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Tetrahedron
Journal Prestige (SJR): 0.8
Citation Impact (citeScore): 2
Number of Followers: 121  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0040-4020
Published by Elsevier Homepage  [3163 journals]
  • Graphical abstract TOC
    • Abstract: Publication date: 9 August 2018Source: Tetrahedron, Volume 74, Issue 32Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 9 August 2018Source: Tetrahedron, Volume 74, Issue 32Author(s):
       
  • Graphical abstract TOC cont'd
    • Abstract: Publication date: 9 August 2018Source: Tetrahedron, Volume 74, Issue 32Author(s):
       
  • Chemical biology of salinomycin
    • Abstract: Publication date: Available online 19 July 2018Source: TetrahedronAuthor(s): Antoine Versini, Lou Saier, Fabien Sindikubwabo, Sebastian Müller, Tatiana Cañeque, Raphaël Rodriguez Cancer stem cells (CSC) have been shown to be refractory to conventional therapeutic agents, can promote metastasis, and have been linked to cancer relapse. The natural product Salinomycin has been identified by means of high throughput phenotypic screening as a selective killer of CSC in vitro and in vivo. In this article, we comprehensively review the chemistry of Salinomycin, documenting early total syntheses, along with strategies that have been developed over the years to effectively modify this natural product at key positions with the view to establish a robust structure-activity-relationship and to delineate the complex mechanism of action of this fascinating molecule in the context of cancer research. Then, we document the biology of Salinomycin, putting forward phenotypic alterations that have been observed in the relevant biological models and highlighting how chemistry has been instrumental in discovering unprecedented physiological features of cancer stem cells that can be exploited for therapeutic benefits.Graphical abstractImage 1
       
  • Chiral NHC ligands bearing a pyridine moiety in copper-catalyzed addition
           of diethylzinc to nitroalkenes
    • Abstract: Publication date: Available online 18 July 2018Source: TetrahedronAuthor(s): Takahiro Soeta, Yuichi Hatanaka, Tomohiro Ishizaka, Yutaka Ukaji Chiral N-heterocyclic carbenes, derived from amino acids containing a pyridine ring, are effective ligands in the enantioselective copper-catalyzed addition of diethylzinc to β-nitroalkenes, which provides access to chiral nitroalkanes. The advantages of this process include high yields, broad and complementary substrate scope, and good to high enantioselectivities.Graphical abstractImage 1
       
  • Total synthesis and cytotoxic activity of dechlorogreensporones A and D
    • Abstract: Publication date: Available online 18 July 2018Source: TetrahedronAuthor(s): Laksamee Jeanmard, Panata Iawsipo, Jiraporn Panprasert, Vatcharin Rukachaisirikul, Kwanruthai Tadpetch The first and convergent total syntheses of polyketide natural products dechlorogreensporones A and D have been accomplished in 17 longest linear steps with 2.8% and 5.4% overall yields, respectively, starting from known methyl 2-(2-formyl-3,5-dihydroxyphenyl)acetate and commercially available R-(+)-propylene oxide and 1,2-epoxy-5-hexene. Our synthesis exploited key Mitsunobu esterification and (E)-selective ring-closing metathesis (RCM) to assemble the macrocycles as well as a Jacobsen hydrolytic kinetic resolution to install the stereogenic centers. Both synthetic compounds were found to display significant cytotoxic activity against seven human cancer cell lines with the IC50 ranges of 6.66–17.25 μM.Graphical abstractImage 1
       
