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

• ]. The CsF binding led to a supramolecular self-assembly process, inducing a sandwich host–guest complex formation in the solid state (Scheme 2). It was established that fluoride is preferred over any other halide anions. The binding of the ion pairs was observed in highly polar solvent media, but in the

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• with poly(ethersulfone) [143]. Highly reactive gaseous species may also generate radicals on polymer surfaces. For example, atomic oxygen radical anions emitted from 12CaO⋅7Al2O3 crystals [144] were used to modify PVC and polystyrene [145][146]. Plasma is also a powerful gas-phase tool for polymer

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• acidic”, which seems to explain the position of the amine molecules in the 1:2 complex. Interestingly, the “proton acidity” in the anions R[4]A2− (pKa3 = 11.28) and R[4]A3− (pKa4 = 11.45) is more than two orders of magnitude lower than the first proton of the hydroxy group in R[4]A (pKa1 = 9.23). This

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

• explored as catalysts for the hydrosilylation of ketones. Besides the type of the ligand in the NHC–Cu(I) complex, the counter anions (BF4 and PF6) also influenced the catalytic activity. Furthermore, the cationic complexes were found to be more efficient than the neutral analogues under similar conditions

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• -hole bond is the non-covalent inter- or intramolecular interaction between the σ-hole of a group IV–VII atom with the electron-rich site of Lewis bases such as anions, hydrides, or even π electrons [24][30]. Halogen bonding is a subset of this bonding classification, represented by the generic bonding

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• aryl halides and trialkylphosphites (14) via a similar conPET mechanism (Figure 7) [47]. Notably, even 4-bromoanisole could be reductively activated and phosphorylated in 58% yield (15b). Reports from Eggins [48], Lund and Eriksen [49] have shown that upon excitation, the radical anions of

• reactions stating that outer sphere ET events generally occur only from the lowest excited state due to the same relaxation pathways [69]. It has been largely proven that this limitation is circumvented by the involvement of excited radical anions and two excitation processes; to access molecular orbitals

• that is subsequently quenched to HBpin by HAT from DBU•+. As an alternative to organic radical anion conPET, the Chiba group reported the use of homoatomic polysulfide anions as cheap, readily available and potent photocatalysts [75]. Based on the ground state redox potentials and the visible light

CO₂ complexation with cyclodextrins

• Cecilie Høgfeldt Jessen,
• Jesper Bendix,
• Theis Brock Nannestad,
• Heloisa Bordallo,
• Martin Jæger Pedersen,
• Christian Marcus Pedersen and
• Mikael Bols

Beilstein J. Org. Chem. 2023, 19, 1021–1027, doi:10.3762/bjoc.19.78

• such as 2 and 3 and did not. Recently the solid complex of CO2 and 1 have been studied as a food product additive [9][10][11]. Anions of 1 in DMSO have been found to have a high capacity for capturing of CO2 [12]. Being cheap, biodegradable and eco-friendly these carbohydrates might form the basis in

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• nitro group. There are two types of independent non-equivalent dications, marked in blue and green, and two types of BF4− anions, marked in red and yellow, in the crystal structure of salt 11c (Figure S68 in Supporting Information File 1). Monomer fragments in both are identical (Table 2, Figure 5). The

• -trifluoromethylphenyl rings. By the way, the qr parameters calculated for two independent molecules of 11c were 0.008 and 0.009, which is slightly less than in the case of compounds 5. As for the crystal packing of 11c, BF4− anions of two types (“red” and “yellow”) interact with cations in different ways. The “red

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• azetidines 19 were also synthesized using this methodology (Scheme 5b). Nitronate anions were also found suitable for Mannich-type trapping reactions [28][29]. Anderson and co-workers accomplished several Cu-catalyzed conjugate additions of R2Zn to nitroolefins 20, followed by subsequent reaction with p

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• molecules around each system, and submitted to periodic simulations where the excess positive charge was neutralized with an equivalent number of chloride anions in monoprotonated systems corresponding to pH 5. Upon gradual heating from 0 K, MD simulations were performed at 300 K for a period of 300 ns

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• has very strong anion-binding affinities for various anions. In 2019, Ol’shevskaya [61] and co-workers synthesized meso-tetratriazole-bridged fluorinated porphyrin-maleimine conjugates 145a–c in 54–58% yields by using the CuAAC reaction between azidoporphyrins 143a,b and N-propargylmaleimide (144) in

