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Journal Cover Tetrahedron Letters
  [SJR: 0.782]   [H-I: 145]   [121 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0040-4039 - ISSN (Online) 1359-8562
   Published by Elsevier Homepage  [3049 journals]
  • A metal-free, one-pot route to substituted benzo[b]thiophenes and their
           hetero-fused analogs via iodine mediated intramolecular arylthiolation of
           in situ generated β-(het)aryl-β-cyanoenethiolates
    • Authors: Saraiah Bonagiri; Anand Acharya; Mohamed A. Pasha; Ila Hiriyakkanavar
      Pages: 4577 - 4582
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Saraiah Bonagiri, Anand Acharya, Mohamed A. Pasha, Ila Hiriyakkanavar
      A metal-free one-pot route to substituted 3-cyanobenzo[b]thiophenes has been developed via iodine mediated intramolecular arylthiolation of 2-(het)aryl-2-cyanoenethiolates generated in situ by base mediated condensation of arylacetonitriles and (het)aryl dithioesters. The methodology has been further extended to the synthesis of 2-aminobenzo[b]thiophenes as well as hetero-fused thiophenes such as thieno[2,3-b]thiophenes, thieno[2,3-b]indoles and thieno[3,2-c]pyrazoles. An electrophilic cyclization mechanism has been proposed based on experimental observations.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.028
       
  • TBAI-mediated regioselective sulfenylation of indoles with sulfonyl
           chlorides in one pot
    • Authors: Yongzhao He; Jun Jiang; Wenhu Bao; Wei Deng; Jiannan Xiang
      Pages: 4583 - 4586
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Yongzhao He, Jun Jiang, Wenhu Bao, Wei Deng, Jiannan Xiang
      A versatile method for the synthesis of 3-sulfenylated indoles via TBAI promoted sulfenylation of indoles with sulfonyl chlorides in one pot has been presented. This system features highly regioselective, metal-free, easy operation, and shows a broad functional group tolerance leading to excellent yields. And this reaction could be easily conducted in 10 mmol scale with high effectivity. A plausible mechanism is proposed.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.040
       
  • Regioselective palladium-catalyzed CH arylation of 4-alkoxy and
           4-thioalkyl pyrazoles
    • Authors: William F. Vernier; Laurent Gomez
      Pages: 4587 - 4590
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): William F. Vernier, Laurent Gomez
      A methodology for the palladium-catalyzed regioselective CH arylation of electron rich pyrazoles has been developed. New ligands and mild conditions (70–90 °C) have been identified for this transformation. An intramolecular application of the methodology provided a novel synthetic route for the regioselective synthesis of 1,5-dihydroisochromeno[4,3-c]pyrazoles and 1,5-dihydroisothiochromeno[4,3-c]pyrazoles.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.047
       
  • Cu-catalyzed oxidation of indoles to isatins
    • Authors: Junfei Luo; Yanchao Zhao; Xing Xu; Junliang Zheng; Hongze Liang
      Pages: 4591 - 4594
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Junfei Luo, Yanchao Zhao, Xing Xu, Junliang Zheng, Hongze Liang
      The first example of Cu-catalyzed oxidation of indoles to isatin derivatives by the use of cheap aqueous tert-butyl peroxide as an oxidant was developed. This methodology is practically convenient and highly functional group tolerant, allowing a variety of indole derivatives to transform into the corresponding isatin derivatives in good yields.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.057
       
  • Nef-Perkow cascade towards imidazo phosphate derivatives
    • Authors: Somayeh Ghorbani; Ebrahim Soleimani; Laurent El Kaïm
      Pages: 4595 - 4597
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Somayeh Ghorbani, Ebrahim Soleimani, Laurent El Kaïm
      A one-pot four-component synthesis of imidazo phosphates has been achieved using a Nef/Perkow sequence followed by addition of propargylamine to form an intermediate amidrazone. The latter is not isolated but directly cyclized to imidazo phosphate derivatives in the presence of silver carbonate.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.055
       
  • Convenient preparation of dichloromethyl alkyl ethers
    • Authors: Yoshikazu Kimura; Takuya Warashina
      Pages: 4598 - 4599
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Yoshikazu Kimura, Takuya Warashina
      Dichloromethyl alkyl ethers have been synthesized from alkyl formates (C1–C4) and oxalyl chloride in the presence of catalytic amount of N-methylformanilide. N,N-Dimethylformamide is not suitable for the reaction. The method has the advantages of simple experimental procedure, which is applicable to large scale synthesis, without use of harmful reagents.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.052
       
  • Novel asymmetric synthesis of spiroindene-1,3dione-pyrrolidines via
           CoII/amino acids complex catalysed asymmetric 1,3-dipolar cycloaddition of
           azomethine ylides and 2-arylidenindane-1,3-diones
    • Authors: Bilel Bdiri; Zhi-Ming Zhou
      Pages: 4600 - 4608
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Bilel Bdiri, Zhi-Ming Zhou
      Cobalt II(l-phenylalanine)2 was used effectively for the first time in a catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides with 2-arylidenindane-1,3-diones, affording a series of novel spiropyrrolidine derivatives with good to high yields (up to 90%), excellent diastereoselectivities (only exo’-3 were detected), and good enantioselectivities (up to 87% ee).
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.060
       
