Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• Lukas Schifferer Martin Stinglhamer Kirandeep Kaur Olga Garcia Macheno Organic Chemistry Institute, Westfälische-Wilhelms University Münster, Correnstraße 36, 48149 Münster, Germany 10.3762/bjoc.17.145 Abstract This review intends to provide an overview on the role of halide anions in the

• the cationic reactive species. Keywords: anion binding; asymmetric catalysis; halide anions; hydrogen donors; noncovalent interactions; Introduction Halogens and the respective anionic halides occupy an essential role in natural and chemical processes [1][2][3][4]. While in chemical syntheses

• halogens are often regarded as surrogates for further functionalization, their role in natural and physiological processes is much more diverse. One of these processes is the ability of large complex molecules and enzymes to recognize halide anions via hydrogen bonds in aqueous media [5]. Amongst others

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• the halide anions Cl−, Br−, and I−-, respectively, UCST behavior can also be induced in polymeric ionic liquids by the addition of a suitable hydrophobic counterion, such as tetrafluoroborate BF4− [288][289]. In both cases, the critical phase transition temperature is strongly affected by the

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• , 11 of them were never synthesized before. Markedly, noncharged structures, negatively charged cyanine bearing Na+ as counter cation, and positively charged cyanines bearing (B(Ph)4−) or (I−) as counter anions were examined as promising NIR light photoinitiating systems. Excellent photoinitiating

• of counter anions and counter cations as well as cyanine structures are discussed. Results and Discussion Synthesis of the different dyes Two different families of cyanines were prepared, differing by the way how the structure is formed. Notably, dyes Ca and Cb differ from the other cyanines by the

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• reagents, a match process which minimizes side reactions. Thus, these N-fluoropyridinium salts made possible the fluorination of a diversity of nucleophilic organic compounds with different reactivities ranging across aromatics, carbanions (Grignard reagents, enolate anions), active methylene compounds

• no α-proton to the N-F site proved to be a good choice for fluorinating enolate anions (Scheme 24). The side reaction, involving HF elimination, and which was a problem in reactions with the Barnette’s reagents 4-1 having the α-proton(s) except for 4-1b [26], was avoided here. The HF elimination is a

•  30). NFSI is a stable and non-hygroscopic crystalline solid with a mp of 114–116 °C. NFSI was shown to fluorinate a variety of nucleophiles. As seen in Scheme 31, trimethylsilyl enol ethers, enolate anions of ketones and esters, and aryl- and vinyllithiums were fluorinated with NFSI in moderate to

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• and restless leg syndrome [53]. Guareschi imides exist in solution predominantly as dicarbonyl tautomers with a cis arrangement of the cyano groups. Conversely, the corresponding anions exist as a mixture of mono- and dienolized tautomers, with a strong preference (≈9:1) for the monoenolized form [8

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• substitution in the 3-position were also tested. The products were usually obtained with a high degree of enantioselectivity in good yields (up to 96%; up to 93% ee; Table 18) [47][49]. An interesting finding was the effect of non-coordinating hexafluorophosphate anions. The addition of 30 mol % NH4PF6

• increased the catalytic activity and allowed to run the reaction at a lower temperature [48]. This can be very useful for substrates that can react with traces of Pd(0) that are formed by minor side reactions. The authors suspected that hexafluorophosphate anions stabilize the cationic Pd species and result

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• anomeric ratio observed initially for mannoside 3c (α/β = 82:18, Scheme 1). Finally, we proved the formation of the fluorosulfite species by employing 19F NMR spectroscopy (Figure 1). Glycosylation of the reaction mixture was treated with Et3N to stabilize the possibly formed fluorosulfite anions in form

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• hydrogen atom to orient towards anions (chloride) in the vicinity and the 3'-nitrogen lone pair engages in a lp → σ* anomeric effect with the antibonding orbital from the adjacent P–O5' bond (Figure 2A). This conjugation is surmised to cause considerably increased rigidity of the phosphoramidate sugar

