Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• in a satisfactory yield. Thus, a series of these catalysts was screened. The best results in term of the yield (83%) and ee (90%) were obtained while using the catalyst having a p-nitrophenyl group on the other side of thiourea moiety in CCl4 in the presence of 4 Å molecular sieves (Table 16). 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

• the putative pyrrolizine product appears to be faster than the rate of cyclization of the enaminone. In particular, decomposition occurred during the attempted cyclization of the 2-nitrophenyl- and 2-iodophenylenaminones 15k and 15l even before all of the precursor had been consumed. In the 2-nitro

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• via intramolecular cyclization reaction of ketones 31, p-nitrophenyl azide (PNA, 32) and amino esters 33 has been described by Dehaen et al. The products were often obtained in good yield and in all cases with the retention of the configuration of the stereocenter. The reaction was carried out by

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• ) and cobaltocene (Cp2Co) in order to create charge-transfer complexes with the purpose of searching for efficient magnetic materials based on fullerenes. It can be seen in Scheme 16 that methanofullerene 52 was obtained from the initial, also para-substituted, ethyl diazo(4-nitrophenyl)acetate in 32

• nitrophenylfullerenes 48 and 50. Synthesis of conjugate 52 of C60 with ethyl diazo(4-nitrophenyl)acetate. Synthesis of fluoride-containing phenylmethanofullerenes 53–56. Synthesis of “bucky ligands” 57–60. The synthetic route to methanofullerene-based palladium–bisaminoaryl complex 62. Synthesis of N-containing

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

• in terms of their experimental application. In this study, we describe solutions for these two issues, using a chemoenzymatic approach to synthesize different ferulate compounds. The overall synthetic routes towards commercially available 5-bromo-4-chloro-3-indolyl and 4-nitrophenyl 5-O-feruloyl-α-ʟ

• -bromo-4-chloro-3-indolyl and 4-nitrophenyl 5-O-feruloylated α-ʟ-arabinofuranosides 1a and 1b. Although these substrates are commercially available, their synthesis involves 7 or 8 steps [15][16][17]. This contributes to their rather high retail costs (e.g., as of July 29th, 2020, 2500 and 778 € per 100

• reasonably cheap 5-bromo-4-chloro-3-indolyl or 4-nitrophenyl α-ʟ-arabinofuranosides. This afforded the corresponding feruloylated derivatives 1a and 1b (Figure 1). The yields (73 and 86% for the indolyl and 4-nitrophenyl derivatives, respectively) characterizing the regioselective enzymatic feruloylation of

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• under optimized conditions to extend the substrate scope. Firstly 2,4,6-collidine (1b) was successfully reacted for 48 h to obtain the successive product 5b in 87% yield (Table 3, entry 1). Next, 2-ethylpyridine (1c) was made to react under standard reaction conditions. To our surprise, 1-(4-nitrophenyl

• different catalysts. Synthesis of azaarene derivatives from different precursors. Our work: catalyst- and solvent-free benzylic addition of aldehydes to azaarenes. Large-scale experiments for the synthesis of 2-(6-methylpyridin-2-yl)-1-(4-nitrophenyl)ethan-1-ol (3a) from 2,6-dimethylpyridine (1a) and 4

• -nitrobenzaldehyde (2a). Plausible mechanism for the formation of 2-(6-methylpyridin-2-yl)-1-(4-nitrophenyl)ethan-1-ol (3a) under standard reaction conditions from 2,6-dimethylpyridine (1a) and 4-nitrobenzaldehyde (2a). Optimization of the reaction conditions.a Variation of the aldehyde component 2.a Variation of

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

• atmosphere (5 atm) in an autoclave at room temperature provided compound 6 in 91% yield. The starting compound 5 was then reacted with commercially available isocyanates comprising p-nitrophenyl isocyanate, p-n-butylphenyl isocyanate, (S)-α-methylbenzyl isocyanate, and (R)-α-methylbenzyl isocyanate. The

• presence of p-nitrophenyl groups. At the same time, the singlets at 8.36 and 9.37 ppm reflected the ureido NH protons (DMSO-d6, 400 MHz, 298 K). The structures of the selected receptors 7a and 7d were further proven by single crystal X-ray studies. The calixarene 7a crystallised in a monoclinic system

• -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

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• compound 1e and the product of its rearrangement to 5-(4-nitrophenyl)aminotriazole 1j [54], when the reaction was carried out in n-butanol at 105 °C (Table 2). Therefore, we can conclude that compound 3t was the product of a tandem reaction involving first the rearrangement of thioamide 1e to 1j followed

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

• provide carbazoles covering a wide substrate and functional group spectrum [41]. Moreover, penta- and heptafused heteroacenes were prepared by the Cadogan reaction by annulation of nitrophenyl or nitrobenzothienyl precursors [42][43][44][45]. In this respect, we recently reported a Cadogan cyclization of

• ) in a similar low yield (16%) as before H-DTP (vide supra) (Scheme 3). The change of the reducing agent to triphenyl phosphite did not lead to a reaction at all. We turned then to related thienothiophene 18, which bears an o-nitrophenyl substituent instead of a 3-nitrothienyl residue in 16. 2-(2