  • Rapid assembly of the procyanidin A skeleton
    • Authors: George A. Kraus; Ivan M. Geraskin
      Pages: 4609 - 4611
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): George A. Kraus, Ivan M. Geraskin
      Arylpropynals and two equivalents of phloroglucinol react to produce pentacyclic ketals. In addition, 4-methoxydibromocinnamaldehyde also reacted to form procyanidin A-skeleton.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.067
       
  • Synthesis of a C3-symmetric tris-imine via dynamic covalent bond formation
           between a trialdehyde and a triamine
    • Authors: Keiko Nakada; Seiya Kondo; Yoshiteru Matsumoto; Masamichi Yamanaka
      Pages: 4612 - 4616
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Keiko Nakada, Seiya Kondo, Yoshiteru Matsumoto, Masamichi Yamanaka
      Dynamic covalent chemistry is an effective technique for the preparation of complex organic compounds. We succeeded in synthesizing a cage-shaped compound through the aggregation of two types of functional molecules. More specifically, a tris-imine 5 was quantitatively obtained by reacting a C 3-symmetric trialdehyde 1 with a triamine 4 in acetonitrile in the presence of a trifluoroacetic acid catalyst. We also achieved the synthesis of the corresponding triamine 9 and the acetylated derivative 10 through reduction of the tris-imine CN double bonds and subsequent acetylation.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.061
       
  • Cyclic peptide conjugate of curcumin and doxorubicin as an anticancer
           agent
    • Authors: Shaban Darwish; Saghar Mozaffari; Keykavous Parang; Rakesh Tiwari
      Pages: 4617 - 4622
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Shaban Darwish, Saghar Mozaffari, Keykavous Parang, Rakesh Tiwari
      The hydrophobicity of curcumin creates hurdle towards its use in the anticancer therapy. Herein, we synthesized a curcumin-doxorubicin conjugated cyclic peptide scaffold to improve the solubility of curcumin and create a conjugate containing two anticancer agents. A solid-phase Fmoc/tBu solid phase methodology was used to synthesize a cell-penetrating nuclear targeting peptide with free thiol and amine groups, which was coupled with the activated doxorubicin (Dox) and curcumin, affording Dox-peptide-curcumin conjugate (DPCC) (10). The antiproliferative activity of the conjugate was evaluated in human leukemia carcinoma cell (CCRF-CEM), human ovarian carcinoma cell (SKOV-3), and normal kidney cell line (LLCPK). Cyclic peptide-doxorubicin conjugate (7) and DPCC (10) did not inhibit the proliferation of normal kidney LLCPK cells after 72 h incubation, but were cytotoxic in CCRF-CEM (73% and 41%, respectively) and SKOV-3 (55% and 30%, respectively) cells under similar conditions, suggesting selectivity of these compounds towards cancer cells while Dox was cytotoxic (60–79%) in all three cell lines under similar conditions, suggesting selectivity of these compounds towards cancer cells.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.065
       
  • Enantioselective organocatalytic α-sulfamidation of aldehydes using
           sulfonyl azides
    • Authors: Raymond J. McGorry; Stacey K. Allen; Micha D. Pitzen; Thomas C. Coombs
      Pages: 4623 - 4627
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Raymond J. McGorry, Stacey K. Allen, Micha D. Pitzen, Thomas C. Coombs
      Enantioselective organocatalytic α-sulfamidation of unbranched aldehydes is described using MacMillan’s second-generation imidazolidinone catalyst and o-nitrobenzenesulfonyl azide. The reactions are highly stereoselective (89.9–96.3% ee) with yields up to 71%. A strong correlation between aldehyde structure and product yield was found to exist, with 3-arylpropanals providing the best results. Application to functionalized amino acid synthesis is presented.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.063
       
  • Synthesis, thermal stability, and computed bond dissociation energies of
           tetraarylphosphonium-based mesothermal ionic liquids bearing a quinoline
           ring system
    • Authors: Mohammad Soltani; Benjamin Siu; E. Alan Salter; Andrzej Wierzbicki; Kevin N. West; James H. Davis
      Pages: 4628 - 4631
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Mohammad Soltani, Benjamin Siu, E. Alan Salter, Andrzej Wierzbicki, Kevin N. West, James H. Davis
      Seven new ionic liquids have been prepared which contain tetraarylphosphonium cations in which one of the aromatic groups is a quinoline ring. These compounds, which differ from each other in the point of attachment of the quinoline to the phosphorous core, were evaluated by DSC and TGA, then screened for thermal stability for 96 h at temperatures up to 300 °C. The observed thermal stabilities of the salts were found to be sensitive to the position of quinoline ring substitution, and correlated well with computed homolytic bond dissociation energies of the quinoline-P bonds.
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      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.073
       
  • Ultrasound assisted, VOSO4 catalyzed synthesis of 4-thiazolidinones:
           Antimicrobial evaluation of indazole-4-thiazolidinone derivatives
    • Authors: Srinivas Angapelly; P.V. Sri Ramya; Routhu SunithaRani; C. Ganesh Kumar; Ahmed Kamal; Mohammed Arifuddin
      Pages: 4632 - 4637
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Srinivas Angapelly, P.V. Sri Ramya, Routhu SunithaRani, C. Ganesh Kumar, Ahmed Kamal, Mohammed Arifuddin
      A simple and expedient multicomponent protocol was developed to synthesize 4-thiazolidinones by employing VOSO4 as a catalyst under ultrasonic irradiation. The significant features of this protocol includes shorter reaction time, high yields, low catalyst loading, and also the catalyst can be recovered and reused up to next four cycles without significant loss in catalytic activity. All the synthesized novel indazole compounds were evaluated for their antibacterial and anti-biofilm activities. Compounds 9n, 9o and 9q showed promising activity (MIC value of 3.9 µg/mL) against K. planticola (MTCC 530). They also exhibited significant bactericidal activity against K. planticola (MTCC 530) (MBC value of 15.6 µg/mL). Additionally, 9n, 9o and 9q inhibited biofilm formation (IC50 values ranging between 20.28–20.79 μg/mL) in this organism.
      Graphical abstract image

