Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• five to seven-membered cyclic compounds [47]. Arylation reactions using diaryliodonium salts can occur through four distinct mechanisms. First, the arylation can occur under metal-free conditions, involving the formation of a three-membered ring transition state through ligand coupling, leading to the

• formation of the Nu–Ar product and aryl iodide [21]. Second, the arylation can take place in the presence of a metal catalyst via oxidative addition, followed by reduction elimination [48][49]. Thirdly, it proceeds through a ligand-coupled arylation which involves a five-membered transition state to yield

• upon binding of the enolate molecule to iodine either through a carbon–iodine or an oxygen–iodine bond. Both intermediates, I and II, are in rapid equilibrium with each other and further undergo two different types of reactions: [1,2]-ligand coupling and [2,3]-rearrangement (Scheme 2). Either of these

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• -glycosylated indirubins act as a ligand for the aryl hydrocarbon receptor (AhR) and also directly inhibit several cyclin-dependent kinases (CDK). A problem is generally the low water solubility of these compounds. The commercially available indirubin-3’-monoxime (34) shows a better solubility, due to the

• collaboration with Jürgen Eberle and his team it was shown that selenoindirubin-N-glycosides β-38a–h showed antiproliferative activity against lung cancer cell lines H157 [38]. The antiproliferative activity against melanoma cells was accompanied by induced apoptosis in combination with the death ligand TRAIL

• (TNF-related apoptosis-inducing ligand). The death ligand TRAIL is a promising strategy for cancer treatment. In contrast to non-glycosylated thioindirubin 35, a significant activity was observed also for non-glycosylated selenoindirubin 40h. This might be due to the fact that selenoindirubin-N

Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide

• Parvathy Mini,
• Michael R. Grace,
• Genevieve H. Dennison and
• Kellie L. Tuck

Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237

• /bjoc.20.237 Abstract The chemosensor properties of a bimetallic terbium(III)/copper(II) complex functionalized with a 4-(2-pyridyl)-1,2,3-triazole ligand for the detection of Cu2+ ions and, aqueous and gaseous hydrogen sulfide was investigated. The 4-(2-pyridyl)-1,2,3-triazole ligand functions both as

• aqueous hydrogen sulfide and 100 ppb for gaseous hydrogen sulfide [16]. However, due to the limited aqueous solubility and ligand dissociation of this chemosensor, and to the weakly luminescent bis species at usable concentrations, we extended this work to the lanthanide–macrocycle binary complexes [Ln

• in an analogous fashion to the Eu.1 complex, via a three-step synthesis as reported previously [16] and depicted in Scheme 1. The corresponding terbium(III) species was synthesized by the combination of three equivalents of the ligand L with terbium(III) trifluoromethanesulfonate under basic

Synthesis and antimycotic activity of new derivatives of imidazo[1,2-a]pyrimidines

• Dmitriy Yu. Vandyshev,
• Daria A. Mangusheva,
• Khidmet S. Shikhaliev,
• Kirill A. Scherbakov,
• Oleg N. Burov,
• Alexander D. Zagrebaev,
• Tatiana N. Khmelevskaya,
• Alexey S. Trenin and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2024, 20, 2806–2817, doi:10.3762/bjoc.20.236

• fingerprints (IFP) between the docking ligands and the protein shows that, similar to the reference ligand voriconazole, the compounds interact with the protein through hydrophobic interactions with hydrophobic residues of the protein and the formation of coordination bonds with the haem iron (Table 3). At the

• -aminoimidazole (1). Results of MEP calculations for the reaction of N-phenylithaconimide (3a) with 2-aminoimidazole (1). Screening of reaction conditions for the preparation of 7-oxo-N-phenyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrimidine-5-carboxamide (4a). Yields of the products 4 and 5. Characterization of ligand

C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• the Suzuki coupling began with investigating first the Suzuki reaction compatibility of boronic acid 14 with porphyrin 13. Porphyrin 13 and phenylboronic acid (14) were subjected to coupling at 85 °C for 48 hours using Pd2dba3/SPhos as a catalyst/ligand giving porphyrin 26 in a 32% yield, based on a

• , even with Ni(II) metalation. There are many other methods available to achieve different desired atropisomeric ratios. These include thermal enrichment [67][68], photoracemization [69][70], axial-ligand coordination [71], precise separation techniques [50] or a combination of the procedures mentioned

• . Conclusion When considering sterically demanding systems with haloaryl and boronic acids as substrates for the Suzuki–Miyaura coupling, many may consider 2,6-alkyl-disubstituted phenyl rings as a model sterically demanding system to test the robust nature of both metal catalyst and ligand, for example, much