  • Targeted synthesis of macrodiolides containing bis-methylene-separated
           Z-double bonds and their antitumor activity in vitro
    • Abstract: Publication date: Available online 18 July 2018Source: TetrahedronAuthor(s): Vladimir A. D'yakonov, Ilgiz I. Islamov, Lilya U. Dzhemileva, Elvina M. Khusainova, Milyausha M. Yunusbaeva, Usein M. Dzhemilev An original strategy has been developed for the synthesis of valuable unsaturated macrocyclic lactones, macrodiolides, containing a 1Z,5Z-diene moiety in 57–79% yields and>98% stereoselectivity by hafnium triflate Hf(OTf)4-catalyzed intermolecular esterification of aliphatic α,ω-dicarboxylic acids with α,ω-alka-nZ,(n+4)Z-dienediols (1,12-dodeca-4Z,8Z-dienediol, 1,14-tetradeca-5Z,9Z-dienediol, 1,18-octadeca-7Z,11Z-dienediol). The diols were obtained by homo-cyclomagnesiation of tetrahydropyran ethers of oxygenated 1,2-dienes with EtMgBr in the presence of Mg metal and Cp2TiCl2 catalyst (10 mol. %). The resulting macrodiolides exhibit high cytotoxic activity in vitro against Jurkat, K562, U937, Hek293 and HeLa tumor cell lines.Graphical abstractImage 1
       
  • Isoquinoline synthesis by C-H activation/annulation using vinyl acetate as
           an acetylene equivalent
    • Abstract: Publication date: Available online 25 May 2018Source: TetrahedronAuthor(s): Nicola J. Webb, Steven A. Raw, Stephen P. Marsden Vinyl acetate is used as an acetylene equivalent in rhodium(III)-catalysed C-H activation/annulation with aryl ketoxime esters. Extension to an aldoxime ester allows for a concise formal synthesis of decumbenine B.Graphical abstractImage 1
       
  • Best practice considerations for using the selectivity factor, s, as a
           metric for the efficiency of kinetic resolutions
    • Abstract: Publication date: Available online 25 May 2018Source: TetrahedronAuthor(s): Mark D. Greenhalgh, James E. Taylor, Andrew D. Smith The suitability of using the selectivity factor, s, as a metric for kinetic resolution reactions and the errors associated with its measurement are considered. Investigation of the analytical error associated with HPLC analysis of a kinetic resolution reveals that one of the largest potential sources of variation arises from the ability of a practitioner to integrate the peaks from a single analysis. The consequences of this error on the reliability of reported s values are discussed, and some general rules for good practice regarding the use and reporting of s as a metric are suggested.Graphical abstractImage 1
       
  • A continuous flow-batch hybrid reactor for commodity chemical synthesis
           enabled by inline NMR and temperature monitoring
    • Abstract: Publication date: Available online 25 May 2018Source: TetrahedronAuthor(s): Christiane Schotten, Joseph L. Howard, Robert L. Jenkins, Anna Codina, Duncan L. Browne Inline, real time NMR and temperature measurements have been used to optimise the continuous flow synthesis of difluoromethyltrimethylsilane (TMSCF2H) by the reduction of the Ruppert-Prakash reagent (TMSCF3). These measurements were used to maximise the space-time-yield, while ensuring this exothermic process remains safe. In this way, a three-fold increase in space-time-yield was achieved compared to the reported batch procedure, isolating 25 g of pure TMSCF2H after 105 min.Graphical abstractImage 1
       
  • Synthetic approaches to phomactins: Novel oxidation of homoallylic
           alcohols using tetra-n-propylammonium perruthenate
    • Abstract: Publication date: Available online 24 May 2018Source: TetrahedronAuthor(s): Timothy J. Blackburn, Eric J. Thomas Previous studies of a synthesis of phomactin A had resulted in the synthesis of a 15-methylenebicyclo[9.3.1]pentadecadiene. The next step in the synthesis was to be the epoxidation of this methylenecyclohexane that was hoped would lead to a 1-(hydroxymethyl)cyclohexene by rearrangement of the exocyclic epoxide, but the epoxidation was difficult to carry out regioselectively on advanced intermediates. However, oxidation of a 15-methylenebicyclo[9.3.1]pentadeca-3,7-dien-14-ol using tetra-n-propylammonium perruthenate and N-methylmorpholine-N-oxide led to conversion of this homoallylic alcohol into the corresponding 14-oxobicyclo[9.3.1]pentadeca-1(15),3,7-triene-15-carboxaldehyde in one step. Reduction of this using DIBAL-H gave a promising intermediate for a synthesis of a phomactin. The scope of this oxidation of homoallylic alcohols was briefly investigated.Graphical abstractImage 1
       