      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.070
       
  • An N-protection free ligation of the peptide thioester and the peptide
           with an N-alkoxy- or N-aryloxyamino group at its N-terminus
    • Authors: Hironobu Hojo; Toru Kawakami; Yuta Hiroyama; Saburo Aimoto
      Pages: 4638 - 4641
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Hironobu Hojo, Toru Kawakami, Yuta Hiroyama, Saburo Aimoto
      Peptides with an N-alkoxy or N-aryloxy amino acid at their N-terminus were synthesized and successfully ligated with a peptide thioester by silver ion activation under a slightly acidic condition without requiring protection of the side chain amino groups. The N-methoxy group was easily cleaved by the SmI2 reduction in CH3OH aq. to obtain the desired peptide with a native peptide bond. This method was successfully applied to the synthesis of the human atrial natriuretic peptide showing the efficiency of the novel ligation.
      Graphical abstract image

      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.074
       
  • Regioselective annulation of propargyl alcohols with ambident-enols: A
           Ca(II)-catalyzed trisubstituted benzochromene synthesis
    • Authors: Srinivasarao Yaragorla; Abhishek Pareek; Ravikrishna Dada
      Pages: 4642 - 4647
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Srinivasarao Yaragorla, Abhishek Pareek, Ravikrishna Dada
      Highly regioselective, 6-endo cyclization between propargyl alcohols and ambident enols such as naphthols, 4-hydroxy coumarin, cyclohexane-1,3-dione, 5,5-dimethylcyclohexane-1,3-dione is described using Ca(OTf)2 under solvent free conditions. The reaction proceeds through a cascade annulation which involves an etherification, Claisen type rearrangement, allene formation and endocyclization. Further, we extended this method to the synthesis of iodo-derivative and demonstrated the reactivity in cross-coupling reactions.
      Graphical abstract image

      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.077
       
  • Palladium(II) acetate catalyzed acylative cleavage of cyclic and acyclic
           ethers under neat conditions
    • Authors: Jean Fotie; Brandy R. Adolph; Shreya V. Bhatt; Casey C. Grimm
      Pages: 4648 - 4651
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Jean Fotie, Brandy R. Adolph, Shreya V. Bhatt, Casey C. Grimm
      During the development of a palladium catalyzed C–H activation cross-coupling reaction involving acyl halides, it was noted that palladium(II) acetate catalyzes the acylative cleavage of tetrahydrofuran (used as a solvent) at room temperature to afford the corresponding 4-chlorobutyl ester derivative. After optimization, the reaction was shown to work well with epoxides, oxetane and tetrahydrofuran, but only barely with oxanes at room temperature. Acyclic ethers systematically failed to react under similar conditions, but underwent complete conversion in a microwave reactor at 100 °C.
      Graphical abstract image

      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.080
       
  • Isoguanosine derivatives from the Northeastern Atlantic sponge Clathria
           (Microciona) strepsitoxa
    • Authors: Daria Firsova; Kevin Calabro; Perrine Lasserre; Fernando Reyes; Olivier P. Thomas
      Pages: 4652 - 4654
      Abstract: Publication date: 6 December 2017
      Source:Tetrahedron Letters, Volume 58, Issue 49
      Author(s): Daria Firsova, Kevin Calabro, Perrine Lasserre, Fernando Reyes, Olivier P. Thomas
      After a chemical screening of subtidal sponges from the Northeastern Atlantic, Clathria (Microciona) strepsitoxa (Poecilosclerida: Microcionidae) was selected for deeper investigation. This first chemical study led to the identification of two new 8-oxoisoguanosine derivatives. The structure elucidation was performed after extensive analyses of spectroscopic (1D and 2D NMR) and HR-ESIMS data and no significant antimicrobial or cytotoxic activity was detected.
      Graphical abstract image

      PubDate: 2017-11-16T10:38:41Z
      DOI: 10.1016/j.tetlet.2017.10.079
       
  • Quaternary ammonium salt-catalyzed carboxylative cyclization of
           propargylic amines with CO2
    • Authors: Akira Fujii; Jun-Chul Choi; Ken-ichi Fujita
      Pages: 4483 - 4486
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Akira Fujii, Jun-Chul Choi, Ken-ichi Fujita
      By employing quaternary ammonium salts as catalysts, the carboxylative cyclization of the propargylic amines with CO2 proceeded to afford the corresponding 2-oxazolidinones. In particular, tetra-n-butylammonium fluoride was the most effective catalyst for the reaction, providing a 2-oxazolidinone derivative in a maximum chemical yield of 99%. From a screening of the structure of a catalyst, it was found that both a quaternary ammonium cation and a basicity of the counter anion were essential to catalyze the carboxylative cyclization of the propargylic amines with CO2.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.016
       
