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

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• , chloro, bromo, methoxy, acetyl, cyano, nitro, and trifluoromethyl, were well-tolerated and afforded the corresponding anti-β-fluoro-α-amino acids 163a–l in moderate to excellent yields [78] (Scheme 40). 3. Synthesis of β,β-difluorophenylalanine derivatives of type IV via 2-phenyl-2,2-difluoroacetaldehyde

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• substituents had a negative effect on the efficiency of the transformation, independently of their electronic effects (Scheme 3, 21–25). Still, halides, nitriles, and ester substituents were tolerated, giving a possible handle for further manipulation. However, the presence of a nitro group impeded the

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• PhMe2Si moiety in a 1,4-manner to unsaturated nitro and cyano derivatives leading to adducts 209–218, each being obtained in high chemical yield and good enantioselectivity (Scheme 37). 1.5 Miscellaneous reactions The Tsuji group developed a mild method for the regio-divergent silacarboxylation of allenes

Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• effect of the substitution on the indole ring. Both electron-donating and withdrawing groups at different positions of the indole ring produced the bis(trifluoromethylthiolated) products 2a–o in moderate to good yields. A wide range of functionalities such as alkyl, alkoxy, nitro, nitrile, ester

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• 10 minutes at 120 °C and 15 psi, rGO/Cu2O (102) was obtained. The nanoparticles of Cu2O with an average size of 5 nm were homogeneously dispersed throughout the rGO sheets (Scheme 23). A mixture of phenylacetylene, benzyl bromides containing methoxy and nitro substitutions, and sodium azide was

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• synthesis of β-nitrate ester carboxamides using tert-butyl nitrite as the nitro source and oxygen as the oxidant through the ring opening of 2-oxazolines [9] (Scheme 1a). Kappe reported a two-step continuous-flow synthesis of N-(2-aminoethyl)acylamides through ring opening/hydrogenation of oxazolines with

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• during irradiation process. On the other hand, the nitro derivative 11 showed the formation of an intermediate with λmax at 385 nm which gradually increased for the first 3 min. This intermediate seems subsequently to act as a light filter absorbing the irradiation energy and to be converted to other

• selective compounds with DNA was good to excellent, as verified with extensive CT DNA-affinity studies. A deeper insight in the photochemical behaviour of the nitro (11) and the chloro (12) derivatives using UV spectroscopy in the absence of DNA was indicative of the disruption of 11 whereas 12 showed a

• activity seems to be located at the nitro group. The explanation of the activity seems to be the ability of 12 to obtain its triplet state and create active radicals able to abstract hydrogen atoms from DNA and cause its damage. This was experimentally verified using acetophenone, as a triplet state

Synthesis and herbicidal activities of aryloxyacetic acid derivatives as HPPD inhibitors

• Man-Man Wang,
• Hao Huang,
• Lei Shu,
• Jian-Min Liu,
• Jian-Qiu Zhang,
• Yi-Le Yan and
• Da-Yong Zhang

Beilstein J. Org. Chem. 2020, 16, 233–247, doi:10.3762/bjoc.16.25

• to activity (I17 > I18, I26 > I27, II1 > II2), and that the introduction a nitro group led to more potent activity compared to that generated by a chlorine atom (except for I6 and I21), such that I15 > I3, I18 > I5, and I24 > I7 in terms of activity. Generally speaking, compounds with a pyrazole ring

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• products 2e–h were obtained in good yields and regioselectivities. In the same way, aldehydes containing electron-withdrawing groups such as the nitro group also reacted without influence of the substituent location to give the corresponding homopropargylic alcohols 2m and 2n in good yields. It is

• interesting to note that the nitro group remained intact under the reaction conditions. Usually, this group is sensitive to reduction when alternative methods involving zinc or tin are used [33]. In addition, aldehydes containing halogens also gave the corresponding products 2j–l in moderate yields. These

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• emission intensity of 3d was too low to identify a maximum, as usually observed with nitro-substituted fluorophores. Unfortunately, the emission quantum yields of 3a–c could not be determined in water because of the compounds’ tendency to dimerize even at very low concentrations (see below). Overall, the

