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

• at room temperature [41][42][43]. The central biphenyl moiety of conjugates 2a–h also rotates freely, forming an equilibrium mixture of P and M conformers. The relative amounts of P and M conformers depend on the chirality of the linked amine moieties. Figure 1a shows the UV and CD spectra of the

• )-5,7-dihydro-6H-dibenzo[c,e]azepin-6-yl]propan-1-ol ((S)-2a). A mixture of m-quaterphenyl probe 1 (290 mg, 0.526 mmol), ʟ-alaninol (48.3 mg, 0.643 mmol) and K2CO3 (294 mg, 2.12 mmol) in CH3CN (12 mL) was stirred at 85 °C for 3 h. After cooling to room temperature, the mixture was filtered through a pad

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

• -synthesis of formamides and formates was achieved in particularly good yield by selective oxidation of DHA using a Cu/Al2O3 catalyst with single active CuII species at room temperature without using a base (Scheme 20). 1-Hydroxypropan-2-one Gu et al. reported the [3 + 2] cyclization reaction of 1

• HFO with benzoic acid amide or furan-2-carboxamide in 1:1 molar ratio at 70 °C for 4–8 h (Scheme 42, path c) [132]. The reaction of HFO with 2-methylfuran in a 1:2.2 molar ratio in diethyl ether solution at room temperature in the presence of catalytic amounts of perchloric acid for 5 hours led to the

Solar thermal fuels: azobenzene as a cyclic photon–heat transduction platform

• Jie Yan,
• Shaodong Sun,
• Minghao Wang and
• Si Wu

Beilstein J. Org. Chem. 2025, 21, 2036–2047, doi:10.3762/bjoc.21.159

• temperature and the Tm of the isomerized cis-azobenzene is below room temperature, while others require solvent-assisted charging mechanisms [70][71]. This structural and functional diversity makes them particularly valuable for solar thermal storage applications. Feng et al. incorporated fluorinated

• azobenzene small molecules into polymer fibers [65], enabling solvent-free charging and discharging under visible light (Figure 6a). This material exhibited good capacity for releasing high-temperature heat (80–95 °C) at room temperature and in cold environments, along with an energy storage lifetime

• azobenzene derivatives [82][83][84][85][86][87][88]. From an energy charging perspective, some solvent-free systems store energy in the solid state [89] or via photoinduced solid–liquid phase transitions [61][69][74], which occur because the melting temperature (Tm) of trans-azobenzene is above room

Switchable pathways of multicomponent heterocyclizations of 5-amino-1,2,4-triazoles with salicylaldehydes and pyruvic acid

• Yana I. Sakhno,
• Oleksander V. Buravov,
• Kostyantyn Yu. Yurkov,
• Anastasia Yu. Andryushchenko,
• Svitlana V. Shishkina and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2025, 21, 2030–2035, doi:10.3762/bjoc.21.158

• -triazoles, pyruvic acid, and salicylaldehydes were studied under different conditions. Upon conventional heating, benzotriazolooxadiazocine-5-carboxylic acids were formed in the three-component reactions as single reaction products. Upon ultrasonic activation or mechanical stirring at room temperature, the

• -aminotriazoles 1a,b having pronounced electron-donating substituents (methylthio- and methoxy groups). On the other hand, the MCR of the reagents 1a, 2a–c and 3 under ultrasonic irradiation for 2 h at room temperature (25 °C) (Scheme 3) afforded a mixture of 5-(2-hydroxyphenyl)-2-(methylthio)-7-((3-(methylthio

• compounds 5d and 6d). Unfortunately, all attempts to separate these mixtures were unsuccessful. However, repeating the reaction under mechanical stirring at room temperature for 72 h yielded tetrahydrotriazolopyrimidine-7-carboxylic acids 5a–c as a mixture of two diastereomers (Scheme 3, Table 2). In the

Aryl iodane-induced cascade arylation–1,2-silyl shift–heterocyclization of propargylsilanes under copper catalysis

• Rasma Kroņkalne,
• Rūdolfs Beļaunieks,
• Armands Sebris,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2025, 21, 1984–1994, doi:10.3762/bjoc.21.154

