, 815, 785, 755; 1H NMR (400 MHz, CDCl3) δ 9.44 (t, J = 1.0 Hz, 1H), 7.69–7.62 (m, 2H), 7.36–7.28 (m, 3H), 7.20 (dd, J = 7.5, 1.0

• (film, cm−1) νmax: 2941, 1784, 1694, 1612, 1495, 1471, 1434, 1377, 1352, 1281, 1247, 1181, 1138, 1092, 1072, 1041, 993, 932, 870; 1H NMR (400 MHz, CDCl3) δ 7.30 (td, J = 7.5, 1.0 Hz, 1H), 7.21 (br d, J = 7.5 Hz, 1H), 7.07 (td, J = 7.5, 1.0 Hz, 1H), 6.84 (br d, J = 7.5 Hz, 1H), 5.07 (d, J = 7.5 Hz, 1H

Synthesis of an aza[5]helicene-incorporated macrocyclic heteroarene via oxidation of an o-phenylene-pyrrole-thiophene icosamer

• Yusuke Matsuo,
• Aoi Nakagawa,
• Shu Seki and
• Takayuki Tanaka

Beilstein J. Org. Chem. 2025, 21, 1561–1567, doi:10.3762/bjoc.21.119

• at 399 nm (Figure 5b). A broad emission was observed at 528 nm, resulting in a relatively large Stokes shift of 6100 cm−1, which can be attributed to the structural relaxation in the excited state, as inferred by the observed broad 1H NMR spectrum at room temperature. Due to the thermal energy loss

Facile synthesis of hydantoin/1,2,4-oxadiazoline spiro-compounds via 1,3-dipolar cycloaddition of nitrile oxides to 5-iminohydantoins

• Juliana V. Petrova,
• Varvara T. Tkachenko,
• Victor A. Tafeenko,
• Anna S. Pestretsova,
• Vadim S. Pokrovsky,
• Maxim E. Kukushkin and
• Elena K. Beloglazkina

Beilstein J. Org. Chem. 2025, 21, 1552–1560, doi:10.3762/bjoc.21.118

• stirred. After that, the reaction mixture was left to stir in the ice bath for 24 hours, allowing it to slowly reach room temperature. Diffusion mixing technique: A small vial (15 mL volume, diameter 1.3 cm) equipped with a magnetic stirring bar was charged with a mixture of dipolarophile 2 (1 equiv

• , 0.150 mmol) and hydroxyimidoyl chloride 4 (1.1 equiv, 0.165 mol) in 4.5 mL of DCM and then placed in larger vial (50 mL volume, diameter 3.5 cm) containing TEA (35.85 mmol, 5 mL). The outer vial was tightly closed with a lid and the reaction mixture was stirred at room temperature for 24 h. In both

Microwave-enhanced additive-free C–H amination of benzoxazoles catalysed by supported copper

• Andrei Paraschiv,
• Valentina Maruzzo,
• Filippo Pettazzi,
• Stefano Magliocco,
• Paolo Inaudi,
• Daria Brambilla,
• Gloria Berlier,
• Giancarlo Cravotto and
• Katia Martina

Beilstein J. Org. Chem. 2025, 21, 1462–1476, doi:10.3762/bjoc.21.108

• δNH2, at around 3370, 3300 and 1596 cm−1, respectively) and by the νCH2 and δCH2 vibrations (curve a) [64][65]. The broad absorption in the high frequency region is characteristic of hydrogen bonding between Si–OH and NH2 groups in functionalised silica materials. After insertion of Cu(I), small

• informative in the low frequency range, where two new broad bands are observed at 1610 and 1515 cm−1, which are compatible with the presence of –NH3+ groups (antisymmetric and symmetric bending modes, respectively) [66][67]. The study also aimed to characterise the catalyst Si-MonoAm-Cu(I) after usage in

• optimised conditions (80 °C, MW, 2 h) with both techniques (curves c in Figure 5). The fingerprints of the aminopropyl groups are still observable in the FTIR spectrum, but new bands are formed at 1660 cm−1 and below 1500 cm−1, with a minor component around 1700 cm−1, which could be related to the

Advances in nitrogen-containing helicenes: synthesis, chiroptical properties, and optoelectronic applications

