Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• ). To mitigate this, the milling experiment was repeated using silica gel (SiO2) as a milling auxiliary. The use of SiO2 did not affect significantly the product composition of the reaction as determined by NMR analysis of an independent experiment milling 1c and NFSI (2.0 equiv) at 30 Hz for 3 h. This

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• the removal of metathesis catalysts is the formation of Ru-DMSO complexes, which do not eluate from a silica column [56]. This allowed us to remove at least the Ru contamination, but we were unable to subject 12 to further modifications such as cross metathesis or thiol-ene click reactions due to poor

Green synthesis of C5–C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni–chitosan nanocatalyst under ultrasonic conditions

• Soumyadip Basu,
• Sauvik Chatterjee,
• Suman Ray,
• Suvendu Maity,
• Prasanta Ghosh,
• Asim Bhaumik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 133–142, doi:10.3762/bjoc.18.14

• for industrial purposes [1][2][3]. In this regard, different insoluble supports, such as alumina [4], silica [5], zeolites [6], polymers [7], carbon nanotubes [8], etc. have been reported. Recently, the use of bio-based natural polymers became one of the interesting features of heterogeneous catalysts

• TAKASHI ultrasonic cleaning bath, and the progress of the reactions was monitored by TLC analysis using silica gel. 1H and 13C NMR spectra were recorded on Bruker 300 MHz and 400 MHz instruments using CDCl3, with TMS as internal reference. Melting points were recorded on an electrical melting point

• and purification of the residue via silica gel (100–200 mesh) column chromatography using ethyl acetate/petroleum ether (bp 60–80 °C) as eluent. FTIR spectra of (a) the Ni–chitosan NPs and (b) bare chitosan. PXRD data for the Ni–chitosan NPs. TEM (a and b) and SEM images (c and d) of the Ni–chitosan

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• separated from the aqueous layer containing the mycelium. Evaporation of the solvent gave 6.54 g of extract from 3 L of culture. The extract (6.54 g) was subjected to silica gel column chromatography with a step gradient of CHCl3/MeOH 1:0, 20:1, 10:1, 4:1, 2:1, 1:1, and 0:1 (v/v). Fraction 4 (4:1) was

Chemical and chemoenzymatic routes to bridged homoarabinofuranosylpyrimidines: Bicyclic AZT analogues

• Sandeep Kumar,
• Jyotirmoy Maity,
• Banty Kumar,
• Sumit Kumar and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2022, 18, 95–101, doi:10.3762/bjoc.18.10

• ) immobilized on polyacrylate (Lewatit), commonly known as Novozyme® 435 and Thermomyces lanuginosus lipase immobilized on silica, commonly known as Lipozyme® TL IM in different organic solvents, such as THF, acetonitrile, toluene, acetone, DIPE and 2-Me-THF. Vinyl acetate was used as acetyl donor at

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

• İlknur Polat,
• Selçuk Eşsiz,
• Uğur Bozkaya and
• Emine Salamci

Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7

• a mixture of products 10 and 11 in a 7:3 ratio was determined by NMR spectroscopy. The reaction mixture was purified using preparative silica gel TLC on a chromatotron with ethyl acetate/hexane (50:50) as the eluent to give carbamate 10 and diol isomer mixture 11 in 65% and 25% yields, respectively

• (Figure 2) [28]. The formation of lactone 10 can again be explained by participation of the neighbouring group, as discussed above. However, during the purification on silica gel of the lactone-Boc product, its transesterification also resulted in corresponding methyl carbamate 10. We then investigated

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• , MeCN, and 1,4-dioxane were refluxed over CaH2; toluene was refluxed over Na with benzophenone as an indicator, and all solvents were freshly distilled prior to use. Flash column chromatography was performed using silica gel (normal phase, 200–300 mesh) from Branch of Qingdao Haiyang Chemical. Petroleum

• ether (PE) used for column chromatography was the 60–90 °C fraction, and the removal of residual solvent was accomplished under rotovap. Reactions were monitored by thin-layer chromatography on silica gel GF254 coated 0.2 mm plates from Institute of Yantai Chemical Industry. Microwave-assisted reactions

