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Search for "key intermediate" in Full Text gives 260 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Oxidative and reductive cyclization in stiff dithienylethenes

  • Michael Kleinwächter,
  • Ellen Teichmann,
  • Lutz Grubert,
  • Martin Herder and
  • Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

Graphical Abstract
  • ][47] as the key intermediate undergoing thermal cyclization or cycloreversion, typically in the context of so-called “ECE” and “EEC” mechanisms, respectively [48]. To contribute to this discussion, nonsymmetrical DAEs bearing two electronically distinct aryl moieties (CF3- and Me-thiazole) [5] or
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Published 09 Nov 2018

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

  • Takashi Go,
  • Akane Morimatsu,
  • Hiroaki Wasada,
  • Genzoh Tanabe,
  • Osamu Muraoka,
  • Yoshiharu Sawada and
  • Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

Graphical Abstract
  • key intermediate 15, of which the sulfanyl group would intramolecularly migrate to produce 16 stereoselectively (path c, not d). The hydrolysis of 16 using TBAH yields diol 17. We further confirmed the mechanism of the 1,7-S shift reaction by performing density functional theory (DFT)-based
  • calculations (Table 2) [36]. Whether the reactions lead to the formation of pyrroloazepines or diols clearly depends on the substituents in the alkenyl group. We performed DFT calculations for the reaction pathways starting from the key intermediate 14 bearing methyl and phenyl groups. The DFT-calculated ΔG
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Published 29 Oct 2018

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

  • Luce Mattio,
  • Loana Musso,
  • Leonardo Scaglioni,
  • Andrea Pinto,
  • Piera Anna Martino and
  • Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

Graphical Abstract
  • key intermediate 13 removing the p-methoxybenzyl group [24][26][27][28] from 11 failed. Finally, compound 13 was successfully obtained by modifying the sequence of reactions. Deprotection of compound 10 with TFA [24], followed by selective alkylation with benzyl tosylate as previously described
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Published 24 Sep 2018

A novel and practical asymmetric synthesis of eptazocine hydrobromide

  • Ruipeng Li,
  • Zhenren Liu,
  • Liang Chen,
  • Jing Pan,
  • Kuaile Lin and
  • Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

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  • ][12][13]. In our prior publication [14], this method was selected as the technology for the development of a process to prepare (R)-(+)-1-(5’-bromopentyl)-1-methyl-7-methoxy-2-tetralone, a key intermediate of dezocine, and N-(p-trifluoromethylbenzyl)cinchonidinium bromide (3) among 17 cinchona
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Published 06 Sep 2018

Studies towards the synthesis of hyperireflexolide A

  • G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

Graphical Abstract
  • cyclopentane 5, a functionalized key intermediate, is presented. Compound 5 is involved in hydrolysis, α-allylation at C-8 and α-methylation at C-10 stereoselectively from the convex face. Then it is subjected to cross metathesis to give α,β-unsaturated ketone 11 as precursor in the total synthesis of
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Published 13 Aug 2018

A switchable [2]rotaxane with two active alkenyl groups

  • Xiu-Li Zheng,
  • Rong-Rong Tao,
  • Rui-Rui Gu,
  • Wen-Zhi Wang and
  • Da-Hui Qu

Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181

Graphical Abstract
  • [36] were synthesized according to the previous literature. The key intermediate compound 5, containing a prior DBA recognition station and possessing alkynyl and ethylenic groups at two terminals respectively, was prepared from aldehyde 1 and amine 2. A “Schiff base” reaction was introduced at first
  • alcohol with saturated NH4PF6 solution to obtain compound 5. For another key intermediate 8, containing an amide site for stabilizing the DB24C8 macrocycle, a 1,2,3-tris(dodecyloxy) benzene group as a stopper and an azide group which is used for the reaction with other moieties, was prepared through the
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Published 08 Aug 2018

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

  • Michael K. Bogdos,
  • Emmanuel Pinard and
  • John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

