Transition-metal-free synthesis of arylboronates via thermal generation of aryl radicals from triarylbismuthines in air

• Yuki Yamamoto,
• Yuki Konakazawa,
• Kohsuke Fujiwara and
• Akiya Ogawa

Beilstein J. Org. Chem. 2024, 20, 2577–2584, doi:10.3762/bjoc.20.216

• somewhat difficult due to strong adsorption or decomposition on silica gel. Since some arylboronates are somewhat unstable, it is desirable to synthesize such compounds and then use them in a one-pot manner for the following reactions without isolation. To gain insight into the reaction pathways, several

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures

• Yohei Haketa,
• Takuma Matsuda and
• Hiromitsu Maeda

Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215

• sheets coated with silica gel 60 (Merck 5554). Column chromatography was performed on Wakogel C-300. Preparation of ion pairs 4,8,12-Tris(2,6-dimethylphenyl)-4,8,12-triazatriangulenium as a BF4− ion pair, 2+-BF4−. According to the literature procedure [26], to a Schlenk tube were added 2,6

• -dimethylaniline (7.0 mL, 59 mmol) and tris(2,6-dimethoxyphenyl)methylium as a Cl− ion pair [22] (504 mg, 1.09 mmol). The Schlenk tube was placed in an oil bath and was heated from rt to reflux over a period of 30 min. The reaction mixture was allowed to reach rt, and then the aniline was removed by short silica

• , 1.38 mmol), and the reaction mixture was stirred at rt for 10 min, followed by filtration, and evaporation to dryness. The residue was purified by silica gel column chromatography (Wakogel C-300; eluent: MeOH/AcOEt/CH2Cl2 1:2:8) and was recrystallized from CH2Cl2/n-hexane to afford 2+-BF4− (143 mg

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

Phenylseleno trifluoromethoxylation of alkenes

• Clément Delobel,
• Armen Panossian,
• Gilles Hanquet,
• Frédéric R. Leroux,
• Fabien Toulgoat and
• Thierry Billard

Beilstein J. Org. Chem. 2024, 20, 2434–2441, doi:10.3762/bjoc.20.207

• derivative 2k, and the estrone derivative 2l were also successfully bis-functionalized. Some products appeared to be sensitive during purification by chromatography on silica gel. Suspecting acid sensitivity, compound 2a was treated with trifluoroacetic acid to confirm this hypothesis (Scheme 3). The product

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles

• Yutaro Miyashita,
• Sae Someya,
• Tomoko Kawasaki-Takasuka,
• Tomohiro Agou and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2024, 20, 2421–2433, doi:10.3762/bjoc.20.206

• in 60% yield. GP-1B (by use of NaClO·5H2O): To a solution of compound 1b [42] (0.2302 g, 1.00 mmol) in 3.0 mL of CH3CN was added NaClO·5H2O (0.3290 g, 2.00 mmol) at 0 °C, and the solution was stirred for 6 h at the same temperature. After the same workup process and purification with silica gel

• in 79% yield after silica gel column chromatography using Hex/AcOEt 6:1 as an eluent. Rf 0.51 (Hex/AcOEt 4:1); 1H NMR (300.40 MHz, CDCl3) δ 0.88 (t, J = 6.9 Hz, 3H), 1.26 (brs, 14H), 1.60 (quint, J = 6.9 Hz, 2H), 2.49 (t, J = 7.5 Hz, 2H), 2.74 (dd, J = 3.6, 17.7 Hz, 1H), 2.83 (dd, J = 9.0, 17.7 Hz

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• product. After silica gel column purification, the isolated yield of these compounds were 64% and 13%, respectively. Additionally, a radical species, showing an ESR peak pattern distinct from that of the DAntM radical and mainly splitting into five peaks with g = 2.0037, was confirmed (Figure 4, Figure S7

Selective hydrolysis of α-oxo ketene N,S-acetals in water: switchable aqueous synthesis of β-keto thioesters and β-keto amides

• Haifeng Yu,
• Wanting Zhang,
• Xuejing Cui,
• Zida Liu,
• Xifu Zhang and
• Xiaobo Zhao