  • Gold-catalyzed synthesis of β-trifluoromethylated α,β-unsaturated
           ketones from CF3-substituted propargylic carboxylates and their reactivity
           in Diels-Alder reactions
    • Abstract: Publication date: Available online 24 May 2018Source: TetrahedronAuthor(s): Arnaud Boreux, Aubin Lambion, Dominic Campeau, Marina Sanita, Ruben Coronel, Olivier Riant, Fabien Gagosz The synthesis of fluorinated synthetic intermediates has become a field of intense research in organic chemistry. In this article, we report the application of a gold-catalyzed rearrangement to the synthesis of β-trifluoromethylated α,β-unsaturated ketones. The scope of the reaction, as well as the valorization of the products in subsequent transformations has been investigated. This study allowed for the preparation of various CF3-substituted enones and fluorinated Diels-Alder adducts from easily accessible starting materials.Graphical abstractImage 1
       
  • Structure-activity relationship study of leucinostatin A, a modulator of
           tumor−stroma interaction
    • Abstract: Publication date: Available online 24 May 2018Source: TetrahedronAuthor(s): Hikaru Abe, Manabu Kawada, Chiharu Sakashita, Takumi Watanabe, Masakatsu Shibasaki Structure-activity relationship study of leucinostatin A, a natural nonapeptide, was performed to gain insight into the structural requirements for leucinostatin A to exhibit antiproliferative activity against DU-145 prostate cancer cells under cocultured conditions with the corresponding stromal cells. Twenty truncated peptide analogs of leucinostatin A revealed that the nonapeptide structure as a whole is essential for the biological activity. Alanine scanning demonstrated the importance of some of the amino acid components, including hydroxyleucine and the second leucine from the N-terminus. Two of the three aminoisobutyric acids could be substituted with one of the enantiomers of alanine, clearly demonstrating that each methyl group in these portions has a distinct influence on the growth-inhibitory activity.Graphical abstractImage 1
       
  • Combining C-H functionalisation and flow photochemical heterocyclic
           metamorphosis (FP-HM) for the synthesis of benzo[1,3]oxazepines
    • Abstract: Publication date: Available online 24 May 2018Source: TetrahedronAuthor(s): Jasraj S. Babra, Andrew T. Russell, Christopher D. Smith, Yuxiong Zhang C-H Activation/functionalisation and Flow Photochemical Heterocyclic Metamorphosis (FP-HM) have been combined to synthesize a library of benzo [1,3]oxazepines, a rarely described heterocyclic family. This combined protocol allows a range of arylated products to be made from simple starting materials, and the cheap flow photochemical system has proven effective for rapid synthesis of gram-quantities of benzo [1,3]oxazepines.Graphical abstractImage 1
       
  • Versatile synthetic route to carbocyclic N-Acetylneuraminic acid
           and its derivatives
    • Abstract: Publication date: Available online 23 May 2018Source: TetrahedronAuthor(s): Sankar Mohan, John R. Thompson, B. Mario Pinto, Andrew J. Bennet Sialic acid (N-acetylneuraminic acid) is a carbohydrate that possess a nine carbon backbone, and it is often found at the termini of glycoconjugates in biological systems. Because of this prominence many syntheses have reported routes to sialic acid and many of its derivatives. Most of these compounds retain the endocyclic oxygen atom that becomes part of the ketal glycosidic linkage that joins sialic acid to the penultimate residue in the glycoconjugate. With respect to carba-sialic acid (replacement of the ring oxygen atom with a methylene group) a single synthesis has been reported (Ogawa et al. (Carbohydr. Res., 1995, 269, 53–78) in 30 steps and 0.5% yield. The current report details a robust synthesis of 6a-carba-α-d-sialic acid that involves 18 steps and give a 5% yield using d-quinic acid as the starting material.Graphical abstractImage 1
       
