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

• , Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama 337-8570, Japan 10.3762/bjoc.21.138 Abstract In single crystals of C–N atropisomeric N-(2-halophenyl)quinolin-2-one and the thione analogue, a unique association based on a halogen–π interaction was detected. In racemic and optically pure

• N-(2-bromo- or 2-chlorophenyl)quinolin-2-ones, homochiral layered polymers, which consist of (P)- or (M)-atropisomers, were formed through intermolecular halogen–π association. The halogen–π association in the racemates is due to a halogen bond (C–X···π) between a σ-hole on the halogen atom and a π

• other C–N atropisomeric compounds. In this article, we report the synthesis of atropisomeric N-(2-halophenyl)quinolin-2-ones (1a: X = Br, 1b: X = Cl) and N-(2-bromophenyl)quinoline-2-thione (2a), and the analysis of halogen–mediated intermolecular interactions (halogen bonding and n–π* interaction

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

• , Bulgaria Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark 10.3762/bjoc.21.105 Abstract Tautomerism in two new azo dyes, based on 7-hydroxyquinoline, has been considered from the viewpoint of the proton crane concept. Although 8-(phenyldiazenyl)quinolin-7-ol exists in

• solution as a mixture of azo and two hydrazone tautomers, as shown by the experimental and theoretical results, upon irradiation switching, based on long-range proton transfer, occurs in a limited extent. 8-(4-Hydroxy-1,2,3,5-tetrafluorophenyldiazenyl)quinolin-7-ol exists as a single enol (azo) tautomer

• azomethine group with an azo group. Therefore, two new compounds, based on 7-hydroxyquinoline (7OHQ), namely (E)-8-(phenyldiazenyl)quinolin-7-ol (1, Scheme 1) and 8-(4-Hydroxy-1,2,3,5-tetrafluorophenyldiazenyl)quinolin-7-ol (2) were synthesized and studied in variety of solvents. The implemented additional

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• , the 3,4-dihydro-1H-quinolin-2-one compounds were obtained in good to excellent yields. To gain further insights into the reaction mechanism, control experiments were conducted. The reaction was significantly inhibited by radical scavengers such as TEMPO, BHT, and hydroquinone, strongly suggesting a

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• the available Microbulbifer genomes [148]. Feeding AQ substrates 2-heptyl-1H-quinolin-4-one (36, HHQ, Figure 12), 2-heptyl-1-hydroxyquinolin-4-one (37, HQHO) to Microbulbifer sp. strain HZ11 yielded the brominated AQ products BrHHQ 38 and BrHQHO 39. A gene encoding a vanadium-depenent haloperoxidase

• ) bulbiferamide A (27) and (B) pseudobulbiferamide A (31). Chemical structures of 2-heptyl-1H-quinolin-4-one (36, HHQ), 2-heptyl-1-hydroxyquinolin-4-one (37, HQHO), and their brominated products BrHHQ 38 and BrHQHO 39. Summary of marine sources, geographical locations, and key characteristics of Microbulbifer

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• leading to product formation with good to excellent isolated yields (Scheme 16). On the other hand, the synthesis of indolo[3,2-b]indoles and indolo[2,3-b]indoles were not selective leading to byproducts such as 5,7-dihydro-6H-indolo[2,3-c]quinolin-6-one, 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-one, and

Chemical and biosynthetic potential of Penicillium shentong XL-F41

• Ran Zou,
• Xin Li,
• Xiaochen Chen,
• Yue-Wei Guo and
• Baofu Xu

Beilstein J. Org. Chem. 2024, 20, 597–606, doi:10.3762/bjoc.20.52

• substructure at C-14 with a methine at C-16, indicated by the methoxy group. The position of the methoxy substituent was established by HMBC correlations, and the 13C NMR data suggested that compound 1 includes a 4-oxo-2,3-dihydro-(1H)-quinolin-3-yl fragment. The planar structure was established from HMBC

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• reaction of 8-aminoquinoline amides using activated and unactivated alkyl bromides as the bromine source (Scheme 1, reaction 4). Results and Discussion At the beginning of this investigation, N-(quinolin-8-yl)benzamide (1a) and ethyl bromoacetate (2a) were selected as model substrates to screen the

• highly efficient C5-bromination protocol has been established. Having identified the optimal reaction conditions for the bromination of N-(quinolin-8-yl)benzamide (1a) with ethyl bromoacetate (2a) (Table 1, entry 12), we next examined the substrate scope and limitations of our method with an array of 8

Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

• Yordanka Mollova-Sapundzhieva,
• Plamen Angelov,
• Danail Georgiev and
• Pavel Yanev

Beilstein J. Org. Chem. 2023, 19, 1804–1810, doi:10.3762/bjoc.19.132

• sensing; Introduction Among the vast number of biologically active quinoline derivatives [1][2], the subclass of 4-quinolones (also referred to as 4-oxo-1,4-dihydroquinolines, quinolin-4(1H)-ones, or 4-hydroxyquinolines) is of great importance with its rich variety of bioactive compounds. Perhaps the

