Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• thiiranium 3 cations, whose participation in the nucleophilic substitution reaction will lead to two different reaction products (Scheme 1). However, particularly, the reaction proceeds via an intermediate seleniranium cation 2. This is explained by the high anchimeric assistance effect of the selenium atom

• was developed during the last ten years based on new directions for nucleophilic substitution reactions proceeding via intermediate seleniranium cations 2 generated from thiaselenole 1. We have carried out new regioselective reactions of thiaselenole 1 with dithiocarbamates [31], ketones [37], thiols

• chemistry. Monitoring the reaction of thiaselenole 1 with KSeCN by 1H NMR spectroscopy (in accordance with the data of Table 1). Reaction conditions: compound 1 (0.5 mmol), KSeCN (0.5 mmol), MeCN (2.5 mL), 0 °C. Possible formation of reaction products starting from 1 via seleniranium 2 or thiiranium cations

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• , entries 1–4 vs 5), which may originate from its higher proton concentration in the reaction system. With H2PO4− as anion, the ILs containing different cations were then synthesized and their catalytic activity on the esterification reaction was investigated. The results (Table 1, entries 5–9) revealed

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• cations, polyoxometallates, and benzophenones [9][80], but a major drawback is the limited availability of photocatalysts that can perform direct HAT. Therefore, there is a high demand for a direct-HAT catalyst that is accessible, metal-free, allows no side reactions, and can be activated by visible light

• flash photolysis measurements, and the monobrominated product selectivity was controlled by the difference in electron transfer oxidation reactivity of 127 and 126 of electron transfer state of photocatalyst (Me·+ moiety) and also on the radical cations reactivity with Br−. Recently, König’s group

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• (3)°, 144.12(7)° and 145.6(3)°. The crystal X-ray analyses of 2-BF4 shows that the diiodotriazolium moiety has formed with the tetrafluoroborate anion a triangle in which only two anions and three cations are assembled and one tetrafluoroborate is independent (Figure 3). 2-BF4 crystallizes in the

• values are 0.72 and 0.73. The single crystal of 2-TFA crystallizes in the monoclinic space group P21/n, but the packing structure of 2-TFA is different. The package diagram shows that two cations and two acetates form a boat shape (Figure 5). The C–I···O distances are 2.631(8) Å, 2.739(8) Å, 2.666(6) Å

Understanding the role of active site residues in CotB2 catalysis using a cluster model

• Keren Raz,
• Ronja Driller,
• Thomas Brück,
• Bernhard Loll and
• Dan T. Major

Beilstein J. Org. Chem. 2020, 16, 50–59, doi:10.3762/bjoc.16.7

• non-interacting residues are labeled in grey, and plus signs note location of the cations. TS structures TS_A_B–TS_G/H_I in the active site model. Interactions are marked by dashed orange lines, the interacting residues are labeled in black, the non-interacting residues are labeled in grey, and the

• plus signs note the location of the cations. Comparison between gas phase and active site model conformations. A) Intermediate D. B) Intermediate E. Mechanism for formation of cyclooctat-9-en-7-ol, published similarly in [42]. Interactions between intermediates and TS structures with active site

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• material containing the propargyl alcohol derivative unit. The chemistry of cationic propargyl dicobalt complexes, recognized as the Nicholas reaction, has become one of the most widely appreciated forms of metalorganic chemistry. These cations are generated most commonly from propargyl alcohol, -ether, or

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• cyclization reactions. Textbook TCs are categorized into two classes and differ in their mechanisms of substrate activation as well as their protein folds [37][50][51][52]. Type I TCs trigger the formation of highly reactive allylic cations by heterolytic cleavage of the terminal pyrophosphate of farnesyl

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• hydrogen bonds, namely C(3)–H(3A)···F(2) and C(17)–H(17A)···F(2) interactions (Supporting Information File 1, Figure S1b). Chemosensing of cations by 3 Compound 3 was employed as a host to study its ability to detect some cations through fluorescence and UV titrations in CH3CN/DMSO, 9:1, v/v at room

• ) did not exhibit any remarkable response to the addition of these cations, except for Cr3+ (ε = 1.1⋅104 mol−1⋅dm3⋅cm−1) as a result of 3·Cr3+ formation (Supporting Information File 1, Figure S2). These results show that 3 is able to effectively distinguish Cr3+ from other cations. To further

• Cr3+ selectively while neglecting other cations, with no remarkable interference being caused in the presence of the latter. In order to probe whether the anions of the chromium(III) salts had effects on the binding of 3 and Cr3+, other chromium(III) salts, CrCl3, CrBr3, Cr2(SO4)3, Cr(NO3)3, and Cr

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• by using the Stokes–Einstein equation [54]. By means of ESI high-resolution mass spectrometry, we were able to verify the Pd2L4 constitution of both cages. The HRMS spectrum of Pd2(stable Z-1)4 shows the signals for the cations [Pd2(stable Z-1)4(NO3)3]+, [Pd2(stable Z-1)4(NO3)2]2+, [Pd2(stable Z-1)4