• ) resulted in the formation of more side products (Table 3, entry 9), and we therefore decided to proceed with 5 mol % of the catalyst for the substrate scope. We also observed that, in the absence of base, even at room temperature, only the protodecupration product 12 was obtained (with up to 69% NMR yield

Asymmetric total synthesis of tricyclic prostaglandin D2 metabolite methyl ester via oxidative radical cyclization

• Miao Xiao,
• Liuyang Pu,
• Qiaoli Shang,
• Lei Zhu and
• Jun Huang

Beilstein J. Org. Chem. 2025, 21, 1964–1972, doi:10.3762/bjoc.21.152

• was initially investigated (Scheme 3). Chan’s diene (16) was subjected to condensation with freshly distilled aldehyde 17 in THF at room temperature, using a catalytic system comprising Ti(OiPr)4/(S)-BINOL complex (2.0 mol %). Subsequent deprotection with pyridinium p-toluenesulfonate (PPTS) at 0 °C

• was treated with p-toluenesulfonic acid (p-TSA) in EtOH at room temperature to afford ketal 24 in 83% yield as a single diastereomer. Subsequently, palladium-catalyzed decarboxylative allylation delivered compound 25 in 89% yield. The efficiency of our first-generation strategy for asymmetric

• -triisopropylbenzenethiol (TRIPSH) through a hydrogen atom transfer (HAT) process to afford intermediate 30 [39], which then cyclized to yield product 21. To install the allyl group at C8 with the desired stereochemistry, we treated compound 21 with p-TSA in EtOH at room temperature, and ketal 31 was obtained in 87% yield

Synthesis of N-doped chiral macrocycles by regioselective palladium-catalyzed arylation

• Shuhai Qiu and
• Junzhi Liu

Beilstein J. Org. Chem. 2025, 21, 1917–1923, doi:10.3762/bjoc.21.149

• (c) MC3. (d) Molecular arrangements of MC3. Hydrogen atoms are omitted for clarity. (a) Absorptions and (b) emissions of compounds 3a, 3b, MC1, MC2, and MC3 measured in dichloromethane at room temperature. The inset shows the photographs under UV light at 365 nm. The concentration is 10 μM

• . Calculated frontier molecular orbitals and relative energy levels of MC1 (left), MC2 (middle), and MC3 (right) calculated at the B3LYP/6-31G(d) level of theory. (a) CD spectra, (b) |gabs|, and (c) glum values of enantiomers of MC1 measured in dichloromethane at room temperature. The concentrations were 10 μM

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

• , 5.4 mmol) and DMAP (132 mg, 1.1 mmol) in CH2Cl2 (45 mL) at room temperature. After 4 d, saturated aqueous NaHCO3 (45 mL) was added and the layers were separated. The organic layer was dried (MgSO4), filtered and evaporated. The residue was purified by column chromatography on silica gel, eluting with

• , dimethyl sulphide (51.3 mL, 693 mmol) was added, and the mixture was warmed to room temperature and stirred. After 16 h, the solvent was evaporated and the residue was purified by column chromatography on silica gel, eluting with EtOAc/petrol 1:1. The product was recrystallised from n-hexane/CH2Cl2 to give

• -methylmaleimide (255 mg, 2.30 mmol) was added and the mixture was heated under reflux. After 3 h, further N-methylmaleimide (128 mg, 1.84 mmol) was added, and the mixture was heated under reflux for a further 1 h. The mixture was cooled to room temperature and the solvent was evaporated. The crude product

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

• enantioselective synthesis of planarly chiral macrocycles through a dynamic kinetic resolution approach [15]. Despite bearing an amino group on the phenyl ring, the configuration of the macrocyclic paracyclophane 32 was found to be unstable at room temperature. Consequently, by employing a CPA-catalyzed asymmetric

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

Fe-catalyzed efficient synthesis of 2,4- and 4-substituted quinolines via C(sp²)–C(sp²) bond scission of styrenes

• Prafull A. Jagtap,
• Manish M. Petkar,
• Vaishnavi R. Sawant and
• Bhalchandra M. Bhanage

Beilstein J. Org. Chem. 2025, 21, 1799–1807, doi:10.3762/bjoc.21.142

• 26% yield. Then, in reaction 3, a one-pot, two-step reaction involving phenylglyoxalic acid (2aa) was carried out. In step 1, compounds 1a and 2aa were stirred at room temperature for 5 minutes in the presence of a catalyst and an additive. Subsequently, in step 2, styrene (2a) was added, and the

