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

• employing a bulkier allyl-transfer reagent 116. They used a novel pre-formed chiral triborate catalyst 115 in tandem with a non-chiral Brønsted acid and expanded the scope to aliphatic homoallylic amines (Scheme 24). The new method established a scalable, chromatography-free purification protocol for the

• of the allyl donor reagent (up to 25 g). Importantly, benzophenone was easily recovered by recrystallisation after the workup (no chromatography, 80% yield) and then converted back into the allyl donor 116 (86% yield), thus boosting the overall atom-economy of the process. Also, the recovery of the

• (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

• unprotected alcohol is tolerated in our procedure, with product 3l delivered at 50% NMR yield; 3l is sensitive to column chromatography, and thus aziridine-opening to a cyclic ether was observed (31% isolated yield) during purification. Aziridination of cis- or trans-4-octene afforded aziridine 3m as a 1.3

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

• 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

Electrochemical allylations in a deep eutectic solvent

• Sophia Taylor and
• Scott T. Handy

Beilstein J. Org. Chem. 2024, 20, 2217–2224, doi:10.3762/bjoc.20.189

• flash column chromatography. In between reactions, the tin electrodes were rinsed with DI water and acetone, then polished using diamond polish. This helped prevent buildup on the electrode surfaces. General C/C procedure with TBAB/EG To a 10 mL ElectraSyn 2.0 vial containing a magnetic stir bar were

• sulfate, filtered, and the solvent removed in vacuo to afford the crude product, which was first analyzed by 1H NMR spectroscopy and then purified using flash column chromatography. The graphite electrodes were not polished in between reactions, but were rinsed with DI water and then acetone. General Sn

• column chromatography. The electrodes were washed with DI water and acetone before polishing. General C/C procedure with CC/EG To a 10 mL ElectraSyn 2.0 vial containing a magnetic stir bar were added the carbonyl compound (0.5 mmol), allyl bromide (0.6 mmol), CC/EG DES (2 mL), and 10% DI water (0.2 mL

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

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

• product which was then purified by silica gel column chromatography (as suitable mixture of ethyl acetate and petroleum ether) to give the anticipated products in 12 (85%), 15 (80%), and 17 (90%) yields. 1-(5,5,10,10,15,15-Hexabutyl-10,15-dihydro-5H-diindeno[1,2-a:1',2'-c]fluoren-2-yl)ethan-1-one (12

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

From perfluoroalkyl aryl sulfoxides to ortho thioethers

• Yang Li,
• Guillaume Dagousset,
• Emmanuel Magnier and
• Bruce Pégot

Beilstein J. Org. Chem. 2024, 20, 2108–2113, doi:10.3762/bjoc.20.181

• was mixed with a sufficient volume of a saturated NH4Cl solution, then extracted 3 times with diethyl ether. The combined organic layers were dried over MgSO4, filtered, concentrated under reduced pressure, and purified by preparative TLC or flash chromatography. [3,3]-Rearrangement of aryl sulfoxides

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

• chromatography followed by ODS HPLC to yield compounds 1–5. Allostreptopyrrole A (1) was obtained as a greenish yellow amorphous solid. The molecular formula was determined to be C15H23NO4 based on a molecular ion peak at m/z 280.1550 [M − H]− (calcd for 280.1554) observed in a negative HRESITOF mass spectrum

• , 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

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

• products were separated by column chromatography and characterized. Heterocyclizations–photochemical [2 + 2]- and [2 + 4]-cycloaddition reactions: The formation of oxetanes as a result of photochemical cycloaddition of fluoroketones or fluoroaldehydes and 1,2-difluoroethylene was previously described by

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

• chromatography (hexane/ethyl acetate) gave the corresponding ring compounds. Cyclic voltammograms for aryl sulfonamides. Radical and ionic intramolecular cyclizations. Electrochemical and photochemical aza-Wacker cyclizations. Scope of electrochemical aza-Wacker cyclization. Reaction conditions: the alkene (0.20

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

• from the dichloromethane extracts of the leaves of Caesalpinia platyloba by column chromatography, they performed a Vilsmeier–Haack formylation at the furan ring (Scheme 14) obtaining aldehyde 35 in 92% yield. This, in turn, was used as starting material in a GBB-3CR performed at room temperature to

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

• purifications using affinity chromatography with a 1 mL His Trap nickel affinity column. Sonication lysis was performed and centrifuged during 30 min, at 8,000 rpm, 4 °C. The supernatants were loaded into the column. The column was washed with 5 column volumes of LanA wash buffer 1 (20 mM Tris pH 7.5, 500 mM

• . Affinity chromatography purification (Figure S7B in Supporting Information File 1) was performed for the C39 peptidase domain, resulting in a purity of approximately 96%, based on densitometric analysis of the Coomassie-stained gel. Protein yield was estimated using spectrophotometric quantification