Beilstein J. Org. Chem. 2024, 20, 2225–2233, doi:10.3762/bjoc.20.190

• silica gel 60 F200) were analyzed under UV light (254 nm). Chromatographic purifications were performed on SDZF silica gel 160. The starting α-oxo ketene N,S-acetals 1 are known compounds [40][41] and easily prepared according to References [40][58]. Typical procedure for the preparation of β-keto

• value of the reaction mixture was adjusted to neutral using a saturated NaHCO3 solution, and the reaction mixture was extracted with CH2Cl2 (3 × 20 mL). The organic solution was dried with anhydrous Na2SO4, and the crude product was purified by column chromatography on 300–400 mesh silica gel (petroleum

• organic solution was dried with anhydrous Na2SO4, and the crude product was purified by column chromatography on 30–400 mesh silica gel (petroleum ether (60–90 °C)/ethyl acetate 20:1, v/v) to give 3a (53.8 mg, 90%). Synthesis of α-keto thioesters and β-keto amides. Synthesis of β-keto thioesters 2

Novel truxene-based dipyrromethanes (DPMs): synthesis, spectroscopic characterization and photophysical properties

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2024, 20, 2163–2170, doi:10.3762/bjoc.20.186

• purified through silica-gel column chromatography. After successfully synthesizing these easy-to-make yet interesting molecules, they were fully characterized by means of the standard spectroscopic techniques (1H NMR, 13C NMR and HRMS). We are of the opinion that these truxene-based systems will be useful

• . Analytical thin-layer chromatography (TLC) was performed on aluminium plates coated with silica gel by using a suitable mixture of EtOAc and petroleum ether for development purpose. Column chromatography was performed by using silica gel (100–200 mesh) with an appropriate mixture of EtOAc and petroleum ether

• crude product was extracted with ethyl acetate. The combined organic layers were washed with water (2 × 100 mL), dried over anhydrous Na2SO4. After evaporation of the solvent the residue was passed through a silica gel (SiO2) to give the final product as a white powder (7.5 g, 95%). The 1H NMR spectrum

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

• performance is crucial to the development of high performance immobilised organocatalysts. Review Characteristics of the solid support Considering the support type, organic polymer-supported, silica-supported [20][21][22][23][24][25], glass beads [26] and magnetic nanoparticle-supported [27][28][29][30][31

• immobilization strategies, including covalent bonding and encapsulation, cater to different polymer types. Soluble polymers enhance diffusion, while insoluble ones ensure stability and high loading capacities [42]. Silica is also widely applied due to its ease of functionalisation and thermal stability [43]. The

• controllability of surface, geometry, and pore size makes silica-based materials sustainable and functionalisable supports for organocatalytic reactions [44]. The particle morphology of mesoporous silica can be tuned to various shapes, including spheres, tubes, and rods of various dimensions [45], by using a co

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• radical, which induces 5-exo cyclization. The following hydrogen abstraction, intramolecular ionic cyclization, and hydrolysis during chromatography on silica gel affords the cyclic amide in good yield. They further applied this radical cyclization reaction as a key step in the synthesis of (±)-α-kainic

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

• pyrazoline, which leads to increased yields. In addition to fully substituted pyrazoles, bispyrazoles can also be synthesized [97]. Other Lewis acid catalysts employed in this method include chloride-functionalized silica gel (SiO2Cl) [98] and Sc(OTf)3 [99]. Importantly, all reactions of this method are

• as [MCM-41-2N-Pd(OAc)2] [130] and Pd-SH-silica bound catalysts [131] have also been successfully employed in this three-component pyrazole synthesis. Interestingly, the latter catalyst system does not require a copper cocatalyst. Tang's research group further extended polymer synthesis by using the

Allostreptopyrroles A–E, β-alkylpyrrole derivatives from an actinomycete Allostreptomyces sp. RD068384

• Marwa Elsbaey,
• Naoya Oku,
• Mohamed S. A. Abdel-Mottaleb and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2024, 20, 1981–1987, doi:10.3762/bjoc.20.174

• fractionated on a silica gel column eluting with CHCl3/MeOH mixtures. Allostreptamide was obtained from the eluate with CHCl3/MeOH 2:1 [24]. HPLC-DAD analysis of a less polar fraction, eluted with CHCl3/MeOH 10:1, detected several peaks with characteristic UV absorptions, which were purified by ODS flash