• (0.36 mmol) and aziridine 2 (0.30 mmol) were added to DCE (1.0 mL) in a sealed 10 mL microwave tube. The resulting solution was stirred at 130 °C for 20 min under microwave heating. After the reaction was completed, the resulting mixture was evaporated in vacuo. The crude residue was purified by silica

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• silica gel (200–300 mesh). Melting points were determined with an XT-4 melting-point apparatus and are uncorrected. 1H NMR spectra were measured with a Bruker Ascend 400 MHz spectrometer, chemical shifts are reported in δ (ppm) units relative to tetramethylsilane (TMS) as an internal standard. 13C NMR

• 1 (0.06 mmol), 2 (0.05 mmol), Et3N (1.0 mg, 0.01 mmol, 0.2 equiv), and DCM (1.0 mL). The mixture was stirred at room temperature for 12 h, then the reaction mixture was concentrated and directly purified by silica gel column chromatography to afford the racemates of 3. 2. Procedure for the synthesis

• of chiral compounds 3 To a dried small bottle were added 1 (0.12 mmol), 2 (0.10 mmol), chiral organocatalyst C4 (2.7 mg, 0.005 mmol, 5 mol %), and DCM (1.0 mL). The mixture was stirred at room temperature for 12‒40 h, then the reaction mixture was concentrated and directly purified by silica gel

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• extracted with 1-butanol. The extract (4.4 g from 3 L) was sequentially fractionated by column chromatographies on silica gel and ODS, and the resulting fractions were purified by reverse-phase HPLC to give 1 (5.2 mg), 2 (2.3 mg), 3 (1.0 mg), 4 (6.3 mg), and 5 (8.0 mg). The molecular formula of 1 was

• between the diastereomer pairs. The enantiomer ratio of 4 was estimated to be S/R = 56:44 or near by chiral phase HPLC analysis of 4' on a cellulose tribenzoate-coated silica gel column (Figure 4). Thus, 4 was concluded to be an enantiomeric mixture of (2E,4E)-7-hydroxy-2,4-dimethyl-2,4-octadienoic acid

• recorded on a Bruker micrOTOF spectrometer. Silica gel 60 (spherical) (Kanto Chemical Co., Inc.) was used for silica gel column chromatography. Cosmosil 75C18-PREP (Nacalai Tesque, Inc.) was used for ODS column chromatography. Routine HPLC separations were performed on an Agilent HP1200 system, and chiral

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• irradiation, the product 11 was isolated in 28% yield, the modest yield reflecting the instability in water and on silica of this compound. The purified N-formyl 11 was then dissolved in buffer (pH 8), and its hydrolysis to amide 12 was assessed (Figure 4, inset). We observed clean first-order kinetics to

First total synthesis of hoshinoamide A

• Haipin Zhou,
• Zihan Rui,
• Yiming Yang,
• Shengtao Xu,
• Yutian Shao and
• Long Liu

Beilstein J. Org. Chem. 2021, 17, 2924–2931, doi:10.3762/bjoc.17.201

• 2-chlorotrityl chloride (CTC) resin with 8 (4 equiv) and DIPEA successfully produced the resin-bound tripeptide 3 in good yield [17]. It should be noted that unreacted 8 can be largely recovered by a quick silica gel chromatography. The N terminus of 3 was then sequentially extended with properly

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• layer was washed with H2O (10 mL × 2), dried by anhydrous Na2SO4, then filtered. The filtrate was concentrated under reduced pressure. Finally, the residue was purified by silica-gel column chromatography (AcOMe/isohexane) to give pure product 5. One-pot synthesis of a functional lactone 6 using PhS−Na

• concentrated under reduced pressure. Finally, the residue was purified by silica-gel column chromatography (Et2O/isohexane) to give pure product 6. General procedure for α-bromination of δ-valerolactone (1a) and the method described in this work. Tetraalkylammonium salt-mediated intramolecular cyclization of