  • Highly enantioselective Michael addition of α,α-disubstituted aldehydes
           to maleimides catalyzed by new primary amine-squaramide bifunctional
           organocatalysts
    • Authors: Zhi-wei Ma; Xiao-feng Liu; Jun-tao Liu; Zhi-jing Liu; Jing-chao Tao
      Pages: 4487 - 4490
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Zhi-wei Ma, Xiao-feng Liu, Jun-tao Liu, Zhi-jing Liu, Jing-chao Tao
      New bifunctional primary amine-squaramides catalyzed asymmetric Michael addition reaction of α,α-disubstituted aldehydes to maleimides has been developed. This organocatalytic asymmetric reaction provides easy access to functionalized succinimides with a broad substrate scope. Both enantiomers of desired succinimide derivatives were obtained in good to excellent yields (up to 98%) with excellent enantioselectivities (up to >99% ee).
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.026
       
  • Diastereomeric process-based chiral resolution of helical quinone
           derivatives using (−)-menthyl chloroformate
    • Authors: Mohammad Shahabuddin; Md. Sharif Hossain; Takao Kimura; Michinori Karikomi
      Pages: 4491 - 4495
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Mohammad Shahabuddin, Md. Sharif Hossain, Takao Kimura, Michinori Karikomi
      Diastereomeric resolution of helically distorted polycondensed bisphenols (1,1′-bibenzo[c]phenanthrene-2,2′-diols: HEBPOLs) 2a–b was conducted utilizing (1R)-(−)-menthyl chloroformate as a chiral resolving agent. Subsequent manipulation produced highly optically pure [>99% enantiomeric excess (ee)] quinone derivatives (P) and (M)-1a–b in very good yields. The absolute configuration of each product was confirmed based on circular dichroism (CD) spectra and X-ray crystal structure analysis.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.027
       
  • An efficient, environmentally benign, and solvent-free protocol for the
           synthesis of 4-substituted 1,5-benzodiazepines catalyzed by reusable
           sulfated polyborate
    • Authors: Krishna S. Indalkar; Manisha S. Patil; Ganesh U. Chaturbhuj
      Pages: 4496 - 4502
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Krishna S. Indalkar, Manisha S. Patil, Ganesh U. Chaturbhuj
      An efficient and environmentally benign method has been developed for the one-pot solvent-free synthesis of 4-substituted-1,5-benzodiazepines via three-component reaction of o-phenylenediamine, dimedone with a variety of aldehydes catalyzed by sulfated polyborate. The major advantages of the present method are good to excellent yields, shorter reaction time, simple experimental procedure, easy workup, solvent-free reaction condition, recyclability of the catalyst and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.030
       
  • Transition metal-free protodecarboxylation of electron rich aromatic acids
           under mild conditions
    • Authors: Jingxian Fang; Dangui Wang; Guo-Jun Deng; Hang Gong
      Pages: 4503 - 4506
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Jingxian Fang, Dangui Wang, Guo-Jun Deng, Hang Gong
      A mild and practical method for the transition metal-free protodecarboxylation of aromatic acids using readily available and safe sodium persulfate as initiator was described. This environment-friendly decarboxylation approach was performed at 60°C in ethanol and could easily scale up to the gram level with a good yield. In Particular, the tandem reactions of decarboxylation and halogenation were achieved by the addition of the corresponding halogenating reagents to the reaction system.
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      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.036
       
  • Synthesis and characterization of a biphenyl-linked hemicryptophane and an
           endohedral cobalt(II) complex
    • Authors: Yoshimasa Makita; Tomofumi Danno; Keisuke Ikeda; Hsien-Han Lee; Taro Abe; Kento Sogawa; Akihiro Nomoto; Shin-ichi Fujiwara; Akiya Ogawa
      Pages: 4507 - 4509
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Yoshimasa Makita, Tomofumi Danno, Keisuke Ikeda, Hsien-Han Lee, Taro Abe, Kento Sogawa, Akihiro Nomoto, Shin-ichi Fujiwara, Akiya Ogawa
      Hemicryptophanes are covalent molecular cages, constructed from a cyclotriveratrylene-based host unit and a functional unit linked by covalent spacers, which have been designed to accommodate endohedral functionalities in the cavity. In this study, the synthesis and characterization of the rigid, biphenyl-linked hemicryptophane 1 were investigated by NMR, ESI-MS, and X-ray crystallography. The structure of the inclusion complex, in which a dichloromethane molecule was constructed encapsulated within 1, was characterized by X-ray crystallography. An endohedral, cobalt(II) hemicryptophane complex 2 was also synthesized and characterized ESI-MS and X-ray crystallography. The X-ray crystal structure of 2 showed that the biphenyl-linked hemicryptophane had three components—a molecule each of chloroform and acetonitrile, and a cobalt(II) ion—within its cavity.
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      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.039
       
  • Copper-catalyzed hydroamination of propargyl imidates
    • Authors: Patrick J. Fricke; Jenna L. Stasko; Dylan T. Robbins; Alexander C. Gardner; Jacqueline Stash; Mark J. Ferraro; Michael W. Fennie
      Pages: 4510 - 4513
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Patrick J. Fricke, Jenna L. Stasko, Dylan T. Robbins, Alexander C. Gardner, Jacqueline Stash, Mark J. Ferraro, Michael W. Fennie
      Propargyl imidates derived from aromatic and aliphatic nitriles cyclize at room temperature in high yields when treated with a catalytic amount of copper (I) iodide. This 5-exo-dig process affords dihydrooxazoles which do not aromatize under the reaction conditions, and which are isolated without chromatography. Investigations of the reaction scope, subsequent functionalization of the reaction products, and preliminary mechanistic data are presented.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.043
       
