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

• 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

A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• -step ynamide annulation and imidazolium ring-formation sequence. Metalation with Au(I), Cu(I) and Ir(I) at the C2 position provides an L-shaped NHC ligand scaffold that has been validated in gold-catalysed alkyne hydration and arylative cyclisation reactions. Keywords: annulation; carbene; gold

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

• 1,8-naphthyridine scaffold can also be formally substituted by an isothiazole group, as can be seen in isothiazolo[3,4-b]pyridine 6 [15]. Thus, several bicyclic heteroaromatic motifs containing two nitrogen atoms serve as structural surrogates of cinmethylin (1), bearing a substituted 7-oxabicyclo

• [2.2.1]heptane scaffold [16]. Based on the findings outlined above and based on other plant-specific modes of action, it is plausible that FAT inhibitors encompass a broader range of structural motifs [16][17]. Herein, we present our approach to complement heteroaromatic lead structures 4–6 by

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

• et al. exploited the same scaffold to control the physical properties of materials. They incorporated planar terpyridine-alkyne Pt complexes as functional units and studied the intercalation of a Pt-complex guest in order to obtain Pt–Pt interactions in solution [23]. In the native state of 3, both

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• observed rate was outside of one standard deviation from the average of 3 trials, confirming the overall reactivity trend. In hindsight, the ligand effect here may be expected to be small since the bisbiphenyl scaffold contains 2 of 3 identical substituents. Nevertheless, these comparisons confirm the

Synthesis of 2,2-difluoro-1,3-diketone and 2,2-difluoro-1,3-ketoester derivatives using fluorine gas

• Alexander S. Hampton,
• David R. W. Hodgson,
• Graham McDougald,
• Linhua Wang and
• Graham Sandford

Beilstein J. Org. Chem. 2024, 20, 460–469, doi:10.3762/bjoc.20.41

• gave no noticeable conversion on analysis by 19F NMR spectroscopy, and a large excess of fluorine led to formation of a dark brown tar from which no useful product could be isolated. On the bases of these failed attempts, coupled with our previous experiences with the DBM scaffold [16][17][36], we used

Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells

• Fumihiro Ishikawa,
• Sho Konno,
• Hideaki Kakeya and
• Genzoh Tanabe

Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39

• investigated the influence of a modification of 2′-OH in the AMS scaffold with different functional groups on binding to target enzymes and bacterial cell penetration. The inhibitor 7 with a cyanomethyl group at 2′-OH showed desirable inhibitory activity against both recombinant and intracellular gramicidin S

• synthetase A (GrsA) in the gramicidin S-producer Aneurinibacillus migulanus ATCC 9999, providing an alternative scaffold to develop novel A-domain inhibitors. Keywords: adenylation domain inhibitor; gramicidin S synthetase; natural product; nonribosomal peptide; nonribosomal peptide synthetase

• mycobactin from Mycobacterium tuberculosis [6]. 5′-O-Sulfamoyladenosine (AMS), a bioisosteric analog of an AMP intermediate, has been used as a non-hydrolysable scaffold for developing A-domain inhibitors. Moreover, 5′-O-[N-(salicyl)sulfamoyl]adenosine (Sal-AMS) and its derivatives show potent inhibitory

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• 100 nm, exhibit various benefits, such as tailoring the scaffold of the catalyst, the recyclability of the nanocompounds, as well as the elevated catalytic activity offered. These benefits stem from their high surface area, that provides more active sites for the reactants to absorb into and collide

Discovery of unguisin J, a new cyclic peptide from Aspergillus heteromorphus CBS 117.55, and phylogeny-based bioinformatic analysis of UngA NRPS domains

• Sharmila Neupane,
• Marcelo Rodrigues de Amorim and
• Elizabeth Skellam

Beilstein J. Org. Chem. 2024, 20, 321–330, doi:10.3762/bjoc.20.32

• genome was initially screened using fungiSMASH to identify scaffolds/contigs encoding secondary metabolites. Scaffold MSFL01000005.1 was further investigated using FGENESH [17] to further refine gene boundaries, introns, and resulting protein sequence (Table S1, Supporting Information File 1

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• precursors inherently limits the applicability of these reactions to the synthesis of π-CPCs containing linearly-fused benzene rings in their core scaffold (i.e., at least an anthracene pattern), or to the deprotection of peripheral benzene rings. To reach a wider variety of structures, novel synthetic