• × 105 M). The nitro-substituted derivative 3d had a slightly lower affinity with Kb = 8.2 ± 0.2 × 104 M, and the methoxy-substituted derivatives had the lowest binding constants of Kb = 4.8 ± 0.1 × 104 M (3b) and 4.1 ± 0.1 × 104 M (3c). Overall, these binding affinities resembled the ones of known DNA

• Information File 1). However, it was observed that further irradiation of the nitro-substituted derivative 3d furnished the dimer in acetonitrile, as shown by the development of the characteristic cyclobutane protons at 4.85–4.95 ppm. In contrast, the NMR-spectroscopic analysis in D2O showed that the

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• ). Starting from 3,5-disubstituted nitrosobenzene E, consecutive Bayer–Mills and deprotection reactions would lead to the target compound 3 in five steps. Furthermore, by using nitrosoarene E, the selective installment of the amine groups, e.g., via acetamide- and nitro group-carrying intermediates, could be

• . The azobenzene building block 8, with an unsubstituted phenyl ring and two orthogonal nitrogen substituents in the 3- and 5-position (Scheme 3), was prepared. The synthesis commenced with the acetylation of 3,5-dinitroaniline (4) in 95% yield, followed by the selective reduction of one nitro group

• (E)-N-(3-nitro-5-(phenyldiazenyl)phenyl)acetamide (8), the reduction of the nitro group was attempted. However, the literature-known procedure of using sodium hydrosulfide did not yield the desired (E)-N-(3-amino-5-(phenyldiazenyl)phenyl)acetamide (9). Alternative reduction attempts, such as using Pd

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• ][4EtOV] were subjected to the coupling reaction under identical conditions. By comparison of the efficiency of conversion of iodobenzene and its electron-donating 4-methoxy (1d) and electron-withdrawing 4-nitro (1m) derivatives with different aliphatic acetylenes (4, 6, and 8), no significant differences

Safe and highly efficient adaptation of potentially explosive azide chemistry involved in the synthesis of Tamiflu using continuous-flow technology

• Cloudius R. Sagandira and
• Paul Watts

Beilstein J. Org. Chem. 2019, 15, 2577–2589, doi:10.3762/bjoc.15.251

• 1a is a potentially explosive compound because of its nitro and azide moieties [14] and its safety concerns need to be dealt with for large scale synthesis. Safety in this reaction was achieved by in situ formation and consumption in flow of the hazardous intermediates (azide 1a and isocyanate 1b

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• conditions applied for the cross coupling of the triflate were similar to those published by Calitree and Detty for the coupling of the triflates derived from the O, S, Se, and Te-xanthones 16 with various phenylboroxines (bearing nitro, carboxylic acid, methyl and methoxy substituents) [29]. Here yields of

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• -nitrobenzaldehyde (8a) to give the corresponding tertiary amine 9a in high yield. The nitro group of 9a was subsequently reduced by SnCl2 in high yield. The resulting aniline 10a was used to obtain the azo compounds 12a–e in varying yields through a Mills reaction with the corresponding nitroso compounds 11a–e

• performed following the strategies shown in Scheme 1 as disclosed for compounds 2a–e. Briefly, a reductive amination of 7 and 8b gave nitro compound 9b, which after reduction to 10b, coupling with nitroso compounds 11a–e to 13a–e and methylation gave iodide salts 3a–e with purities of trans-isomers ≥99% and

• ). The electron-donating groups in this series (Me and OMe) also increase the electron density of the azobenzene system. The synthesis of 4a–d and 4f–i was performed following the route shown in Scheme 1. Briefly, 7 was used in a reductive amination with 2-chloro-3-nitrobenzaldehyde (8c) to give nitro

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• [33]. This transformation is particularly well suited for 4-chloroquinolines with electron withdrawing substituents (ester and nitro) in the 3-position. Both the initial displacement of the 4-chloro-substituent and the cleavage of the 4-alkoxyquinoline is auto-catalyzed and takes place under neutral

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• addition, 2-methoxy and 2-trifluoromethyl-functionalized benzoyl chloride can be applied to the reaction (3c,d). The 4-methoxy group was also tolerated in the reaction (3e). Substrates with strong electron-withdrawing groups such as 4-trifluoromethyl, 4-nitro and 4-cyano groups reacted with moderate to