Unique halogen–π association detected in single crystals of C–N atropisomeric N-(2-halophenyl)quinolin-2-one derivatives and the thione analogue

• Mai Uchibori,
• Nanami Murate,
• Kanako Shima,
• Tatsunori Sakagami,
• Ko Kanehisa,
• Gary James Richards,
• Akiko Hori and
• Osamu Kitagawa

Beilstein J. Org. Chem. 2025, 21, 1748–1756, doi:10.3762/bjoc.21.138

• vapour diffusion of hexane into a methanol solution of the compound at room temperature) and their X-ray crystal structural analyses were performed (Figure 2) [33]. In the crystals of rac-1a, a π-type intermolecular interaction between the bromine atom and the benzene ring of the quinolinone was found

• observed in the crystals of optically pure forms (P)-1a,b (Figure 3, single crystals of (P)-1a,b were obtained by vapour diffusion of hexane into a methanol solution of the compound at room temperature) [34]. Meanwhile, the halogen atoms in (P)-1a,b were found to interact with the C4 atom on the lactam

• racemic quinolinones rac-1 in Figure 2 (single crystals of rac-2a were obtained from slow evaporation of hexane/methanol (1:1) mixture at room temperature) [37]. That is, in contrast to rac-1, in which homochiral layered polymer chains were formed, crystallization of quinoline-2-thione rac-2a led to the

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

• are uncorrected. tert-Butyl 3-(2-methoxy-2-oxoethyl)-1H-indole-1-carboxylate (21). A solution of indol-3-yl acetic acid (20, 5.1 g, 29.0 mmol, 1.0 equiv) in dry MeOH (200 mL) was cooled to 0 °C, and SOCl2 (10.5 mL, 145 mmol, 5.0 equiv) was added slowly. After stirring for 12 h at room temperature, the

• DMAP (0.63 g, 5.2 mmol, 0.2 equiv) were added [32]. The mixture was stirred for 2 h at room temperature after which the solvent was removed under reduced pressure. The residue was dissolved in EtOAc (250 mL) and subsequently washed with saturated aqueous NH4Cl (150 mL), saturated aqueous NaHCO3 (150 mL

• , 3 equiv) in H2O (250 mL) was added to a solution of 21 (5.0 g, 17.2 mmol, 1.0 equiv) in THF (300 mL) and MeOH (150 mL). After stirring for 18 h at room temperature, the mixture was concentrated in vacuo and a 10% aqueous solution of citric acid (100 mL) was added. The aqueous layer was extracted

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

• samples were analyzed in CHCl3 at room temperature. Photoluminescence (PL) spectra were recorded on a JASCO FP-8500 spectrofluorometer, and samples were analyzed in CHCl3 at room temperature. Absolute PL quantum efficiency was calculated on a JASCO FP-8500 with an ILF-835 integrating sphere. The PL

• with CHCl3 as a solvent at room temperature. Circularly polarized luminescence (CPL) spectra were recorded on a JASCO CPL-300 with CHCl3 as a solvent at room temperature. Materials Commercially available compounds used without purification are as follows: Pd2(dba)3, SPhos (2-dicyclohexylphosphino-2',6

• 16 h. After the reaction mixture was cooled to room temperature, the solvent was removed with a rotary evaporator. The residue was purified by column chromatography on SiO2 (CHCl3/hexane = 1/4 v/v as an eluent) and by recyclable HPLC (CH2Cl2 as an eluent) to afford (Sp)-3 (24.6 mg, 0.031 mmol, 39

Chemical synthesis of glycan motifs from the antitumor agent PI-88 through an orthogonal one-pot glycosylation strategy

• Shaokang Yang,
• Xingchun Sun,
• Hanyingzi Fan and
• Guozhi Xiao

Beilstein J. Org. Chem. 2025, 21, 1587–1594, doi:10.3762/bjoc.21.122

• in mannosyl PVB 8 (1.0 equiv) in the presence of TMSOTf as catalyst proceeded smoothly at 0 °C to room temperature, affording the α-Man-(1→3)-Man PVB disaccharide. The further coupling of the above PVB disaccharide with the poorly reactive 2-OH in mannoside 9 (0.9 equiv) under activation with NIS and

