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Journal Cover Tetrahedron
  [SJR: 0.991]   [H-I: 189]   [123 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0040-4020
   Published by Elsevier Homepage  [3043 journals]
  • Synthesis and identification of metabolite biomarkers of 25C-NBOMe and
           25I-NBOMe
    • Authors: Xiongyu Wu; Caroline Eriksson; Ariane Wohlfarth; Jakob Wallgren; Robert Kronstrand; Martin Josefsson; Johan Dahlén; Peter Konradsson
      Pages: 6393 - 6400
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Xiongyu Wu, Caroline Eriksson, Ariane Wohlfarth, Jakob Wallgren, Robert Kronstrand, Martin Josefsson, Johan Dahlén, Peter Konradsson
      Synthetic routes have been developed for synthesis of potential metabolites of 25C-NBOMe and 25I-NBOMe. Nine potential metabolites have been synthesized, among which compounds 8 and 20a could be used as metabolite biomarkers of 25C-NBOMe and 20b of 25I-NBOMe in urinary detection at forensic laboratories to prove intake.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.024
       
  • An aryl-bridged dixanthene scaffold for building multinucleating ligands
           and supramolecular assemblies: Syntheses and structures
    • Authors: Matthew Mudge; Alpesh Ramanlal Patel; Murat Bingül; Mohan Bhadbhade; Stephen B. Colbran
      Pages: 6401 - 6409
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Matthew Mudge, Alpesh Ramanlal Patel, Murat Bingül, Mohan Bhadbhade, Stephen B. Colbran
      An aryl-bridged dixanthene scaffold is quickly prepared and readily derivatized with functional groups at the four 4,5-positions adjacent to the oxygen atoms of the two xanthene groups: syntheses of five potentially tetradentate, multinucleating, metal-binding ligands illustrate the usefulness of the methodology.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.026
       
  • Strategies for the synthesis of HBGl3, a glutamic acid derived ligand
           bearing phenolic and azacarboxylate donor groups at the nitrogen atom
    • Authors: Raminder S. Mulla; Melissa T. Walden; Dmitry S. Yufit; Tanya Desa; Elena Lurie-Luke; J.A. Gareth Williams
      Pages: 6410 - 6420
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Raminder S. Mulla, Melissa T. Walden, Dmitry S. Yufit, Tanya Desa, Elena Lurie-Luke, J.A. Gareth Williams
      The development of a route applicable to the preparation of acyclic glutamic acid-based chelating ligands bearing two different auxiliary donor groups linked to the nitrogen atom by methylene spacers is described and applied to the synthesis of the new polydentate ligand HBGl 3 , the first example of such a structure. The synthesis is accomplished using a strategy employing reductive amination and t-butyl ester protected intermediates. The most basic pKa values for the HBGl 3 ligand have been estimated via potentiometric and UV–Visible titration techniques.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.032
       
  • Janus-faced 5-methyl group in 2-hydroxy-5-methyl-[1,4]-benzoquinone
    • Authors: Thomas Rosenau; Nele Sophie Zwirchmayr; Takashi Hosoya; Andreas Hofinger-Horvath; Markus Bacher; Antje Potthast
      Pages: 6421 - 6427
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Thomas Rosenau, Nele Sophie Zwirchmayr, Takashi Hosoya, Andreas Hofinger-Horvath, Markus Bacher, Antje Potthast
      The 5-methyl group in 2-hydroxy-[1,4]-benzoquinone shows a peculiar reactivity that depends on the pH of the reaction medium. Under acidic conditions, ortho-quinone methide tautomers of the parent para-quinones are present in equilibrium. The 5-methylene group is stabilized by resonance, incorporating canonic structures with a positive charge at this position and now acting as carbenium equivalent. These ortho-quinone methide intermediates can be trapped in hetero-Diels-Alder reactions with inverse electron demand or by reaction with trimethylsilyl chloride. Under alkaline/basic conditions, the 5-methyl group is deprotonated, this time performing as carbanion equivalent being once more stabilized by resonance. This facet of reactivity was used for instance in regioselective perdeuteration of the 5-methyl position or in Michael additions. The reaction medium is thus able to govern the chemical behavior of the 5-methyl group, to effect its umpoling and to switch the reactivity to the opposite. Like the Roman god Janus, these methyl groups have two faces, and the reaction medium decides which one is presented.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.038
       
  • [Cu(maloNHC)]-catalyzed synthesis of 2-aryl pyrazolo[5,1-a]isoquinolines
           by annulation of N′-(2-((trimethylsilyl)ethynyl)benzylidene)hydrazides
           with terminal aromatic alkynes
    • Authors: Huixin Liu; Le Lu; Ruimao Hua
      Pages: 6428 - 6435
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Huixin Liu, Le Lu, Ruimao Hua
      A [Cu(maloNHC)]-catalyzed synthesis of 2-aryl pyrazolo[5,1-a]isoquinolines via annulation of N′-(2-((trimethylsilyl)ethynyl)benzylidene)hydrazides with terminal aromatic alkynes was developed.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.037
       
  • Synthesis of tricyclic units of indole alkaloids: Application of Fischer
           indolization and olefin metathesis
    • Authors: Sambasivarao Kotha; Vikas R. Aswar; Gaurav Singhal
      Pages: 6436 - 6442
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Sambasivarao Kotha, Vikas R. Aswar, Gaurav Singhal
      Simple synthetic approaches to pyridocarbazole and azepinocarbazole derivatives have been reported via Fischer indolization, Grignard reaction and olefin metathesis as key steps. In addition, a combination Sonogashira coupling and Pauson-Khand reaction has been used to assemble extended pyridocarbazole derivative.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.039
       
  • Chiron approach for the total synthesis of (+)-synargentolide B
    • Authors: Jun Liu; Yangguang Gao; Linlin Wang; Yuguo Du
      Pages: 6443 - 6447
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Jun Liu, Yangguang Gao, Linlin Wang, Yuguo Du
      A concise and efficient chiron approach for the total synthesis of natural product synargentolide B was achieved in 10 steps with overall yields of 11.3% from D-mannitol and L-ethyl lactate. The key reactions included anti-Barbier allylation, cross-metathesis, and an intramolecular Yamaguchi esterification.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.041
       
