Regio- and stereochemical stability induced by anomeric and gauche effects in difluorinated pyrrolidines

• Ana Flávia Candida Silva,
• Francisco A. Martins and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2024, 20, 1572–1579, doi:10.3762/bjoc.20.140

• -fluoroalkylamines and the respective cations [6]. Intramolecular hydrogen bonds involving either the carboxy or hydroxy group of 4R- and 4S-hydroxyproline have been identified as key factors in stabilizing the favored conformations in the gas phase. Therein, the contribution of a gauche effect due to electron

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• the relative stability of primary, secondary and tertiary benzylic radicals and cations. As a result, the presence of benzylic C(sp3)–H bonds in bioactive molecules can be problematic as they are particularly labile to enzymatic oxidation [16], and hence, their functionalisation has become a strategy

• and oxidation potentials. Electrochemical methods Synthetic electrochemistry is a powerful tool offering excellent control over reaction kinetics and selectivity [86]. Electrochemical oxidation has been demonstrated as an efficient means for generating benzylic cations, allowing for the introduction

• prolonged reaction times or upon increasing the applied cell potentials. In 2024, Lennox and co-workers reported their investigation in exploring how alternative electrolysis waveforms might assist in the generation of reactive primary benzylic cations for nucleophilic fluorination (Figure 43) [104]. The

Predicting bond dissociation energies of cyclic hypervalent halogen reagents using DFT calculations and graph attention network model

• Yingbo Shao,
• Zhiyuan Ren,
• Zhihui Han,
• Li Chen,
• Yao Li and
• Xiao-Song Xue

Beilstein J. Org. Chem. 2024, 20, 1444–1452, doi:10.3762/bjoc.20.127

• heterolytic BDEs are performed using M06-2X/def2-TZVPP in the SMD (acetonitrile) Implicit solvent model at 298.15 K. Due to the instability of some transfer group cations, such as +OCH3, +OCF3, +OCOCF3, +OCOPh, +OTf and +SCF3, it is difficult for us to investigate their heterolytic BDEs. From Table 2, it can

A comparison of structure, bonding and non-covalent interactions of aryl halide and diarylhalonium halogen-bond donors

• Nicole Javaly,
• Theresa M. McCormick and
• David R. Stuart

Beilstein J. Org. Chem. 2024, 20, 1428–1435, doi:10.3762/bjoc.20.125

• work (Scheme 2). Given the similarities drawn between hypervalent and halogen bonding [20], we considered the association of the diarylhalonium cations 1–8 with chloride anion as well as the association of the monovalent subunits 25–36 with chloride anion (Scheme 3). We also considered the association

• , whereas the association of chloride with pentafluorophenyl(mesityl)bromonium (6) was ΔG = −13.2 kcal/mol. The overall charge on the halogen-bond donor also has an impact on the energy of association. The association of chloride with the diarylhalonium cations 1–8 had ΔG values that ranged from −5.9 to

• −23.1 kcal/mol (see Supporting Information File 1 for exact values). Likewise, the association of chloride with imidazolium halides 37–40 ranged from −3.7 to −14.3 kcal/mol, which overlaps with the range observed for the diarylhalonium cations. We delved deeper into the periodic trends related to the X

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• triggered to carry out energy transfer and electron transfer or proton-coupled electron transfer when it absorbs light of an appropriate wavelength (Figure 2). These processes generate highly reactive species, such as radical cations or anions, which can initiate the desired organic transformations

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• alkene 2 to provide alkyl radical species B. Further single-electron reduction by 1,3-DCB•− or at the cathode followed by protonation of B provides hydroarylation product 3. Meanwhile, the sacrificial anode is oxidized to form Al cations. Although the exact role of visible-light irradiation in the

Synthesis and physical properties of tunable aryl alkyl ionic liquids based on 1-aryl-4,5-dimethylimidazolium cations

• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2024, 20, 1278–1285, doi:10.3762/bjoc.20.110

• Stefan Fritsch Thomas Strassner Physikalische Organische Chemie, Technische Universität Dresden, 01062 Dresden, Germany 10.3762/bjoc.20.110 Abstract We present a new class of tunable aryl alkyl ionic liquids (TAAILs) based on 1-aryl-4,5-dimethylimidazolium cations with electron-withdrawing and

