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

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• fragmentation rate constants or the N–O bond dissociation energies of radical anions and neutral radicals derived from RAEs are not available in the literature. Lumb and co-workers recently published a study on the conversion of biaryl-derived NHPI esters into spirocyclic cyclohexadienones through a

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

• small peptides [3][4][9], however, unguisin A has been shown to bind a series of anions [10]. Recently the biosynthesis of unguisins A and B from Aspergillus violaceofuscus CBS 115571 was reported [5]. A seven module non-ribosomal peptide synthetase (NRPS; UngA) was heterologously expressed in

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

• ). In this case, the participation of the acenaphthylene derivative seems quite logical, since this should facilitate the SNAr reaction and inhibit the formation of type 7 anions (under the action of methoxide as a base), which are inactive to subsequent nucleophilic attack. Dimethoxyacenaphthylene 14

• acenaphthylene 8) or as a result of double protodebromination (giving acenaphthene 5). Overall, the observed process resembles a redox transformation. Benzyl-type anions, which have hydride mobility and are formed in an alkaline environment from 15, may act as a reducing agent here. We tried to stop this

• 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

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

• + 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

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

• weakly coordinating or not-coordinating organic or inorganic anions. They have interesting physicochemical properties that differentiate them from the organic solvents commonly used in synthesis [74][75][76][77]. Importantly, they have a very low vapour pressure, and therefore do not behave as air

• 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

• 1-butyl-3-methylimidazolium cation unchanged, anion variation also affected the reaction yield. Indeed, in the presence of triflate, acetate or trifluoroacetate anions the desired product was obtained only in trace amounts (Table 3, entries 10–12). This could be explained by the fact that these

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

• –16 was as in the amide series from 8 and thus supported entropic contributions to anion–π catalysis. Steric increase of the secondary amide in 17 impeded anion–π catalysis, presumably because the catalytic π surface next to the ammonium cation became inaccessible for anions paired with the tethered

• fullerenes as well. The unique polarizability of fullerene monomers like 1 is thought to induce strong anion–π interactions and thus account for the observed catalytic activity (Figure 7A) [12]. This polarizability should further increase in fullerene dimers like 36 [80]. Anions, anionic reactive

Controlling the reactivity of La@C₈₂ by reduction: reaction of the La@C₈₂ anion with alkyl halide with high regioselectivity

• Yutaka Maeda,
• Saeka Akita,
• Mitsuaki Suzuki,
• Michio Yamada,
• Takeshi Akasaka,
• Kaoru Kobayashi and
• Shigeru Nagase

Beilstein J. Org. Chem. 2023, 19, 1858–1866, doi:10.3762/bjoc.19.138

• , the third carbon allotrope, have unique spherical molecular structures and exhibit high reactivity as electron-deficient polyolefins. The excellent redox properties of fullerenes are useful for their chemical derivatization and practical applications [1][2][3][4][5]. Fullerene anions can be easily

• added to the solution to precipitate excess TBAF which was then removed by filtration. The La@C2v-C82 anion ([La@C2v-C82]PF6) was collected as the filtrate (with a 78% yield estimated from the molar absorbance coefficient). This step was repeated to ensure a sufficient amount of La@C2v-C82 anions for

• @C2v-C82 anion with 1a. 110 °C, 2 h. (b) La@C2v-C82 with 1a. 110 °C, 2 h. (c) La@C2v-C82 anion with 1a. hv > 350 nm, 1 h. (d) La@C2v-C82 with 1a. hv > 350 nm, 1 h. Black line is the HPLC profiles of La@C2V-C82 at the same concentration as the reaction. Reaction mixtures with La@C2v-C82 anions were

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

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

• (located and refined for 1bH, geometrically placed for the others). Structures of the cations from the single crystal structures of 1g+I− (left), 1h+PF6− (center), and 1i+PF6− (right), shown with 50% thermal ellipsoids and excluding hydrogen atoms and counter anions. Cyclic voltammograms (50 mV s−1, THF

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