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• developments and illustrates the influences of copper salt, ligand, and substitution pattern of the substrate on the regioselectivity and stereoselectivity. Keywords: copper-catalysis; copper vinyl allenylidene intermediate; 1,3-enyne; 1,4-enyne; yne-allylic substitution; Introduction Copper is earth

• demonstrated that the terminal alkyne unit is crucial for the process and the reactions using different isomers all proceed via the same intermediate. Nonlinear relationship experiments proved that the active catalyst is a mono-copper complex containing one ligand. A catalytic cycle is proposed in which copper

• confirmed that a copper–ligand monomer complex exists in the mechanism through nonlinear relationship experiments and kinetic studies (Scheme 17). He et al. [68] developed the regio- and enantioselective monofluoroalkylation of yne-allylic esters using fluorinated malonates as the starting materials, giving

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• imidazolium ring formation. The resulting carbene was metalated at the C2 position with Au(I), Cu(I), and Ir(I), obtaining an L-shaped NHC ligand scaffold. Līpiņš et al. introduced a new method for synthesizing 4-azido-6,7-dimethoxy-2-alkyl/arylsulfonylquinazolines, which are key intermediates in the

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• complex, C(sp3)–H bonds underwent azidation with high chemoselectivity, even in the absence of a directing group. The proposed mechanism involves the formation of the active catalyst Mn(III)(N3) via ligand exchange, followed by anodic oxidation to a Mn(IV)(N3)2 complex. This high–valent Mn(IV) species

• product (Scheme 34). To date, only a few enantioselective reactions using metal catalysis and electrochemistry have been reported. Very recently, Ackermann and coworkers employed Co(OAc)2 as a catalyst and a salicyloxazoline derivative as a chiral ligand to achieve the electrochemical atroposelective C–H

• bonded to the nitrogen atom of the aniline substrate. The methodology showcases a broad scope for carboxylic acids and demonstrates multiple examples of LSF of pharmaceuticals and natural products. The proposed mechanism begins with the formation of Ru(II) diacetate through ligand exchange between the

Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• (R)-VANOL ligand 115 was attained by column chromatography in 92%. In 2015, further development of the 2-aza-Cope rearrangement strategy was reported by Johnson [43]. This work expanded the scope of the reaction to β-formyl amides 119 under the conditions of dynamic kinetic resolution (DKR) by

Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

• Phong Thai,
• Lauv Patel,
• Diyasha Manna and
• David C. Powers

Beilstein J. Org. Chem. 2024, 20, 2305–2312, doi:10.3762/bjoc.20.197

• N-tert-butyl-α-phenylnitrone (PBN) afforded the aziridine product 3b in 60% NMR yield (Scheme 4d), suggesting a radical pathway was unlikely to be operative. An 1H NMR experiment was carried out to probe the speciation of 2a in HFIP, and we observed that 2a underwent reversible ligand exchange with

• iminoiodinane reacts directly with the olefin to generate a short-lived alkyl-bound iodinane 7 or iodonium species 8 (Scheme 4f). Ligand coupling from 7 or extrusion of iodobenzene from 8 would furnish a carbocation intermediate 9 which could undergo C–C bond rotation prior to ring closure to form the aziridine

Factors influencing the performance of organocatalysts immobilised on solid supports: A review

• Zsuzsanna Fehér,
• Dóra Richter,
• Gyula Dargó and
• József Kupai

Beilstein J. Org. Chem. 2024, 20, 2129–2142, doi:10.3762/bjoc.20.183

• catalyst closer to the support, impacting electronic properties and ligand conformation. With large catalyst molecules, the pores of an ordered mesoporous material being similar in size to the catalyst can create significant diffusion barriers as the catalyst attempts to enter the pores. As a result, the

Computational toolbox for the analysis of protein–glycan interactions

• Ferran Nieto-Fabregat,
• Maria Pia Lenza,
• Angela Marseglia,
• Cristina Di Carluccio,
• Antonio Molinaro,
• Alba Silipo and
• Roberta Marchetti

Beilstein J. Org. Chem. 2024, 20, 2084–2107, doi:10.3762/bjoc.20.180

• –ligand complexes, and analyse MD outcomes. Moreover, selected case studies have been reported to highlight the importance of computational tools in studying protein–glycan systems, revealing the capability of these tools to provide valuable insights into the binding kinetics, energetics, and structural

• state can be performed with the same tools described below in the protein–ligand interactions section. Computational tools to study proteins in the free state Knowledge on the three-dimensional structure of a protein is essential for understanding the functions and the dynamics of protein interactions

• study protein–ligand complexes Detailed investigations of protein–ligand interactions, combining experimental and computational methods, provide an indispensable basis to depict holistic pictures of molecular complexes allowing to modulate them at will. The computational approach involves i) predicting