• weakly coordinating anions like bis(trifluoromethylsulfonyl)imide [NTf2]− [25]. In addition, dicationic salts or anions containing metal complexes have been described [26][27]. Due to the numerous combinations of different anions and cations, ILs can also be described as designer solvents [28]. We

• [PhImC4H9]+, the unsubstituted 4,5-dimethyl-1-phenyl cation of TAAIL 37 and the cations of TAAILs 40 (4-CH3) and 49 (4-CF3). The structures of the cations were optimized with Gaussian 16 [56], using the hybrid functional Becke3LYP [57][58][59][60] with the split valence triple-ζ basis set 6-311++G(d,p) [61

Stability trends in carbocation intermediates stemming from germacrene A and hedycaryol

• Naziha Tarannam,
• Prashant Kumar Gupta,
• Shani Zev and
• Dan Thomas Major

Beilstein J. Org. Chem. 2024, 20, 1189–1197, doi:10.3762/bjoc.20.101

• -covalent interactions plots. Despite the structural similarities between germacrene A and hedycaryol cations, they possess a somewhat different stability trend. These differences are attributed to C+···OH intramolecular interactions present in some hedycaryol cations, which are absent in the carbocations

• the germacrene cations, among the first set of compounds, i.e., 6-6 bicyclic molecules (Figure 2 and Figure S1 in Supporting Information File 1), A and C are most stable, D is less stable by 2.9 kcal/mol, while B is the least stable (8.3 kcal/mol). In the case of the 5-7 bicycles with a seven-membered

• for the difference in free energy, we analyzed the NCI plots for germacrene cations A–D. Despite being isomers, these carbocations possess quite different geometric arrangements. For instance, molecule A is more planar than the puckered B. It is clear from visual inspection of the NCI plots that B

Confirmation of the stereochemistry of spiroviolene

• Yao Kong,
• Yuanning Liu,
• Kaibiao Wang,
• Tao Wang,
• Chen Wang,
• Ben Ai,
• Hongli Jia,
• Guohui Pan,
• Min Yin and
• Zhengren Xu

Beilstein J. Org. Chem. 2024, 20, 852–858, doi:10.3762/bjoc.20.77

• either IM-9 or IM-11 cations. A direct dyotropic rearrangement, or two stepwise 1,2-alkyl migrations of IM-9, are possible pathways en route to cation IM-10. The presence of these intermediates IM-9, -10, -11 could be inferred by the identification of GJ1012B/D (5/6, Scheme 1D) [11], cattleyene (7) [19

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

• ]octane ring-system via the chlorosulfite intermediate. Analogous allylic alcohols with endocyclic and exocyclic unsaturations underwent chlorination without rearrangement due to formation of allylic cations. The rearrangement was also demonstrated using Appel conditions, which gave similar results via

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• the alkene in the first step, providing a carbocation that subsequently reacts with a chloride anion to yield the Markovnikov product. While this ionic mechanism is commonly illustrated in textbooks by showing “naked” cations as intermediates, several recent studies suggest a molecular concerted or

• , HCl gas was bubbled through neat alkene 1 for several hours, as depicted in Scheme 3A [35]. This example highlights an intriguing regioselectivity that might have been challenging to predict through a simple analysis of the stability of the corresponding cations. Alternatively, the HCl gas was bubbled

• a mixture of E- and Z-octene (67) (Scheme 10). They also mentioned in a footnote that 2-chlorooctane (41) was contaminated by "some 3-chlorooctane” (68). The formation of regioisomers through hydride or alkyl shifts is a common occurrence in hydrochlorination reactions involving secondary cations

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

• known ability to coordinate with metal cations [22][23]. Dual-mode naked-eye molecular switches controlled by both light and changes in the ionic composition of the medium can be used as elements of electronic devices, for optical recording of information as well as in photopharmacology, light-gated

• effect: a visually distinguishable color change of the solutions from yellow to dark orange (Figure 5). Other cations did not demonstrate a measurable effect (Figure 6). Complexes 2a–c with Fe2+ in acetonitrile and DMSO were nonfluorescent. According to spectrophotometric titration data and the isomolar

• ) were used. 1 mL of a 2a–c solution and 1 mL of a perchlorate solution were mixed directly in the cuvette and thoroughly stirred. Hence, the working concentration of the compounds 2–c and the cations was 5.0 × 10–5 mol⋅L−1 and 1.0 × 10−5 mol⋅L−1. HRMS analysis was performed on a Bruker UHR-TOF Maxis

