Journal Cover Tetrahedron
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   ISSN (Print) 0040-4020
   Published by Elsevier Homepage  [3177 journals]
  • Oxidopyrylium [5+2] cycloaddition chemistry: Historical perspective and
           recent advances (2008–2018)
    • Authors: Lauren P. Bejcek; Ryan P. Murelli
      Pages: 2501 - 2521
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Lauren P. Bejcek, Ryan P. Murelli
      The following review article provides an overview of oxidopyrylium [5+2] cycloaddition chemistry, with a particular emphasis placed on seminal historical developments and advancements made over the last decade. It is our hope this review serves as a valuable resource to those interested in the oxidopyrylium cycloaddition chemistry, and helps inspire future advancements.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.006
       
  • Recent advances in the synthesis, structural diversity, and applications
           of mesoionic 1,2,3-triazol-5-ylidene metal complexes
    • Authors: Kostiantyn O. Marichev; Siddappa A. Patil; Alejandro Bugarin
      Pages: 2523 - 2546
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Kostiantyn O. Marichev, Siddappa A. Patil, Alejandro Bugarin
      Beyond the classic N-heterocyclic carbenes (NHCs) there is a subclass of NHCs called mesoionic carbenes (MICs). This review focuses on recent advances in the area of 1,2,3-triazol-5-ylidenes as the most abundant class of MICs and their metal complexes. The study of mesoionic 1,2,4- and 1,3,4-trisubstituted 1,2,3-triazol-5-ylidene transition metal complexes is a research area with a history of just ∼10 years. During this relatively short period, hundreds of these complexes have appeared in the literature, reflecting their high stability and simpler synthesis compared with NHCs. Specifically, this review is focused on advances in the synthesis of 1,2,3-triazol-5-ylidene metal complexes derived from palladium, silver, gold, ruthenium, iridium, rhodium, iron, molybdenum, cobalt, nickel, platinum, and osmium, together with their catalytic, medicinal, and photophysical applications.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.013
       
  • Chemoselectivity in the Kosugi-Migita-Stille coupling of bromophenyl
           triflates and bromo-nitrophenyl triflates with (ethenyl)tributyltin
    • Authors: Nurul N. Ansari; Matthew M. Cummings; Björn C.G. Söderberg
      Pages: 2547 - 2560
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Nurul N. Ansari, Matthew M. Cummings, Björn C.G. Söderberg
      Kosugi-Migita-Stille cross coupling reactions of (ethenyl)tributyltin with all isomeric permutations of bromophenyl triflate and bromo-nitrophenyl triflate were examined in order to determine the chemoselectivity of carbon-bromine versus carbon-triflate bond coupling under different reaction conditions. In general, highly selective carbon-bromine bond cross couplings were observed using for example bis(triphenylphosphine)palladium dichloride (2 mol-%) in 1,4-dioxane at reflux. In contrast, reactions using the same pre-catalyst but in the presence of a three-fold excess of lithium chloride in N,N-dimethylformamide at ambient temperature were in most cases selective for coupling at the carbon-triflate bond. Overall, isolated yields and the selectivity for carbon-bromine bond coupling were significantly higher compared to carbon-triflate bond coupling.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.02.051
       
  • Synthesis of chiral α-amino anilides via a DMEDA-promoted selective C─N
           coupling reaction of aryl halides and α-aminoamides
    • Authors: Xiangting Min; Xiaoyu Li; Yu Wang; Yawen Dong; Jingjing Tang; Jing Wang; Jianhui Liu
      Pages: 2561 - 2566
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Xiangting Min, Xiaoyu Li, Yu Wang, Yawen Dong, Jingjing Tang, Jing Wang, Jianhui Liu
      A DMEDA-promoted and copper-catalyzed approach has been designed for the coupling of aryl halides and chiral α-aminoamides to afford a range of functionalized chiral α-amino anilides. This method has a higher yield and better reproducibility than those under ligand-free conditions. Of the two amino groups in the same molecule, only the amide NH2 is observed to react, showing high regioselectivity. In addition, no racemization occurs, and the ee can reach 99%. For certain hydroxyl-containing substrates, such as l-tyrosine amide and l-threonine amide, addition of a phase transfer catalyst (15-Crown-5) is necessary for such a transformation.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.03.003
       
  • Synthesis of apocarotenoids by acyclic cross metathesis and
           characterization as substrates for human retinaldehyde dehydrogenases
    • Authors: Marta Domínguez; Raquel Pequerul; Rosana Alvarez; Joan Giménez-Dejoz; Eszter Birta; Sergio Porté; Ralph Rühl; Xavier Parés; Jaume Farrés; Angel R. de Lera
      Pages: 2567 - 2574
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Marta Domínguez, Raquel Pequerul, Rosana Alvarez, Joan Giménez-Dejoz, Eszter Birta, Sergio Porté, Ralph Rühl, Xavier Parés, Jaume Farrés, Angel R. de Lera
      A new synthesis of three apocarotenoids, namely 14′-apo-β-carotenal, 12′-apo-β-carotenal and 10′-apo-β-carotenal, has been achieved that is based on the acyclic cross-metathesis of the hexaene derived from retinal and the corresponding partners. These compounds can be enzymatically converted to their carboxylic acids by the human aldehyde dehydrogenases involved in retinaldehyde oxidation. Their kinetic parameters suggest that these enzymes might play a role in the physiological metabolism of apocarotenoids.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.03.050
       
