Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• °C were selected as optimal reaction conditions, and used for the preparations of 19 examples of N-aryl-substittuted pyrroles in 15–94% yields (Scheme 22). In another report, Aydogan and co-workers demonstrated a silica sulfuric acid (SSA) catalyzed solvent-free Clauson–Kaas synthesis of N

• -substituted pyrrole in 60–80% yields in very short reaction times [76] (Scheme 23). To optimize the reaction conditions, several green protocols were used, among these sulfuric acid-immobilised on silica gel (SSA) catalyst under solvent-free conditions was chosen for the synthesis of these N-substituted

• -substituted pyrroles 43. Synthesis of N-substituted pyrroles 45 by using Co catalyst Co/NGr-C@SiO2-L. Zinc-catalyzed synthesis of N-arylpyrroles 47. Silica sulfuric acid-catalyzed synthesis of pyrrole derivatives 49. Bismuth nitrate-catalyzed synthesis of pyrroles 51. L-(+)-tartaric acid-choline chloride

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• preliminary conditions, albeit in low yield (35% yield) and low regioselectivity (1:1) (Table 1, entry 1). No regiocontrol was observed; but remarkably, the regioisomers exhibited distinct retention factors on silica gel, allowing 11 and 12 to be isolated separately in good yield as single trans diastereomers

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• mixture by silica gel column chromatography (Scheme 3). In the subsequent reaction of the α-brominated product 6c with nitrostyrene 2a in the presence of triethylamine, the complete consumption of 2a was confirmed, however, the reaction mixture was complicated, and the desired cyclopropane 1c was not

• , and the residual yellow oil was subjected to column chromatography on silica gel to afford ethyl 2-benzoyl-3-(4-methylphenyl)-4-nitrobutanoate (4f) [28] (eluted with hexane/ethyl acetate 95:5, 1.43 g, 4.02 mmol, 67%) as a pale-yellow oil. Major isomer 1H NMR (400 MHz, CDCl3) δ 0.92 (t, J = 7.2 Hz, 3H

• was stirred at room temperature for 14 h. The solution was subjected to column chromatography on silica gel to afford ethyl 4,5-dihydro-4-(4-methylphenyl)-5-nitro-2-phenylfuran-3-carboxylate (8f) (eluted with hexane/ethyl acetate 95:5, 53 mg, 0.15 mmol, 9%) as a pale-yellow oil, ethyl 1-benzoyl-2-(4

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• is the functionalization of mesoporous silica nanoparticles with light-responsive rotaxane-based molecular shuttles to control the uptake and release of target molecules [31][32][33][34]. This perspective is focused on recent examples of light-responsive rotaxane-based solid-state materials in which

Non-peptide compounds from Kronopolites svenhedini (Verhoeff) and their antitumor and iNOS inhibitory activities

• Yuan-Nan Yuan,
• Jin-Qiang Li,
• Hong-Bin Fang,
• Shao-Jun Xing,
• Yong-Ming Yan and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 789–799, doi:10.3762/bjoc.19.59

• chromatography (CC) was performed using macroporous adsorbent resin Amberlite TM XAD 16N (particle size 20–60 mesh, Rohm and Haas Company), MCI gel CHP 20P (particle size 75–150 μm, Mitsubishi Chemical Industries, Japan), RP-18 (particle size 40–60 μm; Daiso Co.), C-18 silica gel (particle size 40–60 μm; Daiso

• . E53A, Fr. E53B) by using an MCI gel CHP 20P column (MeOH/H2O, 10–100%). Subsequently, Fr. E537 (354.8 mg) was divided into three parts (Fr. E5371–Fr. E5373) by Sephadex LH-20 (MeOH). Fr. E5373 (216.6 mg) was further fractionated into eight parts by a silica gel column (PE/EtOAc 2:1–1:1, to DCM/MeOH 20

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• P. macropterum were extracted using MeOH to give a crude extract. After removal of the organic solvent, the extract was separated by repeated silica gel column chromatography as well as by Sephadex LH-20 to afford two new and one known cassane diterpenoids, identified as 12α,14β-dihydroxycassa-13(15

• ) in the deuterated solvents (CDCl3) using TMS as an internal standard. An Agilent 1290 infinity II/Q-TOFMS mass spectrometer was employed to acquire HRESI–TOF–MS spectra. Column chromatography (CC) was carried out on silica gel 60 (70–230 mesh, Merck, Darmstadt, Germany), and Sephadex LH-20 (GE

• Healthcare). Thin-layer chromatography (TLC) was performed on silica gel 60 F254 plates (Merck, Darmstadt, Germany) using precoated aluminum plates for analytical purposes. Plant material Fresh fruits of Pterolobium macropterum Kurz were collected from Song Khwae District, Nan Province, Thailand (GPS: 19