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• pathway enables the synthesis of 3,5-bis(biphenyl)-1-methyl pyrazole. To stabilize the catalyst, additional triphenylphosphane is added as a ligand during the Suzuki coupling. The resulting products fluoresce blue, with the five biaryl-substituted derivatives 113 showing the highest quantum yields of up

Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate

• Masahiro Terada,
• Zen Iwasaki,
• Ryohei Yazaki,
• Shigenobu Umemiya and
• Jun Kikuchi

Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173

• moderate yield (entry 1: 42%, cf. batch reaction: 76%). Lowering the reaction temperature to 25 °C reduced the yield (Table 1, entry 2: 35%), but decreasing the amount of the phosphine ligand from 20 mol % to 5 mol % markedly improved the yield (Table 1, entry 3: 53%). Even when the flow rate was increased

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• meso form in high combined yield (90%, Scheme 16) [94]. The product was used as a ligand for the preparation of transitional metal carbonyl complexes. The addition reaction of trichlorofluoromethane (CFC-11) to 1,2-difluoroethylene in the presence of aluminum chloride under pressure was described [51

• transitional metal complexes with 1,2-difluoroethylene as a ligand should be mentioned [109][110][111]. Conclusion In conclusion, our literature analysis demonstrated that radical processes are most typical for 1,2-difluoroethylene, while examples of electrophilic reactions are scarce, and nucleophilic

Regioselective alkylation of a versatile indazole: Electrophile scope and mechanistic insights from density functional theory calculations

• Pengcheng Lu,
• Luis Juarez,
• Paul A. Wiget,
• Weihe Zhang,
• Krishnan Raman and
• Pravin L. Kotian

Beilstein J. Org. Chem. 2024, 20, 1940–1954, doi:10.3762/bjoc.20.170

• -3 as a bidentate ligand to the Na+ cation from NaH. The tight ion pair would direct alkylation under conditions A to N1. As this and other postulations exist, we explored the possible mechanisms of each reaction conditions computationally. All calculations were performed in implicit THF at the

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

• template, selecting the ligand building blocks with highest affinity and bringing them in proximity within the binding site. Building blocks are opportunely chosen to have complementary reactivity and therefore to react irreversibly within the binding site and assemble into the final ligand. Before the

• compatibility of the GBB reaction with typical KTGS conditions, such as aqueous solvent at near-physiological pH and high dilution, and the achievement of selective ligand amplification. First, molecular modeling studies were carried out to verify that building blocks and intermediates could bind the target

Discovery of antimicrobial peptides clostrisin and cellulosin from Clostridium: insights into their structures, co-localized biosynthetic gene clusters, and antibiotic activity

• Moisés Alejandro Alejo Hernandez,
• Katia Pamela Villavicencio Sánchez,
• Rosendo Sánchez Morales,
• Karla Georgina Hernández-Magro Gil,
• David Silverio Moreno-Gutiérrez,
• Eddie Guillermo Sanchez-Rueda,
• Yanet Teresa-Cruz,
• Brian Choi,
• Armando Hernández Garcia,
• Alba Romero-Rodríguez,
• Oscar Juárez,
• Siseth Martínez-Caballero,
• Mario Figueroa and
• Corina-Diana Ceapă

Beilstein J. Org. Chem. 2024, 20, 1800–1816, doi:10.3762/bjoc.20.159

• S5B and S5C in Supporting Information File 1) and compared to the protein PCAT1 [22] (the closest homologous protein with a structure resolved by crystallography, here presented in complex with its peptide ligand (PDB 6V9Z). The amino acid sequence identity between CloPt1 and PCAT1 was 29%, while for

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides

• Samuel M. G. Dearman,
• Xiang Li,
• Yang Li,
• Kuldip Singh and
• Alison M. Stuart

Beilstein J. Org. Chem. 2024, 20, 1785–1793, doi:10.3762/bjoc.20.157

• major products were phenyliodane 23, presumably a result of ligand exchange and reduction, and iodoalcohol 18. Different solvents, temperatures and activators were investigated and the results are shown in Table S3 in Supporting Information File 1. Fluorobenzene was only ever observed in trace amounts

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• of a new chiral centre. Advances in understanding ligand–receptor interactions have facilitated the determination of optimal molecular conformations to enhance binding affinity, which can be achieved, in part, by introducing a spiro annelated ring to impart rigidity to the molecule. From a medicinal

• phosphine-based ligand (L). This methodology was applied to the alkynol moiety of ethinylestradiol (8) (86% yield), and alkynols derived from ethisterone, levonorgestrel, lynestrenol, and epiandrosterone (epi-ADT), obtaining excellent yields (85–93%) and high diastereoselectivity (dr > 20:1) in all cases. α