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• -poor N-aryloxyamides 160, indole derivative 161, and carbonate or other multicharge anions in CH3CN (Scheme 56). The corresponding products can be given in good yield by modifying substituents on the amide moiety in 160 or N-substituted indoles. Inorganic-base electron donors formed transient complexes

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• classic organic dyestuffs. In that study, two highly fluorescent dibenzosuberenone-based dihydropyridazine dyes, 3a,b, were synthesized, and it was found that they can be used as a selective and sensitive sensor of fluoride anions (Scheme 1, Table 1) [55]. In another work, we reported the design

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• A and B, the geometry optimization was performed for the isolated molecules A and B. In a solid phase the Cu(II) central ion is five-coordinated by three nitrogen atoms of 7 and two chloride anions. The CuN3Cl2 coordination center adopts the strongly distorted square pyramidal geometry with the five

• coordination bonds. The coordination sphere of the Cu1 and Cu2 central ions is completed with Cl1, Cl2 and Cl3, Cl4 chloride anions, respectively. In the molecules A and B the pyridin-2-yl substituents are twisted in opposite directions relative to the mean plane of the 1,2-diazine moiety with the dihedral

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• methanol) such an increase of acidity should be also distinct but it is known that polar protic solvents much better solvate anions and thus decrease their nucleophilicity. Therefore, dimethylformamide has been chosen as the best solvent. Indeed, when dimethylformamide (DMF) was used as the solvent for the

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• cation, shown in Figure 2, and two bromide anions. The structure of the cation is close to C2 symmetry, with an rms deviation of its non-hydrogen atoms from ideal positions of 0.1320 Å. In the salt 9, the lengths of the tetrazole ring bonds and the exocyclic C–N bond are given in Table 3 together with

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• , BF3⋅Et2O, etc.). These cobalt-cluster-stabilized propargylium ions exhibit a surprisingly high thermodynamic stability, comparable to that of triarylmethylcarbenium ions and are readily observable by NMR spectroscopy or isolable as salts with relatively weakly coordinating anions (BF4−, PF6−, etc

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• and 12 hours for complex 6a-Au(III) (Table 1, entries 2 and 5), where the ligand seems to stabilize and deactivate the Au(III) during the reaction. Attempts to improve the 6b-Au(III) complex stability by anion exchange with less coordinating anions failed, as addition of different standard silver

• salts resulted in decomposition of the Au(III) complex. Consequently, the counter-anion exchange method was not possible. Since the ligand 6b seems to de-coordinate, resulting in the cyclam Au(III) complex not being the active catalyst, and the presence of chloride anions, the activity of the 6b-Au(III

Benzothiazolium salts as reagents for the deoxygenative perfluoroalkylthiolation of alcohols

• Armin Ariamajd,
• Nils J. Gerwien,
• Benjamin Schwabe,
• Stefan Dix and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2021, 17, 83–88, doi:10.3762/bjoc.17.8

• synthesized that serve as convenient sources of hitherto underexplored perfluoroalkylthiolate anions. An investigation of their reactivity in a deoxygenative nucleophilic substitution reaction led to the development of an unprecedented process that provides pentafluoroethyl and heptafluoropropyl thioethers

• heavily fluorinated thiolate anions and the potential for deleterious side-reactions resulting from β-fluoride elimination [28][29][30][31][32][33][34]. Only a handful of perfluoroalkylthiolate salts are known and, to the best of our knowledge, only one general direct nucleophilic perfluoroalkylthiolation

• of an alkyl electrophile has been reported to date [35]. This process used an umpolung strategy with activation of typically electrophilic perfluoroalkylsulfenamide reagents by iodide, releasing −SC2F5 or −SC3F7 anions in situ, which could then react with a selection of alkyl halides (Scheme 1b). In

