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Search for "metal free" in Full Text gives 289 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

  • Ashish Kumar Mazumdar,
  • Gyana Prakash Nanda,
  • Nisha Yadav,
  • Upasana Deori,
  • Upasha Acharyya,
  • Bahadur Sk and
  • Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

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  • Ashish Kumar Mazumdar Gyana Prakash Nanda Nisha Yadav Upasana Deori Upasha Acharyya Bahadur Sk Pachaiyappan Rajamalli Materials Research Centre, Indian Institute of Science, C. V. Raman Road, Bangalore, Karnataka, 560012, India 10.3762/bjoc.18.122 Abstract Metal-free organic emitters with
  • as well as the relevance for fluorescence-based acid–base sensing. Keywords: intramolecular charge transfer; molecular aggregates; sensing; thermally activated delayed fluorescence (TADF); Introduction Metal-free organic solid-state emitters have gained increasing interest in recent years due to
  • base fumes, etc. [10][11]. However, the fluorescence quantum yield of such emitters in the solid state is relatively low due to the aggregation-caused quenching (ACQ) effect [12][13][14] and limits practical applications. Hence, metal-free emitters with high photoluminescence quantum yield (PLQY) in
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Published 08 Sep 2022

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

  • Yara Cristina Marchioro Barbosa,
  • Guilherme Caneppele Paveglio,
  • Claudio Martin Pereira de Pereira,
  • Sidnei Moura,
  • Cristiane Storck Schwalm,
  • Gleison Antonio Casagrande and
  • Lucas Pizzuti

Beilstein J. Org. Chem. 2022, 18, 1079–1087, doi:10.3762/bjoc.18.110

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  • de Caxias do Sul, 95070-560, Caxias do Sul-RS, Brazil 10.3762/bjoc.18.110 Abstract The broad application of 1H-indazoles has prompted the development of several approaches for the synthesis of such compounds, including metal-free, palladium-, or copper-promoted intramolecular N-arylation of in situ
  • reaction of hydrazones and p-benzoquinones [16], and Co3+/Cu2+-catalyzed C−N/N−N coupling of imidates with anthranils as both aminating reagents and organic oxidants [17]. Additional established routes to 1H-indazoles comprise transition metal‐catalyzed [18][19][20] and metal-free [21][22] intramolecular
  • ‐substituents, and others suffer from poor regioselectivity for substrates without a directing group [18][19][21][22]. On the other hand, methods based on metal-free [23], palladium- [24][25], and copper-promoted [26][27][28][29][30][31] intramolecular N-arylation of in situ-generated or isolated o
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Published 23 Aug 2022

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

  • Dharmendra Das,
  • Akhil A. Bhosle,
  • Amrita Chatterjee and
  • Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

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  • dihalogenations. As known, the decarboxylation (or desulfonation) was observed in the case of salicylic acids and anthranilic acids (or sulfanilic acids) leading to 2,4,6-trihalogenated products when 3 equiv of NXS was used. Simple instrumentation, metal-free approach, cost-effectiveness, atom economy, short
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Published 09 Aug 2022

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

  • Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

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  • (Scheme 5) [25]. The metal-free intramolecular oxidative C–H bond amidation of methyl and ethyl 2,6-dimethylphenylphosphonamidates 24, 26, and 28 is an interesting strategy for the synthesis of 1-methoxy/ethoxy-7-methyl-2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxide derivatives 25, 27, and 29 in
  • -arylmethylidene-2,3-dihydrobenzo[c][1,2]azaphosphole 1-oxides via the TBAF-mediated cyclization of N-alkyl-P-(2-ethynylaryl)-P-phenylphosphinamides. Synthesis of 2-hydrobenzo[c][1,2]azaphosphol-3-one 1-oxides via the metal-free intramolecular oxidative C–H bond formation of alkyl 6-substituted 2
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Published 22 Jul 2022

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

  • Sadanobu Iwase,
  • Shinsuke Inagi and
  • Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

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  • , these methods require various metal and organometallic reagents. On the other hand, electrochemical organic synthesis is a metal-free process and does not require any hazardous reagents and it produces less waste than conventional chemical syntheses. Therefore, electrochemical synthesis is desirable
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Published 20 Jul 2022

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

  • Durbis J. Castillo-Pazos,
  • Juan D. Lasso and
  • Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

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  • synthetic chemistry, we report the synthesis of a series of bench-stable α-(perfluoroalkylsulfonyl)propiophenones. Their application as photocleavable reagents was tested with electron-rich aromatics under metal-free, redox- and pH-neutral conditions to enable late-stage perfluorooctylation
  • , the expansion of our previously reported propiophenone family of reagents was envisioned as suitable alternative to produce a bench stable, organic soluble, and iodine-free perfluroalkylation source. In 2017, our group developed a metal-free and redox-neutral protocol for the photoinduced alkylation
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Published 04 Jul 2022