• corresponding bis(thiophenyl) thioether, which then underwent successive bromination and iodination to give intermediate 18. Next, a two-fold Suzuki–Miyaura cross-coupling occurring chemoselectively on the iodinated positions allowed the symmetric extension of the hydrocarbon scaffold, with the insertion of two

• thermal- and photostability by the choice of oxygen as heteroatom, while keeping the possibility to trigger chalcogen extrusion via a radically different mechanistic route, as a result of the injection of electrons. Here, the presence of the imide functions appended to the naphthyl scaffold is crucial

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

• ]. As an alternative to the chemical synthesis of indigo, environmentally friendly biological approaches towards constructing the indigo scaffold are also being developed for nearly a century [5][6][7][8]. The biosynthetic methods include production of indigo by microorganisms and enzymatic synthesis

• (DPT). Taking together, the main indigo scaffold is not photochromic. However, substitution of the hydrogen atom in the NH groups of indigo can change the photochemical behavior significantly. Photochromic indigo derivatives In 1954, the first photochromic indigo derivative, namely N,N'-diacetylindigo

• isomerization of the indigo derivatives that led to the disassembly of well-shaped vesicles and formation of irregular aggregates. The thermal Z–E relaxation of the indigo scaffold provided the restoration of the vesicle structure. The system contributed to the development of red-light-controllable biomedical

Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

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

• Over the past decades, the 8-aminoquinoline motif that could be found in several natural products [1] has attracted significant attention for its widespread usage in pharmaceuticals [2], agrochemicals [3], and functional materials [4]. In particular, the aminoquinoline scaffold has emerged as an

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

• photosensitizers based on benzo[c]quinolizinium derivatives because their particular mode of activity may offer complementary applications in addition to the already established photosensitizers. Overall, the benzo[c]quinolizinium scaffold offers some advantageous properties for its use as DNA-targeting agent

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• a subsequent Glaser–Hay coupling reaction, a RA acceptor unit was introduced to provide a DTF-IF-RA donor–acceptor scaffold with a low-energy charge-transfer absorption and multi-redox behavior. Keywords: alkynes; chromophores; fused-ring systems; heterocycles; redox chemistry; Introduction

• acetylenic scaffolds comprised of enediyne units are known to behave as good electron acceptors [15][16], and we became interested in combining the IF-DTF scaffold with such motifs to generate novel multi-redox systems. For example, the radiaannulene moiety RA shown in Figure 1 (or its truncated counterpart

• the terminal alkynes afforded the macrocyclic DTF-IF-RA scaffold 23. Molecular sieves (4 Å) were added to the reaction mixture as this has previously been shown to significantly promote the Glaser–Hay coupling [28]. Compounds 20 and 21 were unfortunately very sensitive compounds that were found to

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

• Xing Liu,
• Wenjing Shi,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1923–1932, doi:10.3762/bjoc.19.143

• [22][23][24][25][26][27]. In addition, spirooxindole is also a privileged structural scaffold, which has been recognized as key structural unit in many bioactive natural products and pharmaceuticals with broad biological activities [28][29][30]. The development of elegant synthetic methodologies for

Anion–π catalysis on carbon allotropes

• M. Ángeles Gutiérrez López,
• Mei-Ling Tan,
• Giacomo Renno,
• Augustina Jozeliūnaitė,
• J. Jonathan Nué-Martinez,
• Javier Lopez-Andarias,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140

• were not fruitful, mostly due to poor solubility. Anion–π catalysis on carbon nanotubes With fullerenes confirmed as privileged scaffold for induced anion–π catalysis but higher oligomers inaccessible [12][67][80], the obvious next move was to switch to carbon nanotubes. Compared to the sixty free

• carbon allotropes, MWCNTs 3 emerge as privileged scaffold for anion–π catalysis because polarizability is possible not only along the tubes but also between the nanotubes, like in π-stacked foldamers (Figure 1E). Numerous reports on catalysis with carbon nanotubes have appeared [45][46][82][83][84][85

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

• emitter based on a pyridine-3,5-dicarbonitrile scaffold (to serve as an electron acceptor) directly linked to a carbazole moiety (to serve as an electron donor) was reported by the groups of Dong and Zhang in 2015 [4]. 2,6-Di(9H-carbazol-9-yl)-4-phenylpyridine-3,5-dicarbonitrile (CPC) showed an extremely

Quinoxaline derivatives as attractive electron-transporting materials

• Zeeshan Abid,
• Liaqat Ali,
• Sughra Gulzar,
• Faiza Wahad,
• Raja Shahid Ashraf and
• Christian B. Nielsen

