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

• being slightly tilted out of the cavity. The corresponding interplanar angles Φ with the aromatic subunits are 81.55°, 80.78°, 77.08°, and 80.57°, respectively, starting counterclockwise from the upper subunit bearing a nitro group (Figure 2a). The 1,3-alternate isomer 4a represents quite an interesting

• the nitro groups or (ii) concomitant reduction of the nitro groups and the allyl moieties. Thus, the reaction of 4a with SnCl2∙2H2O in ethanol gave the corresponding amine 5 in 57% yield after column chromatography on alumina. On the other hand, the four-day stirring of 4a with Pd/C under a H2

• calixarene. Comparing the complexation constants for the otherwise identical receptors (7a vs 8a or 7b vs 8b), it is obvious that the presence of allyl vs propyl substituents does not impose much difference in terms of absolute K values and selectivity. As expected, the nitro-substituted receptors 7a and 8a

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• (hetero)aromatic units and either electron-donating (methyl, methoxy) or electron-withdrawing groups (carboxy, nitro, etc.) pending on the imine substrate. The molecular structures of all synthesized α-(arylamino)acetonitriles 2a–j were fully characterized by spectroscopic methods. The MS spectra

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

• superior electrophile in comparison to the ester function. Indeed, this bielectrophilic reagent reacted only at the nitro group, providing the amide 20 as the sole product. The yield was quite marginal, primarily due to decomposition of the fragile ester functionality under the harsh reaction conditions

• bar was charged with 2-nitro-1-phenylethan-1-one (1h, 330 mg, 2.00 mmol), 2-picolylamine (12, 108 mg, 1.00 mmol), 87% polyphosphoric acid (500 mg), and phosphorous acid (500 mg). The flask was capped with a septum, placed into an oil bath preheated to 160 °C, and stirred for 2 h. Upon reaction

Selective and reversible 1,3-dipolar cycloaddition of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones under microwave irradiation

• Alexander P. Molchanov,
• Mariia M. Efremova,
• Mariya A. Kryukova and
• Mikhail A. Kuznetsov

Beilstein J. Org. Chem. 2020, 16, 2679–2686, doi:10.3762/bjoc.16.218

• with carbon disulfide [26], diphenylketene [27], β-nitrostyrenes [28][29], if ionic liquids (IL) were used as reaction media. The reaction of β-nitrostyrenes with azomethine imines proceeds giving mixtures of Michael and anti-Michael-type adducts, containing a nitro group at the C2- or C1-position of

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• nitrogen heteroatoms were synthesized in multistep synthetic routes. A Buchwald–Hartwig amination of brominated precursors, thermolysis of azide precursors, and a Cadogan reaction of nitro-substituted precursors were successfully applied to eventually build-up pyrrole rings to stable and soluble fused

• of azide precursors, and a Cadogan cyclization of nitro-substituted precursors were applied to prepare various unknown derivatives. These represent novel core molecules, which by further derivatisation, for example with terminal acceptor groups, would lead to interesting π-conjugated materials for

• derivatives by Cadogan reaction of nitro-substituted precursors. Another possibility for the preparation of fused pyrrole rings is established by the Cadogan reaction [40]. Well-known examples are the reductive cyclization of 2-nitro-1,1’-biphenyls with triethyl phosphite or phosphanes as reducing agent to

Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction

• Tony Jin,
• Malickah Hicks,
• Davis Kurdyla,
• Sabahudin Hrapovic,
• Edmond Lam and
• Audrey Moores

Beilstein J. Org. Chem. 2020, 16, 2477–2483, doi:10.3762/bjoc.16.201

• stabilizing dispersed metal nanoparticle catalysts, along with increased solubility in aqueous media. Very recently, we have shown that these bio-based nanomaterials could stabilize highly disperse Au species on the surface of these nanocrystals to create a highly active catalyst for aromatic nitro reduction

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

• on the results of the stoichiometric reaction, a secondary amine-catalyzed nitro-Michael reaction is performed as well which afforded reasonable diastereoselectivities. Keywords: Diels–Alder reaction; enamine catalysis; hierarchical helicates; remote-control; stereoselectivity; Introduction Carbon

• stereocontrol and achiral catalytically active ligands. Enamine-catalyzed nitro-Michael reactions The nitro-Michael reaction [37][38][39][40] seemed to be suitable to be performed at hierarchically assembled helicates due to the reaction’s “benchmark character” [41]. Therefore, ligands bearing secondary amine

• measurement of the yield and the diastereoselectivity was possible by NMR spectroscopy. The nitro-Michael reaction of 3 equivalents propanal (14) and β-nitrostyrene (15) with 25 mol % of 13a-H2 after 2 days at room temperature resulted in 45% yield of product 16 and a nearly 1:1 diastereomeric ratio (Table 2