  • Synthesis of 1,10-seco-triterpenoids by the Beckmann fragmentation from
           allobetulin
    • Authors: Irina A. Tolmacheva; Alexey V. Nazarov; Maxim V. Dmitriev; Eugene I. Boreko; Victoria V. Grishko
      Pages: 6448 - 6455
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Irina A. Tolmacheva, Alexey V. Nazarov, Maxim V. Dmitriev, Eugene I. Boreko, Victoria V. Grishko
      A new convenient route to synthesize 1,10-seco-triterpenoids from allobetulin was demonstrated. Stereoisomerism of starting oleanane 1-oximes was determined by X-ray crystallography and additionally confirmed by the structure of the obtained Beckmann rearrangement products. Absolute configuration of chiral centers of 1,10-secotriterpenoids was found to be identical to that of stereocenters in respective precursors. Antiviral activity of 1,10-seco-derivatives was studied against herpes simplex virus type I.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.044
       
  • Highly regioselective synthesis of 2,3-disubstituted 2H-1-benzopyrans:
           Brønsted acid catalyzed [4+2] cycloaddition reaction with a variety of
           arylalkynes via ortho-quinone methides
    • Authors: Kenta Tanaka; Mayumi Sukekawa; Yosuke Shigematsu; Yujiro Hoshino; Kiyoshi Honda
      Pages: 6456 - 6464
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Kenta Tanaka, Mayumi Sukekawa, Yosuke Shigematsu, Yujiro Hoshino, Kiyoshi Honda
      A highly regioselective one-pot synthesis of 2,3-disubstituted-2H-1-benzopyrans has been developed through Brønsted acid catalyzed [4+2] cycloaddition reaction with a variety of arylalkynes via ortho-quinone methides. A catalytic amount of trifluoromethanesulfonic acid effectively promotes the [4+2] cycloaddition reaction of salicylaldehydes with arylalkynes to afford the corresponding 2H-1-benzopyrans in good yields with high regioselectivities. Treatment of the cycloadduct 2,3-diphenyl-2H-1-benzopyran with some nucleophiles led to 4H-1-benzpyrans and 2H-1-benzopyran according to reagents. The present reactions provide versatile access to functionalized 2,3-disubstituted-2H-1-benzopyrans that would be a useful tool for the synthesis of biologically and photochemically active molecules.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.045
       
  • Sulfonylative alkoxyhydroxylation of 2-arylpropenes
    • Authors: Huei-Sin Wang; Yan-Shin Wu; Meng-Yang Chang
      Pages: 6465 - 6470
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Huei-Sin Wang, Yan-Shin Wu, Meng-Yang Chang
      One-pot three-step sulfonylative alkoxyhydroxylation of 2-arylpropenes 1 affords oxygenated sulfonylcumenes 4 in moderate yields via a sequential route: (i) NBS-mediated allylic bromination of 2-arylpropenes 1 in CH2Cl2, (ii) sodium sulfinates 2-promoted nucleophilic substitution of the resulting styryl bromides in a co-solvent of alcohol and water, and (iii) V2O5/H2O2 mediated alkoxyhydroxylation of corresponding styryl sulfones 3 in alcohol. The synthetic route provides a highly effective protocol for the 1,2,3-tricarbofunctionalization of 2-arylpropenes 1 via two carbon-oxygen and one carbon-sulfur bond formations.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.047
       
  • Rose Bengal-photosensitized oxidation of tertiary amines for the synthesis
           of bis-1,3-dicarbonyl compounds
    • Authors: Ling-Ling Wu; Li Tang; Shui-Gen Zhou; Yi-Jie Peng; Xiao-Dong He; Zhi Guan; Yan-Hong He
      Pages: 6471 - 6478
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Ling-Ling Wu, Li Tang, Shui-Gen Zhou, Yi-Jie Peng, Xiao-Dong He, Zhi Guan, Yan-Hong He
      We report an example of Rose Bengal-photosensitized oxidation of tertiary amines for the synthesis of bis-1,3-dicarbonyl compounds. This protocol employs Rose Bengal as a visible-light absorbing photocatalyst without the need of a transition metal, and air as a green oxidant. Various functional groups were well tolerated to afford products with yields of up to 80% under mild reaction conditions.
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      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.050
       
  • Effects of aromatic stabilization energies of aryl rings of symmetrical
           diarylethenes
    • Authors: Huitao Xu; Shasha Wei; Congbin Fan; Gang Liu; Shouzhi Pu
      Pages: 6479 - 6485
      Abstract: Publication date: 9 November 2017
      Source:Tetrahedron, Volume 73, Issue 45
      Author(s): Huitao Xu, Shasha Wei, Congbin Fan, Gang Liu, Shouzhi Pu
      Four symmetrical diarylethenes bearing a variable aryl unit were synthesized and their crystal structures and photochromic performances were systematically studied to elucidate the effects of the aromatic stabilization energy (ASE) of aryl units. Experimental results revealed strong correlations of the thermal stability, as well as cyclization quantum yield, photoconversion ratio, and molar absorption coefficient of the darylethenes with the ASE of aryl units.
      Graphical abstract image

      PubDate: 2017-10-17T14:03:24Z
      DOI: 10.1016/j.tet.2017.09.049
       
  • Progress in the total synthesis of epoxyquinone natural products: An
           update
    • Authors: Goverdhan Mehta; Saumitra Sengupta
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Goverdhan Mehta, Saumitra Sengupta
      Epoxyquinone natural products continue to attract the attention of organic synthesis community worldwide, owing to their increasingly diverse and complex molecular architectures and broad spectrum biological activities associated with them. The last decade, in particular, has witnessed considerable activity and advances towards the total synthesis of this family of natural products with some notable successes. These efforts, deploying appropriate, contextual and emergent synthetic methodologies have led to the total synthesis of numerous epoxyquinone natural products spread over the entire structural landscape, with the added value of generating new chemical diversity space around their scaffold. This flurry of activity since 2005 lends some urgency to provide an update that documents and highlights the achievements in the intervening years and reflects on the new opportunities and challenges that lie ahead.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.030
       