• -Nitrophenyl)thieno[3,2-b]thiophene (18) was similarly prepared by Pd-catalyzed Stille-type reaction of monostannylated thienothiophene 14 and o-iodonitrobenzene (17) in 86% yield. Successive Cadogan cyclization of 18 with triethyl phosphite under reflux gave tetracyclic 9H-thieno[2’,3’:4,5]thieno[3,2-b]indole

Catalytic trifluoromethylation of iodoarenes by use of 2-trifluoromethylated benzimidazoline as trifluoromethylating reagent

• Tatsuhiro Uchikura,
• Nanami Kamiyama,
• Taisuke Ishikawa and
• Takahiko Akiyama

Beilstein J. Org. Chem. 2020, 16, 2442–2447, doi:10.3762/bjoc.16.198

• the reaction towards various substrates under the optimized conditions (Figure 2). Electron-deficient aryl iodides were well tolerated furnishing the corresponding trifluoromethylation products in high yields. Among the tested nitrophenyl derivatives, p- and o-nitrophenyliodide gave the products in

Microwave-assisted efficient one-pot synthesis of N²-(tetrazol-5-yl)-6-aryl/heteroaryl-5,6-dihydro-1,3,5-triazine-2,4-diamines

• Moustafa Sherief Moustafa,
• Ramadan Ahmed Mekheimer,
• Saleh Mohammed Al-Mousawi,
• Mohamed Abd-Elmonem,
• Hesham El-Zorba,
• Afaf Mohamed Abdel Hameed,
• Tahany Mahmoud Mohamed and
• Kamal Usef Sadek

Beilstein J. Org. Chem. 2020, 16, 1706–1712, doi:10.3762/bjoc.16.142

• ), 8.65 (s, 1H), 10.94 (s, 1H), 11.29 (s, 1H); 13C NMR (150 MHz, DMSO-d6) δ 60.55, 127.39, 127.98, 130.30, 131.05, 131.42, 137.07, 154.52, 157.71, 158.04, 162.31; anal. calcd for C10H10ClN9: C, 41.17; H, 3.46; Cl, 12.15; N, 43.22; found: C, 41.30; H, 3.34; Cl, 12.30; N, 43.38. 6-(3-Nitrophenyl)-N2-(5H

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

• WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt] (Figure 5) and SRB (sulforhodamine B) (Figure 6) assays revealed that DHBER significantly reduced the cancer cell proliferation as compared to untreated cells both at 24 and 48 h of incubation

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• catalysts in a similar transformation [17]. In another study, Reiser and co-workers described a related allylation process of organic halides with allyltributyltin in the presence of [Cu(I)(dap)2]Cl as the catalyst [16]. This reaction was applied to a broad range of substrates, including a para-nitrophenyl

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• incorporations of nitrobenzene into the polymer chains. The 2-nitrobenzoic acid used to form a silver carboxylate in the reaction system is the origin of the nitrophenyl group. Three different types of chains are represented, corresponding to incorporation of I/nitrophenyl, H/nitrophenyl, and two nitrophenyl end

• accounts for the formation of a carboxylate radical 11, explaining the presence of 2-nitrophenyl incorporation into the polymer chain. Additionally, this explains the formation of a phenyl radical at room temperature, and the poor control in which the nitrophenyl groups are incorporated into the chain

• Scheme 1. The region from 4–4.5 ppm indicates the interior indole repeat units compared with the terminal indole units. MALDI–TOF MS of PIn, indicating octylindole repeat units with three different types of end groups. These include 2-nitrophenyl, iodine, and hydrogen. A high yielding, highly selective

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

• ). None of the benzyl (Bn), phenyl (Ph), p-methoxyphenyl (PMP) or p-nitrophenyl (PNP) derivatives showed any activity [Figure 5A, wells 3–6, respectively]. On the contrary, both p-chlorophenyl (PCP) and p-fluorophenyl (PFP) showed the best photocleaving action, exhibiting a percentage of ds cleavages, as

• examine the transitions (S0 → T1 and S0 → S1) we find that there are major differences in the nature of the transitions. In particular, for the transition S0 → T1 the excitation is localized on the pyridine moiety for 12, while for 11 it is localized on the p-nitrophenyl group. As far as the S0 → S1

• vertical transition is concerned, for molecule 12 the excitation is localized again on the pyridine ring (involving a π* molecular orbital), whereas for 11 the excitation is of π(Ο–Ν–Ο) → π*(nitrophenyl) type. These observations differentiate the two molecules giving them different photochemical

Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea

• Aleksandr I. Kobelev,
• Nikita A. Tretyakov,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Michael Rubin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 2864–2871, doi:10.3762/bjoc.15.280

• )thiourea, N-(3,5-dimethylphenyl)thiourea, N-(4-nitrophenyl)thiourea, and N-1-naphtylthiourea) reacted with FPD 1a unselectively, forming a mixture of four inseparable adducts (the reaction mixtures were analyzed by UPLC–MS) (Scheme 7). Unfortunately, we did not succeed to find any conditions for a