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

  • Conrad Kuhwald,
  • Sibel Türkhan and
  • Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

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  • inductive heating technology has also been used in multistep processes targeting drugs or important molecules in the fragrance industry. The first example deals with a metal-free carbon–carbon-bond formation process between tosylhydrazones generated from the corresponding aldehydes 74 and boronic acids 76
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Published 20 Jun 2022

DDQ in mechanochemical C–N coupling reactions

  • Shyamal Kanti Bera,
  • Rosalin Bhanja and
  • Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

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  • green and eco-friendly methodology due to its solvent-free and metal-free nature. So, it can also be regarded as an alternative pathway to the traditional solution-based protocols. We anticipate that our developed strategy will have a substantial impact on the field of organic synthesis. Our work on
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Published 01 Jun 2022

BINOL as a chiral element in mechanically interlocked molecules

  • Matthias Krajnc and
  • Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

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  • spectrum of (R)-10 shows intense signals at 321 and 344 nm, which were assigned to the diyne thread located inside the chiral environment of the BINOL-based macrocycle (see Figure 3). An example of a metal-free template approach for the synthesis of a BINOL-based [2]rotaxane was reported by Stoddart and co
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Published 06 May 2022

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

  • Sayan Pramanik and
  • Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

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  • and operational simplicity through one pot reaction. Keywords: chemoselective conjugate reduction; dispirocyclopentanebisoxindole scaffolds; metal-free; one-pot operation; reductive cyclization; Introduction There is a vast demand of the structurally complex spirooxindole scaffold which is an
  • important functional group transformation for the synthesis of heterocyclic and carbocyclic building blocks and reactive intermediates. Besides the use of various reducing agents, it is observed that tosylhydrazine develops the transition-metal-free and highly chemoselective conjugate reduction of α,β
  • dimerization produces dispirocyclopentanebisoxindoles in a transition-metal-free protocol (Scheme 1). Results and Discussion There is extensive application of 3-phenacylideneoxindoles generating diverse reaction strategies following the regioselective and diastereoselective synthesis of carbocyclic and
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Published 27 Apr 2022

Menadione: a platform and a target to valuable compounds synthesis

  • Acácio S. de Souza,
  • Ruan Carlos B. Ribeiro,
  • Dora C. S. Costa,
  • Fernanda P. Pauli,
  • David R. Pinho,
  • Matheus G. de Moraes,
  • Fernando de C. da Silva,
  • Luana da S. M. Forezi and
  • Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

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Published 11 Apr 2022

Regioselectivity of the SEAr-based cyclizations and SEAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

  • Jonali Das and
  • Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

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  • generated via 1,6-hydride shift in both I and II. Finally, an intramolecular Mannich-type cyclization then furnishes products 27. The cascade protocol enjoys several advantageous synthetic features, including high step- and atom-economy, transition-metal-free and room temperature conditions. In all cases
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Published 08 Mar 2022

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

  • José G. Hernández,
  • Karen J. Ardila-Fierro,
  • Dajana Barišić and
  • Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

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  • . To assist the metal-free amidation of the aromatic C–H bond in 5, we repeated the milling experiment at 40 °C using a heat gun to increase the temperature of the milling jar (see Supporting Information File 1, Figure S2) [42], which gave a mixture of 5 and 6 (ratio 85:15). The same experiment at 60
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Published 07 Feb 2022

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

  • Irina Kuznetcova,
  • Felix Bacher,
  • Daniel Vegh,
  • Hsiang-Yu Chuang and
  • Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

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  • copper(II) complexes prepared revealed an enhanced aqueous solubility and bioavailability indeed, along with very high cytotoxicity [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Moreover, the metal-free ligands and copper(II) complexes derived from backbone D revealed cytotoxicity in the
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Published 26 Jan 2022

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

  • Yuki Yamamoto,
  • Akihiro Tabuchi,
  • Kazumi Hosono,
  • Takanori Ochi,
  • Kento Yamazaki,
  • Shintaro Kodama,
  • Akihiro Nomoto and
  • Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

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  • facilitate the industrial use of α-bromolactones as important intermediates. Keywords: α-bromolactone; metal-free; one-pot operation; tetraalkylammonium hydroxide; two-phase system; Introduction Lactones are important heterocycles in the organic chemistry, materials science, and medicinal chemistry fields
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Published 09 Dec 2021

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

  • Ilya A. P. Jourjine,
  • Lukas Zeisel,
  • Jürgen Krauß and
  • Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

