Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• was subjected to a third round of chromatography (toluene/ethyl acetate 3:2 → toluene/ethyl acetate/acetone 2:2:1) to afford the title compound as an oil (661 mg, 47%). Rf 0.35 (dichloromethane/methanol 9:1); 1H NMR (400 MHz, CD3OD) δ 1.02 (d, J = 6.5 Hz, 3H), 1.03 (d, J = 6.5 Hz, 3H), 1.59 (s, 3H

• of water with toluene (2 × 50 mL). The residue was purified by column chromatography (toluene/ethyl acetate/acetone 3:2:0–12:8:5) to afford the title compound as a yellow amorphous solid (345 mg, 56% corrected for the presence of ≈10 wt % toluene). The data are consistent with literature values [22

• ]. Rf 0.10 (toluene/ethyl acetate/acetone 2:2:1); mp 128 °C [lit. mp not given]; IR νmax 3234br, 2958m, 1667m, 1571s, 1517s, 1437s, 1197m, 730m; 1H NMR (400 MHz, CD3OD) δ 1.01 (d, J = 6.5 Hz, 3H), 1.02 (d, J = 6.5 Hz, 3H), 1.58 (s, 3H), 1.65 (ddd, J = 13.0, 10.5, 7.5 Hz, 1H), 1.93 (ddd, J = 13.0, 6.5

Regioselective chemoenzymatic syntheses of ferulate conjugates as chromogenic substrates for feruloyl esterases

• Olga Gherbovet,
• Fernando Ferreira,
• Apolline Clément,
• Mélanie Ragon,
• Julien Durand,
• Sophie Bozonnet,
• Michael J. O'Donohue and
• Régis Fauré

Beilstein J. Org. Chem. 2021, 17, 325–333, doi:10.3762/bjoc.17.30

• g, reusable) was added to a solution of alcohol (0.30 mmol, 1 equiv) and the vinyl ferulate 2 (100 mg, 0.45 mmol, 1.5 equiv) in acetonitrile (6 mL). The reaction mixture was stirred overnight at 37 °C, then filtered, the filter cake was washed with acetone, and the filtrate was evaporated to dryness

• equiv) in acetone/water 2.5–1, v/v (3.5 mL) was treated at 25 °C under stirring with NMMO (106 mg, 0.90 mmol, 1.2 equiv) and osmium tetroxide (2.5 wt % solution in tert-butanol, 38 µL) and stirred at room temperature for 18 h. 10% (w/v) aqueous sodium sulfite (0.5 mL) was added, and stirring was

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• -2-thione species 6a in a high yield (Scheme 1, route 2). The red color of the reaction mixture belonging to the parent o-quinone rapidly turns into a brown color of o-quinone 6a. o-Quinone 6a was isolated as red-brown crystals by cooling the acetone/ether mixture. It is a structural analogue of o

• was discussed previously [29]. The reaction of 4 with malononitrile-derived gem-dithiolate (5b, Scheme 1, route 2) also proceeded under mild conditions in DMF and bicyclic o-quinone 6b was obtained in a good yield. The brown crystals suitable for X-ray analysis were grown from an acetone/diethyl ether

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• )-monoacetate (S)-80, respectively (Scheme 32). As for the transesterification, a high yield (96.5%) and enantioselectivity (91.3% ee) were obtained using lipase PS in benzene. In the case of the deacetylation, the use of Amano PS lipase in acetone gave a high yield (86.2%), enantioselectivity (91.7% ee), and

Total synthesis of decarboxyaltenusin

• Lucas Warmuth,
• Aaron Weiß,
• Marco Reinhardt,
• Anna Meschkov,
• Ute Schepers and
• Joachim Podlech

Beilstein J. Org. Chem. 2021, 17, 224–228, doi:10.3762/bjoc.17.22

• . Biphenyl-derived mycotoxins. Synthesis of arylboronates 6. Conditions: a) TBSCl, DMAP, imidazole, DMF, 50 °C, 4 h (96%); b) NBS, MeCN, rt, 71 h (quant.); c) NBS, MeCN, rt, 72 h (R = TBS, 96%); d) BnBr, KI, K2CO3, DMF/acetone, 70 °C, 29 h, (R = Bn, 86%); e) R = TBS: BuLi, 2-isopropoxy-4,4,5,5-tetramethyl