• (NO3)]3+, [Pd2(stable Z-1)4]4+ (Figure 3). For Pd2(stable E-1)4, the peaks corresponding to the cations [Pd2(stable E-1)4(NO3)2]2+ and [Pd2(stable E-1)4(NO3)]3+ were observed (Figure 3). For both isomers, the experimental isotopic patterns and exact m/z values match the simulated patterns. A single

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• 1,2-phenyl shifts, while Figure 2 shows those for a 1,2-biphenyl shifts. In each case, the energy reference is arbitrarily chosen as the linear ipso cation 12c or 12d for phenyl or biphenyl shift, respectively. Predicted barriers for rearrangements of ipso cations are all in the range of 9–22 kcal/mol

• difference between ipso cations and their non-ipso counterpart which might be formed rapidly by secondary 1,2-hydride shifts. In principle, the equilibrium product in these complex reactions might correlate with relative energies of the neutral quaterphenyl isomers. Reliable heats of formation for

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• . Furthermore, the ability of the new [10]ferrocenophane 2a to bind transition metal cations is outlined, and the redox properties of the new ferrocenophanes are studied by cyclovoltammetry. Results and Discussion The substrates 1a and 1b for the RCAM toward the desired ferrocenophanes 2a and 2b were

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• to the electron-poor nature of the pyridine ring. Herein, we demonstrate the encapsulation of Me4N+ cations inside a dimeric hydrogen-bonded pyridine[4]arene capsule, which contradicts with earlier assumptions. The complexation of a cationic guest inside the pyridine[4]arene dimer has been detected

• the π-acidic character of pyridine rings, such as 2-oxo-6-oxypyridine, is rather weak [9][10]. Thus, pyridine[4]arenes may be expected to show a dual binding behavior towards anions and cations [8]. In addition to anion complexes also 2:1 complex formation with neutral carboxylic acids and amides have

• size are well-known for their ability to encapsulate small alkylammonium cations inside the dimer, especially quaternary ammonium cations [12][13][14]. As the cavity sizes of both pyridinearene and resorcinarene dimers are comparable, alkylammonium cations were chosen as the guests for complexation

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• . These silver(I) complexes adopted similar structures in solution and in the solid state. As each sulfur atom in the ligand is prochiral, macrocycles L2M2 were obtained as mixtures of diastereoisomers, depending on the configurations of the sulfur atoms coordinated to silver cations. The X-ray structures

• three nitrate anions as coordinating bridges between the two symmetric M3L2 units (Figure 2). The resulting coordinated macrocycle M6L4 had a globular shape that displayed the polyaromatic ligands towards the exterior and fully encapsulated two nitrate anions and the silver(I) cations. This silver

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• value of 1.26 indicated that one molecule of 2a is involved in the formation of the active transporter. The promising ion transport activity of 2a encouraged us to explore its cation and anion selectivity study by varying either cations (for MCl, M+ = Li+, Na+, K+, Rb+, and Cs+) or anions (for NaA, A

• − = F−, Cl−, Br−, I−, NO3−, SCN−, AcO− and ClO4−) of the extravesicular salt, respectively. Thus, variation of external cations, in the presence of 2a (0–10 µM), showed minor changes in the transport activity with the sequence: Na+ > Rb+ > Li+ > K+ ≈ Cs+ (Figure 7A), which suggest lesser influence of

• alkali metal cations in the transport process. However, variation of extravesicular anions demonstrated the changes in the transport behaviour with the following selectivity sequence: Cl– >> AcO– ≈ SCN– ≈ F– > NO3– >> Br– ≈ I–, showing highest selectivity for the Cl– ion (Figure 7B). Overall, anion

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• . Lipophilic cations such as the phosphonium cation or rhodamines are known to accumulate selectively within the mitochondria, driven by the mitochondrial plasma membrane potential [39][40]. Thereby, the high lipophilicity facilitates the diffusion through the lipid bilayers of the cell and mitochondrial

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• intramolecular electron transfer phenomena and application in molecular devices [1][2][3][4][5]. The radical cations of bistriarylamine derivatives bis(NAr3) are well-known MV compounds having π-conjugated bridges (where NAr3 = triarylamine) [6][7][8][9][10][11][12][13][14][15][16][17][18]. These studies focused

• characteristics of the bis(NAr3)•+ radical cations are well documented due to their good availability through common N–C bond-forming reactions and the stability of the NAr3•+ unit [6][7][8][9][10][11][12][13][14][15][16][17][18]. Photoswitchable mixed valency has recently been demonstrated with bis(NAr3

• )•+ radical cations having dithienylethene bridges [21][22]. This was achieved by a regulation of the π-conjugation length through photoinduced formation/dissociation of σ bonds in the bridge, which was accomplished with changeovers from a localized system (class I) to a moderately delocalized one (class II