• Meng Qiu,
• Jing Du,
• Nai-Te Yao,
• Xin-Yue Wang and
• Han-Yuan Gong

Beilstein J. Org. Chem. 2025, 21, 1422–1453, doi:10.3762/bjoc.21.106

• FWHM of 22 nm. Notably, 2b and 2c demonstrate strong chiroptical activity with |gabs| values of 6.7 × 10−3 and 1.0 × 10−2, |glum| of 2.4 × 10−3 and 7.0 × 10−3, and BCPL values of 9.1 and 95.2 M−1 cm−1, respectively. Shortly thereafter, Gong’s group further expanded the π-system by constructing a tris

• -hexabenzo[7]helicene 3 with a carbazole core, which emits at 595/628 nm (PLQY = 0.40), displays |gabs| = 2.98 × 10−3, and achieves a BCPL of 32.5 M−1 cm−1 [16]. In 2025, Babu’s group synthesized two regioisomeric π-extended azahelicenes, 4a and 4b, which differ in the position of attachment to the carbazole

• seconds. In contrast, 4b exhibits superior chiroptical properties, with |gabs| and |glum| values of 3.91 × 10−3 and 1.12 × 10−3, respectively, and an impressive BCPL of 45.77 M−1 cm−1 (Table 1). In 2021, several research groups reported structurally diverse heterohelicene systems exhibiting distinctive

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

• 125 MHz for 13C NMR in CD2Cl2 and 600 MHz for 1H NMR and 151 MHz for 13C NMR in CDCl3 and CD3CN. ATR-FTIR spectra of the compounds were recorded on a Bruker Tensor 27 FTIR spectrophotometer in the range of 4400–600 cm−1 with a resolution of 2 cm−1 at room temperature. The external reflection diamond

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

• 153. The nanoribbon is soluble in common organic solvents and exhibits conductivity values up to 1.5∙10−3 S∙cm−1 when doped by TFA in the thin film state. The serendipitous synthesis of azulene-embedded [5]helicenes was reported by Usui, Suemune, and co-workers [99]. The unexpected formation of an

• coefficients (ε) of compounds 172, 22, and 104 are relatively low (below 1000 M−1 cm−1), reflecting the partially forbidden nature of the S0→S1 transitions. Incorporating strongly electron-withdrawing

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

• Table 2). Analysis of the Huang-Rhys factors delivered that the meta-chlorinated phenyl units do indeed restrict the rotation of the donor. Moreover, the reduction of the LE character of the D1-excited state and a reduction of coupled vibrational modes in the regime from 1000–2000 cm−1 seem to decrease

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

• and 150 or 100 MHz for 13C. Melting points were measured on a Meltemp apparatus in open capillary tubes and are uncorrected. IR spectra were measured on a Thermo Nicolet NEXUS 670 FT/IR spectrometer by attenuated total reflectance (ATR) and are reported in cm−1. Mass spectrometry was performed using a

• high vacuum to yield C1 as a white solid (0.3444 g, 68% yield). Mp > 300 °C; IR (ATR, cm−1): 3456 (w), 1720 (m), 1472 (m), 1378 (w), 1226 (m), 1101 (s), 1023 (m), 972 (w), 790 (w); 1H NMR (400 MHz, D2O) 6.71 (s, 4H), 5.67 (d, J = 15.4 Hz, 2H), 5.57 (d, J = 15.8 Hz, 4H), 5.46 (d, J = 8.9 Hz, 2H), 5.42

Asymmetric synthesis of fluorinated derivatives of aromatic and γ-branched amino acids via a chiral Ni(II) complex

• Maurizio Iannuzzi,
• Thomas Hohmann,
• Michael Dyrks,
• Kilian Haoues,
• Katarzyna Salamon-Krokosz and
• Beate Koksch

Beilstein J. Org. Chem. 2025, 21, 659–669, doi:10.3762/bjoc.21.52

• (HREIMS) were measured on a MAT 711 (Varian MAT, Bremen, Germany). Electron energy for EI was set to 70 eV. Infrared spectra (IR) were measured on an ALPHA II (Bruker, Billerica, USA) spectrometer. Characteristic absorption bands are given in wave numbers (cm−1). Qualitative thin-layer chromatography (TLC

• , CDCl3) δ −56.23 (t, J = 20.7 Hz), −140.45 (dq, J = 28.6, 11.9, 11.1 Hz); ATR-FTIR (neat): 3587, 2975, 2868, 1634, 1500, 1333, 1249, 1137, 870, 820, 709 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ calcd for C35H23Cl3F7N3NiO3, 853.9916; found, 853.9958. Ni(II)-Schiff base complex of bisTfMePhe 7: Under inert