  • SET-promoted photoaddition reactions of fullerene C60 with tertiary
           N-trimethylsilylmethyl substituted α-aminonitriles. Approach to the
           synthesis of fulleropyrrolidine nitriles
    • Authors: Suk Hyun Lim; Dae Won Cho; Jungkweon Choi; Hyunjun An; Jun Ho Shim; Patrick S. Mariano
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Suk Hyun Lim, Dae Won Cho, Jungkweon Choi, Hyunjun An, Jun Ho Shim, Patrick S. Mariano
      Photoaddition reactions of C60 with tertiary N-arylmethyl-N-trimethylsilylmethyl substituted α-aminonitriles were explored. The results show that these photoreactions produce both trimethylsilyl- and cyano group containing fulleropyrrolidines as major products through pathways involving 1,3-dipolar cycloaddition of azomethine ylide intermediates. The ylides are formed either by SET from α-aminonitriles to the triplet excited state of C60 (in N2-purged solutions) followed by desilylation or deprotonation, or by hydrogen atom abstraction by singlet oxygen (in O2-purged solutions). In contrast, photoreactions of C60 with analogous amines that do not contain trimethylsilyl group form fulleropyrrolidines that contain aryl- and cyano substitutents on the pyrrolidine ring. The efficiencies of these photoaddition reactions are influenced by several factors including reaction condition (N2 or O2-purged), solvent polarity, the electronic and structural nature of α-aminonitriles and additive. The presence of trimethylsilyl group in the α-aminonitrile substrates plays a crucial role in enhancing the efficiencies of the fulleropyrrolidine forming reactions.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.08.057
       
  • Neuroprotective phenylethanoid glycosides with dioxane units from the
           fruits of Forsythia suspensa
    • Authors: Si-Yuan Shao; Fan Zhang; Zi-Ming Feng; Ya-Nan Yang; Jian-Shuang Jiang; Pei-Cheng Zhang
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Si-Yuan Shao, Fan Zhang, Zi-Ming Feng, Ya-Nan Yang, Jian-Shuang Jiang, Pei-Cheng Zhang
      Six new phenylethanoid glycosides possessing dioxane moieties, named forsyoxasides A−F (1–6), together with four known such compounds (7–10) were isolated from the fruits of Forsythia suspensa. These structures were illustrated by extensive NMR spectroscopic techniques and by comparing their NMR data with the related literatures. Notably, forsyoxaside A (1) is a novel dioxane phenylethanoid glycoside with an axial aromatic ring, which is rare in the natural sources. Compounds 1, 4, 7 and 8 showed remarkable bioactivities against rotenone induced PC12 cell damage. Furthermore, 1 and 7 displayed strong activities against serum deprivation induced damage on the same cells.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.008
       
  • Synthesis of novel 4-ferrocenyl-1,2,3,4-tetrahydroquinolines and
           4-ferrocenylquinolines via α-ferrocenyl carbenium ions as key
           intermediates
    • Authors: Aleksandra Minić; Dragana Stevanović; Mirjana Vukićević; Goran A. Bogdanović; Matthias D'hooghe; Niko S. Radulović; Rastko D. Vukićević
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Aleksandra Minić, Dragana Stevanović, Mirjana Vukićević, Goran A. Bogdanović, Matthias D'hooghe, Niko S. Radulović, Rastko D. Vukićević
      A series of novel 4-ferrocenyl-1,2,3,4-tetrahydroquinolines were synthesized in high-to-excellent yields (up to 99%) starting from the corresponding ferrocenoylethyl aryl amines. These Mannich bases were reduced (NaBH4) to the corresponding 3-(arylamino)-1-ferrocenylpropan-1-ols and submitted to an intramolecular cyclization prompted by acetic acid, proceeding via the corresponding α-ferrocenyl carbenium ion intermediates. Subsequently, the obtained tetrahydroquinolines were smoothly oxidized (aromatized) by means of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to provide the corresponding 4-ferrocenylquinolines (up to 93%).
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.014
       
  • The value of 2JP–CO as a diagnostic parameter for the structure and
           thermal reactivity of carbonyl-stabilised phosphonium ylides
    • Authors: R. Alan Aitken; Youcef Boubalouta; Da Chang; Lee P. Cleghorn; Ian P. Gray; Nazira Karodia; Euan J. Reid; Alexandra M.Z. Slawin
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): R. Alan Aitken, Youcef Boubalouta, Da Chang, Lee P. Cleghorn, Ian P. Gray, Nazira Karodia, Euan J. Reid, Alexandra M.Z. Slawin
      A survey of 20 carbonyl-stabilised phosphonium ylides with recently reported X-ray structures shows a strong correlation between the CP to CO torsion angle and the value of 2 J P–CO, with high values being associated with an anti configuration and low with syn. Seven new X-ray structural determinations are reported, several for types of ylide not crystallographically characterised before, and these also conform to this pattern. The value of 2 J P–CO is then correlated with whether or not thermal extrusion of Ph3PO occurs to give alkynes for over 200 ylides and an empirical rule developed that the extrusion never occurs for ylides where this value is > 11 Hz. This is used to rationalise the anomalous behaviour of some trioxo ylides and cyclic ylides, two of which afford cycloalkynes, isolated after rearrangement as the isomeric 1,3-dienes. The rule also holds for a family of novel highly fluorinated ylides which afford fluorinated alkynes in good yield upon flash vacuum pyrolysis.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.016
       
  • The relevance of the relative configuration in the folding of hybrid
           peptides containing β-cyclobutane amino acids and γ-amino-l-proline
           residues
    • Authors: Ona Illa; José Antonio Olivares; Pau Nolis; Rosa M. Ortuño
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Ona Illa, José Antonio Olivares, Pau Nolis, Rosa M. Ortuño
      Four new series of diastereomeric β,γ-di- and β,γ-tetrapeptides derived from conveniently protected (1R,2S)- and (1S,2S)-2-aminocyclobutane-1-carboxylic acid and cis- and trans-γ-amino-l-proline joined in alternation have been synthesized. High resolution NMR experiments show that peptides containing trans-cyclobutane amino acid residues adopt a more folded structure in solution than those containing a cis-cyclobutane residue, which adopt a strand-like structure. The cis/trans relative configuration of the cyclobutane residue is the origin of the folding pattern of each peptide due to either intra- or inter-residue hydrogen-bonded ring formation, whereas the cis/trans isomerism of the γ-amino-l-proline residue does not have a significantly relevant role on the folding ability of these peptides.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.011
       
  • Mitsunobu C-alkylation of β-alkoxycarbonyl 2-nitrobenzenesulfones and its
           use for the rapid synthesis of novel benzothiazine derivatives
    • Authors: Martina Drábiková; Soňa Krajčovičová; Miroslav Soural
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Martina Drábiková, Soňa Krajčovičová, Miroslav Soural
      Herein, we report the first examples of the Mitsunobu alkylation of β-alkoxycarbonyl 2-nitrobenzenesulfones. Wang resin was acylated with α-halocarboxylic acids followed by the reaction with 2-nitrothiophenols. After oxidation with m-chloroperbenzoic acid, the immobilized β-alkoxycarbonyl 2-nitrobenzensulfones were subjected to alkylation with various alcohols. The reaction outcome strongly depended on the selection of the alkylating species. After the reduction of the nitro group, acid-mediated cleavage and subsequent cyclization, the C2-(di)substituted benzothiazin-3(4H)-one 1,1-dioxides were obtained in high crude purities and good overall yields.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.017
       