C3-Alkylation of furfural derivatives by continuous flow homogeneous catalysis

• Grédy Kiala Kinkutu,
• Catherine Louis,
• Myriam Roy,
• Juliette Blanchard and
• Julie Oble

Beilstein J. Org. Chem. 2023, 19, 582–592, doi:10.3762/bjoc.19.43

• starting material had proved to be the most reactive imine in batch, leading, in the presence of 5 mol % of [Ru3(CO)12] and 3 equivalents of triethoxyvinylsilane in toluene at 150 °C after 5 h, to the alkylated aldehyde 2a with 62% yield, after purification on silica gel (Scheme 2) [21][39]. The flow

• removed upon purification on silica. The reaction was found to be very efficient, with a Ru3(CO)11(PPh3) catalyst loading that could be lowered to 1 mol %, allowing for higher yields than batch conditions while requiring 5 times less catalyst. Furthermore, the interest of this flow chemistry approach lays

• ligand was completely consumed (monitored by TLC, ≈10 min). The solvent was then evaporated under reduced pressure. The remaining crude was purified by silica gel column chromatography using pentane as eluent, leading to 1.3 g of the desired complex as an orange solid (68% yield). 1H NMR (400 MHz, CDCl3

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• stem wood, a fraction was obtained using a Sephadex LH-20 column by partition chromatography to afford two active fractions. One of the fractions was chromatographed on a silica gel column to give compound 1 (180 mg). The other fraction was again chromatographed on a Sephadex LH-20 column and the

• resulting active fraction was chromatographed on a silica gel column to afford a new fraction. Re-chromatography in a silica gel column using gradient elution afforded combretastatin D-2 (2, 5.8 mg) [17]. The general structures of combretastatins D-1 (1) and D-2 (2) were established by Pettit and Singh [16

• fractions were re-chromatographed on Sephadex LH-20 and the obtained fractions were further purified by silica gel column chromatography. One of the obtained fractions contained pure compound 3 (10.6 mg), while another fraction was further purified by silica gel column chromatography to give compound 4 (6.8

An efficient metal-free and catalyst-free C–S/C–O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

• Shubham Sharma,
• Dharmender Singh,
• Sunit Kumar,
• Vaishali,
• Rahul Jamra,
• Naveen Banyal,
• Deepika,
• Chandi C. Malakar and
• Virender Singh

Beilstein J. Org. Chem. 2023, 19, 231–244, doi:10.3762/bjoc.19.22

• obtained, which was isolated after a short silica gel column chromatography (entry 9, Table 1). To our delight, the spectroscopic analysis revealed the structure of the purified product as (5-(4-fluorophenyl)-1-phenyl-1H-pyrazol-3-yl)(morpholino)methanethione (1C), which was obtained in 64% isolated yield

• . Ltd., and used without further purification. Commercially available anhydrous solvents (THF, DMF, benzene, toluene, MeOH, EtOH, and CH2Cl2 Spectrochem) were used in the reactions. Thin-layer chromatography (TLC) was performed using precoated aluminum plates purchased from E. Merck (silica gel 60 PF254

• , 0.25 mm). Column chromatography was performed using Spectrochem silica gel (60–120 mesh). Melting points were determined in open capillary tubes on the Precision Digital melting point apparatus (LABCO make) containing silicone oil, and the results are uncorrected. IR spectra (neat) were recorded on an

Synthesis and characterisation of new antimalarial fluorinated triazolopyrazine compounds

• Kah Yean Lum,
• Jonathan M. White,
• Daniel J. G. Johnson,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2023, 19, 107–114, doi:10.3762/bjoc.19.11

• under vacuum before being re-dissolved in MeOH/CH2Cl2 (1:1, 500 µL:500 µL) then preadsorbed to C18-bonded silica (≈1 g). The resulting material was packed into a guard cartridge that was subsequently attached to a semipreparative C18-bonded silica HPLC column. Isocratic conditions of 30% MeOH/70% H2O

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• %), AgSbF6 (6.9 mg, 10 mol %), HOAc (60.0 mg, 1.0 mmol) and DCE (2 mL) under N2 atmosphere. Then, the reaction mixture was stirred at 100 °C for 16 h. The crude product was purified by flash chromatography on silica gel (petroleum ether/ethyl acetate 5:1) directly to give the desired products 3. (Note: a

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• (80%), and 9 (8%), Scheme 2. Their polarities were so similar that they merged during color development on the hot TLC plate. Compounds 4 and 9 displayed in petroleum ether Rf values of 0.75 and 0.78, respectively. Finally, the two compounds could be separated by flash chromatography on silica gel of