• , K2CO3, DMF/acetone 1:2, 80 °C, 43 h (98%). Final steps in the synthesis of biaryl 1. Conditions: h) Pd(OAc)2, SPhos, Cs2CO3, dioxane/H2O 7:1, 70 °C, 18 h, (R = TBS: 98%, containing non-separable impurities; R = Bn: 89%) ; i) R = Bn: Pd/C (10%), H2, THF, 8 bar, 24 h, 40 °C (88%). NMR data of natural and

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• functionalized oxazoles using acetone as the solvent (Scheme 1c) [28]. Inspired by these recent reports, we became interested in the development of an eco-friendly strategy for the safe preparation of highly functionalized NH-aziridines from acyclic precursors. Herein, we report a sustainable mixed flow-batch

• flow procedures involved acetonitrile, dichloromethane and acetone as solvents, however, incompatible with the utilization of reactive alkali organometals. An exception is made for toluene, used by Kirschning for the photoinduced azirine formation [27]. Therefore, we investigated the thermally induced

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• ) PCC, CH2Cl2, 70–72%. Synthesis (+)-euphococcinine (2). Reagents and conditions: i) H2O2, SeO2 (cat), acetone, rt, 88%; ii) 25, THF, −78 °C, 52% (67:33 diastereomeric mixture); iii) H2O2, FIEt+.ClO4 (cat.), MeOH, 0 °C, 55%; iv) AlCl3, CH2=CHCH2MgBr, THF, −78 °C, 54%; v) Ni2O3, CHCl3, rt, 54%; vi) Raney

• acetal, cat. (CH2OH)2, BF3·Et2O, 85%; x) 1. Luche reduction, 98%; 2. a) NaH; b) CS2, c) MeI, 88%; 3. Bu3SnH, AIBN, heat, 75%; xi) 1. cat. Pd(MeCN)2Cl2, wet acetone, 95%; 2. H2, Pd-C, 90%. Synthesis of (+)-euphococcinine (2). Reagents and conditions: i) 1. Cp2ZrCl2,AlMe3, CH2Cl2; 2. p-menthyl-3

Metal-free nucleophilic trifluoromethylselenolation via an iodide-mediated umpolung reactivity of trifluoromethylselenotoluenesulfonate

• Kevin Grollier,
• Alexis Taponard,
• Arnaud De Zordo-Banliat,
• Emmanuel Magnier and
• Thierry Billard

Beilstein J. Org. Chem. 2020, 16, 3032–3037, doi:10.3762/bjoc.16.252

• species could also possess the CF3Seδ−–Iδ+ inverted polarity. Thus, based on the previously developed conditions, reagent 1a was reacted with benzyl bromide (2a) in the presence of tetrabutylammonium iodide (TBAI) in acetone at 40 °C (Table 1, entry 1). The observed result was moderate (Table 1, entry 1

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• dichloromethane, acetonitrile, and acetone (Table 1, entries 1–3), whereas 4-chlorobiphenyl (2a) was observed in traces as the only product in neat methanol (30% of 1a consumption, Table 1, entry 4). Interestingly, the addition of water (a methanol/water 2:1 mixture) increased the overall yield of the product 2a

• ). The yields started to be satisfactory, however, when performing the reaction at 310 nm using 2,2,2-trifluoroethanol (TFE) as the solvent (45% yield, entry 8 in Table 1). We thus decided to replace part of the rather expensive and toxic solvent TFE with acetone (Table 1, entries 9–12) and the best

• results were obtained when using a TFE/acetone 4:1 mixture (Table 1, entry 10) with an isolated yield of 2a of 67% along with 2b (4% yield) as the byproduct. A further increase in the concentration of the substrate (Table 1, entries 13 and 14) resulted in a lowering of the selectivity (the undesired

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• -nitrophenyl moieties, exhibiting several close CAr···CAr contacts at a 3.373 Å distance (Figure 3b). The receptor 7d crystallised in a triclinic system, space group P1, as a 1:3 complex with acetone (used as solvent for crystallisation). The main packing motive (see Figure 4) was represented by an infinite

