Highly distinguishable isomeric states of a tripodal arylazopyrazole derivative on graphite through electron/hole-induced switching at ambient conditions

• Himani Malik,
• Sudha Devi,
• Debapriya Gupta,
• Ankit Kumar Gaur,
• Sugumar Venkataramani and
• Thiruvancheril G. Gopakumar

Beilstein J. Org. Chem. 2025, 21, 1496–1507, doi:10.3762/bjoc.21.112

• Supporting Information File 1. The AFM images of the ultra-thin film reveal domains of assembled molecules shown as bright contrast, marked by green and yellow dashed lines in Figure 2a,b. The pristine graphite surface has a median contrast. The molecular domains are growing as long islands with well-defined

• graphite lattice, which has 3-fold symmetry [33][34][35]. Each of the orientations has a mirror domain as well, making a total of six orientations for the islands on the surface. The orientations of the islands are marked by yellow and green 3-fold arrowheads in Figure 2a,b. The mirror orientations are

• deposited from ethanolic solution on HOPG (0001) and are obtained from independent areas. Domains in the 1D phase of FNAAP are marked by green and yellow dashed lines. The green and yellow three-fold arrows depict the orientation of the long edges of the islands with respect to each other. A few graphite

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

• transitions from pale yellow to deep blue in the solid state upon exposure to TFA, while 63b and 63c in CH2Cl2 exhibit new absorption bands at 570 and 575 nm, respectively – reversibly decolorized upon triethylamine treatment (Table 22). This work demonstrates the potential of helicene-containing polymers as

• -containing hetero[5]- and [6]helicene-like structures 68a–g in high yields [82]. These compounds display diverse photophysical behaviors: compound 68d emits yellow fluorescence in both solution and solid state, exhibiting solvatofluorochromism due to a twisted intramolecular charge transfer (TICT) mechanism

N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B

• Joy E. Rajakulendran,
• Emmanuel Tope Oluwabusola,
• Michela Cerone,
• Terry K. Smith,
• Olusoji O. Adebisi,
• Adefolalu Adedotun,
• Gagan Preet,
• Sylvia Soldatou,
• Hai Deng,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2025, 21, 1388–1396, doi:10.3762/bjoc.21.103

• purification by a reversed-phase high pressure liquid chromatography (HPLC) system which led to the isolation of four compounds, trivially named pseudomonins D–G (1–4) and three known compounds 5–7 (Figure 1). Compound 1 was isolated as a yellow oil. The molecular formula C11H13NO5 (Δ: −0.7 ppm, 6 degrees of

• by HPLC with a wavelength monitored at 340 nm of the derivatized amino acid residuals in the hydrolysate and threonine standards (see Supporting Information File 1, Figure S24). Compound 3 was isolated as a yellow oil. Its molecular formula of C11H11NO4 (Δ: −0.3 ppm, calcd. for C11H10NO4, 220.0615

• ). Pseudomonin D (1): Yellow oil; HRESIMS (m/z): [M − H]− calcd. for C11H12NO5, 238.0721; found 238.0723(Δ: −0.7 ppm); NMR data, see Table 1 and Supporting Information File 1, Figures S1–S5 [23]. Pseudomonin E (2): Reddish oil; HRESIMS (m/z): [M + H]+ calcd. for C16H21N4O4, 333.1557; found, 333.1556 (Δ: +0.4 ppm

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

• ® and purified by flash chromatography on silica gel (n-hexane/acetone 3:1). Then, the crude product was suspended in n-hexane, the supernatant separated by filtration and the precipitate was dried under vacuum to afford aroyl-S,N-ketene acetal 1i (1.78 g, 4.93 mmol, 99%) as a yellow solid. Mp 159 °C

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

• black cross. B: Distribution of correct (green), semi-correct (yellow), and wrong (red) predictions for the same molecules, evaluated with an energy threshold of 1.0 kcal·mol−1. Molecules with five potential reaction sites that are predicted wrong by the QM workflow. The experimentally observed and

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

• Henry S. T. Smith,
• Ben Giuliani,
• Kanchana Wijesekera,
• Kah Yean Lum,
• Sandra Duffy,
• Aaron Lock,
• Jonathan M. White,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

• described in Supporting Information File 1. Pure fractions (≥95%) obtained from reversed-phase HPLC separation were then combined to obtain the desired product, 3-(4-chlorophenyl)-N-phenethyl-[1,2,4]triazolo[4,3-a]pyrazin-8-amine (2) as yellow needles (115 mg, 82%). General method for the synthesis of the