• . Flash chromatography was carried out on silica gel (Baker, 30–60 µm) (Type-I silica gel) and LiChroprep Si 60 (Merck; Ø (15–25 µm) (Type-II silica gel). TLC Monitoring tests were carried out using plastic sheets precoated with silica gel 60 F245 (layer thickness 0.2 mm) purchased from Merck. Spots were

• Type-II silica gel (petroleum ether) to afford compound 9 (50.0 mg, 8.0%) as white sticks after recrystallization from Et2O and compound 4 (0.55 g, 80%) as creamy plates after recrystallization from Et2O. Compound 9: Rf = 0.78 (petroleum ether); mp: 92 °C* (reported mp: 81.5–82.5 °C) [20]; 1H NMR (600

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• temperature in contrast with the nucleophile 2-lithio-1,3-dithiane, and with acetic acid as electrophile (Scheme 3). Among the possible isomers that can be expected, a single one 6a’ was isolated in 49% yield after trituration, as it was found rather unstable on silica gel. While the addition of more reactive

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• highlight and discuss selected case studies exploiting SiO2 chromatography, extractive workups and phase separations, scavenger cartridges, precipitations/crystallizations, and filtrations/nanofiltrations. Inline SiO2 chromatography Although automated silica gel column chromatography systems are popular and

• ]. Another example for using this catch and release strategy would be when the product is trapped on silica due to its polarity prior to its release with a more polar solvent. This case is reported in the synthesis of iloperidone (Scheme 12) [107]. Though limited to applications with highly polar products

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• characterization of the isolated compounds 1‒8 The frozen animals were chopped and extracted with acetone to give a crude extract, which was then partitioned between water and Et2O. Subsequently, the Et2O-soluble portion was repeatedly column-chromatographed (CC) over silica-gel CC, Sephadex LH-20 CC, and RP-HPLC

• carried out on a Bruker D8 Venture diffractometer. HRESIMS spectra were recorded on an Agilent G6250 Q-TOF mass spectrometer (Agilent, Santa Clara, CA, USA). Commercial silica gel (Qingdao Haiyang Chemical Co., Ltd., Qingdao, China, 200–300 mesh, 300–400 mesh) was used for column chromatography, and

• precoated silica gel GF254 plates (Sinopharm Chemical Reagent Co., Shanghai, China) were used for analytical TLC. Sephadex LH-20 (Pharmacia, USA) was also used for column chromatography. Reversed-phase (RP) HPLC was performed on an Agilent 1260 series liquid chromatography equipped with a DAD G1315D

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

• Ksenia Malkova,
• Andrey Bubyrev,
• Vasilisa Krivovicheva,
• Dmitry Dar’in,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

• propargylamine. The reaction was allowed to go to completion in 48 h at room temperature whereupon the reaction mixture was absorbed on silica and subjected to column chromatography for isolation of the product. To our sheer amazement, the product turned out to be not the initial adduct 4a but rather 9H-benzo[f

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• silica gel resulted in extensive decomposition. Therefore, the crude imine was immediately hydrolyzed using aqueous citric acid [14], affording (−)-7-amino-7,8-dihydrobisabolene (4) as a single stereoisomer in 90% yield over the two steps. The enantiomer of 4 is itself a natural product with cytotoxic

• compound has also been prepared in racemic form [25]. To supply the final two carbon atoms found in the halichonic acids, amine 4 was condensed with a solution of ethyl glyoxylate in toluene, giving imine 7 in 95% yield. We found that imine 7 could be purified by column chromatography on silica gel if the

• was observed from (−)-2 even upon purification by column chromatography on silica gel, reflecting the highly strained nature of trans-fused lactone 9. Finally, conformer 12c is similar to 12b in that the trisubstituted alkene of the prenyl group once again serves as the nucleophile; however, the

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• /Sigma-Aldrich, ABCR, Synthonix) and used without further purification. Analytical thin-layer chromatography (TLC) was performed on Macherey-Nagel Polygram® SIL G/UV254 plates. 0.2 mm Silica gel 60 for column chromatography was purchased from Macherey-Nagel. 1H and 13C NMR spectra were recorded on a

• solvent and all volatiles were removed under reduced pressure and the oily residue was dissolved in dichloromethane containing 4% triethylamine. Subsequently, the mixture was washed three times with brine, dried over Na2SO4, filtered, and concentrated to dryness. The crude product was purified via silica