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• substitution could be catalyzed by iodide anions accumulating in the reaction mixture. Finally, the deoxygenation of the N-oxide fragment may proceed via consecutive protonation and electron-transfer steps [28]. Conclusion In summary, a one-step method for the synthesis of tetrafluorinated piperidines starting

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

• Giovanna Zanella,
• Martina Petrović,
• Dina Scarpi,
• Ernesto G. Occhiato and
• Enrique Gómez-Bengoa

Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255

• facilitates the protodeauration in the last step (TS9), which occurs exothermically and with a barrier of only 6.5 kcal⋅mol−1. The easiness of the two-step process from IV to XII is remarkable given the low basicity of the triflate anion, suggesting that other possible anions present in the medium could also

Metal-free nucleophilic trifluoromethylselenolation via an iodide-mediated umpolung reactivity of trifluoromethylselenotoluenesulfonate

• Kevin Grollier,
• Alexis Taponard,
• Arnaud De Zordo-Banliat,
• Emmanuel Magnier and
• Thierry Billard

Beilstein J. Org. Chem. 2020, 16, 3032–3037, doi:10.3762/bjoc.16.252

• , Institut Lavoisier de Versailles, 78035 Versailles Cedex, France CERMEP-In vivo imaging, Groupement Hospitalier Est, 59 Bd Pinel, 69677 Lyon, France 10.3762/bjoc.16.252 Abstract We report herein a practical method to generate CF3Se− (and RFSe−) anions from shelf-stable reagents under iodide activation

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• of calix[4]arene immobilised in the 1,3-alternate conformation led to a system possessing a preorganised ureido cavity hemmed with chiral alkyl units in the near proximity. As shown by the 1H NMR titration experiments, these compounds can be used as receptors for chiral anions in DMSO-d6. The chiral

• for N-acetyl-ʟ-phenylalaninate. The structures of some receptors were confirmed by single crystal X-ray analysis. Keywords: anion recognition; calixarene; chiral receptor; complexation; enantiodiscrimination; Introduction The recognition and complexation of anions has become undoubtedly one of the

• most important branches of modern supramolecular chemistry, as can easily be demonstrated by an immense number of recent reviews [1][2][3][4][5][6] and books [7][8][9][10][11] devoted to this topic. Due to the omnipresence of anions in biological systems, their irreplaceable roles in cell functioning

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• , UMP, TBAP, MMP or other anions (SO42−, NO3−, HCO3−, CH3COO−) does not show any enhancement of fluorescence enabling the probe as selective for nucleoside triphosphates. The probe 1 is not toxic and has been demonstrated by fluorescence imaging of ATP in HeLa cells (Figure 2A, inset). Nucleic acid

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• ]: They can associate themselves with the F− anions and generate bifluoride HF2 anions or even polyfluorides F(HF). The presence of fluoride anions can produce a Hoffman elimination on the alkyl chain of TBA giving rise to tributylamine, butene, and HF. We can suppose that the anion S2− could also be

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• anions to amplify homoleptic cages by driving a 2-fold narcissistic self-sorting. When an excess amount of BPh4– was added, NMR and ESIMS peaks indicated only formation of the homoleptic species (Figure 6c). The amplification to homoleptic species is realized through the peripheral binding of the anion

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• sensing is an active area of research which has developed tremendously in the last few decades [1][2][3][4]. The importance of anion sensing stems from its importance in various practical applications which range from identifying and detecting environmentally toxic anions to medical diagnostics. In recent

• years, anion responsive materials [5][6] have also emerged as an interesting class of stimuli-responsive materials. Among the different varieties of anionic species, the selective and sensitive detection of bio-anions is particularly important due to their involvement in various biological functions

• general challenging to design high-affinity synthetic probes for anion sensing under such competitive conditions [7]. One of the strategies that has proven to be quite successful in this regard, not only for bio-anions, rather for a variety of several other analytes also, is multivalency [8][9][10][11