• TMSOTf at 0 °C to room temperature, successfully furnished the desired α-Man-(1→3)-α-Man-(1→3)-α-Man trisaccharide 10 in 87% yield in a one pot manner. Removal of TBDPS group in 10 with 70% HF·pyridine and subsequent phosphitylation of the resulting free alcohol with phosphoramidite 11 provided the

• all Bz groups with 1 M NaOH (dioxane/MeOH/H2O, room temperature). The monophosphorylated trisaccharide 1 was obtained in 60% overall yield over two steps from 12 after purification over a SephadexTM LH-20 column. It was noted that the switch of deprotection sequences (first Bz groups, second Bn and

Thermodynamic equilibrium between locally excited and charge transfer states in perylene–phenothiazine dyads

• Issei Fukunaga,
• Shunsuke Kobashi,
• Yuki Nagai,
• Hiroki Horita,
• Hiromitsu Maeda and
• Yoichi Kobayashi

Beilstein J. Org. Chem. 2025, 21, 1577–1586, doi:10.3762/bjoc.21.121

• the degree of electronic interaction between the donor PTZ and acceptor Pe moieties, as indicated by the decreased overlap between HOMO and LUMO. UV–vis absorption spectra of the Pe–PTZ derivatives were recorded in benzene at room temperature (Figure 3a). All compounds exhibited characteristic

• phenothiazine derivative, 12-phenyl-12H-benzo[a]phenothiazine, in toluene at room temperature has been estimated to be 28 ps (with an additional minor 0.7 ps component attributed to small-scale structural changes) [17]. It is also noted that the relaxation dynamics depend on the molecular structure and the

• -31+G(d,p)//B3LYP/6-31+G(d,p) level of theory. Steady-state (a) absorption and (b) emission spectra of Pe–PTZ, Pe–PTZ(TPA), Pe–PTZ(TPA)2, and Pe–Ph–PTZ(TPA)2 in benzene at room temperature. The excitation wavelength was 420 nm for Pe–PTZ, Pe–PTZ(TPA)2, and Pe–Ph–PTZ(TPA)2, and 415 nm for Pe–PTZ(TPA

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

• acyclic heteroaromatics [26][27]. Thus, to a solution of 4 in CH2Cl2 was added 15 equivalents of PIFA at −78 °C and stirred for 3 h. The mixture was then allowed to warm to room temperature to give a dark solution. The system was worked-up with NaBH4/MeOH for 10 minutes followed by extraction with CH2Cl2

• and evaporation of the solvent to afford a crude product, which was recrystallized from THF to give 5 in 58% yield. Due to its poor solubility in common organic solvents, the 1H NMR spectrum could only be recorded in DMSO. At room temperature, the 1H NMR spectrum in DMSO-d6 exhibited broad signals in

• 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

• decomposing even at room temperature. Taking these into account, we have synthesized compound 5c using an alternative route starting from the chloro oxime 4a and 5-iminothiohydantoin 2j (Scheme 4), obtained similarly to other dipolarophiles [22]. The total yield of the product 5c in this case turned out to be

• 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

Ambident reactivity of enolizable 5-mercapto-1H-tetrazoles in trapping reactions with in situ-generated thiocarbonyl S-methanides derived from sterically crowded cycloaliphatic thioketones

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Marcin Palusiak,
• Heinz Heimgartner,
• Marta Denel-Bobrowska and
• Agnieszka B. Olejniczak

Beilstein J. Org. Chem. 2025, 21, 1508–1519, doi:10.3762/bjoc.21.113

• stable 9 into the more stable 10 was observed in some cases (derived from 1c) in the CDCl3 solution at room temperature. Therefore, it seems likely that the first step of the reaction is the N–H insertion process. The compositions of the obtained crude mixtures suggest that the final addition step

• the sterically most hindered dispiro-cyclohexyl-substituted thiocarbonyl S-methanide 2d. Notably, in some cases spontaneous isomerization of the generally less stable thioaminals 9 in CDCl3 solution at room temperature was also observed. It seems likely that this isomerization follows an

