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Search for "metal-free" in Full Text gives 288 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

  • Cansu Esen and
  • Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

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  • novelty. Here, a metal-free semiconductor graphitic carbon nitride (g-CN)-embedded hydrogel as an initial network was synthesized via redox-couple initiation under dark conditions. Post-photomodification of so-formed hydrogel, thanks to the photoactivity of the embedded g-CN nanosheets, was exemplified in
  • -sustainable semiconductors are slowly being replaced by a new generation of semiconductors. Graphitic carbon nitride (g-CN) is a metal-free polymeric semiconductor that is mainly composed of carbon and nitrogen elements by tri-s-triazine, triazine imide, or heptazine repeating units [16][17][18]. g-CN
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Published 21 May 2021

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

  • Guido Gambacorta,
  • James S. Sharley and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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Published 18 May 2021

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

  • Guanglong Pan,
  • Qian Yang,
  • Wentao Wang,
  • Yurong Tang and
  • Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

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  • radical initiator under mild conditions. A wide range of structurally diverse nitrogenous heterocyclic compounds including indolines, oxindoles, isoquinolinones, and isoquinolinediones have been accessed in high yields. This heterogeneous protocol features base- and transition metal-free, good catalyst
  • byproduct 15 after deprotonation. Conclusion We have demonstrated the application of a heterogeneous CN-K semiconducting photocatalyst in the cyanomethylarylation of alkenes with acetonitrile utilizing a readily available NHPI ester as radical initiator. This transition metal-free protocol tolerates a broad
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Published 17 May 2021

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

  • Jan Bartáček,
  • Jan Svoboda,
  • Martin Kocúrik,
  • Jaroslav Pochobradský,
  • Alexander Čegan,
  • Miloš Sedlák and
  • Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

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  • ]. Evaluation of current state and outlook Asymmetric addition reactions to enones have so far been described in the literature in connection with catalysis. The catalyst is usually a complex of a transition metal with a suitable ligand. However, metal-free catalysis is also known [64]. Among the most
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Published 10 May 2021

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

  • Rashmi Singh,
  • Tomas Horsten,
  • Rashmi Prakash,
  • Swapan Dey and
  • Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

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  • . Electrophilic substitution and further condensations give polycyclic systems, including oxazolo- and chromeno-fused analogues. Keywords: benzofuropyridines; benzoquinones; dibenzofurans; Meerwein reaction; metal-free synthesis; Introduction Dibenzofurans are important oxygen-containing heterocycles present in
  • work focuses on a metal-free approach for the synthesis of benzofuropyridine analogues. Results and Discussion The synthesis of target compound 13 involved three steps (Scheme 1). C–H Arylation, as needed in the first step, is usually carried out using transition metal catalysis [31]. Furthermore
  • we plan to expand this chemistry and carry out a bioactivity study in due course. Biologically relevant 2-oxydibenzofuran-containing structures 1–6. Representative bioactive structures containing benzofuro-fused pyridine analogues 7–9. Strategy for metal-free access to benzofuropyridine 13
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Published 30 Apr 2021

Metal-free glycosylation with glycosyl fluorides in liquid SO2

  • Krista Gulbe,
  • Jevgeņija Lugiņina,
  • Edijs Jansons,
  • Artis Kinens and
  • Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

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  • equilibrium. Keywords: fluorosulfite; glycosyl fluoride; Lewis acid; liquid sulfur dioxide; metal-free glycosylation; Introduction The glycosylation reaction is still one of the most important and basic synthetic strategies in carbohydrate chemistry that provides access to the various types of
  • not possess the participating group at C2 position, still react through the oxocarbenium ion intermediate. Conclusion In summary, novel sulfur dioxide-assisted and metal-free glycosylation conditions by employing a combination of glycosyl fluoride as the glycosyl donor and liquid SO2 as both solvent
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Published 29 Apr 2021

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

  • Dat Phuc Tran,
  • Yuki Sato,
  • Yuki Yamamoto,
  • Shin-ichi Kawaguchi,
  • Shintaro Kodama,
  • Akihiro Nomoto and
  • Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 866–872, doi:10.3762/bjoc.17.72

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  • derivatives having various substituents on the ethylene moiety. In particular, synthetic methods that do not use metal catalysts and reagents are expected to be very effective in manufacturing precision materials and pharmaceuticals [32][33][34][35][36][37]. To develop metal-free methods for the synthesis of
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Published 20 Apr 2021

