Search results

Search for "TEMPO" in Full Text gives 174 result(s) in Beilstein Journal of Organic Chemistry.

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

  • Laura Holzhauer,
  • Chloé Liagre,
  • Olaf Fuhr,
  • Nicole Jung and
  • Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

Graphical Abstract
  • -diisopropylethylamine; OLED, organic-light emitting diode; SCE, saturated calomel electrode; TADF, thermally activated delayed fluorescence; TEMPO, 2,2,6,6-tetramethylpiperidinyloxyl; TIQ, triazoloimidazoquinoxaline. UV–vis absorption spectra of the obtained metal complexes (18 µM solutions) in acetonitrile at 20 °C
PDF
Album
Supp Info
Full Research Paper
Published 24 Aug 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

Graphical Abstract
  • performed radical trapping experiments using TEMPO and BHT in the reaction of substrate 1c (Figure 5a). Under the standard reaction conditions in the presence of TEMPO or BHT, the expected product 2c was formed in 66 and 72% yields. These results indicate that a radical pathway may not be involved in the
PDF
Album
Supp Info
Full Research Paper
Published 01 Jun 2022

Earth-abundant 3d transition metals on the rise in catalysis

  • Nikolaos Kaplaneris and
  • Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

Graphical Abstract
  • allow for indirected C–H transformations and herein, homolytic C–H cleavages are described for transformative manganese-catalyzed brominations of tertiary C–H bonds [14]. Finally, electrooxidation enabled the site-selective alkynylation of tetrahydroisoquinolines within a TEMPO/copper regime [15]. As
PDF
Editorial
Published 07 Jan 2022

DABCO-promoted photocatalytic C–H functionalization of aldehydes

  • Bruno Maia da Silva Santos,
  • Mariana dos Santos Dupim,
  • Cauê Paula de Souza,
  • Thiago Messias Cardozo and
  • Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

Graphical Abstract
  • could also be arylated using the same protocol (18, 34%). Mechanistic investigations were conducted to support the proposed HAT mechanism by DABCO. Radical trapping with TEMPO completely shuts down product formation, proving a radical mechanism is operating. Moreover, an acyl-TEMPO adduct was formed and
  • amines (Table 1, entries 9 and 10 and Supporting Information File 1, Scheme S2). Radical trapping experiments with TEMPO also showed a radical path mechanism, and the acyl radical was detected as an intermediate (Supporting Information File 1, Table S4). The absence of product formation in the Giese
PDF
Album
Supp Info
Letter
Published 21 Dec 2021

Iron-catalyzed domino coupling reactions of π-systems

  • Austin Pounder and
  • William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Graphical Abstract
  • -rich phenols, as well as those bearing halogen substituents, were suitable substrates under these reaction conditions. In Lei’s report, the reaction shuts down in the presence of TEMPO and in the absence of DDQ; thus, the formation of a phenoxy radical was proposed. In 2018, Zhong and co-workers
PDF
Album
Review
Published 07 Dec 2021

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

  • Chuanhua Qu,
  • Run Huang,
  • Yong Li,
  • Tong Liu,
  • Yuan Chen and
  • Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

Graphical Abstract
  • of the radical inhibitor 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was subjected to the model reaction system, however, the reaction was not inhibited (Scheme 6B). This result suggests that no radical pathway is involved in this transformation. Based on the above experiments, a proposed mechanism
PDF
Album
Supp Info
Full Research Paper
Published 02 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

Graphical Abstract
  • nitrate (CAN) [41], 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO)/CuCl [51], K2S2O8 [36], dimethyl sulfoxide (DMSO)/O2 [52], PhI(OAc)2/benzoyl peroxide (BPO) [47], Dess-Martin periodinane, N-bromosuccinimide (NBS), N-hydroxyphthalimide (NHPI)/Co(OAc)2/O2 [53], H2O2/tetrabutylammonium iodide (TBAI) [43], CBr4
  • cyclization was explored. As a radical mechanism appeared very likely, the standard reaction with aqueous TBHP was run in the presence of the radical quenchers TEMPO and BHT (4 equivalents respectively) in separate experiments. While trapping a radical species of interest in form of a TEMPO ester was
PDF
Album
Supp Info
Correction
Full Research Paper
Published 02 Nov 2021

Electrocatalytic C(sp3)–H/C(sp)–H cross-coupling in continuous flow through TEMPO/copper relay catalysis

  • Bin Guo and
  • Hai-Chao Xu

Beilstein J. Org. Chem. 2021, 17, 2650–2656, doi:10.3762/bjoc.17.178

Graphical Abstract
  • terminal alkynes has been achieved in a continuous-flow microreactor through 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)/copper relay catalysis. The reaction is easily scalable and requires low concentration of supporting electrolyte and no external chemical oxidants or ligands, providing straightforward
  • electrochemistry is an ideal tool for promoting dehydrogenative cross-coupling reactions as no external chemical oxidants are needed [11][12][13][14][15][16][17][18][19]. In this context, Mei and co-workers have reported an elegant TEMPO/[L*Cu] co-catalyzed asymmetric electrochemical dehydrogenative cross-coupling
  • electrocatalytic dehydrogenative cross-coupling reaction of tetrahydroisoquinolines with terminal alkynes in continuous flow (Scheme 1D). These reactions require low loadings of supporting electrolyte and proceed through Cu/TEMPO relay catalysis without need for additional ligands. Results and Discussion The
PDF
Album
Supp Info
Letter
Published 28 Oct 2021