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• and NPP3. Absorbance was taken at wavelength of 405 nm as pre-read by using a microplate reader (BioTek FLx800, Instruments, Inc. USA). After pre-read the artificial substrate p-nitrophenyl 5'-thymidine monophosphate (pNP-TMP), 400 µM for NPP1 and 600 µM in case of NPP3, was added followed by a second

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• acetonitrile, forming the BAPTA precursor 1b. The palladium-catalyzed benzyl cleavage was followed by a double alkylation with 2, reactant 2 being synthesized from 4-(4-nitrophenyl)butanoic acid. The 4-nitrobenzene groups of the pendant arms were subsequently reduced yielding the corresponding anilines (1e). A

• the calcium-cage nitrophenyl-EGTA (Kd of 0.080 μM on excitation at 350 nm with a quantum yield of 0.23) [16]. For comparison, molecule 1 has a similar Kd and the quantum yield is in the same order of magnitude as nitrophenyl-EGTA but is around 3 times lower, thus in principle it could sequester

• ( t, J = 7.2 Hz, 12H, CH3) ppm; 13C NMR (CDCl3, 75 MHz) δ 171.9, 150.9, 144.0, 140.4, 115.7, 108.0, 106.7, 68.0, 61.1, 53.7, 14.2 ppm; HRMS–ESI (m/z): [M + Na]+ calcd for C30H40N2O12Na, 643.2468; found, 643.2573. Tetraethyl 2,2',2'',2'''-[1,2-ethanediylbis(oxy{5-[4-(4-nitrophenyl)butoxy]-2,1-phenylene

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• various diseases. Hence, we also modified the N-propargyl alcohol derivative 21 to 1,2,3-triazolo alcohol derivative 24 by click chemistry using 4-nitrophenyl azide (23) and the corresponding triazolo alcohol derivative 24 was obtained as yellow solid in 80% yield (Scheme 9) [58]. All alcohol derivatives

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

• Ana M. Belenguer,
• Adam A. L. Michalchuk,
• Giulio I. Lampronti and
• Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

• of bis(2-nitrophenyl) disulfide and bis(4-chlorophenyl) disulfide in the presence of a small amount of the base catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to produce 4-chlorophenyl 2-nitrophenyl disulfide (see Scheme 1). Reliable experimental procedures have already been established for this

• formation of the heterodimer. The homodimers (0.34 mmol) bis(2-nitrophenyl) disulfide (1-1, 104.83 mg) and bis(4-chlorophenyl) disulfide (2-2, 97.66 mg) were accurately weighed, resulting in a load of 200 mg. The material was quantitatively transferred to a 14.5 mL snap closure stainless steel grinding jar

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• yellow oil: Spectral data was identical to literature compound [38]. 1H NMR (300 MHz, CDCl3) δ 7.52 (d, J = 8.4 Hz, 2H), 7.43 (d, J = 8.4 Hz, 2H), 2.24–2.15 (m, 1H), 1.18–1.07 (m, 2H), 0.74–0.65 (m, 2H). Cyclopropyl(4-nitrophenyl)sulfane (1l). The general procedure was followed on 0.400 mmol scale

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• group and linker still need nucleophilic cleavage. Palladium is expensive and difficult to remove from ODN. Photoirradiation can damage ODNs. The (p-nitrophenyl)ethyl (Npe) and (p-nitrophenyl)ethyloxycarbonyl (Npeoc) groups were also explored for sensitive ODN synthesis under non-nucleophilic conditions

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• character, 2,2,6,6-tetramethyl-1-(1-(2-(4-nitrophenyl)benzofuran-6-yl)ethoxy)piperidine (2a) and its regioisomer 2b, were designed and synthesized. The one-photon (OP) (365 ± 10 nm) and TP (710–760 nm) triggered release (i.e., uncaging) of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical under air

• -responsive photo-labile protecting group [56][57][58] with simple cyclic stilbene structures such as 2-(4-nitrophenyl)benzofuran (NPBF) that absorb in the NIR region of 710–760 nm for the uncaging of bioactive substances such as glutamate and Ca2+ [59][60][61][62][63][64]. Herein, we report the synthesis of

• addition to the fundamental study. Results and Discussion The caged-TEMPOs 2a and 2b were synthesized as shown in Scheme 2. The new compounds, 5-ethyl- and 6-ethyl-2-(4-nitrophenyl)benzofuran (5a and 5b), were synthesized from 1-ethynyl-4-nitrobenzene (4) that was prepared from the commercially available 1

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• -nitrophenyl chloroformate (7) and triethylamine in the ball mill to form the activated DAG anhydride derivative 8a (Scheme 5b). Analysis by 1H NMR spectroscopy of the reaction mixture revealed the presence of DAG 8a along with its isomeric DAG 8a’. Formation of the latter compound could have been facilitated

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• [22][23], or the Baeyer–Mills reaction via Zn/NH4Cl [25]. We chose the Ba(OH)2/Zn method because it provided superior yields even at larger scales. The syntheses of the functionalized diazocines 4–7 started with (4-methyl-3-nitrophenyl)methanol (8a) and (4-methyl-3-nitrophenyl)ethanol (8b). In a first