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

  • Shivani Gulati,
  • Stephy Elza John and
  • Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

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Published 19 Apr 2021

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

  • Soumyaranjan Pati,
  • Renata G. Almeida,
  • Eufrânio N. da Silva Júnior and
  • Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

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  • , MG, Brazil 10.3762/bjoc.17.66 Abstract Desulfonylative alkylation of N-tosyl-1,2,3-triazoles under metal-free conditions leading to β-triazolylenones is reported here. The present study encompasses the synthesis of triazoles with a new substitution pattern in a single step from cyclic 1,3-dicarbonyl
  • -triazoles with alkynes and Rh catalysed N1 and N2 selective alkylations [24][25]. As for metal-free approaches, besides synthesizing N-alkylated triazoles via 1,3-dipolar cycloaddition of alkyl azide with enols generated from carbonyl compounds under transition metal-free conditions [26], a direct
  • functionalization of triazoles under metal-free conditions has been reported. These include the Broensted acid-catalysed N2 alkylation [27], organocatalytic N1 alkylation [28][29], N2-arylation using hypervalent iodine (Scheme 1c) [30], N2-alkylation involving radical intermediate [31], pyridine-N-oxide-mediated N1
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Published 31 Mar 2021

Valorisation of plastic waste via metal-catalysed depolymerisation

  • Francesca Liguori,
  • Carmen Moreno-Marrodán and
  • Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

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  • described in detail. Solvolytic depolymerisations can also be promoted by metal-free soluble acid or base catalysts. However, concentrated solutions, quasistoichiometric amounts or strong mineral acids (HNO3, H2SO4, H3PO4) or bases (NaOH, KOH, potassium butoxide) are often required, particularly for
  • [ZnCl3] (bmim = 1-butyl-3-methylimidazolium, Table 4, entry 2) [228] were recently studied, showing higher catalytic activity compared to metal-free ionic liquids (i.e., bmim chloride), the conventional catalysts (i.e., ZnCl2, Zn(OAc)2) or the analogous Mn, Co and Cu ionic liquids. Typically, 80–85% BHET
  • 3) [229]. Based on infrared studies, the higher catalytic activities of the metallated ILs was attributed to their higher Lewis acidity compared to both the metal-free catalysts and the metal salts. A mechanism was therefore proposed in which a synergistic effect of the metallated ILs takes place
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Published 02 Mar 2021

Metal-free visible-light-enabled vicinal trifluoromethyl dithiolation of unactivated alkenes

  • Xiaojuan Li,
  • Qiang Zhang,
  • Weigang Zhang,
  • Jinzhu Ma,
  • Yi Wang and
  • Yi Pan

Beilstein J. Org. Chem. 2021, 17, 551–557, doi:10.3762/bjoc.17.49

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  • successfully studied. However, the disproportionate dithiolation of alkenes is unknown. Herein, a transition-metal-free protocol is presented for the vicinal trifluoromethylthio–thiolation of unactivated alkenes via a radical process under mild conditions with a broad substrate scope and excellent tolerance
  • . Keywords: alkenes; difunctionalization; metal-free; photoredox; trifluoromethylthiolation; Introduction The incorporation of fluorine atoms into drug molecules will significantly enhance the physical, chemical, and biological properties of the pharmaceuticals [1][2][3][4][5][6]. Modifying drug candidates
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Published 24 Feb 2021

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

  • Geetanjali S. Sontakke,
  • Rahul K. Shukla and
  • Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

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  • -aminoquinoline motif are shown in Figure 1 [46][47]. As a result, a variety of transition metal-catalyzed C2-selective aminations of azine N-oxides were explored extensively [28][29][30][31][32][33][34]. Additionally, various transition metal-free C2-aminations of these scaffolds were also investigated [35][36
  • to amination and amidation, there are few reports on metal-free C2-heteroarylation of pyridine N-oxides. In 1984, Rogers demonstrated the synthesis of 2-triazolylpyridines from 2-azidopyridines and phenylacetylene [51]. Along the same lines, Keith reported methodologies for the C2-imidazolylation and
  • derivatives, we performed a sequential one-pot synthesis by combining a Cu(I)-catalyzed “Click” reaction of phenylacetylene (7) with TsN3 and a metal-free C2-heteroarylation of quinoline N-oxide (1a, Scheme 6b). Remarkably, the yield of the desired product 3a in the one-pot synthesis (80%) was comparable to
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Published 17 Feb 2021