• steroids 124a–e, adducts 125a–d and 126a–e were easily obtained as single diastereomers via a Pictet–Spengler condensation with coumarins A and B (used as fluorophores) under acidic conditions (Scheme 35). Computational binding studies of compound 126c in the ligand-binding pocket of enzyme 17β-HSD5

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• : 3.61 Å [31]). Beginning with the electron-deficient and thereby highly reactive NHIs 1a and 1c, we explored the potential for a ligand-exchange process on the iodane via 1H NMR spectroscopy by combining equimolar quantities of NHI and n-octanol (2). When the tetrazole-substituted hydroxy(aryl)iodane 1a

• in Figure 3a. This indicates a ligand exchange of the hydroxy group resulting in a loss of electron density and the formation of the alkoxy-NHI 2'. The chemical shift is consistent with previously measured alkoxyiodanes [32]. The experiments were repeated using activated p-tolylmethanol (3a), again

• experiment no formation of an alkoxyiodane was observed, indicating that the formation of this ligand-exchanged intermediate is slower than the dehydrogenation. As a consequence, we attempted to accelerate the ligand exchange through the addition of a Lewis acid and the performance of the NHIs was compared

Divergent role of PIDA and PIFA in the AlX₃ (X = Cl, Br) halogenation of 2-naphthol: a mechanistic study

• Kevin A. Juárez-Ornelas,
• Manuel Solís-Hernández,
• Pedro Navarro-Santos,
• J. Oscar C. Jiménez-Halla and
• César R. Solorio-Alvarado

Beilstein J. Org. Chem. 2024, 20, 1580–1589, doi:10.3762/bjoc.20.141

• first equivalent of aluminum chloride to give the corresponding adduct PIFA–AlCl3. Next, a chlorine atom is transferred to the iodine(III) center to yield I-1–Cl via TS1–Cl with the release of the complex TFAO–AlCl2. Then, the second equivalent of aluminum chloride coordinates the TFAO ligand, giving

• , respectively). Then, the tetracoordinate TFAO–AlCl2 salt is released, giving rise to intermediate I-1–Cl (ΔG = −25.2 kcal/mol), which contains the key Cl–I(III) bond, in a formal TFAO/Cl ligand exchange. The Cl–I bond length is 2.46 Å, with the halogen atom sharing the hypervalent iodine bond in the equatorial

• position. Next, the second equivalent of aluminum chloride coordinates to the TFAO ligand, forming active chlorinating species I-2–Cl (ΔG = −18.3 kcal/mol). This energetically favored step is in equilibrium with the ion pair I-3–Cl (ΔG = −0.5 kcal/mol). It is worth mentioning that the slight difference in

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

• -(trifluoromethyl)aniline in conjunction with external ligand 5 facilitated the formation of a series of fluorinated α-amino acids. Xu and co-workers also disclosed a palladium-catalysed protocol for the fluorination of simple benzylic substrates bearing a bidentate directing group (Figure 8) [42]. Yields varied

• secondary and tertiary substrates too. In 2012, Lectka reported a fluorination of mostly aliphatic C–H bonds that used a molecularly defined copper catalyst with a bis imine ligand, along with co-catalytic N-hydroxyphthalimide and a phase-transfer catalyst [51]. Although only a few benzylic substrates were

• is subsequently oxidised to Mn(V)-oxo species II by hypervalent iodine oxidant PhIO. This can perform a HAT from the benzylic substrate, in turn generating a benzylic radical and Mn(IV)-hydroxy species III. Ligand exchange with the fluoride source affords complex IV, which performs FAT with the

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• using acetonitrile as the solvent frequently led to the observation of Cu deposition at cathode (Table 1, entry 4). We reasoned that DMF could coordinate to the copper center, acting as a ligand to prevent copper from cathode reduction. Constant current electrolysis is also applicable to the reaction

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• bacterial infections occur by adhesion to host tissues through receptor–ligand interaction between bacterial carbohydrate-binding proteins (lectins) and oligosaccharides at the host cell surface. Pseudomonas aeruginosa (PA), a Gram-negative, opportunistic and ubiquitous environmental bacterium, is known as

• factor up to 1.6 has been observed for the divalent ligand [23]; while almost no difference of inhibition was observed for LecA and LecB upon irradiation, probably due to the low photoisomerization of glycodendrimers [24]. Very recently, the group of Wittmann reported an arylazopyrazole-linked divalent N

• -acetylglucosamine targeting lectin wheat germ agglutinin [25]. The binding affinity Kd evaluated by isothermal titration calorimetry (ITC) showed a variation by a factor of 12.5 upon photoisomerization. However, a direct photomodulation of a monovalent lectin ligand has not been achieved up to date. Based on our