A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• salts are generated in situ and converted to radicals through irradiation with visible light. Reaction products precipitate from the solvent, eliminating the need for purification and thus providing a novel green method for the synthesis of versatile bis-electrophiles. Keywords: benzoquinone; diazonium

• eosin Y and green light as a reducing agent an array of substrates were functionalized. Common among reports on the radical CH-arylation of benzoquinones is the use of multiple equivalents of starting material to prevent bis-arylation. The latter inherently relies on the use of an excess of radical

• functionalizing 2,5-dichlorobenzoquinone (1), using conditions similar to those reported by König et al. [28], differing only in the use of an excess of radical precursor. As expected, exposing a mixture of 1, aryldiazonium salt 2a and eosin Y in DMSO to green light resulted in a complex reaction mixture

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• , but also to cation–H or π–π interactions. Some of the advantages of multidentate, supramolecular anion-binding catalysis were recently exploited by the Feringa group, who designed an anion-binding catalyst 86 that fuses the known triazole binding properties with a light-switchable molecular motor. In

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• developments in the field of photoredox nickel-catalyzed C‒H functionalization reactions with a range of applications until summer 2021. Keywords: C–H activation; functionalization; nickel; photocatalysts; photoredox; visible light; Introduction During the last decades, transition-metal-catalyzed

• developments, which enables a diverse range of previously inaccessible organic transformations in milder reaction conditions [31][32][33][34][35][36][37][38][39][40]. Here, by absorbing visible light, a photocatalyst can function as a single-electron redox mediator through an oxidative or reductive quenching

• were found to be suitable to achieve the transformation in satisfactory yields under visible light irradiation (Scheme 2). The authors hypothesized that the key α-nitrogen carbon-centered radical 5 could be generated via a photoredox-driven N-phenyl oxidation and α-C–H deprotonation sequence from

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• ., bacteria, biomolecules [15], enzymes [16]) or physical stimuli (e.g., light [17][18][19], temperature [12][18], mechanical forces, as well as electric [20][21] and magnetic fields [22][23][24]) [1][25][26]. As a result of these environmental triggers, smart materials exhibit a defined reversible change in

• their physicochemical properties (e.g., solubility, viscosity) and can respond to stimuli in several ways by altering light transmitting abilities, shape, color, conductivity, as well as wettability [27][28]. Therefore, such functional polymers have a huge potential in numerous areas of application

• various methods, such as turbidimetry [83], 1H NMR spectrosocopy [84], and dynamic light scattering [85][86]. In this context, the cloud-point is the phase transition temperature at a certain polymer concentration, which can be located at any point on the binodal curve, and therefore, the polymer

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• proved to not going via a Minisci-type silyl radical addition [55], as the reaction with pyridine did not afford any product. Bell studied the properties of such molecules which are similar to those used in OLED devices (organic light emitting diodes) in 2017. The molecule 34 was synthesized by base

• -mediated reaction of bisindole derivative 32 with Ph2SiCl2 (33, Scheme 5b) [56]. The dissociation of the indole C-2–Si bond upon UV light excitation generates a hole transport layer (HTL) in these materials, facilitating the optical activity [57]. In 1996, Frenzel reported the synthesis of bis(indol-3-yl

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• surface modification, we also observe bulk polymerization, which is expected for this method, and currently limits the controllability of this procedure. Keywords: additive manufacturing; light-induced polymerization; self-initiated photografting and photopolymerization; surface-initiated polymerization

• improved by a variety of methods like plasma treatment, NaOH hydrolysis treatment or a micro deposition system. This study outlines a potential approach to coat medical-grade PCL with a thin hydrogel that requires no initiator or catalyst – just a deoxygenated aqueous monomer solution and UV light. We

• experimental setup consisted of a closed chamber, which was equipped with a valve for argon supply and a slot for the UV lamp (Supporting Information File 1, Figure S1). Initially, static conditions were used to determine the influence of exposure time, distance between light source and substrate on the PHEMA

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• and safe near-infrared (NIR) light is still the subject of intense research efforts but remains a huge challenge due to the associated low photon energy (wavelength from 0.78 to 2.5 µm). In this study, a series of 17 NIR dyes mainly based on a well-established cyanine scaffold is proposed. Remarkably

• , 11 of them were never synthesized before. Markedly, noncharged structures, negatively charged cyanine bearing Na+ as counter cation, and positively charged cyanines bearing (B(Ph)4−) or (I−) as counter anions were examined as promising NIR light photoinitiating systems. Excellent photoinitiating

• polymerization of acrylate/epoxy monomer blends) can also be carried out upon NIR light with the proposed systems. Keywords: cyanine; NIR light; photochemistry; Introduction Photopolymerization processes are well established due to the specific features and advantages. Indeed, the reaction is carried out at