1,2,3-Triazoles as leaving groups: SNAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

  • Dace Cīrule,
  • Irina Novosjolova,
  • Ērika Bizdēna and
  • Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

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  • ][45][46][47][48][49][50]. In the case of C-nucleophiles there are a few precedents of transition-metal-free substitution of chloro [51][52][53][54][55] or 1,2,4-triazolyl [56] moieties as leaving groups at the C6 position of purine. These transformations usually require prolonged time and elevated
  • its HSQC spectrum, in which a cross peak clearly indicated the C(2’’)–H system. Conclusion The SNAr reactivity of 2,6-bis(1,2,3-triazol-1-yl)purine derivatives was extended with their substitution with O- and C-nucleophiles. The reactions proceeded under transition metal free conditions and revealed
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Published 11 Feb 2021

CF3-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

  • Anthony J. Fernandes,
  • Armen Panossian,
  • Bastien Michelet,
  • Agnès Martin-Mingot,
  • Frédéric R. Leroux and
  • Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

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Published 03 Feb 2021

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

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  • 19, Kamala Nehru Nagar, Ghaziabad, UP-201002, India 10.3762/bjoc.16.259 Abstract A convenient practical approach for the synthesis of 2-(pyridin-2-yl)ethanols by direct benzylic addition of azaarenes and aldehydes under catalyst- and solvent-free conditions is reported. This reaction is metal-free
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Published 23 Dec 2020

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

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  • . Metal-free nucleophilic trifluoromethylselenolations have been then performed with this in situ-generated anion. Perfluoroalkylselenolations have also been described. Keywords: fluorine; nucleophilic substitution; perfluoroalkylselenolation; selenium; trifluoromethylselenolation; Introduction Because
  • reagent able to perform electrophilic, radical or nucleophilic reactions depending on the conditions. The iodide-mediated, metal-free method is complementary to the previous one using TDAE. Thus, the umpolung reactivity of trifluoromethylselenotoluenesulfonate can be performed under reductive or oxidative
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Published 10 Dec 2020

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

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  • Hisham Qrareya Lorenzo Meazza Stefano Protti Maurizio Fagnoni PhotoGreen Lab, Department of Chemistry, viale Taramelli 12, 27100 Pavia, Italy Industrial Chemistry Department, Arab American University, 240 Jenin 13, Zababdeh, Palestine 10.3762/bjoc.16.250 Abstract A metal-free route for the
  • . Keywords: aryl phosphates; biarenes; metal-free synthesis; photochemistry; photoextrusion; Introduction It is difficult to overestimate the importance of aromatics in drug development. Indeed, introducing an aromatic or a heteroaromatic ring, most often a (substituted) phenyl ring, into a biologically
  • nowadays a growing interest in the forging of Ar–Ar bonds under transition-metal-free conditions [24][25]. Apart the most common pathways, e.g., the Friedel–Crafts functionalization [26] or nucleophilic aromatic substitution [27], alternative approaches have emerged that make use of photogenerated
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Published 08 Dec 2020

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

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  • catalysis and photochemistry. Where transition metal catalysis provides one strategy for C–H bond activation, transition-metal-free photochemical C–H fluorination can provide a complementary selectivity via a radical mechanism that proceeds under milder conditions than thermal radical activation methods
  • visible-light-inactive molecules using PSCats 3.1 Benzylic C–H fluorination A seminal paper in the field of transition-metal-free direct C–H fluorination comes from Chen and co-workers, who applied aryl ketones as PSCats [135]. They discovered that the choice of the PS impacted the selective formation of
  • mono- vs difluorinated products at the benzylic position; 9-fluorenone affords benzylic monofluorination and xanthone affords benzylic difluorination (Scheme 5). Importantly, this metal-free direct C–H fluorination proceeded without the need for any specialized photochemical equipment; under visible
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Published 03 Sep 2020