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• the reaction mixture was heated under microwave irradiation at 90 °C for 10 min and monitored by TLC until starting material was consumed. Then, the reaction mixture was concentrated under reduced pressure followed by column chromatography over silica gel using petroleum/EtOAc (0 to 10%) as eluent to

• mixture was stirred at 80 °C for 10 h and monitored by TLC. Then, the reaction mixture was concentrated under reduced pressure followed by column chromatography over silica gel using petroleum/EtOAc 10:1 to ≈5:1 as eluent to afford the desired product 4. Selected bioactive compounds. Crystal structure of

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• silica gel 60 (230–400 mesh). Kieselgel columns were packed with silica gel GF254 (Merck 7730). Flash chromatography was carried out on handpacked columns of Merck silica gel 60 (0.040–0.063 mm). Melting points were determined on a Stuart SMP3 hot stage apparatus. The structurally most important peaks of

Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation

• Lukáš Ďurina,
• Anna Ďurinová,
• František Trejtnar,
• Ľuboš Janotka,
• Lucia Messingerová,
• Jana Doháňošová,
• Ján Moncol and
• Róbert Fischer

Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188

• the proline catalysis are of higher purity (after purification by silica gel column chromatography), than those synthesized by other methods [16]. Definitely, the effective asymmetric organocatalytic conjugate additions of hydroxylamines to enals using various catalysts provide access to

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• performed on Merck silica gel Si 60 (0.015–0.040 mm). NMR spectra (1H, 13C, DEPT, H,H-COSY, HSQC, HMQC, HMBC) were recorded at 23 °C on an Avance III 400 MHz Bruker BioSpin or Avance III 500 MHz Bruker BioSpin instrument. Chemical shifts δ are stated in parts per million (ppm) and are calibrated using

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• diastereomers by silica gel column chromatography and reaction with lead tetraacetate provided the key oxathiolane derivative 31. In 1995, Jin et al. [46] carried out the reaction of 1,4-dithiane-2,5-diol (3q) with glyoxylic acid (3g) hydrate at reflux temperature in tert-butyl methyl ether, which provided the

• . [40] described coupling of crude 1,3-oxathiolane precursor 20 with silylated acetylcytosine utilizing TMSOTf as a Lewis acid, which gave a mixture of α- and β-anomers (1:2 ratio) of 81 (Scheme 30). The mixture of anomers was further separated by silica gel column chromatography. (+)-BCH-189 (1a) and

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• study. Substituted phenylboronic acids and vinyl triflates led to the formation of enamides 2 with high stereoselectivity and in good to high NMR yields (Scheme 2). However, isolated yields were found to be lower due to the decomposition of the formed enamides 2 during column chromatography on silica

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• solution of NaHCO3 (3 × 40 mL), dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel (eluent, hexane/ethyl actate 7:1→5:1), affording the product as dark orange oil in 86% yield. Rf 0.5 (hexane/EtOAc 3:1); IR (ATR): 2971, 2089, 1390

• 30 min. The resulting mixture was concentrated in vacuo and the desired product was isolated by column chromatography on silica gel (EtOAc/MeOH/NH4OH 60:1:0.6→50:1:0.5). (S)-tert-Butyl 2-((3-((R)-tert-butylsulfinyl)thioureido)methyl)pyrrolidine-1-carboxylate ((S,R)-5a) −87.8 (c 1.0, MeOH); 1H NMR

• chromatography on silica gel (EtOAc/MeOH/NH4OH 60:1:0.6→50:1:0.5). (S)-tert-Butyl 2-((3-((R)-tert-butylsulfinyl)ureido)methyl)pyrrolidine-1-carboxylate ((S,R)-5b) −87.3 (c 0.5, MeOH); 1H NMR (600 MHz, CDCl3) δ 9.22 (s, 1H), 6.96 (s, 1H), 4.17–4.09 (m, 1H), 3.76–3.67 (m, 1H), 3.49–3.38 (m, 2H), 3.36–3.31 (m, 1H

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• ) [13]. Interestingly, when this mixture was subjected to silica gel chromatography, not only could the isomers of 38 not be separated, they also underwent silica-catalyzed α-ketol rearrangement to cyclobutane 39. This rearrangement, however, was of no consequence because addition of sodium methoxide to