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• described an elegant aryl–aryl cross-coupling procedure suppressing the formation of Grignard homocoupling byproducts relying on the use of FeF3 as catalyst, associated with strong N-heterocyclic carbenes (NHCs) and a source of fluoride anions [28]. A similar procedure involving sodium alkoxide additives

• -depth mechanistic studies were so far reported regarding the reactivity of the enol phosphate electrophiles (Scheme 3 and Scheme 4, and Table 2, entry 4). Phosphate free anions released at each catalytic cycle could act either as NMP or alkoxides, that is, as ligands to the magnesium cations, or as

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

•  18B). An interesting idea realized in this process is the alcohol activation for α-hydrogen atom abstraction by hydrogen bonding between the alcohol OH group and dihydrophosphate anions. It should be noted that alcohol-derived α-hydroxy radicals frequently do not undergo successful C–C coupling due to

1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes

• Artem N. Semakin,
• Ivan S. Golovanov,
• Yulia V. Nelyubina and
• Alexey Yu. Sukhorukov

Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148

• ), although lattice methanol molecules and chloride anions are present in the structure. The larger tris-Boc derivatives 4c·HCl and Bn-4c form the same guest–host complexes with methanol (Figure 3d). Thus, these TAAD-based systems may exhibit molecular recognition properties. Deprotected N-TAADs such as 19e

• -tetraazaadamantane motif in X-ray structures of the obtained N-TAAD derivatives (representation of non-hydrogen atoms as thermal ellipsoids at 50% probability level). Anions and crystal-solvate molecules are omitted for clarity. (a) 4a·HCl·H2O·MeOH. (b) 4c·HCl·3.5MeOH. (c) Bn-4c·3CD3OD (bromide salt). (d) 8a. (e

Computational model predicts protein binding sites of a luminescent ligand equipped with guanidiniocarbonyl-pyrrole groups

• Neda Rafieiolhosseini,
• Matthias Killa,
• Thorben Neumann,
• Niklas Tötsch,
• Jean-Noël Grad,
• Alexander Höing,
• Thies Dirksmeyer,
• Jochen Niemeyer,
• Christian Ottmann,
• Shirley K. Knauer,
• Michael Giese,
• Jens Voskuhl and
• Daniel Hoffmann

Beilstein J. Org. Chem. 2022, 18, 1322–1331, doi:10.3762/bjoc.18.137

• to efficiently bind to oxo-anions such as carboxylates [10]. These compounds were already used to specifically address carboxylates on the surface of proteins. Many artificial receptors based on guanidinium scaffolds use hydrogen bonding, charge pairing, and hydrophobic interactions to complex oxo

• -anions [11]. The guanidiniocarbonyl-pyrrole (GCP) is able to bind oxo-anions even in aqueous solvents with competing ions and salts. Schmuck et al. also discovered that an additional positive charge increases the binding affinity to oxo-anions [10]. These unique properties make the GCP oxo-anion binder

Ferrocenoyl-adenines: substituent effects on regioselective acylation

• Mateja Toma,
• Gabrijel Zubčić,
• Jasmina Lapić,
• Senka Djaković,
• Davor Šakić and
• Valerije Vrček

Beilstein J. Org. Chem. 2022, 18, 1270–1277, doi:10.3762/bjoc.18.133

• /bjoc.18.133 Abstract A series of N6-substituted adenine–ferrocene conjugates was prepared and the reaction mechanism underlying the synthesis was explored. The SN2-like reaction between ferrocenoyl chloride and adenine anions is a regioselective process in which the product ratio (N7/N9-ferrocenoyl

• analogous reaction is regioselective and resulted in the formation of two products, i.e., N7- and N9-regioisomers (Scheme 1). In no case, the N1-, N3-, or N6-products were formed, which is comparable to the results reported for the reaction between benzoyl chloride (BzCl) and purine anions [25]. The two

• no case, however, the ferrocenoylation reaction at the N6 position was observed in 1H NMR spectra. This is expected, as the nucleophilic addition pathway involving the quaternary ammonium intermediate is not viable. In all purine anions, according to the calculated Fukui functions f–, the N7 atom is

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• radical anions influenced by substituents in the cyclopropane ring are discussed. Optimization of the reaction conditions opens a route to the non-proteinogenic amino acid derivatives containing an α–β or β–γ double C=C bond in the side chain; the regioselectivity can be tuned by the addition of Lewis

• stereoselective functionalization has not been probed as yet. Herein, reductive three-membered ring opening in the chiral α,α-cyclopropanated amino acids involved in the Ni(II)–Schiff base coordination environment is reported. Follow-up transformations of thus formed radical anions will be discussed, including