  • Synthesis and characterization of non-symmetrical photoswitchable DTE(OMe)
           sensitizers
    • Abstract: Publication date: Available online 22 May 2018Source: TetrahedronAuthor(s): Nandor Ziebart, Pierre Schroeer, Karola Rueck-Braun DTE-BODIPY 2 and BTD-DTE 3 were designed for reversible light modulation of electron- and energy-transfer processes on TiO2, and showed almost complete ring closure. In BTD-DTE 3 the BTD is an acceptor group in the open form (OF), and an energy donor group in the closed form (CF), but this property is depending on the solvent. Quantum yields for ring closure decreased (BTD-DTE 3: factor 5; DTE-BODIPY 2: factor 12) compared to DTE 1, because of π-system elongation in OFs, and also cycloreversion quantum yields became smaller (BTD-DTE 3: factor 1.4; DTE-BODIPY 2: factor 2.2).Graphical abstractImage 1
       
  • 1,1-Diacyloxy-1-phenylmethanes as versatile N-acylating agents
           for amines
    • Abstract: Publication date: Available online 21 May 2018Source: TetrahedronAuthor(s): Robert. S.L. Chapman, Joshua. D. Tibbetts, Steven. D. Bull 1,1-Diacyloxy-1-phenylmethanes and 1-pivaloxy-1-acyloxy-1-phenylmethanes have been used as bench stable N-acylating reagents for primary and secondary amines and anilines under solvent-free conditions to afford their corresponding amides in good yield.Graphical abstractImage 1
       
  • A novel Barton decarboxylation produces a 1,4-phenyl radical rearrangement
           domino reaction
    • Abstract: Publication date: Available online 19 May 2018Source: TetrahedronAuthor(s): Alejandro Manchado, Mercedes García, Mateo M. Salgado, David Díez, Narciso M. Garrido A novel 1,4-Phenyl radical rearrangement (1,4-PhRR) is described in a typical Barton decarboxylation procedure. While carrying out this reaction in presence of a N,N-disubstituted β-amino acid derivative, the decarboxyphenyl rearranged derivative is obtained, as well as in presence of β-N,N-acylamide. On the other hand, secondary amines give the β-lactam derivative without rearrangement, as well as N-Fmoc derivatives give the normal decarboxylation reaction. In regards of amines which are far away from the carboxylic group, such as δ-amino acid derivatives, the reaction occur through a typical Barton decarboxylation without rearrangement. The diversity of the reaction proves synthetic usefulness paving the way to interesting biologically active compounds.Graphical abstractImage 1
       
  • Chiral phosphoric acid-catalyzed enantioselective three-component Mannich
           reaction of acyclic ketones, aldehydes and anilines
    • Abstract: Publication date: Available online 19 May 2018Source: TetrahedronAuthor(s): Shuo Tong, Qian Wang, Mei-Xiang Wang, Jieping ZhuGraphical abstractImage 1
       
  • A stereocontrolled total synthesis of (±)-saframycin A
    • Abstract: Publication date: Available online 18 July 2018Source: TetrahedronAuthor(s): Shinya Kimura, Naoki Saito A thirteen-step total synthesis of (±)-saframycin A from a tricyclic lactam intermediate is described. The key step of this total synthesis is the stereocontrolled construction of a pentacyclic saframycin framework via a modified Pictet-Spengler type cyclization generating a bis-carboxylic acid ester derivative, followed by decarboxylation. The cytotoxicity profiles are also presented.Graphical abstractImage 1
       
