Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• free energies were calculated at the B3LYP-D3/def2-tzvp//B3LYP/6-31G(d) level in MeCN. b) Spin density of IN4 (isovalue = 0.004). c) IRC analysis of TS2 (red line) and bond-length changes of C19–C3 (yellow line) and C19–C12 (blue line) along IRC path. d) Mayer bond order changes of selected structures

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

• solvents. Furthermore, the evidence suggests that the majority of these solvents is hazardous and their utilization is to be avoided. As demonstrated in Figure 8a, the color of the spheres of the customary proportional solvents employed in [3 + 2] cycloadditions is red or yellow, thereby substantiating the

Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis

• Peng-Xi Luo,
• Jin-Xuan Yang,
• Shao-Min Fu and
• Bo Liu

Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177

• : reactive substrates exhibited λmax < 460 nm (yellow-orange), whereas unreactive ones showed λmax > 460 nm (dark red-purple). This suggests insufficient excitation energy for Norrish type-II hydrogen abstraction in the latter. Such chromophore-dependent reactivity provides critical insights for designing

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

• , green; H-bonds, yellow-red striped. Cross-eyed stereoview of: a) a molecule of G2W1 in the crystal, b) the packing of G2W1 along the xz-diagonal in the crystal. Color code: C, grey; H, white; N, blue; O, red. a) Plot of removal efficiency of methylene blue (240 μM, 1 mL) from water after incubating with

A chiral LC–MS strategy for stereochemical assignment of natural products sharing a 3-methylpent-4-en-2-ol moiety in their terminal structures

• Rei Suo,
• Raku Irie,
• Hinako Nakayama,
• Yuta Ishimaru,
• Yuya Akama,
• Masato Oikawa and
• Shiro Itoi

Beilstein J. Org. Chem. 2025, 21, 2243–2249, doi:10.3762/bjoc.21.171

• tool for the structural determination of diverse MPO-containing natural products in future studies. Representative natural products sharing the 3-methylpent-4-en-2-ol (MPO) moiety in their terminal structures, with the moiety highlighted in blue (assigned configuration) or yellow (undetermined

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

• , filtered and washed with water to give 5a (6.56 g, 94%) as a yellow powder. Mp 160.5–161.5 °C (EtOH); 1H NMR (600 MHz, DMSO-d6) δ 7.64 (m, 2H), 7.21 (br s, 1H), 7.00 (m, 1H), 4.51 (br s, 2H), 3.33 (s, 3H), 2.40 (s, 3H); 13C{1H} NMR (150 MHz, DMSO-d6) δ 149.6, 147.3, 134.1, 129.1, 116.0, 114.6, 112.9, 34.7

• , 130.4 mmol) was added dropwise. After refluxing for 26 h, the reaction mixture was evaporated to dryness, the residue was triturated with water, filtered and washed with water to give 5b (3.65 g, 93%) as a yellow powder. Mp 165–166 °C (EtOH); 1H NMR (600 MHz, DMSO-d6) δ 7.67 (d, J = 8.4 Hz, 1H), 7.58 (m

• products. 8-(2-Cyclohexylidenehydrazino)-2,4-dimethyl-2H-1,2,3-benzothiadiazine 1,1-dioxide (7e). Prepared according to the general procedure, using 5a and 6e as the starting materials. Yield: 111.0 mg (83%), yellow crystals. Mp 99–100 °C (EtOH); 1H NMR (600 MHz, DMSO-d6) δ 9.19 (br s, 1H), 7.80 (d, J

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

Understanding the origin of stereoselectivity in the photochemical denitrogenation of 2,3-diazabicyclo[2.2.1]heptene and its derivatives with non-adiabatic molecular dynamics

• Leticia A. Gomes and
• Steven A. Lopez

Beilstein J. Org. Chem. 2025, 21, 2007–2020, doi:10.3762/bjoc.21.156

• trajectories form inverted housane, and the yellow trajectories lead to a diradical intermediate. The quantum yield for each species is provided below its structure. (a) Geometrical parameters. H–C–C–C dihedral angles plotted against each other for S1-to-S0 hopping point geometry of 1 (b), 3 (c), and 5 (d

Photochemical reduction of acylimidazolium salts

• Michael Jakob,
• Nick Bechler,
• Hassan Abdelwahab,
• Fabian Weber,
• Janos Wasternack,
• Leonardo Kleebauer,
• Jan P. Götze and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2025, 21, 1973–1983, doi:10.3762/bjoc.21.153

• the formation of the fully reduced product 2 under photocatalytic conditions, the independently synthesized 3 was irradiated with 1 equivalent of DIPEA and 4CzIPN under the conditions shown in Table 1, entry 16 (Scheme 1, in yellow box). After 24 h at rt, clean conversion into 2 (77% 1H NMR yield) was

• 3 into the 2-benzylimidazolium salt 2 was observed (1H NMR yield = 8%) with 90% of 3 remaining unreacted after 24 h at rt (Scheme 2, in yellow box). To gain more insight into the reaction course in the absence of a photocatalyst, the reduction of 1 with DIPEA (1 equiv) under UV-A irradiation was

Rhodium-catalysed connective synthesis of diverse reactive probes bearing S(VI) electrophilic warheads

• Scott Rice,
• Julian Chesti,
• William R. T. Mosedale,
• Megan H. Wright,
• Stephen P. Marsden,
• Terry K. Smith and
• Adam Nelson