• spectrum of clostrisin and cellulosin was acquired from the non-native affinity chromatography sample. Additionally, the MS2 spectra of the N27-C87 fragment with five and six dehydrations were obtained from the trypsin digestion of the cellulosin precursor peptide. Finally, the MS2 spectrum of the -K26 to

Harnessing unprotected deactivated amines and arylglyoxals in the Ugi reaction for the synthesis of fused complex nitrogen heterocycles

• Javier Gómez-Ayuso,
• Pablo Pertejo,
• Tomás Hermosilla,
• Israel Carreira-Barral,
• Roberto Quesada and
• María García-Valverde

Beilstein J. Org. Chem. 2024, 20, 1758–1766, doi:10.3762/bjoc.20.154

• chromatography column, while the more eco-friendly second strategy needs an additional stage for the reduction of the nitro group on the Ugi adduct. In order to find a more efficient synthesis, we thought that the second nitrogen in the diazepine nucleus could be incorporated without the need of surrogates or

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

• methanol to collect all reaction mixture. The solvents were evaporated under reduced pressure, and the crude purified by column chromatography to isolate the product. General procedure B: hydrolysis of acetals To a solution of the quinone acetal (0.15 mmol) in acetic acid (4 mL) were added 2 drops of conc

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• showed that the cis-azobenzene previously isolated by extensive irradiation [2], liquid chromatography [22], or preparative TLC [21][33] contained some of the trans-isomer. Their work highlights the care that needs to be taken to obtain correct values for the molar absorptivities of cis-azobenzene. This

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

• equiv) and method A: aqueous HCl (37%, 500 µmol, 41.6 µL, 1.00 equiv) in EtOAc (2.5 mL) or method B: TBACl (500 µmol, 137 mg, 1.00 equiv) in MeCN (2.5 mL), respectively, were stirred at 60 °C for 2.5 h, quenched with Me2S (2.00 equiv) and the reaction mixture was purified via flash column chromatography

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

• phosphite in the presence of zinc(II) bromide allowed the formation of diethyl [hydroxy(4-hydroxyphenyl)methyl]phosphonate (11) and tetraethyl [(4-hydroxyphenyl)methylene]bis(phosphonate) (13), which were separated by column chromatography (Scheme 3). The synthesis of pure tetraethyl [(4-hydroxyphenyl

• -hydroxyphenylphosphonate (2) in THF, with DIPEA as base, gave a mixture of products which was purified by column chromatography to afford the desired trisubstituted compound TP4 (Scheme 6). Since this reaction had a very low yield (17%), another base, Na2CO3, was used and compound TP4 was obtained in a good yield (76

• , purification of the crude product by column chromatography led to the decomposition of compound TP7. Another strategy was devised to obtain the desired triazinephosphonate TP7: The first step was the nucleophilic substitution of the chlorine atoms of triazine 1 by 4-hydroxybenzaldehyde (12), followed by 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

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

• CHCl3 for 4–14 h. Next, Ac2O (0.52 mmol, 50 µL) was added followed by DABCO (0.1 mmol, 11 mg) and the reaction mixture was further stirred for 2 h at 30–32 °C. aIsolated yield of 3 or ent-3 after column chromatography. bEnantiomeric excess (ee) was measured by HPLC analysis using a stationary phase

• mol % catalyst II, 30 mol % A5 (for ent-3) in 1.0 mL CHCl3 for 14 h. Next, Ac2O (0.52 mmol, 50 µL) was added followed by DABCO (0.1 mmol, 11 mg) and the reaction mixture was further stirred for 2 h at 30–32°C. aIsolated yield of 3 or ent-3 after column chromatography. bEnantiomeric excess (ee) was

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

• decomposition and also some decarboxylation during column chromatography or upon prolonged reaction times. Also, tests with analogous β-ketoketones and β-ketoamides (compare with azidation products 5 and 6, Scheme 3) did not give any products but resulted in the formation of a variety of unidentified side

• 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

• vacuo. In most cases the products were already obtained in sufficiently high purity (>95%) after this work up. If necessary, further purification by silica gel column chromatography can be carried out. Safety considerations: It is known that the combination of inorganic azides and halogenated compounds

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

• residual water during column chromatography. Unfortunately, attempts to assign the absolute configuration of products 5 failed, as we have not been able to obtain any crystals suited for single crystal X-ray diffraction analysis. Finally, we also tested the suitability of products 5 to access acyclic α-AA

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

• equivalents of dihydroxyazobenzene 6 were used for the selective monoglycosylation step, with the excess of azobenene being recovered after column chromatography. Under these conditions, no bisglycosylated azobenzene was observed [28]. The observed 1,2-trans glycosylation could be explained either by the

• 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

• concentrated under reduced pressure and purified by flash chromatography (cyclohexane/EtOAc 7:3) to give the thioglycoside. General procedure IV for the Zemplén deacetylation: To a seal tube containing the galactose derivatives in dry MeOH (0.15 M), NaOMe (30 mol %, 0.5 M sol. in MeOH) was added. The mixture