Beilstein J. Org. Chem. 2023, 19, 1694–1712, doi:10.3762/bjoc.19.124

• )aromatic compounds (Qx53) with a chalcogenodiazolo[3,4-b]pyrazine scaffold. These compounds exhibited narrow bandgaps (from 1.25 to 1.44 eV) and demonstrated n-type organic semiconductor properties [56]. Jin and co-workers focused on improving the charge-transfer characteristics of a semiconducting

• . synthesized a tetrapodal scaffold using diazatriptycene with thiol anchors (Qx57) to demonstrate electrostatic dipole engineering in n-type OFETs. The scaffold was designed to enforce upright functional groups, particularly quinoxaline subunits, and utilized OFETs as prototypes to showcase the potential of

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• scaffold can be found in many biologically active compounds and natural products such as 1-epiaustraline, hyacinthacine A1, (−)-isoretronecanol, and (−)-supinidine (Figure 2) [68][69]. After the method development work, a pseudo-five-component double cycloaddition reaction of glycine with two equivalents

A series of perylene diimide cathode interlayer materials for green solvent processing in conventional organic photovoltaics

• Kathryn M. Wolfe,
• Shahidul Alam,
• Eva German,
• Fahad N. Alduayji,
• Maryam Alqurashi,
• Frédéric Laquai and
• Gregory C. Welch

Beilstein J. Org. Chem. 2023, 19, 1620–1629, doi:10.3762/bjoc.19.119

• the previously reported N-annulated PDI (PDIN-H) and nitrile functionalized N-annulated PDI (CN-PDIN-H) compounds (Figure 1c) as the scaffolds for modification [18]. The PDIN-H scaffold was modified by N-functionalization with a benzyl (PDIN-B) or pentafluorobenzyl group (PDIN-FB). Similarly, the CN

• -PDIN-H scaffold was functionalized with a benzyl (CN-PDIN-B) or pentafluorobenzyl group (CN-PDIN-FB). Addition of the benzyl and pentafluorobenzyl groups was to enhance solubility in green solvents, while nitrile functionalization was done to further stabilize the LUMO of the compounds. These materials

Secondary metabolites of Diaporthe cameroonensis, isolated from the Cameroonian medicinal plant Trema guineensis

• Bel Youssouf G. Mountessou,
• Élodie Gisèle M. Anoumedem,
• Blondelle M. Kemkuignou,
• Yasmina Marin-Felix,
• Frank Surup,
• Marc Stadler and
• Simeon F. Kouam

Beilstein J. Org. Chem. 2023, 19, 1555–1561, doi:10.3762/bjoc.19.112

• in the (+)-HRESIMS spectrum (Figure S8 in Supporting Information File 1). Its 1H NMR spectrum (Figure S9, Supporting Information File 1) allowed the deduction of an alternariol scaffold [13] with signals of a chelated hydroxy proton at δH 10.33, two pairs of meta-coupled protons at δH 6.68 and 6.55

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• -trisubstituted-1,2,3-triazoles, with a pendant morpholine at the C-4 position are formed with complete regiocontrol via β-fluoride elimination in an SNV-like transformation (Figure 1C). 1,2,3-Triazoles are a privileged scaffold in medicinal chemistry with a myriad of pharmacological activities against cancer [11

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• to be around 25 kcal mol−1 for model imidazol-2-ylidenes [7]. The ylidic structure confers NHC a nucleophilic character. Bertrand reported a new class of mesoionic carbenes 10 based on a 1,2,3-triazolium scaffold [8][9]. These NHCs, also known as remote or abnormal N-heterocyclic carbenes (aNHCs

Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction

• Ziying Xiao,
• Fengshun Xu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1234–1242, doi:10.3762/bjoc.19.91

• group in the neighboring oxindole scaffold. Therefore, it can be concluded that the obtained dispiro compounds 3a–m have this kind of relative configuration on the basis of 1H NMR spectra and crystal structure determination. It should be pointed out that ammonium acetate was employed as nitrogen source

• dimedone moiety is also in trans-position to the carbonyl group in the neighboring oxindole scaffold. To demonstrate the synthetic value of this three-component reaction, 3-phenacylideneoxindole adducts of 1,3-cyclohexanedione were also employed in the reaction. In the presence of piperidine, the three

• , the nucleophilic addition of the amino anion to the carbonyl group in the of 1,3-cyclohexanedione scaffold resulted in cyclic intermediate C. Thirdly, the elimination of water from intermediate C gave the isolated product 3. In the case of the intermediate B2 with a benzoyl group, there are two kinds