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• application of several organic materials, such as organic light-emitting diodes (OLEDs) [5], organic field-effect transistors (OFETs) [6], polymeric materials [7], and other kinds of materials [8][9][10]. For example, OLEDs fabricated with 9,10-diphenylanthracene derivatives 1 and 2 are blue light emitters

• employed palladium(II) acetate and visible light under O2 in the reactions between ethyl acrylate (192) and substituted diaryl carboxylic acids 193, to produce anthraquinones 194 in low to moderate yields (30–68%). In a direct comparison with the methodology proposed by Hong for the synthesis of

• anthracenes, previously shown in Scheme 7 [41], the key to obtaining anthraquinones was the photooxidation induced by visible light, which afforded the substituted anthraquinones 194. In this case, the effect of the aromatic ring substituents also affected the yield of the anthraquinones, as can be seen from

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• acetylcholinesterase inhibitors [11][12][13], being LSPN223 the most potent compound (Figure 2). Furthermore, coumarin derivatives have been used as fluorescent probes, laser dyes, fluorescent chemosensors, light absorbers for solar cells, optical brighteners, and organic light emitting diodes (OLEDs) [14][15]. From a

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• has been selectively feasible without activating a C(sp2)–H bond in the arene moiety. Verma and co-workers [91] have reported the use of VO(acac)2 immobilized over graphitic carbon nitride (VO@gC3N4) under visible light irradiation to perform a photocatalytic C–H activation of arene methides and

• are crucial. In 2018, Ackermann and co-workers described a novel room temperature C–H arylation by using a continuous visible light photo-flow technique, allied with a manganese photocatalyst CpMn(CO)3 [142]. The new flow protocol enabled the synthesis of several arene- and heterocyclic-based

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• , azidated N-protected memantine 13a was successfully generated by employing electricity and visible-light irradiation in the presence of a Mn catalyst. High regioselectivity was observed at tertiary or benzylic positions (see 13a–c). For commercially available drug derivatives, methyl esters of ibuprofen

• is also oxidized to Mn(III)/L–N3. Azide radical addition to Mn(II)/L to form Mn(III)/L–N3 was considered as a possible route. Concurrently, the photocatalyst is irradiated by blue LED light to induce hydrogen atom transfer (HAT) at the C–H bond of substrate 12, generating alkyl radicals and enabling

• excluded. This late-stage process by Mn catalysis, electrochemistry, and visible-light catalysis exhibits high value as a sustainable tool to investigate problematic synthetic transformations. Recently, the Ackermann group disclosed a convenient manganese-catalyzed late-stage C–H azidation of bioactive

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• ; aldehydes; cerium; oxidation; ketones; visible light; Introduction The selective oxidation of alcohols to carbonyl compounds [1][2] is an important process for producing a wide range of value-added fine chemicals [3][4][5][6]. In the traditional oxidation process stoichiometric amounts of oxidants such as

• acting as the terminal oxidant [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Most aerobic oxidation reactions utilize either metal complexes and nanoparticles or persistent radical reagents as catalysts [21]. In the past ten years, visible light-induced

• generating oxygen-centered radicals, that lead to carbon-centered radicals through intra/intermolecular hydrogen atom transfer (HAT) processes, radical decarboxylative or radical deformylation [57][58][59]. In continuation of our research interest on visible-light-driven cerium photocatalysis [59][65], we

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• acrylonitrile (left), acrylamide (middle), and divinyl sulfone (right; double bond conversion is given; light sections of the bar represent the share of 3monoa–d, dark sections represent the share of 3dia–d) with the alcohols propan-2-ol (a), propan-1-ol (b), prop-2-en-1-ol (c), and prop-2-yn-1-ol (d) catalyzed

• boxes) at room temperature (23 °C); no solvent used. Left: double-bond conversion of the polymerization of 4 initiated by 5 mol % TPP, MMTPP or TMTPP after 1 h at room temperature (23 °C) and at 80 °C as well as after 24 h at 23 °C and at 80 °C; light sections of the bars represent the share of Rauhut

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• to target DNA or RNA is less useful than the increase in signal intensity. Chen and co-workers found that 5-benzothiopheneuracil (btU, Figure 10) modified PNAs increased the fluorescence upon binding to dsRNA, acting as light-up triplex-forming PNA probes [148]. This was the first report of a

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• ][38][39] and were reported to be promising candidates for potential use as organic light emitting diodes [40]. Thus, various synthetic methodologies for the preparation of acridine-based molecules have been developed [41][42][43][44][45][46][47]. Tetrahydroacridine, containing a partially hydrogenated

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• by column chromatography on silica gel (petroleum/EtOAc 20:1, with 1% Et3N) yielded 3aa (87.4 mg, 89%, Z/E = 13:1) as a light yellow solid. mp 67–68 °C; 1H NMR (CDCl3, 600 MHz) δ 8.13 (ddd, J = 5.0; 1.9; 0.9 Hz, 1H), 7.90 (dd, J = 7.6; 1.0 Hz, 1H), 7.85–7.82 (m, 1H), 7.70 (d, J = 1.2 Hz, 1H), 7.56