  • Enhancing solution-phase supramolecular interactions between monomeric
           porphyrins and [60]fullerene by simple chemical modification
    • Authors: Michio Yamada; Gota Murakami; Shuhei Kobayashi; Yutaka Maeda
      Pages: 4514 - 4518
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Michio Yamada, Gota Murakami, Shuhei Kobayashi, Yutaka Maeda
      The supramolecular interactions of N-methylporphyrin and iridium porphyrin with C60 in toluene solution were investigated using NMR spectroscopy and absorption spectroscopy. Our results demonstrate that both the N-methylation and iridium metalation of porphyrin are effective means to enhance the binding affinity to C60, resulting in 1:1 complexation for N-methylporphyrin/C60 and 2:1 complexation for iridium porphyrin/C60.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.037
       
  • Intermolecular Pauson–Khand reactions of N-substituted maleimides
    • Authors: ChristiAnna L. Brantley; Thomas C. Coombs
      Pages: 4519 - 4524
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): ChristiAnna L. Brantley, Thomas C. Coombs
      Co2(CO)8-mediated intermolecular Pauson–Khand reactions of N-substituted maleimides with terminal alkynes are described, producing maleimide-fused cyclopentenones. The transformation differs from other intermolecular Pauson–Khand-type reactions of electron-deficient olefins, which react with Co2(CO)8 and alkynes to produce conjugated dienes, or generally require terminal, monosubstituted olefins to generate cyclopentenones. The reaction works well for N-benzyl, N-aryl, and N-alkyl substituted maleimides, and tolerates branching at the 3-position of the terminal alkyne. N–H maleimide, N–CO2Me maleimide, and maleic anhydride do not take part in the transformation.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.042
       
  • Copper mediated coupling of 2-(piperazine)-pyrimidine iodides with aryl
           thiols using Cu(I)thiophene-2-carboxylate
    • Authors: Liza Shrestha; Hardik J. Patel; Yanlong Kang; Sahil Sharma; Gabriela Chiosis; Tony Taldone
      Pages: 4525 - 4531
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Liza Shrestha, Hardik J. Patel, Yanlong Kang, Sahil Sharma, Gabriela Chiosis, Tony Taldone
      A copper-mediated synthesis of diaryl sulfides utilizing Cu(I)-thiophene-2-carboxylate (CuTC) is described. We demonstrate the use of CuTC as a soluble, non-basic catalyst in the coupling of aryl iodides and aryl thiols in the synthesis of synthetically advanced diaryl sulfides. This method allows for the successful coupling of challenging substrates including ortho-substituted and heteroaryl iodides and thiols. Additionally, most of the aryl iodide substrates used here contain the privileged piperazine scaffold bound to a pyrimidine, pyridine, or phenyl ring and thus this method allows for the elaboration of complex piperazine scaffolds into molecules of biological interest. The method described here enables the incorporation of late-stage structural diversity into diaryl sulfides containing the piperazine ring, thus enhancing the number and nature of derivatives available for SAR investigation.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.041
       
  • Naphthalene-derived Al3+-selective fluorescent chemosensor based on PET
           and ESIPT in aqueous solution
    • Authors: Xiao-li Yue; Zhao-qing Wang; Chao-rui Li; Zheng-yin Yang
      Pages: 4532 - 4537
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Xiao-li Yue, Zhao-qing Wang, Chao-rui Li, Zheng-yin Yang
      A simple fluorescent chemosensor HL based on naphthalene with high selectivity and sensitivity towards Al3+ over other commonly coexisting metal cations in fully aqueous solution to enhance the potential applications of the fluorescent chemosensor was developed. HL exhibited a significant fluorescence enhancement at 475 nm in the presence of Al3+ over other competitive metal ions with a low detection limit of 0.43 μM due to the inhibition of the photo induced electron transfer (PET) and the excited-state intramolecular proton transfer (ESIPT). The 1:1 binding stoichiometry between HL and Al3+ was corroborated by the Job plot and the ESI-MS spectrum. Importantly, the reversible recognition process of HL to Al3+ will make HL could be used circularly and repeatedly in practical applications by addition of Na2EDTA. In addition, the binding behavior and sensing mechanism of HL to Al3+ were illustrated in detail by the 1H NMR titration experiment.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.044
       
  • Efficient synthesis of α-substituted ethylphosphonates via CuH-catalyzed
           conjugate reduction of terminal alkenylphosphonate
    • Authors: Li Zhang; Yewen Fang; Xiaoping Jin; Ting Guo; Ruifeng Li; Yan Li; Xie Li; Yi Yang; Meijuan Yuan; Zongming Tian
      Pages: 4538 - 4541
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Li Zhang, Yewen Fang, Xiaoping Jin, Ting Guo, Ruifeng Li, Yan Li, Xie Li, Yi Yang, Meijuan Yuan, Zongming Tian
      An unprecedented approach toward synthesis of α-substituted ethylphosphonates based on CuH-catalyzed conjugate reduction of vinylphosphonates has been successfully developed. This protocol features mild conditions, broad substrate scope, good functional group compatibility, high overall efficiencies, and easy gram-scale synthesis. The Cu-catalyzed reduction takes place in a highly selective manner on the phosphono substituted CC bond in the case of the reaction of alkenylphosphonates bearing both phosphono and alkyl or aryl substituted alkene moieties. Furthermore, the result of competitive reaction indicates that the Cu-catalyzed conjugate reduction of vinylphosphonate is more challenging and reproducible than the corresponding acrylate’s reaction.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.045
       