  • Asymmetric double donor-π-acceptor dyes based on phenothiazine and
           carbazole donors for dye-sensitized solar cells
    • Authors: Bo-ye Zhu; Liang Wu; Qin Ye; Jian-rong Gao; Liang Han
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Bo-ye Zhu, Liang Wu, Qin Ye, Jian-rong Gao, Liang Han
      Four organic dyes with asymmetric double donor-π-acceptor system were designed, synthesized and utilized in dye-sensitized solar cells (DSSCs), where phenothiazine and carbazole were introduced as double donors, butyl or octyl chain as the linker and cyanoacetic acid or rhodanine acetic acid as the electron acceptor. The design of double donor-π-acceptor system contributes to a distinctive increase of the molar extinction coefficient and benefits light-harvesting capability of these dyes. Due to superior electron injection efficiency, CPC-series dyes with cyanoacetic acid acceptor exhibit broader IPCE spectra and high IPCE responsive value compared with rhodanine-3-acetic acid acceptor, leading to higher J SC . Long alkyl chain favors antiaggregation effect and low charge recombination rate is observed for dyes with octyl chain which display higher V OC than those with butyl chain. Among four dyes, dye with octyl chain and cyanoacetic acid acceptor exhibits the highest short-circuit photocurrent density (9.64 mA cm−2) and open-circuit photovoltage (720 mV), leading to the best overall power conversion efficiency of 4.76%.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.018
       
  • Unusual visible-light photolytic cleavage of tertiary amides during the
           synthesis of cyclolignans related to podophyllotoxin
    • Authors: Kamil Lisiecki; Krzysztof K. Krawczyk; Piotr Roszkowski; Jan K. Maurin; Armand Budzianowski; Zbigniew Czarnocki
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Kamil Lisiecki, Krzysztof K. Krawczyk, Piotr Roszkowski, Jan K. Maurin, Armand Budzianowski, Zbigniew Czarnocki
      During the attempted photochemical cyclization of 2,3-bisbenzylidene-γ-hydroxybutyric acid cyclic amide ester, it was observed that a γ-butyrolactone ring was formed, which was concurrent with the release of the amine fragment from the amide. The process occurs with high yield giving rise to the formation of β-apopicropodophyllin and its regioisomer. Additional experiments confirmed the photochemical nature of this transformation, and that it is independent from the photocyclization of the benzylidene groups – a typical reactivity for the members of the fulgide family. In contrast to the latter UV-driven cyclization, the photochemical cleavage of the amide was proven to proceed under irradiation with visible light.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.021
       
  • Expanding the scope of methyl xanthate esters - From Barton-McCombie
           reaction auxiliary to versatile protective group
    • Authors: Karin Thorsheim; Sophie Manner; Ulf Ellervik
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Karin Thorsheim, Sophie Manner, Ulf Ellervik
      The methyl xanthate ester is presented as a versatile protective group for alcohols. Hydroxyl groups can easily be transformed into methyl xanthate esters by several methods and are commonly used as an auxiliary in the Barton-McCombie reaction. We show that these methyl xanthate esters can readily and chemoselectively be cleaved under mild conditions by the action of diethylenetriamine using microwave heating. This method is orthogonal to many common hydroxyl protective groups that can be introduced and cleaved in the presence of methyl xanthate ester.
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      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.022
       
  • Mechanism of С-Н cyclization of alkynylanthraquinones into
           thienoanthraquinones with the participation of sodium sulfide
    • Authors: Lidiya Fedenok; Fedor Dultsev; Igor Barabanov; Nikolay Polyakov
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Lidiya Fedenok, Fedor Dultsev, Igor Barabanov, Nikolay Polyakov
      The CH-cyclization of alkynyl-9,10-anthraquinones 1 into thienoanthraquinones 2 is shown to be initiated by the neutral S2 molecule and not by the sulfide anion as it is assumed in the existing model of CH-cyclization with the nucleophiolic substitution of H. The formation of S2 takes place in the reaction medium due to the partial reduction of the substrate 1 by Na2S into the corresponding anthrahydroquinone, which is inactive in the main reaction. We present a new cyclization mechanism with the key stage involving the electrophilic displacement of H, which results in the formation of the reaction product 2 and elimination of S. In the reaction medium atomic sulfur is transformed into S2, which initiates the next cyclization act. This determines the chain nature of cyclization with the participation of S2. Within this model, the route to increase the yield of target thienoanthraquinones is proposed through the introduction of a neutral quinone able to generate S2 by means of easy reduction.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.023
       
  • Diels-Alder reactions of fused 5-, 6- and 7-membered ring 2-vinylindoles:
           Synthesis of annulated tetrahydrocarbazoles
    • Authors: Wayland E. Noland; Ryan J. Herzig; Honnaiah Vijay Kumar; Venkata Srinivasarao Narina; Pavel K. Elkin; Karen I. Valverde; Briana L. Kim
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Wayland E. Noland, Ryan J. Herzig, Honnaiah Vijay Kumar, Venkata Srinivasarao Narina, Pavel K. Elkin, Karen I. Valverde, Briana L. Kim
      Scaffolds of tetrahydrocarbazoles are an important class of biologically active compounds found abundant in nature. In the present investigation, functionalized polycyclic tetrahydrocarbazoles were synthesized using Diels-Alder cycloaddition between fused 5-, 6- and 7-membered ring 2-vinylindoles and various dienophiles. The dienophiles used were N-phenylmaleimides, 1,4-naphthoquinone, and dimethyl acetylenedicarboxylate (DMAD). When 1,4-naphthoquinone was used as a dienophile, the 5-membered ring Diels-Alder adduct was obtained in the oxidized form, but this form was not observed in the case of 6- and 7-membered ring Diels-Alder adducts. The desired product yields ranged from 60–70% and the structure of final compounds were determined using 1D and 2D NMR analysis. 1H NMR studies confirmed excellent diastereoselectivity (>99% de).
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.025
       
