Introduction of peripheral nitrogen atoms to cyclo-meta-phenylenes

• Koki Ikemoto and
• Hiroyuki Isobe

Beilstein J. Org. Chem. 2024, 20, 1207–1212, doi:10.3762/bjoc.20.103

• configurations preferred over T-shaped stackings [22]. In our study, we observed that pyridine–pyridine stacks were preferred in the crystal stacking (Figure 3), which might be attributed to the biased ESPs on the macrocycles. Finally, we found that nitrogen locations altered chemical characteristics of nitrogen

• shown. (b) Packing structures. Chloroform molecules in the crystal of 3b are omitted for clarity. X-ray charge density analyses of 3a and [6]CMP. (a) Deformation map (Fo – Fc) of a pyridine ring in 3a (contour interval: 0.05 e·Å−3, positive: red, negative: blue). (b) Electrostatic potential maps mapped

Synthesis of 1,4-azaphosphinine nucleosides and evaluation as inhibitors of human cytidine deaminase and APOBEC3A

• Maksim V. Kvach,
• Stefan Harjes,
• Harikrishnan M. Kurup,
• Geoffrey B. Jameson,
• Elena Harjes and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2024, 20, 1088–1098, doi:10.3762/bjoc.20.96

• obtained in 84% yield after silica gel purification. Removal of the Boc protecting group from 6 in the presence of trifluoroacetic acid in DCM at room temperature overnight, followed by cyclisation in boiling pyridine/triethylamine, led to 4-hydroxy-1,4-azaphosphinan-2,4-dione (7) in 84% yield. The free

• dichlorophosphane 9 from commercially available PCl3 and ethyl vinyl ether using a previously published procedure [68]. Compound 9 reacted with 1 equiv of benzyl alcohol in absolute Et2O and pyridine at −78 °C, followed by quenching of the reaction mixture with H2O. This procedure provided phosphinate 10 in more

• chloroacetate, Et3N, TMSCl, CH2Cl2, rt, 5 d, 84% yield; v) trifluoroacetic acid, CH2Cl2, rt, overnight, then 5 h reflux in pyridine/Et3N, 84% yield; vi) BnOH, O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TBTU), Et3N, DCE, reflux, 3 h, 65% yield; vii) BnOH, absolute Et2O, pyridine, −78

Mild and efficient synthesis and base-promoted rearrangement of novel isoxazolo[4,5-b]pyridines

• Vladislav V. Nikol’skiy,
• Mikhail E. Minyaev,
• Maxim A. Bastrakov and
• Alexey M. Starosotnikov

Beilstein J. Org. Chem. 2024, 20, 1069–1075, doi:10.3762/bjoc.20.94

• the basis of readily available 2-chloro-3-nitropyridines via the intramolecular nucleophilic substitution of the nitro group as a key step. The previously unknown base-promoted Boulton–Katritzky rearrangement of isoxazolo[4,5-b]pyridine-3-carbaldehyde arylhydrazones into 3-hydroxy-2-(2-aryl[1,2,3

• either annulation of an isoxazole fragment to a pyridine cycle or vice versa formation of a pyridine ring based on appropriately substituted isoxazoles. In the first case (Scheme 1A) 3-halo- [11][15][16][17][18][19] or 3-hydroxypyridines [8][20] bearing a suitable functionality in position 2 were used

• isoxazolo[4,5-b]pyridine core synthesis have been summarized in a microreview [22]. Here, we wish to report an efficient method for the synthesis of isoxazolo[4,5-b]pyridines bearing electron-withdrawing groups (EWG) at positions 3 and 6 starting from readily available 2-chloro-3-nitro-6-R-pyridines as

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• [2,3-e]pyrazine-11,12-dicarbonitrile (3a) An oven dried sealed tube was charged with 5,6-diaminopyrazine-2,3-dicarbonitrile (12) (56.6 mg, 0.353 mmol), 1,2-aceanthrylenedione (56.6 mg, 0.244 mmol) and dry pyridine (3 mL). The resulting orange suspension was heated to 80 °C for 72 hours. After this time

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

• and by adding pyridine and CsF as additives. By this route the products were obtained under mild reaction conditions applying low pressure of CO, temperature of 80 °C for 12 h. A stoichiometric amount of I2 was necessary to restore the catalyst that underwent a possible reduction (Scheme 41). Another

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• catalytic system of B2cat2 and 4-phenylpyridine to form pyridine-boryl radicals which initiated ring expansion. The method was shown to be similarly tolerable of functional groups as Procter’s synthesis. Intramolecular crossed [2 + 2] cycloadditions offer an alternative approach to 1,2-disubstituted BCHs