  • Synthesis of bicyclic tripeptides inspired by the ABC-ring system of
           vancomycin through ruthenium-based cyclization chemistries
    • Authors: Xin Yang; Lucas P. Beroske; Johan Kemmink; Dirk T.S. Rijkers; Rob M.J. Liskamp
      Pages: 4542 - 4546
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Xin Yang, Lucas P. Beroske, Johan Kemmink, Dirk T.S. Rijkers, Rob M.J. Liskamp
      The synthesis of a bicyclic tripeptide that mimics the ABC ring system of vancomycin is described by using a ring closing metathesis (RCM) – peptide coupling – ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) strategy.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.046
       
  • Synthesis and structure of 2-substituted pyrene-derived scaffolds
    • Authors: Lília I.L. Cabral; Marta S.C. Henriques; José A. Paixão; Maria L.S. Cristiano
      Pages: 4547 - 4550
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Lília I.L. Cabral, Marta S.C. Henriques, José A. Paixão, Maria L.S. Cristiano
      Pyrenes bear a propensity to form fluorescent excimers, and thus this chromophore is often found in sensors and fluorescent probes. 2-Functionalized pyrenes are of particular interest, however the preparation of these scaffolds is not trivial, involving synthetic routes that require 4,5,9,10-tetrahydropyrene as a key intermediate. Herein, the development and optimization of routes for the synthesis of 2-functionalized pyrene-derived building blocks, with potential to be used as tags in the preparation of fluorescent probes, is described. Additionally, the crystal structures of ethyl 4,5,9,10-tetrahydro-2-pyrene-5-oxopentanoate and 2-acetyl-4,5,9,10-tetrahydropyrene revealed distinct conformations of the saturated tetrahydropyrene rings.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.058
       
  • Tricyclic heterocycles as precursors to functionalized spirocyclic oximes
    • Authors: Silas A. Griffin; Cody R. Drisko; Kevin S. Huang
      Pages: 4551 - 4553
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Silas A. Griffin, Cody R. Drisko, Kevin S. Huang
      An efficient synthesis of functionalized spirocyclic oximes from tricyclic heterocycles is reported. This novel method accomplishes high diastereoselectivity via an intramolecular 1,3-dipolar cycloaddition with a regenerating Michael linker strategy. Ring opening of the tricyclic N-(trimethylsilyloxy)pyrrolo[3,4-c]isoxazolidine framework was found to be essential for successful N-alkylation of the tertiary amine on the polymer support. β-Elimination of the quaternary salt releases the spirocyclic oximes from the solid support in overall yields of 45–60%.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.056
       
  • Synthesis and utility of 3-silylthiophenes having perfluoroalkyl groups
    • Authors: Mitsunori Honda; Yusuke Taniguchi; Tomohiro Hayashi; Ko-Ki Kunimoto; Masahito Segi; Takahiro Yamaguchi
      Pages: 4554 - 4558
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Mitsunori Honda, Yusuke Taniguchi, Tomohiro Hayashi, Ko-Ki Kunimoto, Masahito Segi, Takahiro Yamaguchi
      The synthesis of a novel class of 3-silyl substituted thiophenes possessing perfluoroalkyl groups on the silicon atom was investigated. The treatment of 3-bromothiophene with n-butyllithium followed by the reaction with halosilanes proceeded to afford the corresponding 3-silyl substituted thiophenes 1 in good yields. The chemical polymerization of the resulting 1 did not work well. However, the electropolymerization of 3-silylthiophenes 1a and 1b provided the corresponding polymers 5a and 5b with head-to-tail regioregularity. The cyclic voltammogram of the resulting polymers 5a and 5b indicated both n- and p-doping properties.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.049
       
  • Ammonium formate-based one-pot reductive Heck reactions for the
           construction of cyclic sulfonamides
    • Authors: Aisha Khalifa; Lorna Conway; Kimberly Geoghegan; Paul Evans
      Pages: 4559 - 4562
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Aisha Khalifa, Lorna Conway, Kimberly Geoghegan, Paul Evans
      A modified method is reported for the conversion of unsaturated sulfonamides into their cyclic saturated counterparts. This method utilises a single palladium catalyst for an intramolecular Heck reaction and subsequent transfer hydrogenation, which is achieved in one-pot following the addition of ammonium formate. Accordingly, a range of fourteen structural variations are reported and under optimal conditions the adducts were generated in typically good to excellent yields. Notably, discrimination of differentially substituted dienes can be accomplished in the case of compounds 28 and 29 and the process was only observed to fail with the more sterically hindered precursor 32.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.053
       
  • One-pot two-step conversion of aromatic carboxylic acids and esters to
           aromatic aldehydes via indium-catalyzed reductive thioacetalization and
           desulfurization
    • Authors: Norio Sakai; Kohei Minato; Yohei Ogiwara
      Pages: 4563 - 4567
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Norio Sakai, Kohei Minato, Yohei Ogiwara
      Described herein is that a new approach to a one-pot two-step conversion of aromatic carboxylic acids/esters to aromatic aldehydes, in which indium(III) iodide effectively catalyzes both the first reductive thioacetalization of carboxylic acids and a subsequent desulfurization of the in-situ formed thioacetal intermediates leading to aldehydes.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.050
       