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

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  • motifs were conveniently synthesized from readily available diphenylphosphine oxides and alkenyl aldehydes via a metal-free tandem phosphinoylation/cyclization protocol. The reaction utilizes K2S2O8 as oxidant and proceeds in DMSO/H2O at environmentally benign conditions with a broad substrate scope and
  • afforded the title compounds in moderate yields. Keywords: chroman-4-ones; diphenylphosphine oxide; metal-free; potassium persulfate; radical cyclization; Introduction The chroman-4-one framework is a privileged structural motif found in numerous natural products and pharmaceuticals with extraordinary
  • appropriate radical precursors through visible-light promoted systems [15][16], transition-metal-catalyzed systems [17][18], or transition-metal-free systems [19][20], have emerged as a powerful strategy for the synthesis of diversely functionalized chroman-4-one derivatives. Organophosphorus compounds are
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Published 12 Aug 2020

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

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Published 22 Jul 2020

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

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  • advantageous: being a one-pot reaction with metal-free reagent, having shorter reaction times, good yields and a very simple purification method. Moreover, using the density functional theory (DFT) method at the M06-2X/6-31+G(d,p) level of theory the mechanism of the cycloaddition reactions has been elucidated
  • using a safe, inexpensive, metal-free reagent, a simple purification method and shorter reaction times via a one-pot reaction. The study presents a useful method for one-pot conversion of epoxides to protected 1,2-diols and 2-amino alcohols in one reaction. In the computational part of the study, the
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Published 21 Jul 2020

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

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  • -metal-free strategy is presented to access novel β-carboline-tethered benzothiophenone derivatives from 1(3)-formyl-β-carbolines using elemental sulfur activated by Et3N/DMSO. This expeditious catalyst-free reaction proceeds through the formation of β-carboline-based 2-nitrochalcones followed by an
  • excellent light-emitting properties with quantum yields (ΦF) up to 47%. Keywords: benzothiophene; β-carboline; metal-free; photophysical properties; sulfur insertion; Introduction The pyrido[3,4-b]indole moiety, commonly referred as β-carboline, is the core unit of about one quarter of all natural
  • a one-pot metal-free approach for the first time. The transformation could be executed from β-carboline-based 2-nitrochalcones via a one-pot, two-step procedure starting from 1(3)-formyl-β-carbolines (a framework represented by alkaloid kumujian C). The combination of Et3N and DMSO played a vital
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Published 20 Jul 2020

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

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  • indole, indolone, or cinnoline derivatives from the same starting material is not yet available. To reach this goal, the Michael reaction between 1,4-diketones and primary amines seems particularly attractive because of its straightforward and metal-free properties, and because they can be performed
  • , the recovery of the proton catalyst, and atmospheric oxygen aromatization, leading to the indole 6 or the cinnoline 8. Conclusion In summary, we have successfully developed a straightforward and metal-free strategy for the synthesis of nitrogen-containing heterocyclic moieties of biological interest
  • ; indoles 6, indolones 7, and cinnolines 8, starting from common substrates 1,4-diketones 5 and primary amines. The protocols developed here used mild conditions, were functional-group tolerant, transition-metal-free, proceeded in moderate to good yield, and could therefore easily be used in medicinal
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Published 17 Jul 2020

Heterogeneous photocatalysis in flow chemical reactors

  • Christopher G. Thomson,
  • Ai-Lan Lee and
  • Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

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  • interest in g-C3N4 photocatalysts was generated in 2009 by Wang, Domen, and co-workers, who reported the metal-free photolysis of water was possible with the all-organic semiconductor material, a sacrificial electron donor, and visible light irradiation [120]. Prior to this report, poly(p-phenylene) had
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Published 26 Jun 2020

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

  • Alessandra Del Tito,
  • Havall Othman Abdulla,
  • Davide Ravelli,
  • Stefano Protti and
  • Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

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  • exploited for the construction of phenanthridine 6-carboxylates (Scheme 12). Notably, the process occurred in water under metal-free conditions in the presence of rose bengal (5 mol %) and made use of molecular oxygen as the terminal oxidant. Thus, N-biarylglycine esters 12.1a–d promoted the reductive
  • desired products 18.3a–d in good yields [91]. Notably, a metal-free version of this strategy, based on the use of the 1-chloroanthraquinone photoorganocatalyst, was likewise reported [92]. A dual-catalytic system, comprising of eosin Y sodium salt (1 mol %) as photoredox catalyst and the thermal catalyst
  • opportunity on the route towards metal-free protocols for the synthesis of the phenanthrene and phenanthridine cores, a topic of current interest also in related thermal methods [94][95]. Bioactive phenanthridine and phenanthridinium derivatives. Carbon-centered and nitrogen-centered radicals used for the
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Published 25 Jun 2020
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