Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• DMF as the solvent was found to be an excellent sulfur activator, leading to the formation of the desired product 2bA in 50% yield after a short silica gel column chromatographic separation (Table 1, entry 1). The structure of 2bA was confirmed on the basis of spectroscopic data. The 1H NMR spectrum

• 42–86% yields after a short silica gel column chromatographic purification. It was observed that N-alkyl-β-carboline-based 2-nitrochalcones 1bA, 1dA, and 1hA reacted faster and delivered the products 2bA, 2dA, and 2hA in better yields (78-86%). Conversely, the substrate 1aA bearing a free NH was

• the anticipated products 2aA–nA, 2bB, and 2hB as depicted in Scheme 4. The synthesized products were purified through silica gel column chromatography and further washed with anhydrous methanol to yield the analytically pure products in 35–83% yields (two-step yield), except for 2kA, which was

Nonenzymatic synthesis of anomerically pure, mannosyl-based molecular probes for scramblase identification studies

• Giovanni Picca,
• Markus Probst,
• Simon M. Langenegger,
• Oleg Khorev,
• Peter Bütikofer,
• Anant K. Menon and
• Robert Häner

Beilstein J. Org. Chem. 2020, 16, 1732–1739, doi:10.3762/bjoc.16.145

• over MgSO4, and the volatile components were removed under reduced pressure. The yellowish residue (crude product) was purified by flash chromatography over silica gel, with a mixture of n-hexane/ethyl acetate 3:2, v/v as eluent. The fractions containing the product (Rf = 0.22 in n-hexane/ethyl acetate

• stirred for 2 h. The mixture was diluted with DCM, washed with brine, and the organic phase was dried with Na2SO4. The purification by column chromatography on silica gel (hexane/EtOAc 6:4, v/v) gave Cit-Dod-NBD (455 mg, 92%) as red oil (Rf = 0.5 in hexane/EtOAc 1:1, v/v). 1H NMR (DMSO-d6, 300 MHz, δ

• under reduced pressure. The resulting material was then dissolved in DCM and purified by flash chromatography on silica gel using ethyl acetate/n-hexane 7:3, v/v as eluent. The fractions containing the intermediate α-4Ac-Man-P-Cit-BZP-yne (Rf = 0.33 using the same solvent system as for the column) were

Synthesis of the tetrasaccharide repeating unit of the O-specific polysaccharide of Azospirillum doebereinerae type strain GSF71^T using linear and one-pot iterative glycosylations

• Arin Gucchait,
• Pradip Shit and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 1700–1705, doi:10.3762/bjoc.16.141

• using silica gel-coated TLC plates. The spots on TLC were visualized by warming ceric sulfate (2% Ce(SO4)2 in 2 N H2SO4) sprayed plates on a hot plate. Silica gel 230–400 mesh was used for column chromatography. NMR spectra were recorded on a Bruker Avance 500 MHz using CDCl3 as solvent and TMS as

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• ). All reagents were purchased from commercial sources and used without further purification. The reactions were followed by analytical thin-layer chromatography on silica gel 60 F254 (Darmstadt, Germany) and on a Shimadzu LC-20 HPLC equipment coupled with an LCMS-2020 mass spectrometer (Kyoto, Japan

Synthesis of new dihydroberberine and tetrahydroberberine analogues and evaluation of their antiproliferative activity on NCI-H1975 cells

• Giacomo Mari,
• Lucia De Crescentini,
• Serena Benedetti,
• Francesco Palma,
• Stefania Santeusanio and
• Fabio Mantellini

Beilstein J. Org. Chem. 2020, 16, 1606–1616, doi:10.3762/bjoc.16.133

• further degradation process. In fact, all attempts to obtain the pure 2a by chromatographic process failed, employing silica gel or aluminum oxide or basified silica gel (by addition of 3% of triethylamine). Having identified the optimal conditions, the reaction scope was enlarged employing the α

• magnetic stirring until the complete disappearance of the starting hydrazono-DHBERs 2a–n (2.0–3.0 h, TLC monitoring). The reaction solvent was then evaporated under reduced pressure. The crude mixture was then purified by column chromatography on silica gel (elution with cyclohexane/ethyl acetate mixtures

• -phenylethylidene)hydrazinecarboxylate (3a): 3a was isolated by chromatographic column on silica gel (ethyl acetate/cyclohexane, 30:70) in 95% yield (109 mg). White amorphous solid; mp: 162–164 °C; 1H NMR (400 MHz, DMSO-d6, 25 °C) δ 1.45 (s, 9H, C(CH3)3), 2.29–2.34 (m, 1H, C(15)H2), 2.62–2.75 (m, 3H, C(15)H2, C(5