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

• terpyridine-bearing platinum–salphen known for their luminescence properties [41]. The closing process of the tweezers 12 was studied by NMR or UV–vis titrations with Zn2+ and other cations such as Pb2+, Fe2+, Cu2+, Eu3+, and Yb3+ indicating in all cases a 1:1 association model. The system can then be

• allosteric binding to alkali K+ cations associated with a shift in the emission maxima. This system offers innovative exploitation of switchable molecular tweezers for allosteric ion recognition with a double selection (metallic ion and counter anion) of the closing stimulus. Closed-by-default tweezers can

•  13) [32]. Such moiety is able to complex two copper(I) cations, both sides of the system acting as independent bipyridine units, giving the possibility of sequential opening of the tweezers one arm at a time. Indeed, when only one copper(I) cation is complexed, tweezers 22a and 22b adopt an “S

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• complex was also formed by mixing a 1:1 mixture of radical cations of [5]- and [10]CPP, [5]CPP•+ (SbCl6−) and [10]CPP•+ (SbCl6−), respectively (Figure 1c, path C). The observed results can be explained by two reasons; one is the oxidation potentials of [10]- and [5]CPPs. In sharp contrast to linear π

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

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

• (Supporting Information File 1, Figure S13). This is a rather low value for chelate-type cations, but at the same time, it is quite logical, as molecule 14 contains a short CH=CH bridge, which increases the internitrogen distance and stretches (that is, weakens) the intramolecular hydrogen bond. For

• increase in the series 3 → 5 → 8 (“clothespin” effect) [30]. The crystal packing patterns in salts 5·HBF4 and 8·HBF4 are quite similar. The main factor here continues to be the tendency of almost flat disk-shaped heterocyclic cations to π-stacking, leading to the formation of dense columns with anions in

• between (Supporting Information File 1, Figure S22). Flat dipyridoacenaphthylene cations 8H+ give a denser packing, which, with an interplanar distance of only 3.328 Å, is the closest among all the studied compounds. Conclusion Using single crystal XRD technique, dipyridoacenaphthene tetrafluoroborate

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

• (λirr = 660 nm). The excited state dynamics of 18c was later studied in detail by Nagasawa and co-workers using femtosecond time-resolved transient absorption spectroscopy [44]. In 2022, Qiao and co-workers attempted to extend the thermal relaxation half-life of compound 18c by addition of cations such

• + cations (500 equiv). At the same time, addition of TBA+ cations showed just a minimal impact on the stability of the Z-form comparable with the effect of counter anions and solvent polarity. In 2021, Tsubaki and co-workers synthesized bridged N,N′-dialkyl-substituted indigos 13 and studied their thermal

• -aryl-N'-alkylindigo photoswitches 22b, 23c and 23d upon addition of Li+ cations. These studies revealed that the presence of the electron-withdrawing groups on the aryl moiety decreased the charge density on the carbonyl groups and weakened the interaction of the Z-isomers with Li+ that accounted for

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

• benzo[c]quinolizinium derivatives is more efficient under resembling conditions. Thus, the isomeric benzo[b]quinolizinium cations showed DNA damage to a lower extent after irradiation for 10 min with 15–20% and 20–25% DNA cleavage under anaerobic and aerobic conditions, respectively [35]. Likewise

Electron-beam-promoted fullerene dimerization in nanotubes: insights from DFT computations

• Laura Abella,
• Gerard Novell-Leruth,
• Josep M. Ricart,
• Josep M. Poblet and
• Antonio Rodríguez-Fortea

Beilstein J. Org. Chem. 2024, 20, 92–100, doi:10.3762/bjoc.20.10

• found for the radical cation products, especially in the gas phase (second column in Table 1). The reaction energies are, however, notably more negative for the radical cation products. Besides, radical cations 1-Cs•+ and 1-D2h•+ show comparable energies. Finally, for the nanotubular-shaped C120-NT-D5d

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• with alternative solvents could represent an important innovation for alkyne hydration. In particular, ionic liquids (ILs) could represent a valid alternative to conventional organic solvents. ILs are generally liquid salts at or near room temperature, formed by large unsymmetrical organic cations and

• the hydration of alkynes, named poly(ionic liquid)s (PILs), using trifluoroethanol as solvent [88][89]. One of the most studied classes of ILs in organic chemistry are 1,3-disubstitued imidazolium cations, which are cheap, liquid over a wide range of temperatures, and possess good solvating properties