  • Convenient two-step synthesis of highly functionalized benzo-fused
           1,4-diazepin-3-ones and 1,5-diazocin-4-ones by sequential Ugi and
           intramolecular SNAr reactions
    • Authors: Simon Vézina-Dawod; Nicolas Gerber; Xinxia Liang; Eric Biron
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Simon Vézina-Dawod, Nicolas Gerber, Xinxia Liang, Eric Biron
      Benzodiazepinones are an important family of heterocycles with very attractive pharmacological properties and peptidomimetic abilities. We report herein a rapid and efficient two-step synthesis of polysubstituted 1,4-benzodiazepin-3-ones and 1,5-benzodiazocin-4-ones using a multicomponent condensation/cyclization strategy. The approach uses an Ugi four-component reaction to condense readily available N α -Fmoc-amino acids, amines and isocyanides with a 2-fluorobenzaldehyde derivative followed by a one-pot Fmoc-group removal, intramolecular aromatic nucleophilic substitution for ring closure and side chain deprotection. The described method gives access to benzo-fused 7- and 8-membered rings bearing a wide variety of functionalized substituents and was applied to efficiently prepare tri- and tetrasubstituted 1,4-benzodiazepin-3-ones and 1,5-benzodiazocin-4-ones in high yields in two straightforward steps.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.028
       
  • 2′-Aminoanalogues of the cruciferous phytoalexins spirobrassinin,
           1-methoxyspirobrassinin and 1-methoxyspirobrassinol methyl ether:
           Synthesis and anticancer properties
    • Authors: Mariana Budovská; Viera Tischlerová; Ján Mojžiš; Marianna Harvanová; Oleksandr Kozlov; Taťána Gondová; Nataša Tomášková
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Mariana Budovská, Viera Tischlerová, Ján Mojžiš, Marianna Harvanová, Oleksandr Kozlov, Taťána Gondová, Nataša Tomášková
      A method for the synthesis of new 2′-aminoanalogues of spiroindoline phytoalexins is reported. 2′-Aminonalogues of spirobrassinin, 1-methoxyspirobrassinin and 2,2′-diamino analogues of 1-methoxyspirobrassinol methyl ether were prepared by substitution of the methylsulphanyl group on the dihydrothiazole ring of corresponding phytoalexins. Final products were obtained by heating the phytoalexins with aniline or substituted aniline in the absence of solvent at 120 or 140 °C. By replacement of the SCH3 moiety of (S)-(−)- or (R)-(+)-spirobrassinin, enantiomers of 2′-aminoanalogues of spirobrassinin were also synthesized. Determination of their enantiomeric compositions using HPLC with chiral stationary phase revealed partial enantiomeric enrichment. The occurence of a SIDA effect of our 2′-aminonalogue of spirobrassinin was evaluated by examination of a non-racemic mixture in non-polar C6D6. Complete enantioresolution and distinct signals for two enantiomers were observed for a number of 1H and 13C NMR resonances. New synthesized compounds were supplied for testing the antiproliferative effect on a panel of six human cancer cell lines. 2′-Aminoanalogue with CF3 functionality exhibited more significant inhibitory effects than natural phytoalexins spirobrassinin.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.033
       
  • Diversity-oriented synthesis of 1,3-benzodiazepines
    • Authors: Gaigai Wang; Chao Liu; Binbin Li; Yingchun Wang; Kristof Van Hecke; Erik V. Van der Eycken; Olga P. Pereshivko; Vsevolod A. Peshkov
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Gaigai Wang, Chao Liu, Binbin Li, Yingchun Wang, Kristof Van Hecke, Erik V. Van der Eycken, Olga P. Pereshivko, Vsevolod A. Peshkov
      A concise assembly of the 1,3-benzodiazepine core from A3-coupling-derived propargylamines and ortho-bromophenylisocyanates is described. The developed synthetic sequence involves the addition of propargylamine to isocyanate followed by palladium-catalyzed intramolecular alkyne hydroarylation that could be accomplished in a stepwise or one-pot manner.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.034
       
  • Synthesis of the AE bicyclic of Daphniphyllum alkaloid yuzurine
    • Authors: Yue Meng Liu; Fei Li; Qi Wang; Jun Yang
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Yue Meng Liu, Fei Li, Qi Wang, Jun Yang
      A concise synthesis of the AE bicyclic system of Daphniphyllum alkaloid yuzurine is described. The synthetic sequence features a Dieckmann condensation to construct ring A, reduction of α, β-unsaturated double bond and propargylation of α-position of lactone to diastereoselectively generate relative stereocenter C-3, C-4 and C-5, and an acid-catalyzed cyclization to assemble ring E.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.035
       
  • Self-recognition behavior of novel frameworks containing both urea and
           carboxylate anion motifs
    • Authors: Zhiqiang Xu; Haojie Ge; Xie Han; Sheng Hua Liu; Xiang-Gao Meng; Jun Yin
      Abstract: Publication date: 2 November 2017
      Source:Tetrahedron, Volume 73, Issue 44
      Author(s): Zhiqiang Xu, Haojie Ge, Xie Han, Sheng Hua Liu, Xiang-Gao Meng, Jun Yin
      Molecular recognition based on hydrogen bond interaction plays a significant role in supramolecular self-assembly. In this work, we successfully developed a class of novel frameworks containing a urea in the recognition site and a carboxylate anion in the guest unit. The self-recognition model based on the interaction between urea and carboxylate anion could induce the molecules to assemble into a highly organized form. The crystal structures showed that they assembled in highly ordered two-dimensional architectures. The optical properties showed that the position of carboxylate anion on the diphenylacetylene backbone had an obvious influence on optical properties. The self-recognition strategy is useful for the construction of highly ordered self-assembled architectures.
      Graphical abstract image

      PubDate: 2017-10-10T12:04:04Z
      DOI: 10.1016/j.tet.2017.09.036
       
  • Reactions of tetracyclic γ-sultones with N-nucleophiles. Novel synthesis
           of 3,4-disubstituted homoadamantanes
    • Authors: Marat R. Baimuratov; Marina V. Leonova; Vadim A. Shiryaev; Yuri N. Klimochkin
      Pages: 6101 - 6108
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Marat R. Baimuratov, Marina V. Leonova, Vadim A. Shiryaev, Yuri N. Klimochkin
      Derivatives of (homo)adamantane sulfonic acids are synthesized through the reaction of tetracyclic γ-sultones with ammonia and hydrazine hydrate. In the presence of a strong base and prolonged heating the reactions of γ-sultones with ammonia or hydrazine hydrate occur through CO cleavage and lead to products with a modified carbon skeleton. Ring opening of trans-γ-sultones proceeds with inversion of configuration of the carbon atom linked to sulfur. The reaction of bromomethyl sultones with secondary amines proceeds through dehydrohalogenation and leads to products of Michael addition.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.08.025
       