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

• the catalyst SiO2@H3PW12O40 [21], the reaction of tetracarbonyl compounds with o-aminothiophenol (1a) [22][23], the reaction of copper(II) chelate of ethyl pentafluorobenzoylpyruvate with o-aminothiophenol (1a, one example) [24] and the reaction of DMAD with 6-nitro-1,3-benzothiazole (one example) [25

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• reaction followed by the reduction of the nitro functionality into the amine group and subsequently performing a Sandmeyer reaction as shown in Scheme 20 [14]. Additionally, they have reported the hydrogenation of sumanene to generate compound 89 having one benzene ring intact in the framework using Pd/C

• Ullmann coupling reaction of 200 to produce the C3-symmetric trinitrotriphenylene 201. Having compound 201 in hand, the nitro groups were further converted into the corresponding amino groups via reduction in the presence of Pd/C under hydrogen gas atmosphere to furnish compound 202 in almost quantitative

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

• = 1.20 Å) [9][14], the fluorine atom is often used as a bioisostere for the hydrogen atom. Furthermore, the trifluoromethyl group was recently identified as a bioisostere for the nitro (NO2) group, which is important due to the strong binding ability of the nitro group and the high reactivity, which is

• and co-workers first synthesized the NFPYs [186]. Further synthesis of similar compounds resulted in the synthesis of N-fluorobis(phenyl)sulfonimide (NFSI) [187], N-fluorobis[(trifluoromethyl)sulfonyl]imide [188][189], N-fluoropyridinium salts [186], N-fluorosaccharinsultam and 4-nitro-substituted N

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• electron-rich aryl substituents. Both nitro- and bromo-substituted systems can be further functionalized to get a new set of products. The tolerance of the reaction for a variety of aryl substituents illustrates the generality of this method for the preparation of a range of highly substituted oxazoles

Convenient access to pyrrolidin-3-ylphosphonic acids and tetrahydro-2H-pyran-3-ylphosphonates with multiple contiguous stereocenters from nonracemic adducts of a Ni(II)-catalyzed Michael reaction

• Alexander N. Reznikov,
• Dmitry S. Nikerov,
• Anastasiya E. Sibiryakova,
• Victor B. Rybakov,
• Evgeniy V. Golovin and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2020, 16, 2073–2079, doi:10.3762/bjoc.16.174

• conjugated nitroolefins in the presence of a chiral Ni(II) complex to give nitro keto phosphonates with two stereocenters with excellent enantioselectivity and moderate to high diastereoselectivity. These products were used for a reductive cyclization leading to pyrrolidin-3-ylphosphonic acid and for

• -ylphosphonic acids and tetrahydropyranylphosphonates, we assumed that the 4-nitro-2-oxophosphonates – the Michael adducts of β-keto phosphonates and nitroolefins – are suitable precursors, considering that the Ni(II)-catalyzed Michael addition was carried out not only enantioselectively, but also

• diastereoselectively, such has been previously described [45]. These considerations prompted us to explore further applications of 4-nitro-2-oxophosphonates containing two contiguous stereocenters for the synthesis of the target compounds. Initially, 4-nitro-2-oxophosphonates 6a–f (Figure 2) were synthesized similar

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

• structural motifs found in numerous natural products and pharmaceuticals with extraordinary biological and pharmaceutical activities [34][35]. However, no desired product (3ka) was obtained when there was a nitro group in the substrate (1k). Then, N-allyl-N-(2-formylphenyl)-4-methylbenzenesulfonamide (1l

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• bearing fluorine and nitrogen atoms involves the asymmetric addition of α-fluoro-β-ketoesters or α-fluoro-α-nitro esters to appropriate electrophiles [84][85][86][87][88][89]. Results and Discussion Initially, we prepared a series of Ugi adducts 8 by varying acid, 2-oxo-aldehyde, amine, and isocyanide

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

• -accepting nitro group (2l) at the para position on the ring showed a good reactivity with ethyl acetoacetate (4) and urea (5) to afford the product 7g in an excellent isolated yield (94%, Table 6, entry 7). Halogen atoms at different positions on the ring of benzaldehyde derivatives (4-F: 2m, 4-Cl; 2n, and

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes

• Haruyasu Asahara,
• Minami Hiraishi and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2020, 16, 1830–1836, doi:10.3762/bjoc.16.150

• ; polysubstituted cyclohexanone; Introduction The 4-nitrophenol framework is characterized by a biased electron density in the ring and an acidic hydroxy group, which can be attributed to the electron-donating hydroxy and the electron-withdrawing nitro groups. The derivatives of 4-nitrophenol are widely used in