• , and isolation Details on the supplier of Allostreptomyces sp. RD068384, fermentation, extraction, and fractionation are described in Supporting Information File 1. While a CHCl3/MeOH 2:1-eluting fraction by silica gel open column chromatography eventually yielded allostreptamide [24], a less polar

• CHCl3/MeOH 10:1 fraction contained compounds with characteristic UV absorption. This fraction, obtained as 395 mg of brown solid from 4 L culture in A-3M medium, was fractionated by octadecyldimethylsilyl (ODS) silica gel column chromatography with a gradient of MeCN/0.1% HCO2H solution (2:8, 3:7, 4:6

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

• moisture-sensitive reagents were performed under a nitrogen or argon atmosphere. Silica gel chromatography was performed using prepacked silica gel columns (RediSep® Rf, Teledyne ISCO). An aluminum block atop a hotplate with a thermocouple was used to heat reactions to the specified temperatures. NMR

• purified by chromatography (silica [24 g], eluting with EtOAc in hexane from 0–70%) to give methyl 5-bromo-1-alkyl-1H-indazole-3-carboxylate, in 90–98%. For 15a, 284.5 mg, 90%, as a white solid. Mp 141.3 °C; 1H NMR (300 MHz, DMSO-d6) δ 8.19 (dd, J = 1.9, 0.7 Hz, 1H), 7.82 (dd, J = 9.0, 0.7 Hz, 1H), 7.65

• (0.5 mL, 12.4 mmol) at 0 °C, followed by adding DEAD (1.718 mL, 10.85 mmol). The resulting mixture was stirred for 10 min at 0 °C, warmed to 50 °C, and stirred for 2 h. After TLC showed completion, the solvent was removed, and the residue was purified by chromatography (silica [24 g], eluting with

A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions

• Vitor A. S. Almodovar and
• Augusto C. Tomé

Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169

• chromatography (TLC) was carried out on precoated sheets with silica gel (Merck 60, 0.2 mm thick). Preparative TLC was carried out on 20 cm × 20 cm glass plates precoated with a layer of silica gel 60 (0.5 mm thick) and activated in an oven at 100 °C for 12 h. Melting points were determined with a Büchi B-540

• and then it was diluted with CH2Cl2 and water. The organic layer was separated and washed with water and brine. The product was isolated by column chromatography on silica gel using CH2Cl2 as the eluent. Yield: 61%; mp: 278–280 °C; 1H NMR (300 MHz, CDCl3) δ (ppm) 7.62–7.66 (m, 4H), 7.47–7.52 (m, 4H

Electrochemical radical cation aza-Wacker cyclizations

• Sota Adachi and
• Yohei Okada

Beilstein J. Org. Chem. 2024, 20, 1900–1905, doi:10.3762/bjoc.20.165

• with stirring. The solution was diluted with water and extracted with dichloromethane. The combined organic layers were dried over Na2SO4, filtered, and concentrated in vacuo. Yields were determined by 1H NMR analysis using benzaldehyde as an internal standard (Table 1). Silica gel column

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

• , respectively. For further investigations, however, CALB was chosen due to its lower cost and easier availability. Optimization of enzyme loading and substrate ratios increased the yield up to 91%. Immobilization of the enzyme on silica particles was not detrimental to the yield, but allowed enzyme recycling

• the addition of tert-butyl isocyanide. On the other hand, the addition of tert-butyl isocyanide on the imine altered the orientation of adduct 19, suppressing the interaction with Ser105 (Scheme 8). Very recently, Tyagi et al. reported the double encapsulation of CALB and Pd(PPh3)4 within silica

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• dimethoxylated quinones are somewhat labile but can be purified by rapid silica gel chromatography and stored for a few weeks. The controlled current and anhydrous conditions helped avoiding overoxidation. The substrates leading to p-quinones were more prone to overoxidation. The electrochemical oxidation of

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

• on silica. Overview of common non-iodine-based (left) and iodine-based (right) oxidizing reagents for the generation of carbonyls from the corresponding alcohols. NHIs investigated for the oxidation of benzylic alcohols and the crystal structure (ORTEP drawing) of 1c (CCDC 2321313), showing the

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• (34%) of Nafion perfluorinated resin solution was purchased from Sigma-Aldrich. Purification of reaction products was done by column chromatography on silica gel (230–400 mesh) with the appropriate eluent mixture and using a positive pressure of nitrogen. Spectroscopic characterization The

Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds

• Ka-Lung Hung,
• Leong-Hung Cheung,
• Yikun Ren,
• Ming-Hin Chau,
• Yan-Yi Lam,
• Takashi Kajitani and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142

• specified. All reactions were performed under nitrogen unless otherwise specified. Analytical thin-layer chromatography (TLC) was performed with Macherey-Nagel silica gel 60 UV254 aluminum plates, and visualization was accomplished by UV light (254 nm or 365 nm) or by staining with phosphomolybdic acid and

• heating. Flash column chromatography was performed using Macherey-Nagel silica gel 60 (230–400 mesh). Deuterated solvents were purchased from Cambridge Isotope Laboratories. UV–vis spectroscopy UV–vis measurements were performed on an Agilent Cary 60 UV–vis spectrophotometer with a quartz cuvette of 1 cm

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

• predominately considered to be stable to isolation conditions, secondary and tertiary suffer from the elimination of HF, especially in the presence of silica gel or glass vessels. Therefore, benzyl fluorides have been derivatised, for example in C–O, C–N and C–C bond-forming reactions [18][19][20], thereby also

• several secondary and tertiary benzyl fluorides were unstable to silica during isolation or storage in glass vessels, and therefore, demonstrated several downstream diversifications of the benzyl fluorides. Sevov, Zhang and co-workers reported in 2023 a stable copper(III) fluoride complex that was capable

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

• Pooja Goyal,
• Akhil K. Dubey,
• Raghunath Chowdhury and
• Amey Wadawale

Beilstein J. Org. Chem. 2024, 20, 1518–1526, doi:10.3762/bjoc.20.136

• temperature. The crude reaction mixture was purified by silica gel (230–400 mesh) column chromatography (petroleum ether/EtOAc as the eluent) to give the product 3 or ent-3. Selected examples of drugs and bioactive molecules bearing a pyrazole core. Single crystal X-ray structure of ent-3ba (CCDC 2234286

Tetrabutylammonium iodide-catalyzed oxidative α-azidation of β-ketocarbonyl compounds using sodium azide

• Christopher Mairhofer,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1510–1517, doi:10.3762/bjoc.20.135

• were recorded on an Agilent QTOF 6520 spectrometer with an ESI source. Melting points are recorded using a Büchi M-560 apparatus and are reported uncorrected. TLC was performed on Macherey-Nagel pre-coated TLC plates (silica gel, 60 F254, 0.20 mm, ALUGRAM® Xtra SIL). Preparative column chromatography

• was carried out using Davisil LC 60 Å 70-200 MICRON silica gel. All chemicals were purchased from commercial suppliers and used without further purification unless otherwise stated. General α-azidation procedure Sodium azide (7.8 mg, 120 µmol, 1.2 equiv) and TBAI (7.4 mg, 20 µmol, 20 mol %) were

• diluted with 8 mL dichloromethane and extracted with 5 mL of sat. aq NaHCO3. The aqueous phase was then extracted twice with 10 mL of DCM. The organic layer and the extracts were then filtered consecutively through a pad of anhydr. sodium sulfate and deactivated silica gel. The solvents were removed in

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• and EtOAc), concentrated under reduced pressure, and subsequently purified by preparative TLC (silica gel, heptanes/EtOAc 4:1) to obtain the products 2 in the given yields and enantiopurities. Details for the parent compound 5a (details for the other targets can be found in Supporting Information File

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

• through alumina or molecular sieves-containing cartridges using a solvent purificator MBRAUN SPS-800. All the reactions with azobenzene-containing substrates were carried out in the dark. Reactions were monitored by TLC on Silica Gel 60F-254 plates with detection by UV (254 nm or 365 nm) or by spraying

• with 10% H2SO4 in EtOH and heating about 30 s at 400–600 °C. Column chromatography purification was performed on CombiFlash® Rf+ and RediSep® RF or RF Gold normal phase silica columns (with UV detection at 254 and 350 nm for all azobenzene derivatives), or by flash column chromatography employing

• silica gel (60 Å pore size, 40–63 µm). 1H and 13C NMR spectra were recorded on a JEOL ECS-400 spectrometer or on Bruker Avance 300 and 400 spectrometers. Structural assignments were made with additional information from gCOSY, HMBC, and gHMQC experiments. High-resolution mass spectra (HRMS) were