  • Synthesis of five-membered unsaturated compounds from ketones via
           cyanophosphates under neutral conditions: [1,5]-CH insertion of alkylidene
           carbenes generated by tetrazole fragmentation
    • Authors: Hiroki Yoneyama; Kenji Uemura; Yoshihide Usami; Shinya Harusawa
      Pages: 6109 - 6117
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Hiroki Yoneyama, Kenji Uemura, Yoshihide Usami, Shinya Harusawa
      Cyanophosphates (CPs) can easily be prepared via the reactions of carbonyl compounds with diethyl phosphorocyanidate (DEPC) in the presence of LiCN (cat.) under non-aqueous conditions. Treatment of ketone-derived CPs with TMSN3/Bu2SnO (cat.) in toluene at reflux produces cyclopentenes or heterocyclic products in good yields under neutral conditions. In this two-step transformation, CPs may form tetrazolylphosphates, which subsequently undergo successive fragmentation to generate alkylidene carbenes, which undergo [1,5]-C–H insertions to yield five membered compounds.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.08.054
       
  • Steric buttressing in the Pauson-Khand reactions of benzyl enynes
    • Authors: Christian E. Madu; H.V. Rasika Dias; Carl J. Lovely
      Pages: 6118 - 6137
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Christian E. Madu, H.V. Rasika Dias, Carl J. Lovely
      The application of the intramolecular Pauson-Khand reaction of 1,n-enynes provides a convenient method for the construction of polycyclic frameworks but this process has largely been limited to the formation of 5,5- and 5,6-fused ring systems. In this report, we describe the application of the Pauson-Khand cyclization to 1,8-enynes embedded in an aromatic ring system wherein it is determined that the presence of steric buttresses in the form of t-butyl groups facilitates the cycloaddition. These reactions proceed in good yields with either thermal or oxidative activation and in the former case, the diastereoselectivities are high. An investigation of the tolerance of this cycloaddition to substitution around the 1,8-enyne demonstrates that only 2,2-disubstitution does not result in productive cyclization. Cycloadditions with hydroxyl groups at the propargylic position while leading to fused rings are compromised by side reactions leading to reduction and in some cases tautomerization. However, these byproducts are easily minimized through conversion of the hydroxyl group to the corresponding silyl ether.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.08.053
       
  • CS and CN bond formation via Mn-promoted oxidative cascade reaction:
           Synthesis of C3-sulfenated indoles
    • Authors: Lin He; Xianwei Li
      Pages: 6138 - 6145
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Lin He, Xianwei Li
      Thioethers are of synthetic value in pharmaceutical molecules and nature products, herein, we report an oxidative cascade reaction that delivers multiple substituted indole thioethers with great efficiency. This transformation utilized ortho-azido aromatic alkynes as the substrates, and sulfonyl hydrazides as the sulfenation reagent promoted by Mn(III) catalyst. Notably, great functional group tolerance, in combination with nitrogen and water as the byproducts, highlighted the sustainable chemistry of this protocol.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.003
       
  • Diversity-oriented synthesis of cyclopropyl peptides from Ugi-derived
           dehydroalanines
    • Authors: David A. Contreras-Cruz; Miguel A. Sánchez-Carmona; Fabio A. Vengoechea-Gómez; Daniel Peña-Ortíz; Luis D. Miranda
      Pages: 6146 - 6156
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): David A. Contreras-Cruz, Miguel A. Sánchez-Carmona, Fabio A. Vengoechea-Gómez, Daniel Peña-Ortíz, Luis D. Miranda
      A three-step synthesis of cyclopropyl peptides is reported. The protocol involves a consecutive Ugi-4CR/elimination reaction to prepare dehydroalanines followed by a Corey-Chaykovsky cyclopropanation reaction. Peptide-like molecules that resemble some pharmacologically active compounds with a variety of substituents in the cyclopropane ring were prepared. When (2-ethoxy-2-oxoethyl) dimethyl sulfonium ylide was used the reaction exclusively gives the cis-diastereoisomer cyclopropanes in good yields from readily prepared starting materials. A collection of 26 highly substituted cyclopropyl peptides were obtained.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.005
       
  • Synthesis and anti-proliferative activity of
           3′-deoxy-3′-fluoro-3′-C-hydroxymethyl-pyrimidine and purine
           nucleosides
    • Authors: Naresh Bhuma; Sachin S. Burade; Aditi V. Bagade; Navanath M. Kumbhar; Kisan M. Kodam; Dilip D. Dhavale
      Pages: 6157 - 6163
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Naresh Bhuma, Sachin S. Burade, Aditi V. Bagade, Navanath M. Kumbhar, Kisan M. Kodam, Dilip D. Dhavale
      A new class of 3′-deoxy-3β′-fluoro-3α′-C-hydroxymethyl-pyrimidine 1a-c and purine 1d nucleosides were synthesized using modified Corey-Link reaction with 3-oxo-d-glucofuranose derivative to get C-3 quaternary carbon with 3β′-fluoro-3α′-C-hydroxymethyl groups, in the sugar frame work. Conformational preferences of fluorinated nucleosides were studied by the DFT calculations. Anti-proliferative activity of nucleosides 1a-d was tested against MDA-MB-231, L-132, HeLa and neural cell lines and found to be moderate active.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.006
       
  • A multiple switching diarylethene dimer with a bis(benzylene)amine-linked
           naphthalimide unit
    • Authors: Shasha Wei; Xue Li; Congbin Fan; Gang Liu; Shouzhi Pu
      Pages: 6164 - 6171
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Shasha Wei, Xue Li, Congbin Fan, Gang Liu, Shouzhi Pu
      A novel photochromic diarylethene dimer with a bis(benzylene)amine-linked naphthalimide unit was synthesized, and its photochemical properties were systematically studied. Upon irradiation with ultraviolet light, a singly-closed isomer and a fully-closed isomer were reversibly formed, which were confirmed by the results of Nuclear Magnetic Resonance spectroscopy (NMR) and High-Performance Liquid Chromatography (HPLC). Additionally, the diarylethene dimer could be used as a multi-addressable fluorescence switch when triggered by light, proton, and metal ions. Moreover, a logic circuit was constructed with the unimolecular platform by using the fluorescence intensity at 445 nm as output and appropriate combinational stimuli of UV light, Al3+, and EDTA as inputs.
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      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.010
       