• -substituted endo-1,5-BCHs (±)-57a–e. Substrate modification was also possible, with oxidative transformation of a bridgehead furan leading to 1,5-BCH acid (±)-60 and pyridine reduction to secondary amine (±)-61 (Scheme 5B) [42]. Furthermore, 1,5-BCH (±)-64 was synthesised as a bioisostere of the fungicide

• the synthesis of polysubstituted BCHeps bearing a wide range of different substitution patterns. Their synthesis utilises boronyl radicals generated from diboron compounds by a pyridine cocatalyst to induce the [2σ + 2σ] cycloaddition of cyclopropanes and bicyclobutanes [87]. Similarly densely

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions

• Martyn Jevric,
• Julian Klepp,
• Johannes Puschnig,
• Oscar Lamb,
• Christopher J. Sumby and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2024, 20, 823–829, doi:10.3762/bjoc.20.74

• 10.3762/bjoc.20.74 Abstract A skeletal rearrangement of a series of 6,8-dioxabicyclo[3.2.1]octan-4-ols has been developed using SOCl2 in the presence of pyridine. An oxygen migration from C5 to C4 was observed when the C4 alcohols were treated with SOCl2/pyridine, giving a 2-chloro-3,8-dioxabicyclo[3.2.1

• chiral auxiliary 10a, and following a survey of conditions and isolation protocols, a 90% yield was obtained when 10a was heated in the presence of 2 equivalents of SOCl2 and 5 equivalents of pyridine in DCE. Flash chromatography of the chloroalkyl ether 11a resulted in significant loss due to hydrolysis

• groups were small, and attempts to prevent the formation of 13d by slow addition of alcohol 10d to a solution of SOCl2/pyridine in DCE reduced the yield of 11d to 14%. Heating sulfite 13d with tetrabutylammonium chloride led only to hydrolysis back to 10d without rearrangement, indicating that these

Synthesis and characterization of water-soluble C₆₀–peptide conjugates

• Yue Ma,
• Lorenzo Persi and
• Yoko Yamakoshi

Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71

• (highlighted by purple arrows). A similar situation was observed in the expanded spectrum of 5b (Figure 6b, middle, measured in pyridine). This phenomenon suggests a symmetry break in the carbon cage moiety of the C60–peptide conjugate upon the addition of chiral peptide anchors to the C60 core. Together with

• crude sample of 5b, with the penta-Glu impurity being soluble in pyridine-d5 (Figures S13–S17, Supporting Information File 1). a) X-band ESR spectra of the 4-oxo-TEMP adduct with 1O2 generated by C60–oligo-Lys (5a) and rose bengal (RB), respectively, in aqueous solutions under irradiation with a green

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• with potential for further modification by cross-coupling. The full scope of the transformation can be found in Supporting Information File 1, Schemes S2 and S3 [45]. Concerning scope limitations, the azido-alkynylation of vinyl-pyridine 1b was unsuccessful and thiazole 1c only afforded 18% of the

• . Pyridine-substituted alkynyl-BF3K 5b could not be transferred, and only traces of the product were observed. When 5c derived from mestranol was involved in the reaction, the corresponding homopropargylic azide was obtained in <23% yield. We noticed that this particular alkynyltrifluoroborate salt has a low

Evaluation of the enantioselectivity of new chiral ligands based on imidazolidin-4-one derivatives

• Jan Bartáček,
• Karel Chlumský,
• Jan Mrkvička,
• Lucie Paloušová,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2024, 20, 684–691, doi:10.3762/bjoc.20.62

• to synthesise ligands featuring two chiral imidazolidin-4-one units linked to the pyridine ring at the 2- and 6- positions (Figure 1 – ligands I and II). These newly designed ligands represent tridentate entities. Such structure modification provides the ligands structurally conformable to well-known

• tridentate chiral ligands: PyBOX [15] and PyBidine [16]. Additionally, we explored further modifications by substituting the pyridine moiety with an imidazole ring in ligand III (Figure 1), motivated by DFT calculations (see Supporting Information File 1, part S4) which confirmed that imidazole has a similar

• donor ability to pyridine. This change reduces the ring size within the ligand structure, potentially increasing the space available for coordinating reacting species, thereby possibly enhancing catalytic activity and enantioselectivity. We also aimed to assess the impact of alkyl groups at the 5

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• Luan A. Martinho Carlos Kleber Z. Andrade Instituto de Química, Laboratório de Química Metodológica e Orgânica Sintética (LaQMOS), Universidade de Brasília, 70904-970, Brasília, DF, Brazil 10.3762/bjoc.20.55 Abstract The imidazo[1,2-a]pyridine moiety is present in drugs with several biological

• existing ones. Keywords: GBB-3CR; imidazo[1,2-a]pyridine; microwave; phosphotungstic acid; Introduction Imidazo[1,2-a]pyridine is a privileged structure that plays an important role in organic synthesis and in the pharmaceutical industry. This scaffold is present in drugs with several biological