Synthesis of acremines A, B and F and studies on the bisacremines

• Nils Winter and
• Dirk Trauner

Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219

• enhance the stability of the molecule, and therefore prevent decomposition, by protection of the non-participating alcohols and attempts to generate the allylic cation from a cyclic ketal [10][11][12], aiming for a Gassman-type reaction mechanism, were also unfruitful. While radical cations are known to

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• candidates for amide bond surrogates. Interestingly, 1,2,3-triazole units can act as sensors for both anions and cations via different binding mechanisms [16][17]. The heterocyclic ring N2 and N3 atoms could realize the selective recognition of the cations whereas the C5–H···anions electrostatic interaction

• [TCNQ]−· radical anion, dragging the second [TCNQ]− near to the cavity by the help of the electrostatic stabilization supplied by the 1,2,3-triazolium cations, coupling of the two [TCNQ]−· anion radicals in the cavity and rapid formation of the sigma-connected dimer, reduction of the photogenerated

Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes

• Marco Santella,
• Eduardo Della Pia,
• Jakob Kryger Sørensen and
• Bo W. Laursen

Beilstein J. Org. Chem. 2019, 15, 2133–2141, doi:10.3762/bjoc.15.210

• functionalities were synthesized and their optical properties were studied. The sulfur functionalities were introduced by aromatic nucleophilic substitution of methoxy groups in triarylmethylium cations with ethanethiol followed by partial or full ring closure of the ortho positions with nitrogen or oxygen

• thioether donor groups. Results and Discussion Firstly, a series of triarylmethylium salts with variable number of para-methoxy substituents was synthesized. The easily achievable cations (TMP)3C+, (DMP)(TMP)2C+ and (DMP)2(TMP)C+ (Scheme 1) were prepared by their respective literature procedures [18][31

Multiple threading of a triple-calix[6]arene host

• Veronica Iuliano,
• Roberta Ciao,
• Emanuele Vignola,
• Carmen Talotta,
• Patrizia Iannece,
• Margherita De Rosa,
• Annunziata Soriente,
• Carmine Gaeta and
• Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

• dialkylammonium axles [17][18][19][20][21][22][23][24][25][26] by exploiting the inducing effect of the superweak tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB) anion that gives free ‘naked’ dialkylammonium cations. In addition, we have reported interesting examples of endo-cavity complexation of

• alkylammonium cations, as TFPB− salts, inside the aromatic cavity of calixarene [20] and dihomooxacalixarene hosts [21][22]. Thus, through this ‘superweak anion’ approach, we have synthesized interesting examples of calixarene/ammonium-based interlocked structures such as calix-rotaxanes [23][24] and calix

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• cavities [22]. We have also shown that the combination of and the interplay between heteroatoms and para-(het)arylenes produce diverse macrocycles with coarse- and fine-tunable cavity shapes and sizes. The resulting coronarenes exhibit interesting molecular recognition properties towards anions, cations

• . Cations and solvent molecules are omitted for clarity. Synthesis of phthalimide-containing O6-corona[3]arene[3]tetrazines. Supporting Information Supporting Information File 372: Experimental procedures, characterization of products and copies of mass and NMR spectra. Acknowledgements We thank the

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• -arylmethyl-substituted benzimidazoles, in yields up to 90%. The reaction intermediates, protonated species derived from starting benzimidazoles in TfOH, were thoroughly studied by means of NMR and DFT calculations and plausible reaction mechanisms are discussed. Keywords: benzimidazoles; cations; Friedel

• their electrophilicity and electronic properties (Table 1). Apart from that, ΔG298 of the formations of cations I–IX from parent benzimidazoles 1–8 were calculated to estimate a thermodynamic possibility of the species formation (Table 1). The calculations were carried out for the solution phase in

• should be reactive electrophiles. While, in the case of hydroxyalkylbenzimidazoles 3–8, N,O-diprotonated species III, V, VII, VIII, the most probably, may be reactive intermediates. The calculation of electrophilic properties of these cations show that species I and II have higher values of

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• similar. However, as shown in Figure 5 and Table 1, the difference in the spectral maxima of the complexes allows detection of each of the studied cations. Conclusion In the current study, we modeled theoretically and experimentally the tautomerism and complexation abilities of a new tautomeric ligand

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• depiction of a single chain is provided in Figure 1, and a partial packing diagram is given in Figure 2. The asymmetric unit contains three alkali metal cations and three substituted allyl anions, all in general positions. Each of the three metal sites is modeled as a site disorder of atoms types K and Cs

• exhibit an average M–C(allyl) bond distance of roughly 3.17 Å). These values do not recreate distances in the homometallic complexes exactly (i.e., the average K–C distance in [KA']∞ is 3.01 Å) [17], but they reflect the relative sizes of the K+ and Cs+ cations. The structure is polymeric in two

• the only recoverable material; extracted with toluene, it crystallized from solution as the solvate. A single crystal X-ray study analysis reveals bent polymeric chains of alternating K+ cations and [A']− anions. Each potassium is capped with a toluene molecule, bonded through cation–π interactions