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• complex obtainable via a straightforward synthesis, with improved solubility, concerning our previous Co(II) complexes [21]. Thus, the new Co(II) complex bears two 1-benzyl-4-(quinolin-2-yl)-1H-1,2,3-triazole (BzQuTr) units, that were obtained through a copper-catalyzed alkyne–azide cycloaddition (CuAAC

• maintaining high selectivity for carbon products. Results and Discussion Synthesis and characterization of the new Co(II)-based catalyst The novel cobalt(II) complex 1 was synthesized in dry methanol (MeOH) by mixing in a 2:1 ratio, the chelating diimine ligand, 1-benzyl-4-(quinolin-2-yl)-1H-1,2,3-triazole

One-pot double annulations to confer diastereoselective spirooxindolepyrrolothiazoles

• Juan Lu,
• Bin Yao,
• Desheng Zhan,
• Zhuo Sun,
• Yun Ji and
• Xiaofeng Zhang

Beilstein J. Org. Chem. 2022, 18, 1607–1616, doi:10.3762/bjoc.18.171

• UMB32 and UMB136 [33][34]. Zhang developed 4-aminoquinolines for the synthesis of fluorinated analogues of acetylcholinesterase (AChE) inhibitors [35] in cascade reactions, such as one-step syntheses of quinolines. Quinolin-4-ols involving histone acetyltransferases (HAT) inhibitors [36][37], as well as

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• )) (10 nm)/X wt % DICzTRZ or ICzTRZ: CzSi (20 nm)/PPF (2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan) (5 nm)/TPBi (1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene) (50 nm)/Liq (lithium quinolin-8-olate) (1 nm)/Al (80 nm), where X is 20 or 30. The PVK layer is applied to facilitate hole injection from

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• , Brazil Laboratório de Bioinorgânica e Materiais Porfirínicos, Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, RS, 97105-900, Brazil 10.3762/bjoc.17.191 Abstract A new series of ten examples of Schiff bases, namely (E)-2-(((2-alkyl(aryl/heteroaryl)-4-(trifluoromethyl)quinolin-6

• (Scheme 1). Results and Discussion Chemistry The synthetic routes and structures for the synthesis of (E)-2-(((2-alkyl(aryl/heteroaryl)-4-(trifluoromethyl)quinolin-6-yl)imino)methyl)phenols 3 are collected in Scheme 2 and Scheme 3. First, a series of six 6-amino-2-alkyl(aryl/heteroaryl)-4-(trifluoromethyl

• reaction (TLC) and cooling the mixture to room temperature, the solid was filtered under reduced pressure. The crude compounds 3 were purified by recrystallization from ethanol to provide the desired (E)-2-(((4-(trifluoromethyl)quinolin-6-yl)imino)methyl) phenols 3 in 20–91% yield. Spectral data (E)-2-(((2

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

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• all dyes 3–7 which was collected by filtration and recrystallized from ethanol to obtain the pure dyes. ((E)-2-(1-(4-Aminophenyl)-3-(2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)allylidene)malononitrile) (3) Dark purple solid; yield: 64%; mp 236–238 °C; FTIR (cm−1): 3441, 3349, 3224, 2920

• recrystallized from ethanol to obtain the pure dyes. (2-((E)-1-(4-(((E)-2-Hydroxybenzylidene)amino)phenyl)-3-(2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)allylidene)malononitrile) (8) Dark purple solid; yield 94%; mp 202–203 °C; FTIR (cm−1): 3479 (broad), 3062, 2943, 2835, 2208, 1614, 1560, 1510

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• perfluoroalkyl benzoic acid derivatives. A plausible mechanism for the perfluoroalkylation of N-(quinolin-8-yl)benzamides is proposed in Figure 34. First, C–H activation of the benzamide substrate with copper produces a cyclometalated complex. Meanwhile, perfluoroalkyl radicals are generated by electron transfer

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• -lactams [6], quinolin-5-ones [7], spirobisglutarimides [8], indolizines [9], and spiro carbocyclic frameworks [10]. However, most of the reported synthetic transformations utilize either allylic hydroxy-protected or allyl halide-substituted MBH adducts [11][12][13][14][15][16][17][18][19][20][21][22][23

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• variety of methods [14][15], and many of the targets exhibited biological activity (Figure 1). For example, bis(2-pyridyl) diselenide I has the potential to mitigate oxidative stress and inhibits the AChE activity [16], bis(quinolin-8-yl) diselenide (II) exhibited antioxidant activity in a skin cell model

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• containing two different aryl groups at α- and β-positions via sequential Pd-catalyzed C–H bond functionalization steps was studied (Scheme 4). The reaction of 1 equiv of 4-(5,6-dihydropyrrolo[3,2,1-ij]quinolin-2-yl)benzonitrile 2 and 1.5 equiv of a set of aryl bromides using again 2 mol % PdCl(C3H5)(dppb