• (insomnia). Some recent synthetic approaches to imidazo[1,2-a]pyridine scaffolds include synthetic pathways of transition metal-catalyzed reactions [14], cyclization [15], condensation [16], heteroannular [17], and photocatalytic reactions [18]. These approaches usually involve non-trivial reaction

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• distance 3.6153(10) Å (shift 1.6063(18) Å, twist and fold angles 0.0°). The closest contact in the phenanthroline fragment (blue plane–blue plane, top fragment in Figure 4) had a plane centroid–plane centroid distance of 3.5398(9) Å (shift 0.4273(18) Å, twist and fold angles 0.00°). One pyridine cycle of

Synthesis and biological profile of 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines, a novel class of acyl-ACP thioesterase inhibitors

• Jens Frackenpohl,
• David M. Barber,
• Guido Bojack,
• Birgit Bollenbach-Wahl,
• Ralf Braun,
• Rahel Getachew,
• Sabine Hohmann,
• Kwang-Yoon Ko,
• Karoline Kurowski,
• Bernd Laber,
• Rebecca L. Mattison,
• Thomas Müller,
• Anna M. Reingruber,
• Dirk Schmutzler and
• Andrea Svejda

Beilstein J. Org. Chem. 2024, 20, 540–551, doi:10.3762/bjoc.20.46

• , Bayer AG, Industriepark Höchst, 65926 Frankfurt am Main, Germany 10.3762/bjoc.20.46 Abstract The present work covers novel herbicidal lead structures that contain a 2,3-dihydro[1,3]thiazolo[4,5-b]pyridine scaffold as structural key feature carrying a substituted phenyl side chain. These new compounds

• -dihydro[1,3]thiazolo[4,5-b]pyridine; acyl-ACP thioesterase; bioisostere; herbicide; heterocycle; Introduction The presence of weed infestations exerts a high strain on food production around the globe by depleting resources for the crops and facilitating the transmission of diseases [1]. Although

• lead structure with ample space for structural variations. By formally replacing one pyridine moiety of 1,8-naphthyridine 4 by a five-membered thiazole unit, we have identified thiazolo[4,5-b]pyridine 5 as a strong inhibitor of acyl-ACP thioesterase, which has further been confirmed via an X-ray co

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• mainly driven by intramolecular hydrogen bonds. The methoxyphenyl-pyridine-methoxyphenyl moiety, developed by Petitjean et al. [19], demonstrates conformational switching upon the addition of acid in aqueous media (Figure 2). The neutral tweezers adopt a "U"-shaped conformation with both arms pointing in

• attached functional arms. The formation of new hydrogen bonds between -OMe groups and protonated pyridine stabilizes a "W"-shaped open conformation. The conformation switch can be easily followed by NMR spectroscopy in solution. Remarkably, the water-soluble tweezers 1, when functionalized with hydrophobic

• signals in the low-range visible/NIR region. Upon protonation of the pyridine, the conformation switch leads to a spatial separation of the active Pt moieties and a release of the guest (Figure 4). Also, the same group demonstrated the induction of chirality and fluorescence with chiral guest molecules

Mono or double Pd-catalyzed C–H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives

• Nahed Ketata,
• Linhao Liu,
• Ridha Ben Salem and
• Henri Doucet

Beilstein J. Org. Chem. 2024, 20, 427–435, doi:10.3762/bjoc.20.37

• obtained in 61% and 73% yield, respectively. Finally, the reactivity of pyridinylboronic acids for the preparation of acenaphtho[1,2-c]pyridine (27) was evaluated. The target product 27 was obtained in 53% yield from pyridin-4-ylboronic acid, while no product 27 was obtained from pyridin-3-ylboronic acid

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• photochemical instability, as evidenced by their low N–O bond dissociation energy (BDE ≈ 42 kcal/mol) [28], the reliance on toxic tin hydrides as reductants and the undesired radical recombination with reactive 2-pyridylthiyl radicals that leads to (alkylthio)pyridine byproducts [26]. More recently, N

• 65. Addition of radical 64 to enyne 62 followed by 6-exo-dig cyclization yields radical intermediate 66. Finally, species 65 acts as a hydrogen atom donor, delivering product 63 while forming pyridine 67 as a byproduct. A similar mechanism would in principle account for EDA-complex-mediated Giese

• , wherein the activation of complex 74 takes place through SET under constant current electrolysis [64]. The Glorius and Y. Fu groups have independently proposed the formation of analogous charge-transfer complexes involving NHPI esters, bis(pinacolato)diboron (B2pin2), and Lewis bases (pyridine or