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  • the sulfonamidation of other heterocycles and was not successful. The authors attribute this lack of reactivity to the limited oxidising power of the excited acridinium salts and to the relative instability of the heterocyclic radical cation, which is a key intermediate in the proposed mechanism
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Published 03 Aug 2018

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

  • Fateh V. Singh,
  • Priyanka B. Kole,
  • Saeesh R. Mangaonkar and
  • Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

Graphical Abstract
  • using PIDA (15) at 4 °C (Scheme 41). This oxidative cyclization of enamide substrate 113 afforded synthetically useful spiroenamide 114, which was used as key intermediate for total synthesis of annosqualine (1). The synthesis of natural product 1 was achieved in two steps starting from synthesized
  • compound 136 was achieved in 87% yield by the reaction of PIDA (15) with the naphthol derivative 135 in trifluoroethanol at room temperature. Additionally, synthesized compound 136 was used as key intermediate in the total synthesis of natural products 137 and 138 (Scheme 50). Additionally, more analogues
  • -mediated radical cyclization wherein the oxazaspiroketal moiety is formed which is further used as key intermediate for the synthesis of the natural product cephalostatin. Additionally, spiroketals 159 were also synthesised by enatioselective spirocyclization of ortho-substituted phenols 158 using similar
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Published 17 Jul 2018

β-Hydroxy sulfides and their syntheses

  • Mokgethwa B. Marakalala,
  • Edwin M. Mmutlane and
  • Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

Graphical Abstract
  • notable synthesis of leukotriene C-1 (119), Corey and co-workers synthesized (−)-methyl trans-5(S),6(S)-oxido-7,9-trans-11,14-cis-eicosatetraenoate leukotriene A methyl ester (120), the key intermediate in its synthesis and biosynthesis, starting from the 2,3,5-tribenzoyl derivative of D-(−)-ribose [82
  • mixture of potassium carbonate and potassium bicarbonate in 95:5 water–methanol at 23 °C for 12 h proceeded quantitatively to afford the product leukotriene C-1 (Scheme 42). The epoxide 120 has been the key intermediate in all syntheses of LTC4, -D4, and -E4; upon exposure to the desired amino acid, it
  • the N-Boc protected β-hydroxy sulfide 130 as a key intermediate. Deprotection of the Boc followed by the imidation of the free amine with protected dipeptides that mimic Leu-Val produced the inhibitors of human renin 131 as depicted in Scheme 44. Yoshioka and co-workers reported two synthetic routes
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Published 05 Jul 2018

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

  • Ruipeng Li,
  • Zhenren Liu,
  • Liang Chen,
  • Jing Pan and
  • Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

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  • 10.3762/bjoc.14.119 Abstract In order to prepare asymmetrically (R)-(+)-1-(5-bromopentyl)-1-methyl-7-methoxy-2-tetralone (3a), a key intermediate of dezocine, 17 cinchona alkaloid-derived catalysts were prepared and screened for the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone with 1,5
  • key intermediate of dezocine, in the catalysis of the quaternary ammonium benzyl bromides from cinchonidine was investigated and the best catalyst (C7) was identified. In addition, the preparation of 3a with the optimized conditions was performed and the product was isolated in 77.8% yield with an
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Published 11 Jun 2018

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

  • Veronika Hladíková,
  • Jiří Váňa and
  • Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

Graphical Abstract
  • reaction pathway to proceed via the corresponding N-phenylnitrilimine. The yields (Table 3) are generally lower than those of reactions performed under thermal conditions – most probably due to the lower stability of the key intermediate – N-phenylnitrilimine – which can undergo dimerization or reverse
  • -oxohexanoic acid with 4-fluoro-3-(4-methylphenyl)sydnone (Scheme 12). Unfortunately the regioselectivity of the reaction was not specified. An aryne generation (Scheme 13) was also used for the synthesis of a key intermediate of the potent antitumor PARP inhibitor – niraparib – containing an indazole core
  • -disubstituted pyrazoles. Unsuccessful reaction with phenylpropiolic acid. Synthetic strategy leading to 1,4,5-trisubstituted pyrazoles. Reaction of sydnones carrying in position 4- six-membered 2-N-heterocyclic ring. Strain-promoted sydnone alkyne cycloaddition (SPSAC). Synthesis of a key intermediate of
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Published 05 Jun 2018