  • Catalyst-free Friedel-Crafts reaction of
           1-(N-acylamino)alkyltriarylphosphonium salts with electron-rich arenes
    • Authors: Jakub Adamek; Anna Węgrzyk; Monika Krawczyk; Karol Erfurt
      Pages: 2575 - 2583
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Jakub Adamek, Anna Węgrzyk, Monika Krawczyk, Karol Erfurt
      Friedel-Crafts reaction of 1-(N-acylamino)alkyltriarylphosphonium salts with arenes or heteroarenes without the need for any catalyst provided access to a wide range of biologically interesting N-(1-arylalkyl)amides or 1-arylalkylphosphonium salts which can be of great interest in the chemistry of ylides and phosphonium ionic liquids. Depending on reaction conditions and substrate structure, the reaction can be conducted selectively with high yields toward each of the above-mentioned products. Mechanistic aspects of the above transformations were also considered.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.03.053
       
  • Regioselective halogenation of pyridinium N-(benzoazynyl) aminides as a
           way to produce N-benzyl-α-aminobenzoazines
    • Authors: Elena Gala; M. Luisa Izquierdo; Julio Alvarez-Builla
      Pages: 2584 - 2595
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Elena Gala, M. Luisa Izquierdo, Julio Alvarez-Builla
      The halogenation of pyridinium N-(benzoazynyl) aminides with N-halosuccinimides provides a mild and regioselective method to functionalize the negatively charged diazine moiety in most cases. In some examples, however, formation of other products is explained. Finally, alkylation of the exocyclic nitrogen and reduction of the N–N bond provides a simple and straightforward strategy to obtain functionalized N-benzyl-benzoazynyl-α-amines.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.03.064
       
  • An efficient synthesis of multisubstituted 4-nitrobuta-1,3-dien-1-amines
           and application in cyclisation reactions
    • Authors: Brigita Vigante; Aiva Plotniece; Martins Rucins; Marina Petrova; Ruslan Muhamadejev; Karlis Pajuste; Sergey Belyakov; Yuriy G. Shermolovich; Arkadij Sobolev
      Pages: 2596 - 2607
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Brigita Vigante, Aiva Plotniece, Martins Rucins, Marina Petrova, Ruslan Muhamadejev, Karlis Pajuste, Sergey Belyakov, Yuriy G. Shermolovich, Arkadij Sobolev
      The synthesis of multisubstituted 4-nitrobuta-1,3-dien-1-amines (nitrodienamines) from 3-aminocrotonates and nitroacetaldehyde potassium salt, has been performed in 45–89% yields. This one-step protocol works efficiently with a broad range of N-H and N-substituted 3-aminocrotonates and delivers both primary and secondary nitrodienamines. In addition, the possible variations of the substituents at the positions 2 and 3 of 4-nitrobuta-1,3-dien-1-amine have been shown. Generally, the yields of secondary 4-nitrobuta-1,3-dien-1-amines were lower than those of primary ones. The synthetic usefulness of obtained 4-nitrobuta-1,3-dien-1-amines has also been demonstrated by achieving the synthesis of multisubstituted 5-nitro-1,6-dihydropyridines in two-component cyclocondensation reactions of 4-nitrobuta-1,3-dien-1-amines with aromatic or aliphatic aldehydes. Lastly, diverse N-H and N-substituted 5-nitro-1,6-dihydropyridines have been obtained in 35–87% yields.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.03.075
       
  • Enhanced shape selective catalysis of mixed cyclic ketones in aerobic
           Baeyer-Villiger oxidation with magnetic Cu-Fe3O4 supported mesoporous
           silica microspheres
    • Authors: Chunming Zheng; Shubin Chang; Chuanwu Yang; Dongying Lian; Chao Ma; Chunrong Zhang; Xiangrui Fan; Shichao Xu; Xiaohong Sun
      Pages: 2608 - 2616
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Chunming Zheng, Shubin Chang, Chuanwu Yang, Dongying Lian, Chao Ma, Chunrong Zhang, Xiangrui Fan, Shichao Xu, Xiaohong Sun
      Various strategies have been developed to improve the conversion for the Baeyer-Villiger oxidation. However, the catalytic effects of the Baeyer-Villiger oxidation for the mixed ketones are rarely reported, though it is also important for the natural and industrial separation processes. In this report, magnetite Cu modified Fe3O4 supported mesoporous silica microspheres (Cu-Fe3O4@mSiO2) have been successfully synthesized by two step direct hydrothermal method (DHT). Over 99% of cyclohexanone conversion was obtained with mild air oxidation and benzaldehyde as sacrificing agent over Cu-Fe3O4@mSiO2. The catalytic system also shows higher conversion rates for small molecular ketones in the mixed ketone reactants, which was attributed to the enhanced mass transfer effect and Fe-Cu composite active sites in the magnetite mesoporous silica microspheres. The catalyst could be recycled for four times with similar catalytic performance, which shows enhanced shape selectivity in aerobic Baeyer-Villiger oxidations for mixed cyclic ketones.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.009
       
  • Influence of sulfur groups on carboxylic acid strengths
    • Authors: Erwin Boschmann; Roger D. Miller
      Pages: 2617 - 2619
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Erwin Boschmann, Roger D. Miller
      The relative acid strength for a series of monocarboxylic acids of the general formula RX(CH2)n COOH and related dicarboxylic acids of the general formula HOOC(CH2)n X(CH2)n COOH, where R = Ph or Me, X = CH2, S, SO, or SO2 ; and n = 1 or 2 as appropriate; have been studied as a function of X. It is found that sulfur containing acids have lower pKa values than the corresponding carbon analogues, that the pKa is highest for the thioacids and lowest for the sulfonyl acids, that the pKas increase as n increases, and that for the dicarboxylic acid systems only the thio members show a significant reduction in pKa (2) – pKa (1) differences upon changing n from 1 to 2.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.007
       