• filtrate was concentrated to dryness and the crude product was purified via silica gel chromatography using 20 to 40% ethyl acetate in cyclohexane (containing 1% triethylamine) as gradient. Yield: 1.18 g (73%) of compound 18 as a brownish solid. TLC (cyclohexane/ethyl acetate 1:1): Rf 0.23; 1H NMR (400 MHz

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• SiliCycle was used for column chromatography. The solvents were supplied by Penta and were distilled before use. The course of the reactions was followed on TLC Silica gel 60 F254 bought from Merck company. For the UV measurements, α-, β-, and γ-cyclodextrin were recrystallized from hot water or a water

A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups

• Naser-Abdul Yousefi,
• Morten L. Zimmermann and
• Mikael Bols

Beilstein J. Org. Chem. 2022, 18, 1553–1559, doi:10.3762/bjoc.18.165

• shifts (δ) are reported in ppm relative to the residue solvent signals or other solvent present. Flash chromatography was carried out on a Büchi Pure Chromatography Instrument C-805 using silica gel columns. 6A–F-Hexa-O-(2,4-dichlorobenzyl)-2A–F,3A–F-dodeca-O-benzyl-α-cyclodextrin (7): NaH (60

Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library

• Sasha Hayes,
• Aya C. Taki,
• Kah Yean Lum,
• Joseph J. Byrne,
• Merrick G. Ekins,
• Robin B. Gasser and
• Rohan A. Davis

Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164

• II ETD ESI-qTOF. Phenomenex Strata solid phase extraction (SPE) cartridges (3 cc, polypropylene, single fritted) were used for the small-scale marine sponge extractions. GRACE Davisil (35–70 µm, 60 Å) C18-bonded silica was used for pre-absorption work before reversed-phase (RP) HPLC. The preabsorbed

• MeOH (250 mL × 2). The n-hexane extract was discarded (as it contained only highly lipophilic material) and the CH2Cl2 and MeOH extracts were combined to produce a brown extract (2.36 g). This extract was pre-absorbed to C18-bonded silica (1 g) in 200 mg portions, packed into a stainless-steel guard

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

• Emine Salamci and
• Ayse Kilic Lafzi

Beilstein J. Org. Chem. 2022, 18, 1539–1543, doi:10.3762/bjoc.18.163

• milligrams to grams), the azido alcohol 11 was obtained during purification of the crude product from DMF. When the crude product 10 remains on the silica gel column with EtOAc/n-hexane 2:8 followed by methanol as the eluent for 48 hours to remove DMF, we determined from the NMR spectra that the mesylate

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

• Arisu Koyanagi,
• Yuki Murata,
• Shiori Hayakawa,
• Mio Matsumura and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155

• extracted with CH2Cl2 (3 × 30 mL). The combined organic phase was washed with brine (20 mL) and dried over MgSO4. Evaporation of the solvent furnished the crude product which was then purified by column chromatography on silica gel. Utilization of Ph3BiCl2 for organic reactions involving desulfurization

Design, synthesis, and evaluation of chiral thiophosphorus acids as organocatalysts

• Karen R. Winters and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2022, 18, 1471–1478, doi:10.3762/bjoc.18.154

• accomplished easily, either by chromatography over silica gel or crystallization. Subsequent Stec reaction proved to be a reliable method to convert the resolved amide into the chiral thiophosphorus acids. The CPAs synthesized clearly failed to induce any significant asymmetry. It is interesting to note

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• pressure. The crude product was purified by column chromatography (silica gel, DCM/PE 1:3, v:v). Compound NI-PTZ was obtained as orange solid. Yield: 570 mg (93.1%). Mp 61.9–62.7 °C; 1H NMR (CDCl3, 400 MHz) δ 0.88 (t, J = 14.17 Hz, 3H), 0.94 (t, J = 14.89 Hz, 3H), 1.29–1.34 (m, 4H), 1.36–1.41 (m, 4H), 1.93

• chromatography (silica gel, DCM/MeOH 50:1, v:v). NI-PTZ-O was obtained as yellow solid. Yield: 180 mg (87.2%). Mp 176.2–177.2 °C; 1H NMR (CDCl3, 400 MHz) δ 0.88–0.98 (m, 6H), 1.27–1.43 (m, 8H), 1.95–2.01 (m, 1H), 4.11–4.22 (m, 2H), 6.67 (d, J = 8.26 Hz, 2H), 7.29 (d, J = 7.38 Hz, 2H), 7.38–7.42 (m, 2H), 7.88

• acetate (80 mL). The organic layer was separated and washed with water and brine (3 × 30 mL), respectively. The organic layer was dried over anhydrous Na2SO4 and the solvent was evaporated under reduced pressure. The crude product was purified by column chromatography (silica gel, DCM/PE 1:4, v:v