• various applications. In particular, 3-arylated-4-nitrophenols have attracted much attention from a biological viewpoint [1][2][3][4][5][6][7][8][9][10][11]; however, they cannot be synthesized by the direct modification of 4-nitrophenol because the ortho-directing hydroxy and the meta-directing nitro

• reaction, a C2 unit possessing a nitro group and an aryl group at the vicinal position is incorporated into the products. This unique reactivity prompted us to probe the synthesis of the 3-arylated-4-nitrophenols 5 by the Diels–Alder reaction of nitrostyrenes 1 with Danishefsky’s diene (2, the

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , ethoxy, trifluoromethyl, nitro, and ester underwent efficiently the desired perfluoroalkylation. This coupling was sensitive to steric hindrance as ortho-substituted substrates were less efficiently converted into the desired products. Furthermore, various perfluoroalkyl iodides with different chain

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

• ][29][30][31]. Moreover, these compounds were also used as synthetic intermediates for various sulfur-containing bioactive molecules (Figure 1) [32][33][34]. In organic synthesis, aromatic compounds having nitro groups play a vital role as building blocks for the synthesis of nitrogen-containing

• functional groups and aza-heterocyclic frameworks. However, organic transformations in which aromatic nitro groups act as leaving groups are less reported and require the use of transition-metal catalysts such as Cu, Rh, Pd, etc. [35][36][37]. Though, several elegant methods have been developed for the

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

• ′-dihydroxybenzophenone (BZP), D-mannose (Man), and 1,12-dodecanediol (Dod, Figure 2). Both the mannose and the phosphodiester bond were introduced via phosphoramidite chemistry to yield the final compounds, as shown in Figure 3. As opposed to the photoclickable probe MPC-1, the 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD

• wherein the NBD can be detected with dithionite. The latter reduces the nitro group of the NBD rapidly into an amino group, rendering the fluorophore nonfluorescent [32][33][34]. While there are no noteworthy difficulties in the synthesis of the molecular probe MPC-1 to report, the same cannot be said for

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• -catalyzed acetylation of these alcohols, which gave the corresponding acetates 2a–d [59]. The nitrenones 3a–d were finally obtained in an acceptable yield by reacting the acetate derivatives with the appropriate nitroalkanes [60]. The next step was the transformation of the nitro group of 3a–d via the Nef

• route remains limited in terms of chemical diversity as it depends on the availability of the corresponding nitro derivative. It was thus decided to move on to the Wittig reaction [57], offering a much more straightforward and efficient route to a panel of new diketones, 5e–k, from 1,2-cyclohexanedione

Fluorohydration of alkynes via I(I)/I(III) catalysis

• Jessica Neufeld,
• Constantin G. Daniliuc and
• Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

• (Scheme 1). Exposing the standard substrate 1 to the general reaction conditions furnished the desired product 2 in a synthetically useful isolated yield of 60%. Introduction of para-substituents was tolerated enabling formation of the chloro, methoxy, and nitro derivatives 3–5 with up to 54% yield. The

One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

• Gui-Feng Kang and
• Gang Zhang

Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120

• reaction, and provided products 6ga and 6ha in still moderate yields. When an electron-deficient aromatic aldehyde such as 4-phenylbenzaldehyde (1i) was used, the reaction effectively afforded product 6ia in 45% yield. Similarly, benzaldehydes having other electron-withdrawing groups such as cyano, nitro

Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

• Alexander V. Nyuchev,
• Ting Wan,
• Borja Cendón,
• Carlo Sambiagio,
• Job J. C. Struijs,
• Michelle Ho,
• Moisés Gulías,
• Ying Wang and
• Timothy Noël

Beilstein J. Org. Chem. 2020, 16, 1305–1312, doi:10.3762/bjoc.16.111

• poor yields. Other synthetically useful substituents, including cyano, nitro, phenylsulphonyl, (pinacolato)boron, and alkyl groups could be tolerated in the reaction (24–30), leading to a yield range between 26 and 65%. The trifluoromethoxylation of pyridine, pyrimidine, and thiophene derivatives also

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• olive stones-based activated carbon depending on the activation method. Chemical activation by H3PO4 form a higher amount of N-containing surface groups, mainly as nitro groups, compared to physical activation with CO2, whereby only less oxidized nitrogen species were formed. They concluded that the

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• -poor aromatic moiety on the oxime to give a radical anion, which then fragments. Electrochemical studies highlighted that O-aryl hydroxylamines bearing nitro groups were within the reduction range of excited eosin Y (Ered between −0.55 and −0.93 V vs SCE, OD13, E(PC•+/PC*) ≈ −1.1 V). Oxidative