  • Syntheses of two kinds of disaccharide subunits of antitumor antibiotic
           bleomycins
    • Authors: Rui Che; Qiwen Zhu; Jie Yu; Jiao Li; Jiahui Yu; Wei Lu
      Pages: 6172 - 6180
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Rui Che, Qiwen Zhu, Jie Yu, Jiao Li, Jiahui Yu, Wei Lu
      Gram-scale syntheses of two kinds of bleomycin disaccharides are described. l-gulose subunit 12 was accomplished with a novel and short route in six steps and 37% overall yield from 4, which could be easily prepared from the commercially available inexpensive material d-sorbitol, while 6-deoxy-l-gulose subunit was synthesized in 11 steps in 8% yield from d-glucolactone. The disaccharides were then prepared in a previously reported glycosidation coupling of the 3-O-carbamoyl-mannosyl donor with the l-gulopyranoside acceptors. Both disaccharides were finally obtained in gram-scale and the total synthesis of disaccharide 2 was achieved the first time.
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      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.009
       
  • N-ferrocenylpyridazinones and new organic analogues: Synthesis, cyclic
           voltammetry, DFT analysis and in vitro antiproliferative activity
           associated with ROS-generation
    • Authors: Tamás Jernei; Szilvia Bősze; Rita Szabó; Ferenc Hudecz; Katalin Majrik; Antal Csámpai
      Pages: 6181 - 6192
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Tamás Jernei, Szilvia Bősze, Rita Szabó, Ferenc Hudecz, Katalin Majrik, Antal Csámpai
      Employing an optimized Pd-catalyzed cross-coupling reaction promoted by CuI, novel N-ferrocenylpyridazinones along with N-phenyl- and N-(2-pyridyl) analogues were synthesized from readily available heterocyclic precursors, iodoferrocene, iodobenzene and 2-bromopyridine. With exception of the ferrocenylation of 6-ferrocenylpyridazin-3(2H)-one yielding both N- and O-substituted products, the studied reactions exclusively afforded N-aryl lactams. The novel compounds exhibited cytotoxicity towards HEPG2 and HT-29 human malignant cells under in vitro conditions. The measured IC50 values supplemented with the results of cyclic voltammetry and DFT calculations suggest that the cytotoxic activity of the N- and O-ferrocenyl-substituted derivatives and the decreased effect of the N-phenyl analogues seem to be at least partly associated with the potential to generate reactive oxygen species (ROS). This interpretation, allowing the prediction of characteristic substituent-dependent SAR, was supported by the results of related studies on the practically inactive N-(2-pyridyl)pyridazinones assumed to be present in protonated chelate forms with highly a decreased propensity to undergo ionization.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.015
       
  • Green synthesis of 2-pyrazinones in deep eutectic solvents: From α-chloro
           oximes to peptidomimetic scaffolds
    • Authors: Serena Perrone; Martina Capua; Francesco Messa; Antonio Salomone; Luigino Troisi
      Pages: 6193 - 6198
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Serena Perrone, Martina Capua, Francesco Messa, Antonio Salomone, Luigino Troisi
      A novel and green synthesis of 2-pyrazinones in deep eutectic solvents (DESs) is described. Treatment of aromatic α-chloro oximes with aliphatic amines at 110 °C in choline chloride based DESs resulted in a straightforward and efficient assembly of 1,3,5-trisubstituted-2(1H)-pyrazinones. The protocol, featuring mild reaction conditions and avoiding common volatile organic solvents, affords a safe and sustainable approach to original peptidomimetic scaffolds.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.013
       
  • Synthesis and preliminary biological evaluation of new phenolic and
           catecholic dehydroamino acid derivatives
    • Authors: Luís S. Monteiro; Sandra Oliveira; Fátima Paiva-Martins; Paula M.T. Ferreira; David M. Pereira; Paula B. Andrade; Patrícia Valentão
      Pages: 6199 - 6209
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Luís S. Monteiro, Sandra Oliveira, Fátima Paiva-Martins, Paula M.T. Ferreira, David M. Pereira, Paula B. Andrade, Patrícia Valentão
      A library of N-phenolic and N-catecholic dehydroamino acid derivatives was prepared using an innovative synthetic strategy that involves mild reaction conditions and simple work-up procedures. The method comprises coupling of phenolic or catecholic acids with β-hydroxyamino acids followed by tert-butyloxycarbonylation of all hydroxyl groups using tert-butyldicarbonate and 4-dimethylaminopyridine as catalyst. Treatment of these amino acids with N,N,N′,N′-tetramethylguanidine affords the corresponding O-tert-butyloxycarbonyldehydroamino acid derivative. Deprotection of the aromatic hydroxyl groups is carried out with trifluoroacetic acid. This synthetic strategy can be applied in a one-pot procedure and yields compounds that can be easily inserted into peptides or other biomolecules after cleavage of the C-protecting group. Preliminary studies of cell viability show that these new compounds display very low or no toxicity. These dehydroamino acids with a phenolic or catecholic moiety can have intrinsic biological activity or used to prepare new hydrogels that mimic mussel adhesive proteins.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.012
       
  • Nonlinear optical properties of the novel kind of organic donor-acceptor
           thiophene derivatives with click chemistry modification
    • Authors: Pengbo Han; Zhou Yang; Hui Cao; Wanli He; Dong Wang; Jingjing Zhang; Yan Xing; Hong Gao
      Pages: 6210 - 6216
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Pengbo Han, Zhou Yang, Hui Cao, Wanli He, Dong Wang, Jingjing Zhang, Yan Xing, Hong Gao
      Two new classes of organic third-order optical chromophores, D-π-A-D and D-π-A-D-A-π–D, were designed and synthesized using a Sonogashira coupling reaction and the high-yielding [2 + 2] click reaction. The photophysical and click chemistry were characterized by means of UV/Vis absorption spectroscopy. The electrochemical properties were characterized by means of cyclic voltammetry. Moreover, the third-order nonlinear properties, including the nonlinear refraction and the nonlinear absorption, were investigated by using Z-scan techniques. The chromophores with a D-π-A-D-A-π-D motif, Bt 1 -X and Bt 2 -X, exhibited the larger third-order susceptibility χ(3) value than the analogues (D-π-A-D), St 1 -X and St 2 -X, whereas the bithiophene chromophores, St 2 and Bt 2 , exhibited a larger χ(3) value than their single thiophene counterparts, St 1 and Bt 1 . Upon the introduction of electron acceptors, third-order nonlinear absorption of the products St n -X showed a typical SA-RSA transition. Interestingly, the chromophores with a D-π-A-D-A-π-D motif, Bt n -X, exhibited more diversified NLO phenomenon. All of the click compounds showed the considerable third-order susceptibility χ(3) values. The results of these studies could provide new molecular-design strategies for third-order nonlinear optical materials for optoelectronic device components.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.020
       