• , the use of a longer reaction time (48 h) allowed to reach an almost complete conversion of 2, and the carbazole 27 was isolated in 62% yield. A slightly lower yield in the carbazole 28 was obtained from (4-(5,6-dihydropyrrolo[3,2,1-ij]quinolin-2-yl)phenyl)(phenyl)methanone 5 and 1,2-dibromobenzene

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• Bebq2 host were employed instead, where Bebq2 is bis(benzo[h]quinolin-10-olato-κN,κO)beryllium(II). In spite of that, much lower LT97 values were observed most likely due to a higher charge and exciton concentration in the host layer at such low doping concentration. Such compound represents the most

Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

• Dandan Li,
• Naoya Oku,
• Atsumi Hasada,
• Masafumi Shimizu and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

• -1 Yanagido, Gifu 501-1193, Japan 10.3762/bjoc.14.122 Abstract Exploration of rhizobacteria of the genus Burkholderia as an under-tapped resource of bioactive molecules resulted in the isolation of two new antimicrobial 2-alkyl-4-quinolones. (E)-2-(Hept-2-en-1-yl)quinolin-4(1H)-one (1) and (E)-2

• -(non-2-en-1-yl)quinolin-4(1H)-one (3) were isolated from the culture broth of strain MBAF1239 together with four known alkylquinolones (2 and 4–6), pyrrolnitrin (7), and BN-227 (8). The structures of 1 and 3 were unambiguously characterized using NMR spectroscopy and mass spectrometry. Compounds 1–8

• ) [15] (Figure 3). Thus, the structure of 3 was concluded to be (E)-2-(non-2-en-1-yl)quinolin-4(1H)-one. The molecular ions of 1 were observed at m/z 242 and m/z 240 in the positive and negative modes, respectively, revealing a 28 Da smaller molecular weight for 1 relative to 3. The 1H NMR spectra of

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• -2-yl, quinolin-2-yl, 5,6-dihydro-4H-1,3-oxazin-2-yl). Such sydnones reacted with potassium 2-substituted acetylene trifluoroborates under boron trifluoride diethyl etherate catalysis to give corresponding pyrazolo[3',4':4,5][1,2]azaborolo[2,3-a]pyridin-5-ium-4-uides (or quinolin-5-ium-4-uide) in

Halogen-containing thiazole orange analogues – new fluorogenic DNA stains

• Aleksey A. Vasilev,
• Meglena I. Kandinska,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• David Sucunza,
• Juan J. Vaquero,
• Obis D. Castaño,
• Stanislav Baluschev and
• Silvia E. Angelova

Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283

• -Chloro-1-methyl-4-((3-methylbenzo[d]thiazol-2(3H)-ylidene)methyl)quinolin-1-ium iodide (TO-7Cl) Procedures A1 and A2: 2,3-Dimethylbenzo[d]thiazolium methyl sulfate (2a, 1 mmol) and the appropriate 4,7-dichloro-1-methylquinolinium methyl sulfate (4a, 1 mmol) were finely ground together in a mortar and the

• , 1450, 1370, 1315, 1110, 974, 780, 750, 725 cm−1; GC–MS (m/z): 324 (100%, [M+] − CH2Ph); elemental analysis (%) for C25H20ClIN2S Mw = 542.86, calcd for N 5.16; found: 5.53. 2-((1-Benzyl-7-(trifluoromethyl)quinolin-4(1H)-ylidene)methyl)-3-methylbenzo[d]thiazol-3-ium iodide (5b): Yield 68%; mp 284–285 °C

• ) νmax: 1600, 1520, 1450, 1455, 1375, 1325, 1280, 1210, 1150, 1120, 885, 865, 790, 725, 610, 550, 401 cm−1; GC–MS (m/z): 480 (100%, [M+] – CH2Ph); elemental analysis (%) for C25H19BrClIN2S Mw = 621.76, calcd for N, 4.51; found: 4.95. 2-((1-Benzyl-7-(trifluoromethyl)quinolin-4(1H)-ylidene)methyl)-5-bromo

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• , and is of considerable pharmacological interest due to the significant cytotoxicity of numerous representatives [3]. A unique subclass of the aporphinoid alkaloids are the oxoisoaporphines (7H-dibenzo[de,h]quinolin-7-ones, e.g., menisporphine, (2)), which at the first glance appear to be not derived

A novel method for heterocyclic amide–thioamide transformations

• Walid Fathalla,
• Ibrahim A. I. Ali and
• Pavel Pazdera

Beilstein J. Org. Chem. 2017, 13, 174–181, doi:10.3762/bjoc.13.20

• phthalizin-1-thiones C7 and C8a. Synthesis of quinolin-2-thiones C9 and quinoxalin-2-thiones C10–C13a. Supporting Information Supporting Information File 60: Additional experimental and analytical data. Acknowledgements We would like to thank the Department of Organic Chemistry, Faculty of Science, Masaryk