• relevant fractions containing high purity product (≥95%) were combined. 3-(4-Chlorophenyl)-N-phenethyl-[1,2,4]triazolo[4,3-a]pyrazin-8-amine (2). Yellow needles (115 mg, 82%); mp 224–226 °C; UV (MeOH) λmax, nm (log ε): 250 (4.09), 293 (3.83); 1H NMR (500 MHz, (CD3)2SO) δH 8.30 (t, J = 5.8 Hz, 1H, H-16

• ; found, 338.1142; [2M + H]+ calcd for C32H3735Cl2N10, 631.2580; found, 631.2572. N1-(3-(4-Chlorophenyl)-[1,2,4]triazolo[4,3-a]pyrazin-8-yl)-N2,N2-dimethylethane-1,2-diamine (10). Pale yellow needles (43 mg, 68%); mp 153–155 °C; UV (MeOH) λmax, nm (log ε): 253 (4.36), 294 (4.08); 1H NMR (500 MHz, (CD3)2SO

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

• its discovery, mostly because of its glittery metallic yellow color and its ability to remain untarnished even after exposure to extremely aggressive conditions. Gold is able to keep its shine for centuries, having been deemed as the most noble of metals [1]. Present in human life since early

• . C skyblue, O red, Br brown, Au yellow. (c) Schematic illustration of the mechanism leading to precipitation (named “supramolecular polymerisation” by the authors) after adding various additives to the solution of β-CD and [AuBr4]− anions. Reproduced from [51] (© 2023 H. Wu et al., published by

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

• the molecule remains mostly planar in the excited state [37]. As a result, we observe weak emission in the yellow to red spectrum, because the respective transition remains symmetry forbidden. Circularly polarized photoluminescence PTM has been developed prior to TTM, as the first stable

• , these molecules display greatly enhanced photostability compared to PTM and TTM. The ortho-positions on the pyridyl ring have been substituted with fluorine, chlorine, and bromine moieties, and it was found that the change in substitution affects the emission color from yellow in case of fluorine, to

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

• color can also be seen by naked eye with the solution changing from pale to dark yellow (cf. Supporting Information File 1, Figure S2). In Table 2, the absorption maxima of Z–PAP derivatives in CH3CN are summarized. For EWGs, such as CF3, CN, or NO2, the absorption maxima are redshifted, while for EDGs

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

• no additional spectroscopic changes, while the initially yellow solution turned deep black in the time frame between 15 and 60 minutes (Supporting Information File 1). Prolonged irradiation overnight ultimately resulted in complete photodecomposition, indicated by the absence of significant signals

Orthogonal photoswitching of heterobivalent azobenzene glycoclusters: the effect of glycoligand orientation in bacterial adhesion

• Leon M. Friedrich and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2025, 21, 736–748, doi:10.3762/bjoc.21.57

• representation of the superimposed most stable ligand–protein complexes from IFD for E- and Z-6αMan 4 (A: E in red, Z in yellow) and E- and Z-3αMan 5 (B: E in turquoise, Z in magenta), as well as of the EE, ZZ, EZ, and ZE isomers of glycocluster 6βGlc3αMan 1 (C) and of 6αMan3αMan 2 (D). The protein FimH (1UWF

Synthesis of HBC fluorophores with an electrophilic handle for covalent attachment to Pepper RNA

• Raphael Bereiter and
• Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 727–735, doi:10.3762/bjoc.21.56

• piperidine and stirred at 100 °C for 20 hours. A strongly yellow-colored solution was obtained and cooled on ice, whereby a precipitate was formed and filtered off. The filter cake was washed with ice-cold ethanol and dried under high vacuum. General procedure C. In a manner similar to [11], the product

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

• tube and centrifuged (7200 rpm, 5 min). The supernatant was carefully poured off. Next, the crude solid was dissolved in 1 M NaOH (25 mL) which results in a yellow and then red solution. Afterwards, EtOH (144 mL) was added which gave a white precipitate that was collected by centrifugation (7200 rpm

• ), b) a mixture of C1 (0.5 mM) and Me6PXDA (1.0 mM), c) a mixture of C1 (0.5 mM) and Me6PXDA (0.5 mM), and d) C1 (0.5 mM). Cross-eyed stereoview of the C1·Me6CHDA complex in the crystal. Color code: C, gray; H, white; N, blue; O, red; S, yellow. Cross-eyed stereoview of the crystal packing observed in

• the molecular cell of C1·Me6CHDA. H-atoms are omitted for clarity. N···O distances less than 4.40 Å are indicated with dashed lines. Color code: C, gray; N, blue; O, red; S, yellow. a) Representative plot of DP (μcal s−1) versus time from the titration of C1 (0.1 mM) in the ITC cell with a solution of