  • Organocatalytic asymmetric Michael addition of pyrazoleamides to
           β-phthalimidonitroethene
    • Authors: Yuan Luo; Ke-Xin Xie; Deng-Feng Yue; Xiao-Mei Zhang; Xiao-Ying Xu; Wei-Cheng Yuan
      Pages: 6217 - 6222
      Abstract: Publication date: 26 October 2017
      Source:Tetrahedron, Volume 73, Issue 43
      Author(s): Yuan Luo, Ke-Xin Xie, Deng-Feng Yue, Xiao-Mei Zhang, Xiao-Ying Xu, Wei-Cheng Yuan
      A highly organocatalyzed asymmetric Michael addition reaction of pyrazoleamides to β-phthalimidonitroethene has been developed with a chiral bifunctional thiourea-tertiary amine as the catalyst. A wide range of γ-nitro β-amino amides were readily obtained in good to excellent yields with high diastereo- and enantioselectivities (up to 99% yield, 99% ee and >20:1 dr). The large scale experiment and transformation of the product have also been demonstrated.
      Graphical abstract image

      PubDate: 2017-10-01T14:00:19Z
      DOI: 10.1016/j.tet.2017.09.019
       
  • Inverse thermoresponse of a water-soluble helicene oligomer in
           aqueous-organic mixed solvent systems
    • Authors: Nozomi Saito; Higashi Kobayashi; Masahiko Yamaguchi
      Pages: 6047 - 6051
      Abstract: Publication date: 19 October 2017
      Source:Tetrahedron, Volume 73, Issue 42
      Author(s): Nozomi Saito, Higashi Kobayashi, Masahiko Yamaguchi
      A water-soluble ethynylhelicene (M)-tetramer with TEG groups exhibited the inverse thermoresponse in water/triethylamine/acetone, in which heating induced the formation of double helix and cooling dissociation. In this study, we examined the solvent effect with regard to water content at temperatures between 5 and 40 °C, and showed that the inverse thermoresponse occurred in different aqueous solution systems. In acetone, the oligomer exhibited the ordinary thermoresponse: Cooling induced the formation of double helix and heating dissociation. The increase in water content to approximately 10% caused the switch to the inverse thermoresponse. Further increase inhibited the association, and did not induce the thermoresponse. When the water content was increased to approximately 50%, the inverse thermoresponse appeared as observed previously study. Two types of inverse thermoresponses, termed type I and II, appeared at high and low water contents, respectively.
      Graphical abstract image

      PubDate: 2017-09-25T00:22:21Z
      DOI: 10.1016/j.tet.2017.08.046
       
  • 5-Nitroso-1,3-diphenyltetrazolium salt as a mediator for the oxidation of
           alcohols
    • Authors: Yuta Matsukawa; Tsunehisa Hirashita; Shuki Araki
      Pages: 6052 - 6056
      Abstract: Publication date: 19 October 2017
      Source:Tetrahedron, Volume 73, Issue 42
      Author(s): Yuta Matsukawa, Tsunehisa Hirashita, Shuki Araki
      We describe the synthesis of a mesoion-derived nitroso compound, 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate (1), and its application in the oxidation of alcohols. The structure of 1 was fully characterized by X-ray analysis, showing that it exists as a monomer in the solid state. In the cyclic voltammetric analysis of 1, a reversible redox peak was observed at 0.43 V (vs. Ag/Ag+ in MeCN) under acidic conditions. It was subsequently shown that the nitrosotetrazolium salt 1 is capable of stoichiometrically oxidizing alcohols to the corresponding carbonyl compounds effectively. This nitroso heterocycle and its reduced form, i.e., the corresponding mesoionic hydroxyamide, participate in a redox cycle involving the catalytic oxidation of alcohols by the aid of HNO3 under mild conditions.
      Graphical abstract image

      PubDate: 2017-09-25T00:22:21Z
      DOI: 10.1016/j.tet.2017.08.055
       
  • One-pot synthesis of (ethoxycarbonyl)difluoromethylthioethers from
           thiocyanate sodium and ethyl 2-(trimethylsilyl)-2,2-difluoroacetate
           (TMS-CF2CO2Et)
    • Authors: Lijun Xu; Hongyu Wang; Changwu Zheng; Gang Zhao
      Pages: 6057 - 6066
      Abstract: Publication date: 19 October 2017
      Source:Tetrahedron, Volume 73, Issue 42
      Author(s): Lijun Xu, Hongyu Wang, Changwu Zheng, Gang Zhao
      An efficient one-pot cascade methodology for the synthesis of (ethoxycarbonyl)difluoromethyl thioethers is described. Benzyl, allyl, alkyl halides or diazonium salts as the starting materials together with thiocyanate sodium and TMS-CF2CO2Et in the presence of CsF or NaOAc afford a variety of the fluoroalkylthiolated products in moderate to good yields.
      Graphical abstract image

      PubDate: 2017-09-25T00:22:21Z
      DOI: 10.1016/j.tet.2017.08.048
       
  • Exploring hydroamination-cycloaddition-fragmentation sequences to access
           polycyclicguanidines and vinyl-2-aminoimidazoles
    • Authors: Ki-Hyeok Kwon; Anne V. Edwards; Miao Yang; Ryan E. Looper
      Pages: 6067 - 6079
      Abstract: Publication date: 19 October 2017
      Source:Tetrahedron, Volume 73, Issue 42
      Author(s): Ki-Hyeok Kwon, Anne V. Edwards, Miao Yang, Ryan E. Looper
      The intramolecular hydroamination of a guanidine on an eneyne unit affords a guanidine-substituted diene capable of reacting with dienophiles. These substrates undergo [4+2]-cycloaddition reactions to generate a series of complex cyclic- and spirocyclic-guanidines. Select substrates can further undergo a ring opening-elimination cascade that ultimately reveals a vinyl-2-aminoimidazole. As such this cascade reaction may find application in the synthesis of oroidin-type natural products and their analogues.
      Graphical abstract image

      PubDate: 2017-09-25T00:22:21Z
      DOI: 10.1016/j.tet.2017.08.052
       
 
 
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