Beilstein J. Org. Chem. 2025, 21, 1924–1931, doi:10.3762/bjoc.21.150

• products observed by analytical HPLC. Structures and structure elucidation of intermolecular reaction products. The relevant reactivity modes are indicated by colour: O–H insertion (green); N–H insertion (blue); formal C–H insertion (yellow); and cyclopropanation (pink). Synthesis of α-diazoamide

Convenient alternative synthesis of the Malassezia-derived virulence factor malassezione and related compounds

• Karu Ramesh and
• Stephen L. Bearne

Beilstein J. Org. Chem. 2025, 21, 1730–1736, doi:10.3762/bjoc.21.135

• yellow viscous oil (52 mg, 60%); 1H NMR (400 MHz, CDCl3) δ 7.46 (d, J = 7.9 Hz, 1H, ArH), 7.30–7.22 (m, 4H, ArH), 7.17 (t, J = 7.6 Hz, 1H, ArH), 7.09 (dd, J = 7.7 and 2.4 Hz, 3H, ArH), 6.99 (s, 1H), 5.24 (s, 4H, 2 × CH2), 6.99 (s, 4H, 2 × CH2) ppm; 13C NMR (100 MHz, CDCl3) δ 207.2, 137.6, 136.7, 128.9

On the aromaticity and photophysics of 1-arylbenzo[a]imidazo[5,1,2-cd]indolizines as bicolor fluorescent molecules for barium tagging in the study of double-beta decay of ¹³⁶Xe

• Eric Iván Velazco-Cabral,
• Fernando Auria-Luna,
• Juan Molina-Canteras,
• Miguel A. Vázquez,
• Iván Rivilla and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2025, 21, 1627–1638, doi:10.3762/bjoc.21.126

• imidazo[1,2-a]pyridine components. In reaction A, an hyperhomodesmotic equation [19] 2 + 3 → 4 + 1 was defined, in which the conjugation of the bicyclic imidazo[1,2-a]pyridine unit was removed, while preserving the ortho-disubstituted phenyl ring, highlighted in yellow in Scheme 1A. This reaction yielded

• phenyl (yellow) and imidazo[1,2-a]pyridine (blue) components of 1 and that these aromatic units preserve their respective aromatic characters. We next examined the aromatic character of benzo[a]imidazo[5,1,2-cd]indolizine 1 by analyzing its geometry in terms of bond equalization. Three possibilities were

• possible. The role of the crown ether and the para-phenylene moieties was also analyzed. The interactions of different sized crown ethers with Ba2+ and coordination with the aromatic ring modeled by means of benzene (14, highlighted in yellow in Scheme 2) were studied computationally. Although the

Synthesis of optically active folded cyclic dimers and trimers

• Ena Kumamoto,
• Kana Ogawa,
• Kazunori Okamoto and
• Yasuhiro Morisaki

Beilstein J. Org. Chem. 2025, 21, 1603–1612, doi:10.3762/bjoc.21.124

• %) as a light yellow solid. Rf = 0.73 (CHCl3/hexane = 1:2 v/v); 1H NMR (CDCl3, 500 MHz) δ 1.20 (s, 42H), 2.97–3.08 (m, 4H), 3.49–3.53 (m, 4H), 7.06 (s, 2H), 7.21 (s, 2H), 7.37–7.40 (m, 4H), 7.60–7.62 (m, 2H), 7.70–7.73 (m, 2H) ppm; 13C NMR (CDCl3, 125 MHz) δ 11.48, 18.84, 32.32, 32.57, 92.38, 93.65

• by recyclable HPLC (CH2Cl2 as an eluent) to afford (Sp)-4 (11.8 mg, 0.025 mmol, 45%) as a light yellow solid. Rf = 0.43 (CHCl3/hexane = 1:2 v/v). 1H NMR (CDCl3, 500 MHz) δ 2.98–3.09 (m, 4H), 3.39 (s, 2H), 3.43–3.55 (m, 4H), 7.09 (s, 2H), 7.21 (s, 2H), 7.37–7.41 (m, 4H), 7.62–7.65 (m, 2H), 7.70–7.73

• , respectively. Dimer (Sp)-6 (6.8 mg, 0.0062 mmol, 16%) was isolated from the first fraction by recyclable HPLC (CH2Cl2 as an eluent) as a light yellow solid. Trimer (Sp)-7 was isolated from the second fraction by recyclable HPLC (CH2Cl2 as an eluent). Further purification of (Sp)-7 was carried out using chiral

Azobenzene protonation as a tool for temperature sensing

• Antti Siiskonen,
• Sami Vesamäki and
• Arri Priimagi

Beilstein J. Org. Chem. 2025, 21, 1528–1534, doi:10.3762/bjoc.21.115

• and solvent polarity, we demonstrate that the degree of protonation, and thus solution color, is highly temperature-dependent, changing from pale yellow to deep red as temperature decreases. We also present mechanistic insights and compare our experimental findings with computational results. Results

• change from pale yellow to bright red. Since the protonated 3 shows minimal absorption between 300–400 nm (Figure 1B), the degree of protonation can be estimated by comparing the absorbance at 358 nm (neutral) and 502 nm (protonated). As the degree of protonation and initial concentration are known, the

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