• radical anions formed are relatively stable, at least in the CV time scale) at close potential values (E1/2 = −1.42 V (1), −1.42 V (2) ; for comparison: E1/2 for AlaNi = −1.53 V [52] vs Ag/AgCl, KCl(sat.)). The complexes containing one (3) or two (4) electron-deficient COOMe groups in the cyclopropane

Electrochemical formal homocoupling of sec-alcohols

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

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• improve the yield of 2a (Table 1, entries 2–4). The present reaction proceeded in the presence of quaternary ammonium salts with different counter anions including the BF4 anion, and Et4NBr was found to be the preferable electrolyte among them (Table 1, entry 1 vs entries 5–7). Next, we examined the

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• known salts, at present used in a wide variety of chemical fields. The first definition of ionic liquids was given by Paul Walden in 1914: “they are materials composed of cations and anions, that melt around 100 °C or below as an arbitrary temperature limit” [1]. ILs are salts formed by non or weakly

• coordinated cations and anions, usually bulky organic cations and inorganic or organic anions such as −BF4, −PF6, −N(CF3SO2)2, etc. [2][3]. The physicochemical properties of RTILs (room temperature ionic liquids) are reported in the literature and include very low vapor pressure, and thus the possibility to

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

• Naoki Kise and
• Toshihiko Sakurai

Beilstein J. Org. Chem. 2022, 18, 956–962, doi:10.3762/bjoc.18.95

• -oxobutyl)phthalides 5 were produced as the sole products by the reaction of 1 with methyl vinyl ketone (2b). It was found by DFT calculations for the cyclization step of the intermediate enolate anions that the product selectivity was in good agreement with the free energy differences (∆G) in the

• Information Supporting Information File 215: Characterization data for compounds, copies of 1H and 13C NMR spectra, X-ray crystallographic data (ORTEP) of 3b, CV data of compounds 1a–h, and DFT calculation data for cyclization of enolate anions. Supporting Information File 216: Cif for 3b. Acknowledgements

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

• Sadanobu Iwase,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

• dithiocarbonate. Cathodic reduction of 1. Indirect cathodic reduction of 1 using o-phthalonitrile as mediator. Mechanism for the formation of product 3. Reaction of compound 1 with PhS anions. Cathodic reduction of compound 1 in the presence of α-methylstyrene at a high current density. Indirect cathodic

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• a result, the polymerization of ε-caprolactone (123) was switched OFF. Addition of chloride anions from n-Bu4NCl led to the substitution of the tertiary amine ligand at both rhodium centers generating the semi-open form [125(Cl)2]. Since the aluminum(III) salen center became now exposed, the

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• the thread (see Figure 16). The stereoselective binding of chiral anions by rotaxanes 64a/b was studied by 1H NMR titration experiments, using the dicationic macrocycle (S)-61-Me22+ (obtained by methylation of the triazole units in (S)-61) as a reference system. As guest molecules, the Boc-protected

• to slightly better stereodiscrimation of the guest molecules (see Figure 17). Subsequently, Beer and co-workers reported the first example of a chiral halogen-bonding [3]rotaxane for the recognition and sensing of dicarboxylate anions [64]. The [3]rotaxane (S)-68 was prepared in a two-fold clipping

• reaction, namely reaction of bis-amine 66 and bis-acid chloride 67 in the presence of the dicationic axle (S)-65. The resulting rotaxane (S)-68 (37% yield, see Figure 18) features a central chiral BINOL unit with two adjacent binding sites for anions, each made of two iodotriazole-XB donors (on the thread

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• selectivity toward 3a/4 decreased (Table 3, entry 3). As mentioned above, this is probably because the protons generated by the oxidation of the THF solvent at anode could easily meet the radical anions of imine 1 generated at cathode due to the very short interelectrode distance. In the electrochemical

• formation of 4 by the reaction between protons and the radical anions of 1. As shown in Table 4, entry 6, the yield of 3a decreased when the electricity was fixed at 2 F mol−1 by increasing the flow rate over the conditions in Table 4, entry 2. On the other hand, as shown in Table 4, entry 7, the yield of

• anions of imine 1 with the terminal dihaloalkane is also considered to be an important factor in the formation of the desired product 3a. Therefore, a model reaction was conducted using dihaloalkanes with different types of terminal halogens (Cl, Br, and I) (Table 7). When the terminal halogen of the

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• by a review article devoted to aza-Michael reactions of amines and amides [17]. The evolution of the understanding of noncovalent activation modes led to the realization that anion-binding is a critical feature in many transformations. Halide anions are highly relevant and widely occurring within