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

  • Yi Liu,
  • Puying Luo,
  • Yang Fu,
  • Tianxin Hao,
  • Xuan Liu,
  • Qiuping Ding and
  • Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

Graphical Abstract
  • amines were reacted well, while amines substituted with strongly electron-withdrawing (such as nitro and trifluoromethyl) groups, heteroaryl amines, and aliphatic amines were not compatible. Control experiments showed that the addition of 2.0 equiv of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) under
  • standard conditions could inhibit the formation of target product. In contrast, the compound TEMPO–N3 was detected by GC–MS analysis. Based on the radical trapping experiment and previous reports, the reaction may undergo a radical process. 2-Carbonylpyrrole is a key subunit of many bioactive natural
PDF
Album
Review
Published 22 Sep 2021

Strategies for the synthesis of brevipolides

  • Yudhi D. Kurniawan and
  • A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

Graphical Abstract
  • subsequent oxidation of the primary alcohol with the TEMPO/BAIB system facilitated the formation of pyrone 107. Initially, Sabitha and Raju intended to synthesize brevipolides K and L by esterification of this furanyl alcohol 107 with (Z)-4-OMe- and (Z)-4-OPMB-cinnamic acid 118 and 119, respectively
PDF
Album
Review
Published 14 Sep 2021

Development of N-F fluorinating agents and their fluorinations: Historical perspective

  • Teruo Umemoto,
  • Yuhao Yang and
  • Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Graphical Abstract
PDF
Album
Review
Published 27 Jul 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

Graphical Abstract
  • inhibition of the catalytic cycle upon the addition of TEMPO revealed that the reaction proceeds through radical intermediates. Next, we carried out UV–vis monitoring experiments in order to verify whether the interaction with the substituted benzyl alcohols and CeIV could lead to a ligand-to-metal charge
PDF
Album
Supp Info
Letter
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

Graphical Abstract
  • -membered sulfur-containing cycle (Scheme 23) [52]. Some reactions were performed to screen the reaction mechanism in detail. To find out if the reaction proceeds through a radical pathway, tetramethylpiperidine-1-oxyl (TEMPO) was added to the reaction. The corresponding product was obtained in high yield
PDF
Album
Review
Published 13 Jul 2021

Double-headed nucleosides: Synthesis and applications

  • Vineet Verma,
  • Jyotirmoy Maity,
  • Vipin K. Maikhuri,
  • Ritika Sharma,
  • Himal K. Ganguly and
  • Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

Graphical Abstract
  • ′-carboxylic acids 65a–c which in turn were prepared through the (2,2,6,6-tetramethylpiperidin-1-oxyl) (TEMPO) and 1,1-bis(acetoxy)iodobenzene (BAIB)-assisted oxidation of the 5′-hydroxymethylene group in adenosine/uridine by following the methodology developed by Epp and Widlanski [53]. The nucleoside-5
PDF
Album
Review
Published 08 Jun 2021

Icilio Guareschi and his amazing “1897 reaction”

  • Gian Cesare Tron,
  • Alberto Minassi,
  • Giovanni Sorba,
  • Mara Fausone and
  • Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

Graphical Abstract
  • posthumously in 1919 [35]. In 1894, Guareschi reported the first high-yield synthesis and the structure elucidation of triacetonamine (6, Scheme 3) [35][36][37], the sterically hindered amine that is the starting material for the synthesis of the popular oxidant TEMPO [38]. Triacetonamine had first been
  • observation was that the presence of radical traps, such as 4-hydroxy-substituted TEMPO, was detrimental for the reaction, which evidently involved free radicals. Anaerobic conditions (degassing with argon) inhibited the reaction, which could be restarted when oxygen was bubbled into the solution. This
PDF
Album
Supp Info
Review
Published 25 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

Graphical Abstract
PDF
Album
Review
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

Graphical Abstract
  • acrylamide 7a (Scheme 7a). When the reaction was conducted in the presence of the radical scavenger 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO), both the desired product 8a and the byproduct 15 were not observed, which indicated that the reaction proceeds through a radical pathway (Scheme 7b). It is worth
PDF
Album
Supp Info
Full Research Paper
Published 17 May 2021

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

  • Mikhail K. Klychnikov,
  • Radek Pohl,
  • Ivana Císařová and
  • Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