  • New tetramic acid derivatives from the deep-sea-derived fungus
           Cladosporium sp. SCSIO z0025
    • Authors: Zhong-hui Huang; Xu-hua Nong; Xiao Liang; Shu-hua Qi
      Pages: 2620 - 2626
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Zhong-hui Huang, Xu-hua Nong, Xiao Liang, Shu-hua Qi
      Eight new tetramic acid derivatives, cladosporiumins A–H (1–8) were isolated from a culture broth of Cladosporium sp. SCSIO z0025 derived from the deep-sea sediment collected from Okinawa Trough. Their structures were elucidated by extensive spectroscopic data analysis. Compounds 1–3 were unique 3-acyltetramic acids with a hexyl enic alcohol side chain and a six-membered lactone ring substituted at C-3 of the 2, 4-pyrrolidinedione skeleton. The absolute configurations of chiral carbons of the 2, 4-pyrrolidinedione unit in 1–4 and 7 were established by quantum chemical calculations of the electronic circular dichroism (ECD) spectra. And the absolute configurations of chiral carbons of the six-membered lactone ring in 1–3 were established by density functional theory calculation of their 13C NMR chemical shifts. In addition, all the compounds were tested for cytotoxic, antibacterial, anti-biofilm, and AchE inhibitory activities.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.010
       
  • Enantiospecific total synthesis of the putative structure of
           cryptopyranmoscatone B2
    • Authors: Kannan Vaithegi; Kavirayani R. Prasad
      Pages: 2627 - 2633
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Kannan Vaithegi, Kavirayani R. Prasad
      Total synthesis of THP tethered pyrone containing natural product cryptopyranmoscatone B2 was accomplished from commercially available 2-deoxyribose. The key THP unit was assembled by FeCl3 catalyzed cyclization of an allyl alcohol. Brown allylation and RCM reactions were employed to construct the lactone unit. The synthesis represents the first total synthesis of the putative structure of the natural product.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.011
       
  • Substrate engineering: Effects of different N-protecting groups in the
           CAL-B-catalysed asymmetric O-acylation of
           1-hydroxymethyl-tetrahydro-β-carbolines
    • Authors: Rita Megyesi; Enikő Forró; Ferenc Fülöp
      Pages: 2634 - 2640
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Rita Megyesi, Enikő Forró, Ferenc Fülöp
      In the frame of substrate engineering, the steric effect of different N-protecting groups on the enantioselectivity and reaction rate of CAL-B-catalysed (S)-selective O-acylation of N-protected 1-hydroxymethyl-tetrahydro-β-carbolines was investigated. Excellent enantioselectivities (E > 200) were observed when the acylation of N-Boc [(±)-1], N-Cbz [(±)-3], and N-Fmoc-protected [(±)-4] substrates was performed with the use of CAL-B and acetic anhydride in toluene at 60 °C. The resolution of N-acetyl-protected substrate (±)-2 showed excellent E (>200) after 30 min, but as the reaction progressed, E started decreasing after 2 days, because of N→O and O→N acyl migrations. Preparative resolutions of (±)-3 and (±)-4 resulted in unreacted amino alcohols (R)-3 and (R)-4 and esters (S)-7a and (S)-8a with good enantiomeric excesses (≥88%) and high yields (≥44%).
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.012
       
  • Synthesis of bis(amidoxime)s and evaluation of their properties as
           uranyl-complexing agents
    • Authors: Jérémy Stemper; Wei Tuo; Eva Mazarío; Ahmed S. Helal; Alexandre Djurovic; Claude Lion; Jean-Michel El Hage Chahine; François Maurel; Miryana Hémadi; Thierry Le Gall
      Pages: 2641 - 2649
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Jérémy Stemper, Wei Tuo, Eva Mazarío, Ahmed S. Helal, Alexandre Djurovic, Claude Lion, Jean-Michel El Hage Chahine, François Maurel, Miryana Hémadi, Thierry Le Gall
      Uranium pollution involves high toxicity and radioactivity and, therefore, constitutes a grave threat to human health and the environment. Chelation is an effective method for sequestering uranium. It is well known that chelators based on oxime groups are able to complex uranyl cations efficiently. To this end, various bis(amidoxime)s were synthesized by reaction of hydroxylamine with the corresponding dinitriles. In these compounds the amidoximes are separated by chains of various lengths, some including a heterocycle (pyridine or 1,3,5-triazine). The abilities of these bis(amidoxime)s to complex uranyl cation in water were evaluated by determining their affinity constants and thermodynamic parameters by means of Isothermal Titration Calorimetry (ITC). DFT calculations were also performed, to determine the optimum structures of the complexes formed between uranyl cations and the oximate groups. A tetrakis(amidoxime), also synthesized in this work, shows good affinity for uranium, and a single molecule is able chelate several uranyl cations. These results are of importance for the remediation of uranium-polluted wastewaters, and open up several perspectives for the design and synthesis of new amidoxime compounds.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.016
       