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

• isomer of azobenzene (AB) is a few days. Arylazopyrazole-based molecular switches are one of the profoundly explored systems in recent times due to their superior bidirectional photoswitching and long half-life (over a thousand days at room temperature) of Z isomers. Herein, we utilize an efficient solid

• barrier and the long lifetime of the non-equilibrium states are at the origin of their remarkable stability at room temperature. The remarkable stability of the states at ambient conditions provides an opportunity to use a single FNAAP molecule as an 8-bit operation. We propose to switch the molecule

Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides

• Nadezhda M. Metalnikova,
• Nikita S. Antonkin,
• Tuan K. Nguyen,
• Natalia S. Soldatova,
• Alexander V. Nyuchev,
• Mikhail A. Kinzhalov and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110

• . Finally, control experiments without irradiation gave only traces of the benzamide 2aa showing no activation by the Ru complex at room temperature (Table 1, entry 24). An experiment conducted under an air atmosphere yielded only 9% of 2aa (Table 1, entry 25) indicating that the presence of atmospheric

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

• in the literature [62][63]. The suspension was stirred magnetically for 6 hours at room temperature, resulting in the formation of a blue-coloured catalyst. We aimed to vary the amount of copper loaded onto the silica surface to achieve different catalyst loadings (Cu wt %) and compared their

• -aminopropyltriethoxysilane (2 mmol) in toluene (10 mL). The suspension was sonicated for 2 h in an US bath (Power 200 W, Frequency 80 kHz). The resulting silica was then filtered, washed with toluene and chloroform, and dried under vacuum at room temperature for 12 hours. The derivatised silica was characterised by means of

• TGA and FTIR. Si-MonoAm (200 mg) and 16 mg of Cu(I)Cl were dispersed in 4 mL of THF. The mixture was stirred at room temperature for 4 hours, filtered under reduced pressure, and the powder was washed with THF and CHCl3. The resulting product was then kept in a desiccator overnight and fully

Wittig reaction of cyclobisbiphenylenecarbonyl

• Taito Moribe,
• Junichiro Hirano,
• Hideaki Takano,
• Hiroshi Shinokubo and
• Norihito Fukui

Beilstein J. Org. Chem. 2025, 21, 1454–1461, doi:10.3762/bjoc.21.107

• of 1.5 kcal mol−1 and 3.2 cal K−1 mol−1, respectively (Figure S26 in Supporting Information File 1). These physical parameters give a free energy ΔG298 of 0.55 kcal mol−1, indicating approximately a 2:5 ratio of figure-eight and bathtub conformations at room temperature. Mono-olefin 3 exhibited

• slightly preferred at room temperature with approximately a 3:2 ratio of figure-eight and bathtub conformations. We have also estimated the activation barriers of the interconversion of 3 and 5 between the figure-eight and bathtub conformations by measuring VT 1H NMR spectra in toluene-d8 because 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

• core [17]. Compared to 4a, compound 4b exhibits bathochromic shifts of 12 nm in absorption and 45 nm in emission, as well as a higher ΦF (0.75 vs 0.68). Both isomers display TADF at room temperature and phosphorescence at 77 K. Notably, 4a demonstrates a long-lived red afterglow persisting for up to 30

• showed more intense phosphorescence and an extended emission lifetime in dilute solution. Notably, it demonstrated room-temperature dual-emission CPL originating from both prompt fluorescence and long-lived phosphorescence, a rare feature in helicene systems. In a subsequent study, the same group

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

• number of industrially used azo dyes [1][3] and therefore its tautomerism is studied in details. The existing experimental data for low polar solvents (cyclohexane and tetrachloromethane) indicate a ΔG value of around 0.4 kcal/mol [53] at room temperature, which gives a prevalence of the E-tautomer (a

• makes possible to analyze the tautomerism in 1 as a function of (E+KE) and KK. The NMR spectra of 1 in acetonitrile-d3 are in agreement with the above analysis of tautomeric equilibration based on theoretical calculations and UV spectra. At room temperature the proton signals are very broad and

• agreement with other integrals in the proton spectrum. This means that at 243 K the mixture 1E+1KE is still dominating, but the content of 1KK slightly increases comparing to room temperature. This is not surprising bearing in mind that in the case of compound 3 the cooling in non-protic solvents (i.e