• -toluenesulfonic acid), five different Lewis acids (Zn(OTf)2, Cu(OTf)2, Sc(OTf)2, silica gel, and montmorillonite K 10), and one base (NaOEt). Of these, silica gel and montmorillonite K 10 had the best yields (95% and 100%, respectively). A substrate scope was then determined for 97 using aryl, n-hexyl, and

• cyclohexyl R groups in the presence of silica gel at 80 °C (Figure 19b). The rearrangements proceeded well with electron-rich aryl groups, regardless of the position of substitution, but the reaction was especially slow for the electron-withdrawing para-trifluoromethyl derivative. A major advantage of the

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• , underwent cyclization in the presence of silica gel to give ethyl 6-(hetero)aryl-2,3-dihydro-1H-pyrrolizine-5-carboxylates within minutes upon microwave heating in xylene at 150 °C. Instead of functioning as a nucleophile, the enaminone acted as an electrophile at its carbonyl group during the cyclization

• temperature and microwave power, although requiring much longer time. A possible mechanism for the cyclization is presented, and further functionalization of the newly created pyrrole ring in the dihydropyrrolizine core is described. Keywords: dihydropyrrolizines; enaminones; microwaves; silica gel

• vinylogous amides such as 11, however, we fortuitously found substituted 2,3-dihydro-1H-pyrrolizines 12 as unexpected products when intermediates 11 were exposed to acidic conditions, including treatment with acetic acid or even during chromatography on silica gel (Scheme 1) [18]. In these cyclizations the

Direct C(sp³)–H allylation of 2-alkylpyridines with Morita–Baylis–Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement

• Siyu Wang,
• Lianyou Zheng,
• Shutao Wang,
• Shulin Ning,
• Zhuoqi Zhang and
• Jinbao Xiang

Beilstein J. Org. Chem. 2021, 17, 2505–2510, doi:10.3762/bjoc.17.167

• -alkylpyridines. Mechanistic hypothesis of the alkylation reaction of 2-alkylpyridines with MBH carbonates. Scope of MBH carbonates 2 with 2-picoline 1a. The reactions were performed using 1a (1.0 mmol, 2 equiv) and MBH carbonate 2 (0.5 mmol, 1 equiv) in CH3CN (2 mL) at 80 °C. Yields are determined after silica

• gel column chromatography. EWG = electron withdrawing group. Scope of 2-alkylpyridine 1 with MBH carbonate 2a. The reactions were performed using 1 (1.0 mmol, 2 equiv) and MBH carbonate 2 (0.5 mmol, 1 equiv) in CH3CN (2 mL) at 80 °C unless indicated otherwise. Yields are determined after silica gel

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• -layer chromatography (TLC). Organic compounds were purified using commercial Merck silica gel (0.043–0.06 mm) with a fluorescence indicator (the visualization was performed under UV light at 254 nm). All solvents for work-up and column chromatography were distilled before use. NMR data were recorded in

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• Information File 1). It should be noted that attempts of chromatographic separation of triflates 4a–c into individual E- and Z-isomers on silica gel led to a decrease of their yields and a change in E/Z-ratio. That reveals instability of these compounds on silica gel. In the same reaction in H2SO4 (Scheme 4

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• solvent was removed under reduced pressure and the resulting crude biaryl carbonyls were purified using silica gel column chromatography (using EtOAc/hexane mixtures as eluent). Experimental details for the preparation of compounds 13a–f can be found in Supporting Information File 1. Oxime ester formation

• saturated NaHCO3 solution (10 mL) and brine (10 mL). The solution was dried over MgSO4 and the solvent was evaporated under reduced pressure. The resulting crude oxime esters were purified by silica gel column chromatography (using EtOAc/hexane mixtures as eluent). Experimental details for the preparation

• (450 W medium pressure Hg lamp, through a quartz filter) for 3 h. The crude residue was purified by silica gel column chromatography (using EtOAc/hexane mixtures as eluent). Experimental details for the preparation of compounds 15a–d and 16a–f as well as compounds 23 and 24 can be found in Supporting