• , 121.5, 71.2, 70.9, 63.3, 58.6, 40.7, 30.8, 23.7; 19F NMR (565 MHz, CDCl3) δ −62.57 (s); ATR-FTIR (neat): 3062, 2982, 2868, 1638, 1463, 1278, 1133, 894, 820, 705 cm−1; HRMS (ESI-TOF) m/z: [M + Na]+ calcd for C36H26Cl3F6N3NiO3, 850.0167; found, 850.0181. Ni(II)-Schiff base complexes of (2S,4R)-TfLeu 11a

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

• for the formation of intermediates. Gao et al. studied the generation of metal acetylide A by IR spectroscopy [65]. When subsequent additions of 1 equiv FeCl3 were made in a solution of alkyne and TMG, the C–H stretch peak at 3277 cm−1 started to decrease as the temperature increased from 30 to 100 °C

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

• at 416 nm is the most red-shifted from ANTH of the listed compounds, resulting in deeper blue fluorescence. It also has the largest Stokes shift of 837 cm−1 (large Stokes shifts are attributed to attenuation of fluorescence by self-quenching processes [30]). Only ANTH obeys the mirror image rule

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

• extinction coefficient (6100 M−1 cm−1) compared to Me2B (4700 M−1 cm−1) at their λmax values of 403 nm and 394 nm in DCM, respectively [19]. This difference in light absorption is further exacerbated by the fact that the irradiation wavelength is not aligned with the λmax of Me2B. Calculating from the

• reported value, the extinction coefficient of Me2B at 405 nm is approximately 4500 M−1 cm−1. As a result, initiating the reaction in Me2B is not as efficient, and may require a shorter wavelength of higher intensity. However, as reported by Kosower et al. [18], bimanes are prone to photoreactions under UV

• crystals were then irradiated for variable periods of time using 405 nm LED (75 mW cm−2) in an Elegoo Mercury Plus Wash and Cure (turntable chamber). Samples were placed approximately 8 cm far from the light source. The average light power measured at this distance was 5 mW cm−2. During the irradiation

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

• decrease to normal values of 1800–2000 cm−1, indicating a complete inhibition of the ESIPT process. These spectral transformations are usually caused by the formation of a strong N–H(O–H)···CN− (F−) hydrogen bond up to deprotonation [28]. Using the principle of “relay recognition” [29], we investigated the

• , CN) (Aldrich) were used to prepare the solutions. Spectral fluorescent experiments were performed using quartz cells (lcuvette 1.0 cm, volume V 2 mL). Stock solutions of compounds 7 or 8 (c 5.0 × 10−5 mol L−1) and tetrabutylammonium salts (c 1.0 × 10−4 mol L−1) in acetonitrile were used. The

• (6) Å, β = 102.590(3)°, V = 1821.55(9) Å3, Z = 4, ρcalc = 1.527 g cm−3, μ(Мо Кα) = 0.520 mm−1, P21/c space group. Intensities of 15441 reflections were measured in the reciprocal space (2θ ≤ 64.14°) using the ω/2θ-scanning method from a single crystal with dimensions of 0.31 × 0.25 × 0.20 mm. An

Synthesis of new condensed naphthoquinone, pyran and pyrimidine furancarboxylates

• Kirill A. Gomonov,
• Vasilii V. Pelipko,
• Igor A. Litvinov,
• Ilya A. Pilipenko,
• Anna M. Stepanova,
• Nikolai A. Lapatin,
• Ruslan I. Baichurin and
• Sergei V. Makarenko

Beilstein J. Org. Chem. 2025, 21, 340–347, doi:10.3762/bjoc.21.24

• IR spectra of compounds 5a–6d containing an alkoxyfuropyran fragment shows that in the case of methyl esters 5a, 6a, and 6c the absorption band of the alkoxycarbonyl function is shifted to a lower frequency region (1714–1721 cm−1), while ethyl esters 5b, 6b, and 6d are characterized by higher

• frequency values (1725–1731 cm−1). This observation may be due to the position of the ester fragment relative to the heterocyclic system. The analysis of the results of X-ray diffraction analysis shows that the torsion angle C(10)–C(3)–C(16)–O(17) of methyl esters 5a and 6c is −0.8(2), and 5(2)°, and of