• chain of calixarene molecules joined together by intermolecular hydrogen bonds between the ureido groups (the C=O···H–N distances were 2.293 and 2.048 Å). One of the ureido functions in the macrocycle also held acetone via a C=O···H–N hydrogen bond (2.085 Å) and via a C=O···H–C bond (2.670 Å) from the

• the dimeric motif. X-ray structure of 7d, showing hydrogen bonds between the ureido units (green) and hydrogen bonding of acetone molecules (black). One alkyl group in each calixarene was removed for better clarity. 1H NMR titration of 7c with N-acetyl-ᴅ-phenylalaninate and N-acetyl-ʟ-phenylalaninate

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• flasks equipped with reflux condensers and magnetic stir bars. All reactions were followed by thin-layer chromatography (TLC) using Silufol UV-254 plates, which were visualized under UV light (254 nm), with acetone, hexane/acetone, or hexane/ethanol/acetone mixtures as eluent. Polyphosphoric acid (87

• , starting from nitromethane (1e, 122 mg, 2.00 mmol) and (5-bromo-6-methoxyquinolin-2-yl)methanamine (18d, 267 mg, 1.00 mmol). Pale yellow solid, yield 72% (198 mg, 0.72 mmol). Mp 177–179 °C; Rf 0.43 (acetone/petroleum ether 1:1, v/v); 1H NMR (400 MHz, DMSO-d6) δ 9.11 (d, J = 0.8 Hz, 1H, 1-H), 8.42 (dd, J

One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity

• Giovanna Bosica,
• Kaylie Demanuele,
• José M. Padrón and
• Adrián Puerta

Beilstein J. Org. Chem. 2020, 16, 2862–2869, doi:10.3762/bjoc.16.235

• reaction was finished. The reaction mixture, obtained as a viscous oil, was filtered through a sinter funnel to remove any catalyst and washed using acetone, which was then evaporated in a rotary evaporator. The resultant crystals were then recrystallized using hot ethanol. The products were then

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• °C, 60 min → 25 °C, 80 min, 94%; ii) NaN3, acetone/water 5:1 (v/v), reflux 20 h, 95%; iii) H2, Pd/C (10%), 1 mol/L HCl (1 equiv), methanol, 25 °C, 8 d, 86%; iv) rac-lipoic acid (for rac-1) or (R)-lipoic acid (for (R)-1), TBTU, DIPEA, DMF, 25 °C, 6 d, rac-1: 51%, (R)-1: 44%. Synthesis of ligand 2

• . Conditions: i) potassium phthalimide, DMF, 25 °C, 18 h, 67%; ii) 2,2'-dipicolylamine, K2CO3, KI, acetone, reflux 14 h, 50%; iii) N2H4⋅H2O, ethanol, 25 °C, 16 h, 56%; iv) (R)-lipoic acid, EDC⋅HCl, DMAP, CH2Cl2, 25 °C, 18 h, 52%. Minimum salt concentrations required to precipitate and to subsequently

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• scale, the average pyrrole shift is a very accurate indicator of the proportion of species with and without a coordinating axial ligand (100% coordination (paramagnetic) 48.9 ppm and 0% coordination (diamagnetic) 9.1 ppm in acetone-d6). It should be noted that the cis/trans ratio does not necessarily

• (1j−) perform surprisingly well (Δ = 77% and 83%). In order to check whether the switching efficiencies would decrease in aqueous environment to a similar extend as in previous cases [3], switching experiments with the protic record players 1e (R = OH), 1h (SH) and 1j (R = COOH) in acetone/water 1:9

• were performed. UV experiments revealed that the switching efficiencies of the protonated species indeed dropped dramatically as compared to those in pure acetone. However, the deprotonated 4-hydroxypyridine 1e− and the pyridine-4-carboxylate 1j− still perform with switching efficiencies of 40% and 28

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• solvent dependence of the stereochemical induction of the Diels–Alder reaction by the phenylethyl-derived ligand 2 was studied using N-benzylmaleimide (8e) as dienophile (Table 1). The solvents dioxane (17% ee) and acetone (14% ee) showed a slight decrease of the enantioselectivity compared to THF (21% ee

• ). The yields of the reactions were rather moderate. On the other hand, the use of acetonitrile had no significant influence on the yield compared to acetone while the enantioselectivity dramatically dropped to 8% ee. In this case the lower selectivity correlated with the increasing lithium solvating