Recyclable hypervalent-iodine-mediated solid-phase peptide synthesis and cyclic peptide synthesis

  • Dan Liu,
  • Ya-Li Guo,
  • Jin Qu and
  • Chi Zhang

Beilstein J. Org. Chem. 2018, 14, 1112–1119, doi:10.3762/bjoc.14.97

Graphical Abstract
  • mechanism for this FPID-mediated amide bond formation reaction was proposed with the acyloxyphosphonium intermediate B being the key intermediate (Scheme 1). Herein, as part of our continuing exploration of the application of FPID in peptide synthesis, we disclose its successful application in solid-phase
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Published 22 May 2018

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

  • Ildikó Bacsa,
  • Dávid Szemerédi,
  • János Wölfling,
  • Gyula Schneider,
  • Lilla Fekete and
  • Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

Graphical Abstract
  • -amino-13α-estrone (13) itself may possess promising pharmacological properties or may serve as a key intermediate in the synthesis of biologically active 2-(subst.)amino-13α-estrones. The structures of the newly synthesized phenylamino derivatives 5–13 were established through 1H, 13C, HSQC and/or HMBC
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Published 04 May 2018

High-yielding continuous-flow synthesis of antimalarial drug hydroxychloroquine

  • Eric Yu,
  • Hari P. R. Mangunuru,
  • Nakul S. Telang,
  • Caleb J. Kong,
  • Jenson Verghese,
  • Stanley E. Gilliland III,
  • Saeed Ahmad,
  • Raymond N. Dominey and
  • B. Frank Gupton

Beilstein J. Org. Chem. 2018, 14, 583–592, doi:10.3762/bjoc.14.45

Graphical Abstract
  • . The commercial HCQ synthesis employs a key intermediate, 5-(ethyl(2-hydroxyethyl)amino)pentan-2-one (6), which is a major cost driver in the process. The protection–deprotection strategy of chloro-ketone starting material 3 used in the commercial route (Scheme 1a) [21] has been targeted as a
  • of 68% for compound 12. With an optimized continuous process for producing the key intermediate 12 in-hand the reaction conditions for the conversion of 12 to HCQ (1) were examined. In the commercial process this step is carried out in batch under neat reactant conditions and requires a relatively
  • were obtained in accordance with those previously reported [38][39]. Commercially available antimalarial drugs. Current batch syntheses of the key intermediate 5-(ethyl(2-hydroxyethyl)amino)pentan-2-one (6). Retrosynthetic strategy to hydroxychloroquine (1). Schematic representation for continuous in
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Published 08 Mar 2018

Progress in copper-catalyzed trifluoromethylation

  • Guan-bao Li,
  • Chao Zhang,
  • Chun Song and
  • Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

Graphical Abstract
  • mechanistic studies (Scheme 35). First, the key intermediate CF3CuILn is generated in situ by the reaction of TMSCF3 with Cu(II) reagent, followed by transmetalation with activated Ar−H generating the (aryl)CuI(CF3) species C, which might be oxidized to the corresponding (aryl)CuIII(CF3) intermediate D
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Published 17 Jan 2018

Photocatalytic formation of carbon–sulfur bonds

  • Alexander Wimmer and
  • Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

Graphical Abstract
  • ]. The thiyl radical was generated as reactive key intermediate from a variety of thiols by photooxidation using [Ru(bpz)3](PF6)2. Aliphatic and aromatic thiols react with aliphatic and aromatic alkenes and alkynes in high to excellent yields to the anti-Markovnikov addition adducts. However, an excess
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Published 05 Jan 2018

Aminosugar-based immunomodulator lipid A: synthetic approaches

  • Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

Graphical Abstract
  • -hexadecanoyloxy-15-methylhexadecanoic acids an efficient cross-metathesis has been employed [98]. Reduction of the 2-azido group with Zn in acetic acid, followed by acylation with the respective 3-O-benzyl protected fatty acid provided the key intermediate 45. Sequential protecting group manipulation (3’-O-Lev, 3
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Published 04 Jan 2018