Graphical Abstract
  • , 12843 Prague 2, Czech Republic 10.3762/bjoc.17.58 Abstract Pyrrolidones are common heterocyclic fragments in various biologically active compounds. Here, a two-step radical-based approach to γ-lactams bearing three to four stereocenters starting from epoxides, N-allylic silylacetamides and TEMPO is
  • access to complex target molecules [74][75]. The principle is illustrated for a merger of nucleophilic opening of allylepoxides 1 with silylacetamides 2/Brook rearrangement [76][77][78] and oxygenation with TEMPO (3) leading to γ-(silyloxy)-α-(aminoxy)amides 5, which can be subsequently subjected to
  • hexafluorophosphate (4) and TEMPO (3) were subsequently added to trigger the single electron oxidation of the formed amide enolates and radical oxygenation affording α-(aminoxy)amides 9a–n in good 51–77% isolated yields. Cyclic units in the allylic N-substituent (Table 2, entries 14 and 15) and the epoxide (Table 2
PDF
Album
Supp Info
Full Research Paper
Published 09 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

Graphical Abstract
  • (Scheme 4). The radical-trapping agent 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO, 3.0 equiv) completely prevented the reaction. When diphenylethylene (3.0 equiv) was added to the reaction mixture, the desired product 5h was not obtained, and the vinyltrifluoromethylsulfide 7 was afforded in 12% yield [46
PDF
Album
Supp Info
Full Research Paper
Published 24 Feb 2021

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

  • Kenji Morokuma,
  • Shuntaro Tsukamoto,
  • Kyosuke Mori,
  • Kei Miyako,
  • Ryuichi Sakai,
  • Raku Irie and
  • Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

Graphical Abstract
  • (rac)-16 (87% yield), followed by alkaline methanolysis (74% yield) [17] and Pinnick oxidation (43% yield) [18][19][20], delivered carboxylic acid (rac)-19. Unfortunately, an attempt to improve the oxidation yield was not fruitful; the oxidation of aldehyde (rac)-18 with TEMPO [21] resulted in a lower
PDF
Album
Supp Info
Full Research Paper
Published 24 Feb 2021

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

  • Yajing Zhang,
  • Qingshan Tian,
  • Guozhu Zhang and
  • Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

Graphical Abstract
  • extremely low yield. Another H-phosphonate, namely dimethyl phosphite, was a suitable substrate for this transformation and provided the products 3 in good yield (Scheme 3). The well-known radical-trapping reagent 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) was used to gain an insight into the reaction
  • mechanism. As illustrated in Scheme 4, the addition of 1 equiv TEMPO suppressed the reaction. In addition, 4-ethynylaniline (1f) reacted with Selectfluor® and dimethyl phosphite under the optimized conditions to afford the expected product in 13% yield, and no competitive electrophilic compound 4f was
PDF
Album
Supp Info
Full Research Paper
Published 18 Dec 2020

Controlled decomposition of SF6 by electrochemical reduction

  • Sébastien Bouvet,
  • Bruce Pégot,
  • Stéphane Sengmany,
  • Erwan Le Gall,
  • Eric Léonel,
  • Anne-Marie Goncalves and
  • Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

Graphical Abstract
  • ]. The modern and green photoredox catalytic activation of SF6 was recently performed for the fluoro- and alkoxypentafluorosulfanylation of styrenes [21][22]. The same type of transformation was also described through the reductive activation of sulfur hexafluoride with TEMPO [23]. To the best of our
PDF
Album
Full Research Paper
Published 01 Dec 2020

Recent developments in enantioselective photocatalysis

  • Callum Prentice,
  • James Morrisson,
  • Andrew D. Smith and
  • Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Graphical Abstract
  • enantioenriched tetrahydrofuran 256 in excellent yields and moderate enantioselectivities (14 examples, up to 82:18 er). Knowles et al. synthesised enantioenriched pyrroloindolines 257 from indoles 258 and TEMPO using an iridium-based photocatalyst and a similar chiral phosphate base 259 to that employed by Luo
  • coupling with TEMPO gives catalyst-bound iminium ion 261, which then cyclises with the nearby amine to produce the desired product 257 in good yields and enantioselectivities (9 examples, up to 97:3 er). Nicewicz et al. developed an enantioselective radical cation Diels–Alder reaction in both an
PDF
Album
Review
Published 29 Sep 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

Graphical Abstract
PDF
Album
Review
Published 03 Sep 2020

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

  • Mysore Bhyrappa Harisha,
  • Pandi Dhanalakshmi,
  • Rajendran Suresh,
  • Raju Ranjith Kumar and
  • Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

Graphical Abstract
  • , the reaction of 1m with potassium thiocyanate 2 under the optimal conditions in the presence of TEMPO furnished azirine and TEMPO, while the same reaction in the presence of BHT afforded the BHT-coupled thiocyanate product (SO-(2,6-di-tert-butyl-4-methylphenyl) (thioperoxocyanate)). These observations
PDF
Album
Supp Info
Full Research Paper
Published 31 Aug 2020
Other Beilstein-Institut Open Science Activities