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• recorded on an Agilent Technologies 6540 UHD accurate mass Q-TOF LC–MS spectrometer. Melting points are uncorrected. The compounds were purified using column chromatography on silica gel (100–200 mesh) using hexane/ethyl acetate and chloroform/methanol as eluent. Typical procedure for quaternary

• concentrated, diluted, and extracted with EtOAc. The combined extracts were washed with brine, filtered through a celite bed, and dried over anhydrous Na2SO4. Thereafter, the solvent was removed, and the isolated crude oily product was purified over silica gel (CHCl3/MeOH) to obtain 3a as a white solid

• layer was washed with brine and dried over anhydrous MgSO4. The removal of the solvent in vacuo afforded the crude product, which was purified over silica gel (using hexane/EtOAc) to acquire 4a as colorless crystals. Proposed mechanism for the synthesis of 1,4-disubstituted triazoles. Proposed mechanism

Five-component, one-pot synthesis of an electroactive rotaxane comprising a bisferrocene macrocycle

• Natalie Lagesse,
• Luca Pisciottani,
• Maxime Douarre,
• Pascale Godard,
• Brice Kauffmann,
• Vicente Martí-Centelles and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2020, 16, 1564–1571, doi:10.3762/bjoc.16.128

• silica gel column chromatography (DCM/ethyl acetate 9:1 (v/v)) afforded 1a as beige solid (129 mg, 41% yield). 1H NMR (300 MHz, CDCl3) δ 8.66 (s, 2H, He), 8.46 (d, J = 1.3 Hz, 4H, Hd), 7.76 (t, J = 5.8 Hz, 4H, Hf), 7.15 (s, 8H, Hh + Hi), 5.45 (br s, 4H, Hg), 4.87 (t, J = 1.8 Hz, 4H, Ha or b), 4.44 (t, J

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• flash column chromatography on silica gel, presumably, owing to facile β-elimination of hydrogen fluoride. To isolate a stable product, the reaction mixture was treated with sodium borohydride in ethanol, which effected the reduction of the keto group affording the corresponding alcohol 4a in 52% yield

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli–Cushman protocol

• Aleksandar Pashev,
• Nikola Burdzhiev and
• Elena Stanoeva

Beilstein J. Org. Chem. 2020, 16, 1456–1464, doi:10.3762/bjoc.16.121

• reported in Hz. Assignments were made by using a combination of 1D and 2D spectra (COSY, HSQC and HMBC). Thin-layer chromatography (TLC) was performed on Merck 1.05554 silica gel 60F254 aluminum plates. Chromatographic filtration and column chromatography were carried out using Merck Kiesegel 60 (0.060

Distinctive reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under photoredox conditions

• Shrikant D. Tambe,
• Kwan Hong Min,
• Naeem Iqbal and
• Eun Jin Cho

Beilstein J. Org. Chem. 2020, 16, 1335–1342, doi:10.3762/bjoc.16.114

• brine. The organic layer was dried over anhydrous MgSO4 and concentrated in vacuo. The desired vicinal diamine product was purified by silica-gel column chromatography using hexane/EtOAc as the eluent. Photocatalytic transformations of imines. Substrate scope for the radical cross-couplings. Reaction

Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration–oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles

• Lívia Dikošová,
• Júlia Laceková,
• Ondrej Záborský and
• Róbert Fischer

Beilstein J. Org. Chem. 2020, 16, 1313–1319, doi:10.3762/bjoc.16.112

• isolated yields of 64–68%. The optimization of the reaction conditions showed that 2 equivalents of the oxidizing agent were necessary to bring the reaction to completion. Even though the ketones 9a–c were isolated by FCC on silica gel in a pure form, they decomposed gradually if kept for a longer time

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• over MgSO4, filtered and the solvent was removed on a rotary evaporator. The crude reaction mixtures were filtered through a plug of silica gel by use of CH2Cl2/EtOAc as eluent and were analyzed by 1H NMR and HPLC–MS (Table 2). Alternatively, a solution of 3 (44 mg, 0.135 mmol) in CH3CN (50 mL) was

• (2 × 50 mL). The organic extracts were dried over anhydrous Na2SO4, and CH2Cl2 and EtOAc were combined. The solutions were filtered and the solvent was removed on a rotary evaporator. The photoproducts were separated by chromatography on a column of silica gel using 2–10% MeOH/CH2Cl2 followed by