  • Further studies on the application of vinylogous amides and
           β-halovinylaldehydes to the regiospecific synthesis of unsymmetrical,
           polyfunctionalized 2,3,4- and 1,2,3,4- substituted pyrroles
    • Authors: John T. Gupton; Alex Shimozono; Evan Crawford; Joe Ortolani; Evan Clark; Matt Mahoney; Campbell Heese; Jeffrey Noble; Carlos Perez Mandry; Rene Kanters; Raymond N. Dominey; Emma W. Goldman; James A. Sikorski; Daniel C. Fisher
      Pages: 2650 - 2663
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): John T. Gupton, Alex Shimozono, Evan Crawford, Joe Ortolani, Evan Clark, Matt Mahoney, Campbell Heese, Jeffrey Noble, Carlos Perez Mandry, Rene Kanters, Raymond N. Dominey, Emma W. Goldman, James A. Sikorski, Daniel C. Fisher
      Highly functionalized pyrroles with appropriate regiochemical functionality represent an important class of marine natural products and potential drug candidates. We describe herein a detailed study of the reaction of α-aminoacid esters with vinylogous amides and also β-halovinylaldehydes for the regiospecific synthesis of 2,3,4-trisubstituted and 1,2,3,4-tetrasubstituted pyrroles. Since the vinylogous amides and β-halovinylaldehydes are readily available precursors, rapid access to a wide variety of unsymmetrically substituted pyrroles is accomplished via this methodology.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.017
       
  • Improved total synthesis of (±)-Tetragocarbone A
    • Authors: Eiji Nishimura; Yoko Yasuno; Tetsuro Shinada
      Pages: 2664 - 2668
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Eiji Nishimura, Yoko Yasuno, Tetsuro Shinada
      Stereoselective total synthesis of (±)-tetragocarbone A isolated from the propolis of an Australian stingless bee, Tetragonula carbonaria, has been developed by focusing on the latent symmetry of 1. The requisite 1R*, 3R*, 6S* stereogenic centers were selectively installed by hydroxy group directing reactions including the late stage desymmetrization of the 1,3-diketone. The target natural product was successfully prepared in 12 steps from phloroglucinol on 300 mg.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.024
       
  • Aerobic intramolecular aminothiocyanation of unactivated alkenes promoted
           by in situ generated iodine thiocyanate
    • Authors: Yangyang Feng; Muhammad Ijaz Hussain; Xiaohui Zhang; Jian Shi; Wen Hu; Yan Xiong
      Pages: 2669 - 2676
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Yangyang Feng, Muhammad Ijaz Hussain, Xiaohui Zhang, Jian Shi, Wen Hu, Yan Xiong
      Aerobic intramolecular aminothiocyanation of unactivated alkenes has been developed by in situ generated iodine thiocyanate under open-flask conditions. This protocol provides a concise and efficient method for synthesizing SCN-containing pyrrolidine, piperidine and indoline derivatives with isolated yields of up to 87%. Furthermore, mixing iodine and sodium thiocyanate with oxygen afforded iodine thiocyanate (ISCN) and dithiocyanatoiodate [I(SCN)2]- which were testified by liquid chromatography mass spectrometry. A mechanistic investigation indicates that iodonium ion and sulfonium ion intermediates might be involved in this transformation.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.023
       
  • Meso-substituted porphyrin photosensitizers with enhanced near-infrared
           absorption: Synthesis, characterization and biological evaluation for
           photodynamic therapy
    • Authors: Dong Pan; Xiangmin Zhong; Weidong Zhao; Zhaofeng Yu; Zhou Yang; Dong Wang; Hui Cao; Wanli He
      Pages: 2677 - 2683
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Dong Pan, Xiangmin Zhong, Weidong Zhao, Zhaofeng Yu, Zhou Yang, Dong Wang, Hui Cao, Wanli He
      Porphyrin derivatives are widely explored and used in photodynamic therapy, for their marvelous therapeutic properties. In order to fill in the gaps of insufficient photosensitizers with near-infrared absorption, three porphyrin molecules, 5,10,15,20-tetrakis(3,4-bis(2-(-2-(2-hydroxyethoxy)ethoxy)ethoxy)benzyl)zinc porphyrin(P1), 5,15-bis(3,4-bis(2-(-2-(2-hydroxyethoxy)ethoxy)ethoxy)benzyl)-10,20-bis(2-(2-(2-(4-ethynylphenoxy)ethoxy)ethoxy)ethanol)zincporphyrin(P2),5,15-bis(3,4-bis(2-(-2-(2-hydroxyethoxy)ethoxy)ethoxy)benzyl)-10,20-N,N-dibutyl-4-ethynylaniline zinc porphyrin(P3), were designed and synthesized targeting for more efficient cancer treatment. Excellent photophysical properties were illustrated by UV–vis absorption and emission spectra with enhanced absorbance between 650 and 750 nm and fluorescence emission within 600–800 nm. Besides, with high 1O2 quantum yield, especially P2 (0.89), all porphyrins were further evaluated in vitro by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay against Hela cells and exhibited negligible dark toxicity and robust phototoxicity. Fluorescence confocal laser microscopy confirmed cellular uptake and diffusion of these porphyrins, therefore demonstrated their potential and promising applications in photodynamic therapy.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.025
       
  • Investigation on sensing mechanism of a fluorescent probe for TNP
           detection in aqueous solution
    • Authors: Yinhua Ma; Li Zhao; Yang Li; Jianyong Liu; Yanqiang Yang; Tianshu Chu
      Pages: 2684 - 2691
      Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21
      Author(s): Yinhua Ma, Li Zhao, Yang Li, Jianyong Liu, Yanqiang Yang, Tianshu Chu
      In this paper, the synthesis and spectral properties of a fluorescent probe Nph-An for TNP detection has been introduced and its sensing mechanism has been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. For TNP detection in aqueous solution the probe shows high sensitivity, selectivity and efficiency. The theoretical results demonstrate that the excited-state intermolecular hydrogen bonding (HB) plays an important role for the TNP detection. In the excited state, the intermolecular HB between Nph-An and TNP is strengthened, and thus strongly facilitates the nonirradiative PET process to induce the fluorescence quenching. Whereas, the probe Nph-An emits strong fluorescence because of the intramolecular charge transfer (ICT) properties, which is confirmed by the solvatochromism effect. The calculated absorption spectra of Nph-An and Nph-An + TNP agree well with the experimental values and theoretical analysis provides a detailed and clear explanation of the sensing mechanism.
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      PubDate: 2018-05-02T06:47:13Z
      DOI: 10.1016/j.tet.2018.04.034
       