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• , because of the low solubility of benzoylpyruvic acid (2a) and o-aminothiophenol (1a) in hexane. To our surprise, carrying out the reaction in chloroform (Table 1, entries 11 and 12) resulted in the formation of multiple side-products and only traces of BTA 3a. When acetone was used as a solvent (Table 1

• , entries 21 and 22), though the target BTA 3a was formed in about 30% yield, side-products were observed, which, possibly, were formed due to the reaction of acetone with o-aminothiophenol (1a). The best yield of BTA 3a was observed in acetonitrile (Table 1, entry 10). Then we tested the effect of common

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• 835 cm−1) were observed. To test the threading step, a 1H NMR experiment was conducted. A mixture of 1 and 2 was dissolved in a 1:1 acetone-d6/DMSO-d6 solution. The spectrum of this solution showed upfield shifts of 0.1 to 0.4 ppm for the methylene protons on the guest and smaller downfield shifts of

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• in moderate yields in acetone and acetonitrile solvents. However, we did not find an alternative 1,2-AS photoproduct. Even a change of the wavelength had no effect on the reactivity and similar results were obtained at 300 and 350 nm. The results are summarized in Table 2. The structures of ketenes

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• photosensitizers is acetone. Frequently, it is used as a solvent or in high concentration where its optical density allows light absorption at approximately 300 nm, even though λmax is about 270 nm [132]. Benzil, 9-fluorenone and 9,10-phenanthrenequinone are also well-established visible light triplet PSCats that

• −H monofluorination photosensitized by 9-fluorenone demonstrated a remarkable scope and reaction efficiency. A range of different photosensitizers (acetone, benzophenone, 9-fluorenone and Ir(ppy)3) were investigated. Acetone as a PSCat gave no product, likely due to its absorption bands (≈280 nm) well

• ketones (79.4 kcal⋅mol−1 for acetone, Table 1) is too high to allow TTET from benzil and therefore triplet excited state intramolecular HAT of the substrate. They rationalized the distribution of the fluorinated products as a result of a radical chain reaction and suggested that linear ketones may promote

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• with 56% decoordination (trans isomer) is less efficient. At the other end of the scale, in acetone only 69% coordination (530 nm) and 75% decoordination (435 nm) is achieved. It should be noted that a high conversion to the inactive state (in photocatalysis as well as photopharmacology) is more

Muyocopronones A and B: azaphilones from the endophytic fungus Muyocopron laterale

• Ken-ichi Nakashima,
• Junko Tomida,
• Tomoe Tsuboi,
• Yoshiaki Kawamura and
• Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 2100–2107, doi:10.3762/bjoc.16.177

• fraction was then separated by silica gel CC using CHCl3/acetone (stepwise gradient, 1:0, 25:1, 10:1, and 0:1 v/v) as the eluent. The fractions were combined according to TLC analysis to yield five fractions. Fraction 2 was recrystallized in MeOH to yield 3 (96.9 mg), while fraction 3 was subjected to

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• difficult to extract product 20 from water. When the reaction was performed in acetone this allowed for a simple filtration of the sodium chloride and bromide salts formed and resulted in very satisfactory yields (91–97%) after column chromatography. An Arbuzov phosphonylation was performed on the crude

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• (Table 2, entry 1). To achieve the target compound 3a, the same reaction was repeated by employing various catalysts (2.5 wt %), such as Fe2O3, Al2O3, KF–alumina, dolomitic limestone, triethylamine, pyridine, and DABCO in different solvents, such as water, acetone, iPrOH, EtOH, and EtOH/H2O 1:1 (Table 2

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• . For the synthesis of oxazolidinones and five-membered cyclic carbonates, the most effective solvent was determined based on the reaction of 8-oxabicyclo[5.1.0]octane (7b) with CSI (Table 1) which was the first reaction performed in this study. The reaction was carried out in acetone, THF, acetonitrile

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

• formation of compounds 2a–n that directly precipitated from the reaction medium. Compounds 2a–n were collected by filtration under vacuum and washed with acetone (5.0 mL). Characterization data of 2a, chosen as representative compound, are given below. 13-(2-(2-(tert-Butoxycarbonyl)hydrazono)-2-phenylethyl