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• may be due to the low hole conductivity, a decrease in the HOMO level of the polymer, and a narrower band gap of visible light absorption [51]. Within the framework of the study of the prospects for polymer derivatives of isoindigo in organic photovoltaics and avoiding the use of the fullerene

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• chromatography was carried out on silica gel (grade 60, mesh size 230–400, Scharlau). Visualization techniques for TLC plates include using ultraviolet light (254 nm) and KMnO4. NMR spectra were collected at room temperature on Bruker-500, or Bruker-700 spectrometers and calibrated to the appropriate solvent

• silica-gel chromatography (100% hexane), to furnish (±)-4 as a yellow solid (6.70 g, 26.5 mmol, 55%), (±)-5 as a yellow crystalline solid (1.68 g, 6.24 mmol, 13%), and 6 as light yellow crystals (2.61 g, 9.15 mmol, 19%). 4-Nitro[2.2]paracyclophane (4) 1H NMR (500 MHz, CDCl3) δ (ppm) 7.22 (d, J = 1.2 Hz

• (5.00 g, 17.5 mmol, 1.00 equiv) in CH3OH (0.20 M, 87.6 mL) was added TFA (1.00 M, 17.5 mL) and stirred at rt for 24 h. The solution was concentrated under reduced pressure yielding a light orange solid, which was purified by flash silica-gel chromatography (gradient of 0% to 60% EtOAc, hexane over 1 h

Substituted nitrogen-bridged diazocines

• Pascal Lentes,
• Jeremy Rudtke,
• Thomas Griebenow and
• Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

• makes them promising candidates for applications in photopharmacology. The halogen substituents allow further functionalization via cross-coupling reactions. Keywords: bridged azobenzene; diazocine; photopharmacology; photoswitch; triazocine; visible light switch; water-soluble switch; Introduction

• ) with light in the visible region [1]. Moreover, the Z-boat configuration is the thermodynamically stable isomer [2][3][4][5][6][7][8][9]. The latter property (i.e., the inverted stability compared to azobenzenes) makes them promising candidates for applications in photopharmacology. In the majority of

• azobenzene-based photopharmacophores, the bent Z configuration is biologically inactive [10][11][12]. Hence, (and in contrast to azobenzenes) the thermodynamically stable and biologically inactive Z-isomer can be administered and switched on with light at the site of interest with spatiotemporal resolution

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• traces of any β-carboline product were observed, which proves that the heterocyclization reaction is highly regiospecific. Optical properties of γ-carbolines Interestingly, the γ-carboline derivatives were found to be highly fluorescent under UV light irradiation. A systematic literature survey revealed

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• products were light yellow solids with the same melting point of 115–116 °C and both had the same measured mass when analyzed by HRMS. The differences were that the specific optical rotation was measured to be +67.0° for compound 8 and +91.4° for compound 9 and their 1H NMR spectra differed for the signals

Analogs of the carotane antibiotic fulvoferruginin from submerged cultures of a Thai Marasmius sp.

• Birthe Sandargo,
• Leon Kaysan,
• Rémy B. Teponno,
• Christian Richter,
• Benjarong Thongbai,
• Frank Surup and
• Marc Stadler

Beilstein J. Org. Chem. 2021, 17, 1385–1391, doi:10.3762/bjoc.17.97

• –ESI (m/z): [M + H]+ calcd for C15H18O4+, 263.1283; found, 263.1276. Fulvoferruginin D (4): light yellow solid; [α]D20 +19 (c 1, MeOH); UV (MeOH) λmax (log ε) 201 (4.4), 249 (4.2) nm; 1H (700 MHz) and 13C NMR (175 MHz) data in CD3OD are collected in Table 1 and copies of spectra are collected in

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• applications ranging from organic thin‐film transistors (OTFTs), organic light-emitting diodes (OLEDs), dye‐sensitized solar cells (DSSCs), fluorescent probes, organic photovoltaics (OPVs) to the high hole mobility semiconductors, blue light-emitting materials, nonlinear optical materials and so forth [5][6][7

Antiviral therapy in shrimp through plant virus VLP containing VP28 dsRNA against WSSV

• Santiago Ramos-Carreño,
• Ivone Giffard-Mena,
• Jose N. Zamudio-Ocadiz,
• Alfredo Nuñez-Rivera,
• Ricardo Valencia-Yañez,
• Jaime Ruiz-Garcia,
• Maria Teresa Viana and
• Ruben D. Cadena-Nava

Beilstein J. Org. Chem. 2021, 17, 1360–1373, doi:10.3762/bjoc.17.95

• 12 h light and 12 h dark was used. The shrimp were fed with a commercial diet twice a day at 3% of their biomass. Shrimp were gradually acclimatized to 16 ppt and kept 15 days in observation before starting the experiment. Filters containing activated carbon were used to maintain an optimum seawater