  • Experimental and theoretical studies on thermodynamics and properties of
           tautomers of 2-substituted
           6(4)-methyl-1,4(1,6)-dihydropyrimidine-5-carboxylates
    • Authors: Hidetsura Cho; Yoshio Nishimura; Hiroshi Ikeda; Mitsuhiro Asakura; Shinji Toyota
      Pages: 2405 - 2413
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Hidetsura Cho, Yoshio Nishimura, Hiroshi Ikeda, Mitsuhiro Asakura, Shinji Toyota
      Experimental and theoretical studies on the thermodynamics and properties of 2-substituted 6(4)-methyl-1,4(1,6)-dihydropyrimidine-5-carboxylates were undertaken by 1H NMR measurements and DFT (density functional theory) calculations. The ratios of tautomers a/b of dihydropyrimidines (DPs) 1, 2, and 3 were determined under various conditions to reveal the effects of temperature, solvent, and concentration on the thermodynamic data. The observed results, the free energy differences (ΔG), enthalpy differences (ΔH), and entropy differences (ΔS), are discussed in terms of the molecular structures, dipole moments (DM), and the electrostatic potential maps calculated by the DFT to clarify the nature of the DPs.
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      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.032
       
  • An efficient synthesis of fully substituted
           pyrazolo[3,4-b]pyridin-5-amines from α-azidochalcones
    • Authors: Mehdi Adib; Fariba Peytam
      Pages: 2414 - 2420
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Mehdi Adib, Fariba Peytam
      A facile, mild and efficient procedure for the synthesis of fully substituted pyrazolo[3,4-b]pyridin-5-amines is reported. A mixture of an α-azidochalcone, a 5-aminopyrazole and t-BuOK was stirred in DMF at ambient temperature for 5 min to afford the corresponding pyrazolo[3,4-b]pyridin-5-amines in good to excellent yields.
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      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.036
       
  • Selective endoperoxide formation by heterogeneous TiO2 photocatalysis with
           dioxygen
    • Authors: Xiaofeng Qiao; Subharanjan Biswas; Wenli Wu; Feng Zhu; Chen-Ho Tung; Yifeng Wang
      Pages: 2421 - 2427
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Xiaofeng Qiao, Subharanjan Biswas, Wenli Wu, Feng Zhu, Chen-Ho Tung, Yifeng Wang
      We report the selective formation of endoperoxides by aerobic TiO2 photocatalysis through the cyclic addition of dioxygen and a non-conjugated diene, the first heterogeneous catalytic system for endoperoxide synthesis. This green protocol does not require any additive and the photocatalyst is abundant and recyclable, providing a yield up to 64% and >20:1 diastereoselectivity. Mechanistic investigations were carried out by using product analysis, kinetic studies, O-18 labelling experiments, electron-spin resonance and a set of quenching experiments. Superoxide (but not singlet oxygen, triplet oxygen or peroxide) is directly involved in the reaction cascade to form the endoperoxide product. The new findings may be helpful for future for designing eco-friendly and energy sustainable strategies for selective oxygenation reactions using semiconductors, O2 and sunlight.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.040
       
  • Potassium tert-butoxide-mediated generation of arynes from
           o-bromoacetophenone derivatives
    • Authors: Denghu Chang; Fei Gao; Lei Shi
      Pages: 2428 - 2434
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Denghu Chang, Fei Gao, Lei Shi
      o-bromoacetophenone derivatives as new versatile aryne precursors are induced to selectively eliminate the CAr Br and CAr C(Ac) bonds in the help of t-BuOK. Furthermore, the active aryne intermediates are successfully applied in a substantial set of reactions including N-arylation and copper-catalyzed coupling with various terminal alkynes. It is important to note that the generation of benzyne intermediate is demonstrated through cycloadditon reaction experiment with furan.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.058
       
  • Binary additive effect of benzoic acid in ipso-Friedel-Crafts-type
           dearomatization of phenols using a chiral silver phosphate
    • Authors: Hiroki Nakayama; Shingo Harada; Ayaka Kanda; Irene Mei-Yi Kwok; Tetsuhiro Nemoto
      Pages: 2435 - 2439
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Hiroki Nakayama, Shingo Harada, Ayaka Kanda, Irene Mei-Yi Kwok, Tetsuhiro Nemoto
      We previously developed a chemoselective asymmetric phenol dearomatization using a silver catalyst and benzoic acid as an additive to enhance the reaction efficiency. The mechanistic role of the additive, however, remained unclear. Herein we describe detailed studies to elucidate the additive effect, which revealed that benzoic acid plays two supporting roles in the silver-catalyzed reaction. First, it promotes protonation of a silver enolate intermediate to improve the chemical yield of a spirolactam. Second, it dissociates a homochiral dimer of silver phosphate to generate a monomeric species.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.060
       
  • Comparing of endocyclic and exocyclic cleavage reactions using mycothiol
           synthesis as an example
    • Authors: Shino Manabe; Yukishige Ito
      Pages: 2440 - 2446
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Shino Manabe, Yukishige Ito
      Glycosides can be cleaved in either an exo- or endocyclic fashion. Specifically, the former pathway is used during conventional glycosylation; whereas the latter pathway has not been the subject of attention. Endocyclic cleavage reaction enable the anomerization of β-glycosides to α-glycosides. Herein, we compared the efficacies of endo- and exocyclic cleavage reactions during the synthesis of mycothiol, a potential drug development target for tuberculosis treatment, in terms of selectivity and product yield. In addition, the direct resolution of benzyl-protected inositol by a highly stereoselective glycosylation reaction was investigated.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.069
       