• . In turn, in the IR spectra (KBr) of compounds 7a–f, absorption bands of the ester fragment in the region of 1714–1750 cm−1 and absorption bands of the carbonyl group of the amide fragment in the region of 1674–1688 cm−1 are observed, which suggests the existence of these compounds in the solid phase

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

• neutral species was measured at 1700 cm−1 and was predicted at 1730 cm−1 for m-1. This band was assigned to the symmetric CC stretching mode of the four bonds that are exocyclic to CBD, ν(CC)exo-CBD, or CBD breathing mode, as indicated by the atomic displacements shown in Figure 4. Other two strong Raman

• features were measured at 1448 and 1355 cm−1. They were predicted at 1468 and 1354 cm−1, respectively, for m-1, being assigned to CC stretching modes with slight contributions of aromatic CH bending vibrations. The complete eigenvector for these vibrations can be seen in Figure S2 in Supporting Information

• File 1. Given that former normal mode mainly involves the CBD moieties, the observed feature at 1700 cm−1 can be considered a suitable marker band of the structural and electronic changes of the antiaromatic CBD rings upon oxidation. The Raman spectra of 1, 1•+, and 12+ are shown in Figure 5. Relative

Synthesis and characterizations of highly luminescent 5-isopropoxybenzo[rst]pentaphene

• Islam S. Marae,
• Jingyun Tan,
• Rengo Yoshioka,
• Zakaria Ziadi,
• Eugene Khaskin,
• Serhii Vasylevskyi,
• Ryota Kabe,
• Xiushang Xu and
• Akimitsu Narita

Beilstein J. Org. Chem. 2025, 21, 270–276, doi:10.3762/bjoc.21.19

• well-structured absorption peaks clearly showing the vibronic progressions. BPP-OiPr 3 also exhibited a small peak located at 442 nm with the molar extinction coefficient (ε) of 1800 M−1 cm−1, which was similar to the previous observations of the dark S1 states for BPP 2 and its mesityl- and tert-butyl

• (Supporting Information File 1, Table S2). The longest-wavelength absorption maximum (S0 → S1), attributed to the HOMO → LUMO transition, was calculated to be at 432 nm (f = 0.5674) for 4. Compared to the S1 states in BPP 2 (ε = 1200 M−1 cm−1) and BPP-OiPr 3 (ε = 1800 M−1 cm−1), corresponding to forbidden

• transitions as previously discussed for other BPP derivatives [21][22], the strikingly enhanced molar extinction coefficient observed for the lowest-energy band of BPP-dione 4 (ε = 17000 M−1 cm−1) indicates that the optical transition to the S1 state becomes allowed by this oxidation. BPP 2 and BPP-OiPr 3

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

• obtained are summarized in Scheme 2 and Table 1. It was found that the size of the vial used to carry out the reaction significantly affected the reaction rate. Thus, in an apparatus consisting of two vials with diameters of 1.3 and 2.8 cm, the conversion of the starting compound was 37 and 31

• %, respectively, when carrying out the reaction in chloroform or methanol over two days (Table 1, entries 3 and 7). In turn, in a system of two vials with diameters of 3.7 and 7.5 cm, and with a loading of diketone 1 that was five times greater, more than two thirds of the starting compound reacted within 24 h

• (1 equiv), 0.05 mmol ʟ-proline and 2.0–5.0 mmol diene (2–5 equiv) in 3–5 mL acetonitrile was placed into a 15 mL vial (diameter 1.3 cm). This vial was then placed into a closed 50 mL vial (diameter 2.8 cm) containing 3–5 mL of formalin, and the reaction mixture was stirred at room temperature for 2

Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory

• Misato Suganuma,
• Daichi Kitagawa,
• Shota Hamatani and
• Seiya Kobatake

Beilstein J. Org. Chem. 2025, 21, 242–252, doi:10.3762/bjoc.21.16

• absorption maxima (λmax) at 299, 307, 291, 301, 307, and 369 nm, respectively. The molar absorption coefficients at λmax of N3(o), N4(o), and I1(o)–I4(o) were determined to be 12200, 12700, 47800, 22700, 12900, and 12700 M−1 cm−1, respectively. Upon irradiation with 365 nm, a new absorption band appeared in