  • Stereochemical assignments of rubiaquinones A–C, naphthoquinone
           derivatives from Rubia yunnanensis
    • Authors: Yoshihiro Suyama; Yusuke Higashino; Naonobu Tanaka; Yutaka Tatano; Hideki Yagi; Kazuyoshi Kawazoe; Kotaro Murakami; Shun-Lin Li; Han-Dong Sun; Yoshiki Kashiwada
      Pages: 4568 - 4571
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Yoshihiro Suyama, Yusuke Higashino, Naonobu Tanaka, Yutaka Tatano, Hideki Yagi, Kazuyoshi Kawazoe, Kotaro Murakami, Shun-Lin Li, Han-Dong Sun, Yoshiki Kashiwada
      Three new naphthoquinone derivatives, rubiaquinones A–C (1–3), were isolated from the roots of Rubia yunnanensis. Rubiaquinone A (1) was a racemic naphthoquinone dimer consisting of a 1,4-dihydroxynaphthalene and a 4-hydroxy-1,2-naphthoquinone moieties with a 2-oxo-propyl group. Rubiaquinones B (2) and C (3) were structurally unique trimeric naphthoquinones with a racemic nature possessing one chiral axis and one chiral carbon in common. The planar structures of 1–3 were assigned by detailed spectroscopic analyses, and enantiomers of 1–3 were obtained by optical resolutions. The absolute configurations of (+)-1 and (−)-1 were elucidated by interpretation of the ECD spectra with the aid of TDDFT ECD calculation, while those of enantiomers obtained from 2 and 3 were assigned by analyses of the composite ECD spectra generated by summing appropriate ECD spectra of enantiomers. Rubiaquinone A (1) exhibited antimicrobial activity against Bacillus subtilis.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.051
       
  • Facile and effective approach for oxidation of boronic acids
    • Authors: Ravindra B. Wagh; Jayashree M. Nagarkar
      Pages: 4572 - 4575
      Abstract: Publication date: 29 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 48
      Author(s): Ravindra B. Wagh, Jayashree M. Nagarkar
      This present work illustrates facile and effective approach for oxidation of boronic acids using environmentally benign dimethyl carbonate (DMC) as a solvent with H2O2 as an oxidant at room temperature. In contrast to previous reaction reports, which make use of metal catalyst, hazardous reagent and oxidants that creates environmental concern. This method provides good to excellent yield of products and showed better tolerance towards various functional groups present on boronic acids. Moreover, this developed process is an alternative in terms of inexpensive, non toxic and easy reaction conditions.
      Graphical abstract image

      PubDate: 2017-11-09T06:05:00Z
      DOI: 10.1016/j.tetlet.2017.10.059
       
  • CuI catalyst heterogenized on melamine-pyridines immobilized SBA-15:
           Heterogeneous and recyclable nanocatalyst for Ullmann-type CN coupling
           reactions
    • Authors: Hojat Veisi; Mona Hamelian; Saba Hemmati; Hadis Javaheri
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Hojat Veisi, Mona Hamelian, Saba Hemmati, Akram Dalvand
      The present study reports the procedure conducted in SBA-15/CCPy/CuI preparation as a new Mesoporous nanocatalyst, whereas melamine bearing pyridine groups on SBA-15 are used to secure CuI catalyst as capping agent. The resultant catalyst was specified by conducting TEM, FESEM, WDX, ICP, and EDS. The SBA-15/CCPy/CuI catalytic behavior was studied to N-arylation of indole, imidazole, pyrazole, benzyl amine, and aniline by coupling reactions of Ullmann-type CN. Also, the heterogeneous catalyst may simply be recovered via filtration and used again for seven cycles with no considerable loss in activity. The findings revealed the privileges of the present method, including the high product yield, experimental simplicity, low catalyst loading, broad substrate scope, and short reaction times.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.cattod.2017.04.033
       
  • Mechanistic aspects of alkene oxidation using chiral hypervalent iodine
           reagents
    • Authors: Morifumi Fujita
      Pages: 4409 - 4419
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Morifumi Fujita
      Recent progress in the area of hypervalent iodine-induced enantioselective oxidation is reviewed with emphasis from a mechanistic point of view. Chiral lactate and lactamide sidechains in hypervalent iodine reagents induce herical chirality around the iodine reaction site, which provides a chiral environment suitable for enantioselective transformations. The stereochemical outcomes of alkene oxidation are also compiled and used for systematically understanding the reaction mechanism of oxidative double bond difunctionalization.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.019
       
  • Recent applications of gold-catalyzed cascade reactions in total synthesis
           of natural product
    • Authors: Kenji Sugimoto; Yuji Matsuya
      Pages: 4420 - 4426
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Kenji Sugimoto, Yuji Matsuya
      From the point of the view of the synthetic efficiency, the concept ‘step economy’ was required in total synthesis of natural product. Recently, versatile gold-catalyzed cascade reactions have been developed, and relating reports on practical applications in total synthesis has increased. This digest focuses and summarizes the gold-catalyzed reaction cascades in natural product synthesis during last five years with brief discussion on the reaction mechanism of the key gold-catalyzed cascade transformations.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.029
       
  • A rapid and highly efficient Michael addition of methoxybenzenes and
           indoles to α,β-unsaturated ketones using BF3·OEt2 as a catalyst
    • Authors: A. Swetha; M. Raghavender Reddy; B. Madhu Babu; H.M. Meshram
      Pages: 4427 - 4431
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): A. Swetha, M. Raghavender Reddy, B. Madhu Babu, H.M. Meshram
      An efficient and general protocol is described for the Michael addition of α,β-unsaturated ketones with electron-rich arenes/indoles to give alkylated arenes/indoles under mild reaction condition at room temperature. Shorter reaction time, convenient and good isolated yields are the significant features of this protocol. Moreover, the procedure is environmentally benign in nature and applicable to variety of arenes/indoles as well as α,β-unsaturated ketones.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.09.016
       