  • Efficient dealkylation of aryl alkyl ethers catalyzed by Cu2O
    • Authors: Lingxian Liu; Zengguang Li; Changjun Chen; Huanrong Li; Lijin Xu; Zhiyong Yu
      Pages: 2447 - 2453
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Lingxian Liu, Zengguang Li, Changjun Chen, Huanrong Li, Lijin Xu, Zhiyong Yu
      An efficient protocol for dealkylation of aryl alkyl ethers under the catalysis of inexpensive and easily reusable Cu2O has been described. The phenol products were obtained in high yields, and a range of functional groups were well tolerated. The choice of solvent is critical to the catalysis, and CH3OH proved to be the optimal choice. Mechanistic investigations showed that this reaction possibly proceeds via a single-electron transfer (SET) process.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.070
       
  • Synthesis and properties of fully conjugated macrocycles composed of
           m-diethynylene-phenylene-bridged two dibenzofuran, dibenzothiophene and
           carbazole units
    • Authors: Toshiaki Shimasaki; Shunsuke Okajima; Rino Ishikawa; Shinji Kawaguchi; Takeshi Akimoto; Naoto Asano; Tetsuo Iwanaga; Motonori Watanabe; Naozumi Teramoto; Mitsuhiro Shibata
      Pages: 2454 - 2465
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Toshiaki Shimasaki, Shunsuke Okajima, Rino Ishikawa, Shinji Kawaguchi, Takeshi Akimoto, Naoto Asano, Tetsuo Iwanaga, Motonori Watanabe, Naozumi Teramoto, Mitsuhiro Shibata
      Fully conjugated macrocycles 1a−1c composed of m-diethynylene-phenylene-bridged two dibenzofuran, dibenzothiophene and carbazole units were synthesized via Sonogashira cross coupling reactions under high-diluted condition. These conjugated macrocycles were fully characterized by 1H NMR, 13C NMR, FT-IR, Mass spectroscopies and elemental analysis. Photophysical and redox properties of 1a−1c were investigated by means of UV–vis/fluorescence spectroscopies and cyclic voltammetry, respectively, and those features were compared with those of the corresponding linear phenylethynyldibenzoheterols 11a−11c. Furthermore, their structural and electronic insights were studied by theoretical calculations at the B3LYP/cc-pVDZ//B3LYP/6-31G(d) level of theory.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.072
       
  • Synthesis and properties of new heterocyclic betaines:
           
    • Authors: Liya D. Funt; Mikhail S. Novikov; Galina L. Starova; Alexander F. Khlebnikov
      Pages: 2466 - 2474
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Liya D. Funt, Mikhail S. Novikov, Galina L. Starova, Alexander F. Khlebnikov
      New heterocyclic betaines, 4-aryl-5-(alkoxycarbonyl)-2-oxo-3-(pyridin-1-ium-1-yl)-2,3-dihydro-1H-pyrrol-3-ides, were synthesized in good yields by the reaction of alkyl 2H-azirine-2-carboxylates with 2-methoxy-2-oxo-1-(pyridin-1-ium-1-yl)ethan-1-ides, generated from the corresponding pyridinium salts. The betaines exist as the NH-tautomers both in solution and in the solid state. Two molecules of the betaine form a dimer by hydrogen bonds of the type NH⋯O in solid state. According to TD DFT calculations the long-wave absorption band in betaines mainly corresponds to the intramolecular charge transfer between the negatively charged pyrrole unit and the positively charged pyridinium group. The blue shift of the long-wave absorption in protic solvents was adequately described in terms of H-complex formation with the nucleophilic centre of the molecular skeleton.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.071
       
  • Synthesis of N-Sulfonylformamidines by tert-butyl
           Hydroperoxide–Promoted, metal-free, direct oxidative dehydrogenation of
           aliphatic amines
    • Authors: Ayijiamali Rouzi; Ruzeahong Hudabaierdi; Abudureheman Wusiman
      Pages: 2475 - 2481
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Ayijiamali Rouzi, Ruzeahong Hudabaierdi, Abudureheman Wusiman
      A direct and convenient metal-free method to prepare sulfonyl amidines in the presence of aqueous tert-butyl hydroperoxide (T-HYDRO) has been developed. Different tertiary and secondary amines were tested for compatibility with the oxidative conditions and could be coupled with sulfonyl azides to form the corresponding amidines in moderate to good yields.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.074
       
  • Cp2TiCl2-catalyzed reaction of symmetrical alkynes with α,ω-dicarboxylic
           acid esters and ЕtAlCl2: An original pathway to С5-С6 cyclic ketones
           and tetrasubstituted furans
    • Authors: Leila O. Khafizova; Nuri M. Chobanov; Mariya G. Shaibakova; Natalya R. Popod'ko; Tatyana V. Tyumkina; Usein M. Dzhemilev
      Pages: 2482 - 2487
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Leila O. Khafizova, Nuri M. Chobanov, Mariya G. Shaibakova, Natalya R. Popod'ko, Tatyana V. Tyumkina, Usein M. Dzhemilev
      An original method for the synthesis of С5-С6 cyclic ketones and tetrasubstituted furans was developed based on the Cp2TiCl2-catalyzed reaction of symmetrical alkynes and α,ω-dicarboxylates in the presence of Mg and ЕtAlCl2. The length of the hydrocarbon chain between carboxyl groups in a,ω-dicarboxylic acid esters affects the chemoselectivity of the reaction. The formation of 2-alkylidene and 2-alkenyl cyclopent(hex)an-1-ones occurred in the reaction with esters of glutaric and adipic acids. α,ω-Dicarboxylic acid esters with more than four methylene units between carboxyl groups gave rise to substituted furans. Stereochemistry of 2-alkenyl cyclopent(hex)an-1-ones was determined based on the analysis of experimental and theoretical data obtained from DFT calculations.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.04.008
       