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

• Grzegorz Mlostoń,
• Mateusz Kowalczyk,
• André U. Augustin,
• Peter G. Jones and
• Daniel B. Werz

Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109

• tetrahydrothiophene. Experimental General information: Solvents and chemicals were purchased and used as received without further purification. Products were purified by standard column chromatography on silica gel. Yields refer to analytically pure samples. NMR spectra were recorded with a Bruker Avance III 600 MHz

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

• Xiaoming Ma,
• Suzhi Meng,
• Xiaofeng Zhang,
• Qiang Zhang,
• Shenghu Yan,
• Yue Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106

• ester 1 (1.2 mmol), 2-bromobenzaldehyde 3 (1 mmol) and maleimide 4 (1.1 mmol) in EtOH (3 mL) with Et3N (1.5 mmol) was heated at 110 °C for 6 h in a sealed vial. The concentrated reaction mixture was isolated by column chromatography on silica gel to afford adduct 5 in 85–90% yield. General procedure for

• on silica gel to afford adduct 6 in 75–85% yield. General procedure for the synthesis of pyrrolo[2,1-a]isoquinolines 9 or 11 To a solution of pyrrolidine adduct 5 or 6 (0.5 mmol), 3-bromopropene (7, 1.5 mmol) in MeCN (3 mL) was added K2CO3 (1 mmol), the mixture was heated at 105 °C for 4 h in a

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• (purchased from Aldrich), 9H-carbazole, copper(II) chloride (purchased from Reakhim), and 2,7-di-tert-butyl-9,9-dimethyl-9,10-dihydroacridine (purchased from Center for Physical Sciences and Technology) were used as received. Thin-layer chromatography was performed using TLC plates covered with silica gel

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• chromatography (TLC) was performed on Macherey-Nagel Polygram® SIL G/UV254 silica gel on polyester sheets, with manganese-activated zinc silicate with green fluorescence for short-wave UV (254 nm) and special inorganic fluorescent pigment with blue fluorescence for long-wave UV (366 nm) as indicators. Fluka

• silica gel (pore size 60 Å, 70–230 mesh, 63–200 μm) was used for gravity column chromatography. C, H, N and S elemental microanalyses were carried out on a Perkin-Elmer 2400-B Series II Analyzer. High-resolution mass spectra-ESI (HRMS-ESI) were recorded using a Bruker MicroToF-Q™ equipped with an API-ESI

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• cultured in A3M liquid medium under shaking conditions at 30 °C for 6 days, and the whole culture broth was extracted with 1-butanol. The extract (14.6 g from 6 L) was fractionated by silica gel column chromatography, followed by ODS column chromatography. Final purification was achieved by reversed-phase

• mycelium. The organic layer was concentrated in vacuo to give 14.6 g of extract from 6 L culture. The crude extract was subjected to silica gel column chromatography with a gradient of a CHCl3/MeOH mixture as eluent (1:0, 20:1, 10:1, 4:1, 2:1, 1:1, and 0:1 v/v). After evaporation, the fraction 5 (2:1) was

• further fractionated by ODS column chromatography with a gradient of MeCN/0.1% HCO2H aqueous solution (2:8, 3:7, 4:6, 5:5, 6:4, 7:3, and 8:2 v/v). The ODS fraction 2 (3:7) was evaporated to yield pseudosporamide (1, 16 mg). The fraction 3 (10:1) of silica gel column chromatography was evaporated and

Palladium-catalyzed regio- and stereoselective synthesis of aryl and 3-indolyl-substituted 4-methylene-3,4-dihydroisoquinolin-1(2H)-ones

• Valeria Nori,
• Antonio Arcadi,
• Armando Carlone,
• Fabio Marinelli and
• Marco Chiarini

Beilstein J. Org. Chem. 2020, 16, 1084–1091, doi:10.3762/bjoc.16.95

• , and solvents were commercially available and were used as purchased. The reaction products were purified by flash chromatography on silica gel by elution with n-hexane/EtOAc mixtures. Compounds 1a [44], 1b,c [41], 1d [45], 1e [46] and 5a–c [47] are known products and were identified by comparison of

• , dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, n-hexane/EtOAc, 65:35 v/v) to afford 1-(4-(3-(benzylamino)prop-1-yn-1-yl)phenyl)ethanone (1f, 385.0 mg, 85%). Typical procedure for the preparation of N-benzyl-2-iodobenzamides (2a–f