  • In pursuit of balgacyclamide A – Discovery of an oxazoline macrocycle
           with multiple myeloma cytotoxicity and penetration
    • Authors: Vinh L. Hoang; Yichao Zhang; Ryan J. Rafferty
      Pages: 4432 - 4435
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Vinh L. Hoang, Yichao Zhang, Ryan J. Rafferty
      Four new oxazoline based macrocycles have been constructed, said cycles were found to possess varying cytotoxicity against six different cancer cell lines: IC50 values of 6.4μM towards HeLa and 11.9μM towards LnCaP being the most potent. Two of the four macrocycles were found to have marginal cytotoxicity against MM.1S and MM.1R, myeloma cancer cell lines, and further evaluation showed that they also possessed rapid cellular uptake and accumulation characteristics. Through the structure-activity relationship comparisons between the four compounds, it was found that the C6 position of the E-ring is amendable to substitution and could possibly serve as a conjugation site for the development of a selective delivery system to MM.1R.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.09.071
       
  • Haloamination of an aminoallenylether and subsequent palladium-catalyzed
           cross coupling reactions to afford dihydrobenzoxazole derivatives
           containing conjugated substituents
    • Authors: Jihye Choi; Guncheol Kim
      Pages: 4436 - 4439
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Jihye Choi, Guncheol Kim
      Haloamination of an aminoallenylether, which was prepared from commercially available 2-aminophenol via a three-step sequence, provided a versatile halovinyldihydrobenzoxazole intermediate. Subsequent Heck, Sonogashira, and Suzuki coupling reactions yielded dihydrobenzoxazoles possessing the corresponding conjugated substituents.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.006
       
  • Thermal decomposition product of
           1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene
    • Authors: Tadatsugu Yamaguchi; Tsuyoshi Nakagawa; Toru Ozeki; Mitsuhiro Fukuda; Masakazu Morimoto; Shizuka Takami
      Pages: 4447 - 4449
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Tadatsugu Yamaguchi, Tsuyoshi Nakagawa, Toru Ozeki, Mitsuhiro Fukuda, Masakazu Morimoto, Shizuka Takami
      1,2-Bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene shows photochromism in n-hexane at room temperature. We have identified a new compound produced by the thermal decomposition in a mixture of cis- and trans-decahydronaphthalene above 100 °C in the absence of light.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.017
       
  • Tandem synthesis of 1-formyl-1,2,3-triazoles
    • Authors: James T. Fletcher; Joseph A. Christensen; Eric M. Villa
      Pages: 4450 - 4454
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): James T. Fletcher, Joseph A. Christensen, Eric M. Villa
      A tandem method for preparing 4-formyl-1,2,3-triazoles via a two-step one-pot acetal cleavage/CuAAC reaction was developed. Using this method, 4-formyl-1,2,3-triazole analogs with both electron-withdrawing and electron-donating substituents were prepared in good yield and purity. Expansion of this method to a three-step tandem reaction that incorporates an additional step of azide substitution was also successful, circumventing the need for organic azide isolation. This one-pot method, noteworthy in its simplicity and mild conditions, utilizes practical, readily available reactants and relies on protic solvent to promote acid-catalyzed acetal cleavage.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.023
       
  • Access to substituted trifluoromethyl ketones using the versatile
           synthetic intermediate
           (E)-1,1-dimethyl-2-(1,1,1-trifluoropropan-2-ylidene)hydrazine
    • Authors: Ted C. Judd; Derek B. Brown
      Pages: 4455 - 4458
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Ted C. Judd, Derek B. Brown
      The N,N-dimethylhydrazone of 1,1,1-trifluoroacetone, (E)-1,1-dimethyl-2-(1,1,1-trifluoropropan-2-ylidene)hydrazine, has been shown to undergo a diverse set of reactions following deprotonation with n-butyl-lithium; including alkylation, addition to ketones and aldehydes, as well as palladium-catalyzed cross-couplings with aryl bromides. Mild hydrolysis of the N,N-dimethylhydrazone products from these transformations affords the corresponding trifluoromethyl ketones in good to excellent yields.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.022
       
  • Concise synthesis and revision of the proposed biogenesis of
           helicascolides
    • Authors: Kuan Zheng; Changmin Xie; Ran Hong
      Pages: 4459 - 4464
      Abstract: Publication date: 22 November 2017
      Source:Tetrahedron Letters, Volume 58, Issue 47
      Author(s): Kuan Zheng, Changmin Xie, Ran Hong
      A concise synthesis of helicascolides A, B and C was achieved in three to five steps from commercially available materials. The key transformations of the synthesis include an Evans-Metternich anti-aldol reaction of the known β-keto imide 10 and strategic base-mediated one-pot cyclization/alkylation. Based on the new chemical evidence of ring-opening reaction of β-keto ester under biocompatible basic conditions, Krohn’s proposal for the biosynthetic relationship between helicascolide A (1) and a naturally co-existing acyclic dienone 4 was suggested in a reverse manner.
      Graphical abstract image

      PubDate: 2017-11-01T11:57:09Z
      DOI: 10.1016/j.tetlet.2017.10.021
       
 
 
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