  • Total Synthesis of Sch 725674
    • Authors: Kannan Vaithegi; Kavirayani R. Prasad
      Pages: 2488 - 2492
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Kannan Vaithegi, Kavirayani R. Prasad
      A concise total synthesis of the macrolactone natural product Sch 725674 is accomplished starting from commercially available 2-deoxy- d -ribose. Pivotal reactions employed in the synthesis include the addition of 4-pentenylmagnesium bromide to the lactol derived from 2-deoxy- d -ribose, olefin cross metathesis and Yamaguchi macrolactonization.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.04.014
       
  • Efficient synthesis of 3-benzoyl Benzo[b]thiophenes and raloxifene via
           Mercury(II)-Catalyzed cyclization of 2-alkynylphenyl alkyl sulfoxides
    • Authors: Shi-Ming Wen; Cheng-Han Lin; Chin-Chau Chen; Ming-Jung Wu
      Pages: 2493 - 2499
      Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20
      Author(s): Shi-Ming Wen, Cheng-Han Lin, Chin-Chau Chen, Ming-Jung Wu
      The unique selective estrogen receptor modulator, Raloxifene (1), and antitubulin agent 2 were synthesized through the key intermediate, 4-methoxybenzyl 2-bromo-4-methoxyphenyl sulfoxide (6), respectively. It was found that compared with the o-sulfanyl aryl bromides, the sulfinyl group at ortho position accelerated the Sonogashira coupling reaction of aryl bromides. Thus, compound 6 was coupled with 3,4,5-trimethoxyphenyl acetylene, followed by mercury-catalyzed cyclization reaction afford compound 2 in 79% overall yield. Raloxifene (1) was prepared from compound 6 in four steps and 33% overall yield via coupling reaction with 1-trimethylsily-2-(4-tert-butyldimethylsiloxy)phenylethyne, mercury-catalyzed cyclization reaction, alkylation and demethylation.
      Graphical abstract image

      PubDate: 2018-04-25T05:24:58Z
      DOI: 10.1016/j.tet.2018.03.067
       
  • Synthesis and biological activity of apratoxin derivatives
    • Authors: Ettore J. Rastelli; Don M. Coltart
      Pages: 2269 - 2290
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Ettore J. Rastelli, Don M. Coltart
      This review covers the total asymmetric synthesis and biological evaluation of derivatives of the marine natural products known as the apratoxins.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2017.11.004
       
  • ProteoFind: A script for finding proteins that are suitable for chemical
           synthesis
    • Authors: Akira Shigenaga; Naoto Naruse; Akira Otaka
      Pages: 2291 - 2297
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Akira Shigenaga, Naoto Naruse, Akira Otaka
      ProteoFind is a computational script for finding proteins that are suitable for fragment ligation-based chemical synthesis. This paper describes the development and case studies of ProteoFind, which searches protein lists obtained from the UniProt website. Its application to visualize areas covered by several one-pot three-fragment ligation methods is also discussed. The results demonstrate that ProteoFind not only saves time when searching for synthetic target proteins, but also proposes many candidate proteins from among which biomedically interesting proteins could be found. It also enables clarification of the features of ligation methods by comparing the areas to which each ligation reaction is accessible.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.030
       
  • Synthesis of α-benzylated amides via electrocatalytic Favorskii
           rearrangement of 1, 3-diarylacetones
    • Authors: Wei Liu; Wei Huang; Tianlei Lan; Haijuan Qin; Cheng Yang
      Pages: 2298 - 2305
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Wei Liu, Wei Huang, Tianlei Lan, Haijuan Qin, Cheng Yang
      Electrolysis of 1,3-diarylacetones with aliphatic amines in Bu4NI/CH3CN to racemic Favorskii amides via benzyl group rearrangement has been developed. The electroconversion is easily conducted in a simple undivided cell under constant-current conditions at room temperature. The electrocatalytic Favorskii rearrangement of 1,3-diarylacetones including electron-withdrawing substituents was favored and gave a good yield of α-benzylated amides. When several unsymmetrical ketones were employed as substrates, this rearrangement with moderate regioselectivity was observed. This chemistry also provides an efficient approach to construct a chiral center at α-position of amides.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.033
       
  • Baylis-Hillman acetates in organic synthesis: A simple two-step strategy
           for oxindole-spiro-α-arylidene-γ-butyrolactone framework
    • Authors: Deevi Basavaiah; Harathi Lingam; Thelagathoti Hari Babu
      Pages: 2306 - 2313
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Deevi Basavaiah, Harathi Lingam, Thelagathoti Hari Babu
      A facile, convenient, and two step strategy for synthesis of spirooxindoles containing α-arylidene-γ-butyrolactone moiety has been developed via monoalkylation of 2-oxindoles with Baylis-Hillman acetates followed by the spirolactonization of the resulting cinnamic esters on treatment with phenyliodine (III) bistrifluoroacetate (PIFA).
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.035
       