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

• (4 × 40 mL), dried over Na2SO4, filtered, and concentrated in vacuo. The crude material was purified by flash column chromatography (SiO2, 0 → 10% MeOH in DCM) to yield 2 as a yellow solid (3.36 g, 9.26 mmol, 67%, 91% purity determined by analytical HPLC). 1H NMR (600 MHz, CDCl3) δ 7.77 (d, J = 7.6

Entry to 2-aminoprolines via electrochemical decarboxylative amidation of N‑acetylamino malonic acid monoesters

• Olesja Koleda,
• Janis Sadauskis,
• Darja Antonenko,
• Edvards Janis Treijs,
• Raivis Davis Steberis and
• Edgars Suna

Beilstein J. Org. Chem. 2025, 21, 630–638, doi:10.3762/bjoc.21.50

• conditions at room temperature, and 2.0 F charge (if not otherwise noticed) with current density of 12 mA/cm2 was passed through the colorless reaction solution. The resulting clear, colorless (sometimes pale yellow) solution was concentrated under reduced pressure and the crude product was purified by

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

• removed in vacuo. Yield (NMR): 9-Br-10-BnF-ANTH (22%), 9,10-(BnF)2-ANTH (45%). Product characterization and NMR spectra 9-ANTH(BnF): white/yellow solid; isolated yield 14% based on ANTH; mp 177–179 °C; 19F NMR (CDCl3, δ/ppm): −73.61 (t, J = 17.7 Hz, 2F), −140.94 (m, 2F), −152.56 (t, J = 20.4 Hz, 1F

• ), −163.31 (m, 2F); 1H NMR (δ/ppm): 8.63 (s, 1H), 8.34 (d, J = 7.83 Hz, 2H), 8.06 (d, J = 7.72 Hz, 2H), 7.49 (m, 4H); EIMS (m/z): [M − H]+ calcd for 393.051; found, 393.120 (exp), 9,10-ANTH(BnF)2: white/yellow solid; isolated yield 17% based on ANTH; mp 211–214 °C; 19F NMR (CDCl3, δ/ppm): −71.73 (t, J

• stacked columns of ANTH moieties are colored red and green, BnF groups are colored in yellow, and H atoms have been omitted for clarity. In the off-side view (bottom right), both, F and H atoms are omitted for a better overview. Absorption spectra of ANTH and 9,10-ANTH(BnF)2 in CH2Cl2 recorded over the

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

• , the crystals changed their appearance from light yellow to dark orange within 15 minutes. An alternative method for solid-state irradiation involved dissolving 5–10 mg of the bimane in a minimal amount of acetone, which was then evaporated in a 25 mL round-bottomed flask, forming a seemingly amorphous

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

• Thomas Brandt,
• Pascal Lentes,
• Jeremy Rudtke,
• Michael Hösgen,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

• diazocine attached to glutamate to form a photoswitchable neurotransmitter [10]. The halogen-substituted N-acetyl diazocines 2–4 were used as the starting compounds for further derivatization via Pd-catalyzed cross-coupling reactions. Solutions of the Z isomers are yellow. The E isomers are red. Synthesis

Identification and removal of a cryptic impurity in pomalidomide-PEG based PROTAC

• Bingnan Wang,
• Yong Lu and
• Chuo Chen

Beilstein J. Org. Chem. 2025, 21, 407–411, doi:10.3762/bjoc.21.28

• shoulder peak (Figure 2, marked with asterisk). A close examination of the UV profile indicated the presence of an impurity. Its removal requires repetitive prep-HPLC purifications that are inefficient and time-consuming. The isolated impurity lacks the characteristic fluorescent yellow color of

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

• -n-butylammonium salts (TBAX: F, Cl, Br, I, CN). Exclusively cyanide and fluoride anions lead to a naked-eye effect due to a change of the solution’s colour from yellow-orange to pale yellow (Figure 5). At the same time, a new fluorescence band appears at 420–440 nm. The Stokes shifts of fluorescence

• equation formalism (IEFPCM) [38]. Biological experiments The MTT colorimetric test for cell viability assessment is based on the reduction by NADPH-H-dependent cellular oxidoreductase enzymes of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, which has yellow color, into

Synthesis, characterization, antimicrobial, cytotoxic and carbonic anhydrase inhibition activities of multifunctional pyrazolo-1,2-benzothiazine acetamides

• Ayesha Saeed,
• Shahana Ehsan,
• Muhammad Zia-ur-Rehman,
• Erin M. Marshall,
• Sandra Loesgen,
• Abdus Saleem,
• Simone Giovannuzzi and
• Claudiu T. Supuran