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• unambiguously established based on COSY, HSQC, and HMBC NMR-spectroscopic data. Further, the 15N NMR spectrum of 5a confirmed the typical pyrrole-like character of the N(12) atom as well as the pyridine-like character of the N(7) and N(14) atoms (Figure S31, Supporting Information File 1) [21][22]. The

Nucleophilic functionalization of thianthrenium salts under basic conditions

• Xinting Fan,
• Duo Zhang,
• Xiangchuan Xiu,
• Bin Xu,
• Yu Yuan,
• Feng Chen and
• Pan Gao

Beilstein J. Org. Chem. 2024, 20, 257–263, doi:10.3762/bjoc.20.26

• reaction system, yielding product 3ak in good yield. Furthermore, heteroaromatic rings, such as pyridine (2l), thiophene (2m), benzoxazole (2n), and benzimidazole (2o) all afforded the desired products (3al–ao) in satisfactory yields. Subsequently, we investigated the substrate scope of amines, which is

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• studied for the first time. In addition to the pronounced tendency of the title compound to form associates with an intramolecular hydrogen bond of the NHN type (new examples with the participation of pyridine rings, including self-associates are shown) and its inertness to amination reactions of the

• pyridine rings, the naphthalene core at positions 5(8) and the CH2CH2 bridge (dehydrogenation) undergo chemical modifications under mild conditions, giving the corresponding acenaphthylenes. The latter can also be obtained in an unusual way by tele-elimination from 5,8-dibromodipyridoacenaphthene by

• , despite the presence of two pyridine nitrogen atoms, is extremely inert towards nucleophilic and oxidative amination reactions. Although molecule 5 does not explicitly contain deactivating electron-donating substituents such as alkoxy and dialkylamino (except for alkyl groups), the observed inertness may

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• irradiation with orange light in several solvents [40]. However, due to the technical limitations of the spectrometer, Pummerer and Marondel were not able to detect the short-living Z-11a in aromatic solvents such as benzene, bromobenzene and pyridine. Nevertheless, the E–Z isomerization of 11a was observed

Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• . Finally, the benzyl-protecting groups in compound 7 were cleaved via hydrogenolysis, followed by co-evaporation of the resulting crude product in pyridine. This yielded a monopyridyl salt, setting the stage for the final lipid coupling and deprotection sequence. To establish the vital lipid diphosphate

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• overnight, then quenched by addition of dry ice (solid CO2) and concentrated under reduced pressure. The residue was co-concentrated with toluene (3 mL), dried in vacuo, dissolved in anhydrous pyridine (3 mL per 0.1 mmol of sialyl donor), and acetic anhydride (3 mL per 0.1 mmol of sialyl donor) was added

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• [c]quinolizinium tetrafluoroborate (3g) According to GP, a solution (c = 0.25 mM) of (E)-5-acetylamino-2-(3,4-dimethoxystyryl)pyridine (30.0 mg, 101 µmol) in a mixture of MeCN/H2O (7:3, 400 mL) was irradiated for 33 min and the crude product was washed with n-hexane (3 mL) and redissolved in dest

• : piperidine, MeOH, reflux (2a,c), ii: Ca(OTf)2, Bu4NPF6, 130 °C (2d,f), iii: N2H4·H2O, Pd/C, MeOH, reflux (2b), iv: NaNO2, CuCl, aq HCl (37%), room temp., 2 h, 60 °C, 30 min (2e), v: acetyl chloride, pyridine, THF, room temp. (2g). Photoinduced formation of styrylpyridine derivatives 2b–g to the benzo[c

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

• Kan Tang,
• Megan R. Brown,
• Chad Risko,
• Melissa K. Gish,
• Garry Rumbles,
• Phuc H. Pham,
• Oana R. Luca,
• Stephen Barlow and
• Seth R. Marder

Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142

• -containing catalysts [32]. We note that another all-organic reductive dimerization of benzyl halides using 2,3,5,6-tetrakis(tetramethylguanidino)pyridine has recently been reported [37]. The less readily reduced halides examined here (1d,e, and 2) are only sluggishly converted, even when using both (N-DMBI)2

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia 10.3762/bjoc.19.139 Abstract The pyridine-3,5-dicarbonitrile moiety has gained significant attention in the field of materials chemistry, particularly in the development of heavy-metal-free pure organic light-emitting diodes (OLEDs). Extensive

• research on organic compounds exhibiting thermally activated delayed fluorescence (TADF) has led to numerous patents and research articles. This study focuses on the synthesis and investigation of the semiconducting properties of polyaromatic π-systems containing two and three fragments of pyridine-2,6

• compounds. In general, polyaromatic π-systems with pyridine-3,5-dicarbonitrile fragments demonstrate promising potential for use in organic electronic devices, such as OLEDs. Keywords: charge transport; intramolecular charge transfer; photophysical properties; pyridine-3,5-dicarbonitrile; Introduction The