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  • group (Scheme 2) [33]. In contrast to transition-metal-mediated approaches [27], metal-free oxidative methods are attractive not only from an ecological point of view, but also due to the typically low cost of the applied oxidants. Biarylcarboxaldehydes were cyclized to fluorenones using K2S2O8 [34
  • cyclic lactones [69]. The intramolecular cyclization of the acyl radical A gives the tricyclic radical species C, which then forms fluorenone (3) after abstraction of a hydrogen radical by an additional equivalent of the tert-butoxy radical. Conclusion In summary, we have demonstrated that the metal-free
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Published 02 Nov 2021

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

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  • metal-free small organic molecules as catalysts has been a landmark advancement in organic synthesis in the recent past [16]. MacMillan and co-workers for the first time in the year 2000 termed these catalysts as ‘Organocatalysts’ [17]. It was followed by intense activity and phenomenal rise in the
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Published 18 Oct 2021

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

  • Songeziwe Ntsimango,
  • Kennedy J. Ngwira,
  • Moira L. Bode and
  • Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

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  • , such as ionic liquid- and transition metal-catalyzed and other metal-free transformations [1]. A strategically diverse route to phenanthridines involves intramolecular cyclization of biaryl oximes, allowing for the formation of a new C–N bond. Such a strategy was explored by Deb and Yoshikai in the Fe
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Published 08 Sep 2021

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

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  • Pieterjan Winant Wim Dehaen Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium 10.3762/bjoc.17.149 Abstract A metal-free protocol for the direct bis-arylation of 2,5-dichlorobenzoquinone with aryldiazonium salts is reported. The reactive
  • issues [38][39]. Since bis-arylated quinones are promising substrates in a range of different applications (vide infra), a simple and effective method of synthesizing these types of compounds would be of great use. Motivated by the results of König et al., we set out to develop a metal-free strategy
  • developed a straightforward metal-free procedure for the synthesis of bis-arylated 2,5-dichlorobenzoquinones. The reaction is tolerant towards a wide range of functional groups, occurs under mild conditions in an environmentally benign solvent and does not require further purification of the reaction
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Published 06 Sep 2021

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

  • Tülay Yıldız,
  • İrem Baştaş and
  • Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

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  • ]. Therefore, there has been an increase in arylation methods using Friedel–Crafts alkylation (FCA) protocols without transition metals [35][36]. Environmentally friendly methods, in which metal-free catalysts are used, have come to the fore and are gaining importance because there are many disadvantages of
  • conversions can occur. Conclusion In this study, a novel transition metal-free FCA method for the synthesis of 9-methyl-9-arylxanthenes has been developed. For this method, starting compounds with alkene structures suitable for our targets were synthesized. Among the synthesis methods of xanthene derivatives
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Published 30 Aug 2021

Chemical syntheses and salient features of azulene-containing homo- and copolymers

  • Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

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  • and larger cathodic shift of the oxidation potential in these polymers compared to their metal-free counterparts. In 2012, Hawker and co-workers [22], along with 17–20, also synthesized a polymer 45 which had azulene and thiophene units connected via the 4,7-positions of azulene. The reaction of 4,7
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Published 24 Aug 2021

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

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  • thermal conditions. Significant advances were made for the oxidation of benzylic alcohols by using metal-based photocatalysts [38][39][40][41][42][43][44][45][46] and metal-free photocatalysis [47][48][49][50][51][52][53] in combination with various oxidants, such as TBHP and DDQ [54][55]. However, the
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Published 23 Jul 2021

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

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  • preparation of 1,4,5-trisubstituted 1,2,3-triazoles have gained much attention in triazole chemistry. Generally, two protocols for the synthesis of this type of triazole derivatives could be mentioned (metal or metal-free catalysis). Contrary to sporadic attempts [34], there is no detailed, systematic, and
  • current review considers the synthesis of diverse 1,4,5-trisubstituted 1,2,3-triazoles via metal- and metal-free catalytic routes. Synthesis and mechanism aspects of this category of fully functionalized triazoles are reported in detail in the current review article. We believe a precise and systematic
  • procedures for the efficient preparation of these significant products is highly required. Review Metal-free synthesis of fully decorated triazoles Developing metal-free protocols for the synthesis of triazole derivatives has been considered as growingly attractive yet challenging objectives in the
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Published 13 Jul 2021

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

  • Thiago S. Silva and
  • Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

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  • radicals via hydrogen atom transfer reactions. In 2018, the Renaud group proposed an elegant solution to circumvent this problem by employing 4-tert-butylcatechol (TBC) as an external hydrogen atom source to regenerate the starting material under transition-metal-free conditions [118]. Employing α-EWG
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Published 07 Jul 2021

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

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  • the literature, there is only a limited number of direct synthetic procedures to prepare γ-carbolines till date [28], and this gives a cutting edge advantage to our new protocol wherein a solvent and metal-free direct access to the γ-carboline core from substituted indole-2-aldehyes and glycine ester
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Published 17 Jun 2021
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