Beilstein J. Org. Chem. 2025, 21, 348–357, doi:10.3762/bjoc.21.25

• . Yellow-colored precipitates of product 5 were formed which were separated via filtration followed by washing with excess of water. After drying, recrystallization was done with ethanol. Mp 265–266 °C; yield: 221 mg (88%). Synthesis of pyrazolo-1,2-benzothiazine-N-aryl/benzyl/cyclohexylacetamides 7a–h

Antibiofilm and cytotoxic metabolites from the entomopathogenic fungus Samsoniella aurantia

• Rita Toshe,
• Syeda J. Khalid,
• Blondelle Matio Kemkuignou,
• Esteban Charria-Girón,
• Paul Eckhardt,
• Birthe Sandargo,
• Kunlapat Nuchthien,
• J. Jennifer Luangsa-ard,
• Till Opatz,
• Hedda Schrey,
• Sherif S. Ebada and
• Marc Stadler

Beilstein J. Org. Chem. 2025, 21, 327–339, doi:10.3762/bjoc.21.23

• (Figure 1) was purified as a yellow amorphous solid. The molecular formula of 1 was determined as C25H29NO5 indicating twelve degrees of unsaturation based on the HRESIMS that revealed a protonated molecule at m/z 424.2126 [M + H]+ (calculated 424.2118) and a sodium adduct at m/z 446.1947 [M + Na

• ]+ (calculated 446.1962). The UV–vis spectrum of 1 (Figure S3, Supporting Information File 1) revealed a prominent absorption peak (λmax) at 434 nm in the visible region reflected by being yellow-colored and suggesting the presence of an extended conjugated π-system in its structure. The 1H NMR and 1H–1H COSY

• that it is a related derivative to two yellow pyridone pigments, farinosones A and B, that were previously reported from Cordyceps farinosa syn. Paecilomyces farinosus [8][9]. A detailed comparison of the 1H and 13C NMR data of 1 and farinosones A/B revealed that instead of a deshielded pyridone

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

• confirmed that the colorless solution of N4(o) turned yellow upon irradiation with UV light and returned to the initial color upon removal of the irradiation. The photophysical properties of N3, N4, and I1–I4 are summarized in Table 1 together with the data of N1 and N2. Thermal back reactivity in n-hexane

• the absorption spectra upon UV irradiation. Notably, compound N4 turns bright yellow under UV light, adding a new color to the photochromic reaction of azadiarylethenes. The analysis of the thermal back reaction revealed activation parameters and highlighted the influence of the substitution position

• -hexane at 253 K for N3 and 203 K for I3: open-ring isomer (black line) and under irradiation at 365 nm (yellow line). (c) Photochromic reaction of N4 in n-hexane at room temperature ([N4] = 7.0 × 10−4 M). Absorbance decay curves and first-order kinetics profiles for (a,b) N3 and (d,e) I3 in n-hexane at

Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)

• Yongming Xiong,
• Xue Lin Ma,
• Shilong Su and
• Qian Miao

Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1

• analysis of it with X-ray crystallography. Interestingly, it is observed that tris(4,5-dehydro-2,3:6,7-dibenzotropone) crystallized from its solution in hexane resulting in colorless and yellow crystal polymorphs, where it adopts conformations of approximate Cs and C2 symmetry, respectively. Furthermore

• yellow crystals from the same solution. X-ray crystallography reveals that in the colorless crystal [27], compound 1 adopts a conformation with approximate Cs symmetry, with the plane of symmetry (σ) shown in the top view in Figure 2a. The structure of Cs-1 in this crystal is essentially the same as that

• ring of Cs-1 is essentially flat, exhibiting the largest torsion angle of 8.15° (C4–C5–C6–C1). Unlike the colorless crystal, the yellow crystal consists of conformers of 1 with approximate C2 symmetry [27]. They exist as a pair of enantiomers, namely, (P,M,P)-1 and (M,P,M)-1, where P and M represent

Efficient synthesis of fluorinated triphenylenes with enhanced arene–perfluoroarene interactions in columnar mesophases

• Yang Chen,
• Jiao He,
• Hang Lin,
• Hai-Feng Wang,
• Ping Hu,
• Bi-Qin Wang,
• Ke-Qing Zhao and
• Bertrand Donnio

Beilstein J. Org. Chem. 2024, 20, 3263–3273, doi:10.3762/bjoc.20.270

• electronic structures of the triphenylenes, and their supramolecular arene–perfluoroarene slipped stacks (J-aggregate) result in G66 with orange-yellow color fluorescence in the solid state. Fluorotriphenylene derivatives and their nonfluorinated homologs obtained by SNFAr from 2,2'-dilithio-4,4',5,5