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

  • Yaochun Xu,
  • Isabelle Correia,
  • Tap Ha-Duong,
  • Nadjib Kihal,
  • Jean-Louis Soulier,
  • Julia Kaffy,
  • Benoît Crousse,
  • Olivier Lequin and
  • Sandrine Ongeri

Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276

Graphical Abstract
  • straightforward methodology and we have adapted Zeng’s synthesis starting from the (R)-Garner’s aldehyde. (2S,3R)-Boc-CF3-Thr(Bzl) was obtained with satisfactory yields (Scheme 1). In this synthetic pathway, the key intermediate 6 was obtained, as a mixture of two diastereoisomers (9:1, evaluated by 19F NMR) via
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Published 21 Dec 2017

CF3SO2X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF3SO2Na

  • Hélène Guyon,
  • Hélène Chachignon and
  • Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

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Published 19 Dec 2017

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

  • Jury J. Medvedev,
  • Ilya V. Efimov,
  • Yuri M. Shafran,
  • Vitaliy V. Suslonov,
  • Vasiliy A. Bakulev and
  • Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

Graphical Abstract
  • ’, as illustrated in Scheme 4. Initially generated from diazoester 2 carbenoid A attacks the sulfur atom of thioamide 1 to give the key intermediate S-ylide B [36][37][38][59][60], which is stabilized by ‘thioamide resonance’ [36][37][38]. The anion center of S-ylide B then attacks the carbon atom of
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Published 30 Nov 2017

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

  • Yaroslav D. Boyko,
  • Valentin S. Dorokhov,
  • Alexey Yu. Sukhorukov and
  • Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

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  • syntheses of alstilobanines A, E and angustilodine, functionalized indole 33 was initially chosen as a key intermediate [33]. However, attempts of its preparation by Michael addition of substituted indole enolate 34 to nitrosoalkene NSA8, generated in situ either from the corresponding chlorooxime 35 or its
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Published 23 Oct 2017

Intramolecular glycosylation

  • Xiao G. Jia and
  • Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

Graphical Abstract
  • would form as the key intermediate. Upon dissociation of the anomeric C–S bond of the sulfonium intermediate 102, an oxygen nucleophile on the boronate ester would attack the C-1 center on the opposite side resulting in 103 with good stereoselection (Scheme 23). Initial trials with 3-methylbenzyl
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Published 29 Sep 2017

A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes

  • Grzegorz Mlostoń,
  • Paulina Pipiak,
  • Róża Hamera-Fałdyga and
  • Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185

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  • chemistry and related sciences. The key intermediate in the reaction is the 1,3-dithiolane carbanion, which, in contrast to the 4,5-unsubstituted analogues, undergoes a spontaneous cycloreversion reaction to give tetraarylethene and dithioformate anion. This method supplements the list of preparatively
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Published 08 Sep 2017

Influence of the milling parameters on the nucleophilic substitution reaction of activated β-cyclodextrins

  • László Jicsinszky,
  • Kata Tuza,
  • Giancarlo Cravotto,
  • Andrea Porcheddu,
  • Francesco Delogu and
  • Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 1893–1899, doi:10.3762/bjoc.13.184

Graphical Abstract
  • differences are also elements of complexity. The mechanical processing of CDs in the absence of solvent therefore promises to simplify the work-up and allows the almost complete utilization of the CD key-intermediate [13], in comparison with the classic method [6]. Moreover, the absence of a solvent, high
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Published 07 Sep 2017

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

  • Santanu Hati,
  • Ulrike Holzgrabe and
  • Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

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  • of molecular oxygen and with catalytic copper acetate (Cu(OAc)2) generated the desired pyrimidine 102 which was converted to the final products in a few more steps. This is one of the noteworthy examples where oxidative dehydrogenation has been utilized for the synthesis of a key intermediate of an
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Published 15 Aug 2017
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