  • One pot synthesis of aminonaphthoquinone derivatives using Cu(II)
           immobilized on hyperbranched polyglycerol functionalized graphene oxide as
           a reusable catalyst under solvent-free conditions
    • Authors: Hossein Naeimi; Maryam Farahnak Zarabi
      Pages: 2314 - 2323
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Hossein Naeimi, Maryam Farahnak Zarabi
      A new Cu(II) immobilized on hyperbranched polyglycerol (HPG) functionalized graphene oxide catalyst was prepared and characterized by FT-IR, TGA, FE-SEM, XRD, and ICP-OES techniques. This catalyst was used efficiently for the preparation of aminonaphthoquinones via one-pot three-component condensation reaction under solvent-free conditions. The catalyst could be easily recovered and reusable several times without a significant loss of activity, which make this method attractive and in a close agreement with green chemistry.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.047
       
  • Iodine-mediated direct synthesis of multifunctional 2-aminobenzimidazoles
           from N-substituted o-diaminoarenes and isothiocyanates
    • Authors: Zhen Wang; Qiongli Zhao; Jiao Hou; Wenquan Yu; Junbiao Chang
      Pages: 2324 - 2329
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Zhen Wang, Qiongli Zhao, Jiao Hou, Wenquan Yu, Junbiao Chang
      Multifunctional 2-aminobenzimidazoles were directly synthesized through sequential addition of N-substituted o-diaminoarenes to isothiocyanates, formation of carbodiimides via I2-mediated oxidative desulfurization, and intramolecular cycloaddition. This efficient and eco-friendly synthetic process provides a facile access to diverse 2-aminobenzimidazole derivatives from readily accessible substrates under mild reaction conditions in a scalable fashion.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.049
       
  • Rhodium(III)-catalyzed CH amination of 2-arylquinazolin-4(3H)-one with
           N-alkyl-O-benzoyl-hydroxylamines
    • Authors: Yuanguang Zhang; Jiang Huang; Zhihong Deng; Xunchun Mao; Yiyuan Peng
      Pages: 2330 - 2337
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Yuanguang Zhang, Jiang Huang, Zhihong Deng, Xunchun Mao, Yiyuan Peng
      N-benzoate alkylamines were used as the aminating agents, a efficient Rh-catalyzed ortho CH amination of 2-arylquinazolin-4(3H)-one has been reported. The reactions exhibit high efficient and good functional group tolerance. Exclusive 2,6-bis-aminated product and good to excellent yields were obtained under mild reaction conditions.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.051
       
  • Combining prolinamides with 2-pyrrolidinone: Novel organocatalysts for the
           asymmetric aldol reaction
    • Authors: Ismini Vlasserou; Maria Sfetsa; Dimitrios-Triantafyllos Gerokonstantis; Christoforos G. Kokotos; Panagiota Moutevelis-Minakakis
      Pages: 2338 - 2349
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Ismini Vlasserou, Maria Sfetsa, Dimitrios-Triantafyllos Gerokonstantis, Christoforos G. Kokotos, Panagiota Moutevelis-Minakakis
      Peptides and especially prolinamides have been identified as excellent organocatalysts for the aldol reaction. The combination of prolinamides with derivatives bearing the 2-pyrrolidinone scaffold, deriving from pyroglutamic acid, led to the identification of novel organocatalysts for the intermolecular asymmetric aldol reaction. The new hybrids were tested both in organic and aqueous media. Among the compounds tested, 22 afforded the best results in petroleum ether, while 25 afforded the products in brine in high yields and selectivities. Then, various ketones and aldehydes were utilized and the products of the aldol reaction were obtained in high yields (up to 100%) with excellent diastereo- (up to 97:3 dr) and enantioselectivities (up to 99% ee).
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.054
       
  • Regioselective synthesis of 2,3-disubstituted 1-alkyl pyrrolo[2,3-b]
           quinoxalines through palladium-catalyzed Heck reaction of chalcones and
           evaluation of their anti-bacterial activities
    • Authors: Tayebeh Besharati-Seidani; Ali Keivanloo; Babak Kaboudin; Akihiro Yoshida; Tsutomu Yokomatsu
      Pages: 2350 - 2358
      Abstract: Publication date: 10 May 2018
      Source:Tetrahedron, Volume 74, Issue 19
      Author(s): Tayebeh Besharati-Seidani, Ali Keivanloo, Babak Kaboudin, Akihiro Yoshida, Tsutomu Yokomatsu
      The regioselective synthesis of 1-alkyl-2-aryl-3-acyl pyrrolo[2,3-b]quinoxalines through palladium-catalyzed Heck coupling reaction/heteroannulation was reported. The reaction of N-alkyl/benzyl-3-chloroquinoxaline-2-amines with chalcones catalyzed by Pd(OAc)2 in the presence of KOtBu, as the base, in DMSO afforded the desired products in good-to-high yields. The MIC and MBC determinations revealed that these compounds could be used in the future research works for the development of antibiotics.
      Graphical abstract image

      PubDate: 2018-04-15T14:42:14Z
      DOI: 10.1016/j.tet.2018.03.055
       
  • Graphical abstract TOC cont'd
    • Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21


      PubDate: 2018-05-02T06:47:13Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21


      PubDate: 2018-05-02T06:47:13Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 24 May 2018
      Source:Tetrahedron, Volume 74, Issue 21


      PubDate: 2018-05-02T06:47:13Z
       
  • Graphical Abstract TOC Cont'd
    • Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20


      PubDate: 2018-04-25T05:24:58Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20


      PubDate: 2018-04-25T05:24:58Z
       
  • Graphical abstract TOC
    • Abstract: Publication date: 17 May 2018
      Source:Tetrahedron, Volume 74, Issue 20


      PubDate: 2018-04-25T05:24:58Z
       
 
 
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