• starting propargylamine (monitored by TLC). Then the reaction mixture was diluted with ethyl acetate, washed with a solution of NH4Cl (0.5 M), dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, n-hexane/EtOAc) to afford the N-benzyl-2

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• imidazopyridine derivative. In addition, the selenide 3 was formed as a minor byproduct, and 2 and 3 were easily separated by silica gel column chromatography (yield of 3b–d, 3f, and 3g, respectively: 6–10%). We next synthesized the selenides 3 using 0.5 equiv of Se powder (Figure 4). The reactions of Se powder

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• g, 1.6 mmol) instead of phenylboronic acid. The crude product was purified by silica gel column chromatography with THF/n-hexane 1:20 as the eluent and recrystallized from the mixture of eluent to get the target compound 4 as white crystals (0.14 g, 41%). Mp 195–196 °C; 1H NMR (400 MHz, CDCl3) δ

• white crystals following the analogous procedure as described for 3 using 4-vinylphenylboronic acid (0.28 g, 1.6 mmol) instead of phenylboronic acid. The crude product was purified by silica gel column chromatography with THF/n-hexane 1:4 as the eluent and recrystallized from the mixture of eluent to

• phenylboronic acid. The crude product was purified by silica gel column chromatography with ethyl acetate/n-hexane 1:10 as the eluent and recrystallized from the mixture of eluent to afford the target compound 6 as white crystals (0.1 g, 34%). Mp 180–181 °C; 1H NMR (400 MHz, CDCl3) δ 7.60 (d, J = 2.1 Hz, 2H

Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions for the synthesis of chiral biaryl compounds with a large steric substituent at the 2-position

• Yongsu Li,
• Bendu Pan,
• Xuefeng He,
• Wang Xia,
• Yaqi Zhang,
• Hao Liang,
• Chitreddy V. Subba Reddy,
• Rihui Cao and
• Liqin Qiu

Beilstein J. Org. Chem. 2020, 16, 966–973, doi:10.3762/bjoc.16.85

• silica gel. The enantiomeric excess value of the product was determined by HPLC by using an AD-H, OD-H or IA-3 column. (R)-MeO-MOP and our ligands. Asymmetric Suzuki–Miyaura coupling. Reaction conditions: 1 equiv N-aryl-bromoaryl compounds, 2 equiv arylboronic acids, 5 mol % Pd, 6 mol % ligand, 3 equiv

Synthesis of new asparagine-based glycopeptides for future scanning tunneling microscopy investigations

• Laura Sršan and
• Thomas Ziegler

Beilstein J. Org. Chem. 2020, 16, 888–894, doi:10.3762/bjoc.16.80

• with 7 M NH3 in MeOH, which afforded the free glycopeptides 10a–f and 11a–f in good to excellent yields (Scheme 3 and Table 2). Since chromatographic purification of the unprotected glycopeptides on silica gel would have been rather difficult due to their zwitterionic character, our simple deprotection

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• washed with water (20 mL), brine (20 mL), and dried over MgSO4, filtered, and concentrated under reduced pressure. The crude material was purified by chromatography on silica gel, using a 98:2 petroleum ether/EtOAc eluent, to afford the alkylated compound. General procedure B for ring closing enyne

• at 170 °C for 17-(4-penten-1-yloxy)steroids, for 1 h under microwave irradiation. The solvent was removed by evaporation, and the resulting crude material was purified by chromatography on silica gel (petroleum ether/EtOAc 99:1) to afford the spirocyclic diene. General procedure C for one-pot RCEYM

• irradiation. The microwave tube was opened and the dienophile (1.2 mmol) was added in one portion. The mixture was stirred at 150 °C for 35 min. The solvent was removed and the crude material was purified by chromatography on silica gel (petroleum ether/EtOAc 8:3) to afford the product. Structure of four 17

Reaction of indoles with aromatic fluoromethyl ketones: an efficient synthesis of trifluoromethyl(indolyl)phenylmethanols using K₂CO₃/n-Bu₄PBr in water

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati and
• Gregor Schnakenburg

Beilstein J. Org. Chem. 2020, 16, 778–790, doi:10.3762/bjoc.16.71

• synthetic protocol for the preparation of trifluoromethyl(indolyl)phenylmethanols is operationally simple and provided products in high yields without requiring silica gel column chromatography. The reaction has a broad substrate scope and proceeds with high regioselectivity. The recovery and reusability of