• experiments were carried out under the conditions reported in entry 9 of Table 1, in order to observe possible variations in the yield of compound 2a. ILs with different anions or cations (compared to BMIm-BF4) were investigated to probe potential interactions with the reagents, the intermediates or the

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

• the electrochemical depolymerization of poly(ethylene terephthalate) [25]. These dimers (D2 = (Y-DMBI)2) undergo reactions with organic semiconductors A to afford two monomeric Y-DMBI+ (D+) cations and two reduced semiconductors, A•−. The effective redox potentials, E(D+/0.5D2), are estimated to be ca

• and photocatalysts used, and (c) schematic for the present approach, along with structures of 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles, (Y-DMBI)2, and the corresponding monomer cations, specifically the first reported in the literature and those used in this work. (a) A

Unprecedented synthesis of a 14-membered hexaazamacrocycle

• Anastasia A. Fesenko and
• Anatoly D. Shutalev

Beilstein J. Org. Chem. 2023, 19, 1728–1740, doi:10.3762/bjoc.19.126

• [1][2][3][4][5][6]. The great interest in PAMs is primarily due to their ability to bind various cations, anions, and neutral molecules [7][8][9][10][11][12][13][14]. In addition, some representatives of PAMs were found in various natural products and play an important role in living systems (e.g

• prepared compounds were able to chelate various metal cations through the N1, N4, N8, and N11 atoms [37][38]. In continuation of our research on 1,2,4,8,9,11-hexaazamacrocycles, which are under-explored representatives of the PAMs family, we were particularly interested in the synthesis of more unsaturated

• ]. Moreover, the size of internal cavity formed by the nitrogen atoms N5, N8, N13, and N16 (≈2.6 Å × 2.8 Å according to the DFT calculations) enables to chelate various metal cations. Herein, we attempted to prepare compounds 11 and 12 by annulation of two 1,2,4-triazole rings onto the macrocyclic core of 5

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• cations, while 4,7-dimethoxy substitution leads to more reducing E(1+/1•) values, as well as cathodic shifts in E(12•+/12) and E(1H•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC61BM. Because 2-aryl groups stabilize radicals, 1b2 and

• strong dopants, reacting with semiconductors more rapidly and predictably than hydride donors such as the corresponding 1H species [8], cleanly only to give SC•– and the corresponding monomeric cations. However, 12 dopants offer the possibility of more planar dopant ions than the organometallic dimers

• donors (1gH, 1hH, 1iH). We also report crystal structures of several of these compounds and of several salts of the corresponding 1+ cations, and compare the electrochemistry and reactivity of these species. Results and Discussion Synthesis Although an unsymmetrical 12-like molecule, 2-diethoxyphosphoryl

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• cations), forming coordination compounds wherein the central ion acquires a square planar [14], square pyramidal [15], or an octahedral coordination environment [16]. On the opposite side, crown ethers are cyclic molecules composed of carbon and oxygen atoms forming the macrocycle. Depending on the size

• /electrostatic interactions [18][19][20]. Replacing oxygen atoms with other elements, such as nitrogen, sulfur, etc., alters the crown ethers' affinity toward cations, extending their role as macrocyclic ligands to transition metals [21]. One can say that in many aspects, porphyrins and crown ethers are

• date back to 1982 when Krishnan and Thanabal reported synthesising a new host molecule with multiple cavities capable of encompassing several guest molecules/ions [39]. The molecule demonstrated an exciting feature of binding Na+, Mg2+, Ca2+, K+, NH4+, and Ba2+ cations. The incorporation of cations

Synthesis and biological evaluation of Argemone mexicana-inspired antimicrobials

• Jessica Villegas,
• Bryce C. Ball,
• Katelyn M. Shouse,
• Caleb W. VanArragon,
• Ashley N. Wasserman,
• Hannah E. Bhakta,
• Allen G. Oliver,
• Danielle A. Orozco-Nunnelly and
• Jeffrey M. Pruet

Beilstein J. Org. Chem. 2023, 19, 1511–1524, doi:10.3762/bjoc.19.108

• variants was largely inspired by a recent report that prepared flexible secondary ammonium cations with structural similarity to chelerythrine, wherein the authors did see notable biological potential in these flexible variants [32]. The influence of a fixed charge was also assessed, as protonated compound