  • Selective, C-3 Friedel-Crafts acylation to generate functionally diverse,
           acetylated Imidazo[1,2-a]pyridine derivatives
    • Abstract: Publication date: Available online 17 July 2018Source: TetrahedronAuthor(s): Brendan Frett, Nicholas McConnell, Anupreet Kharbanda, Gunaganti Naresh, Benjamin Rounseville, Christina Warner, John Chang, Natalie Debolske, Hong-yu Li Carbon-carbon bonds are integral for pharmaceutical discovery and development. Frequently, C-C bond reactions utilize expensive catalyst/ligand combinations and/or are low yielding, which can increase time and expenditures in pharmaceutical development. To enhance C-C bond formation protocols, we developed a highly efficient, selective, and combinatorially applicable Friedel-Crafts acylation to acetylate the C-3 position of imidazo[1,2-a]pyridines. The reaction, catalyzed by aluminum chloride, is both cost effective and more combinatorial friendly compared to acetylation reactions requiring multiple, stoichiometric equivalents of AlCl3. The protocol has broad application in the construction of acetylated imidazo[1,2-a]pyridines with an extensive substrate scope. All starting materials are common and the reaction requires inexpensive, conventional heating methods for adaptation in any laboratory. Further, the synthesized compounds are predicted to possess GABA activity through a validated, GABA binding model. The developed method serves as a superior route to generate C-3 acetylated imidazo[1,2-a]pyridine building-blocks for combinatorial synthetic efforts.Graphical abstractImage 1
       
  • Synthetic studies toward longeracemine: The intramolecular [4+2]
           cycloaddition of 3H-pyrroles
    • Abstract: Publication date: Available online 17 July 2018Source: TetrahedronAuthor(s): Joshua B. Cox, John L. Wood Model studies to develop a tetracyclization approach mimicking the proposed biosynthesis of the secodaphnane-type alkaloid longeracemine are described. These studies have culminated in the successful implementation of a 3H-pyrrole [4+2] cycloaddition that delivers a longeracemine-like azabicycle containing three contiguous quaternary stereocenters.Graphical abstractImage 1
       
  • Ethynyl-bridged porphyrin-corrole dyads and triads: Synthesis, properties
           and DFT calculations
    • Abstract: Publication date: Available online 17 July 2018Source: TetrahedronAuthor(s): Baris Temelli, Mine Gündüz, Dilek Yüksel Ethynyl-bridged porphyrin-corrole dyads and triads were synthesized by using Pd(0) mediated coupling reactions and their structures were characterized by NMR, FT-IR, UV/Vis and fluorescence techniques. Besides spectroscopic techniques, computational studies at B3LYP/6-311G(d,p) level of DFT were also used to elucidate the minimum energy geometries and the molecular orbital characteristics of the new dyads and triads. DFT calculations pointed out the presence of charge separated donor-acceptor property between macrocycles of dyads and triads, and the emission studies indicated an excited state interaction between macrocycles, and energy transfer from the porphyrin to the corrole unit.Graphical abstractImage 1
       
  • Discovery of 2,4-dimethoxypyridines as novel autophagy inhibitors
    • Abstract: Publication date: Available online 17 July 2018Source: TetrahedronAuthor(s): Lucas Robke, Tiago Rodrigues, Peter Schröder, Daniel J. Foley, Gonçalo J.L. Bernardes, Luca Laraia, Herbert Waldmann Autophagy is a catabolic process, which mediates degradation of cellular components and has important roles in health and disease. Therefore, small molecule modulators of autophagy are in great demand. Herein, we describe a phenotypic high-content screen for autophagy inhibitors, which led to the discovery of a dimethoxypyridine-based class of autophagy inhibitors, which derive from previously reported, natural product-inspired MAP4K4 inhibitors. Comprehensive structure-activity relationship studies led to a potent compound, and biological validation experiments indicated that the mode of action was upstream or independent of mTOR.Graphical abstractImage 1
       
  • A one-pot access to pyridine/benzo fused cyclododecanes via
           multi-component tandem reactions
    • Abstract: Publication date: Available online 17 July 2018Source: TetrahedronAuthor(s): Sundaravel Vivek Kumar, Mani Anusha Rani, Abdulrahman I. Almansour, Raju Suresh Kumar, S. Athimoolam, Raju Ranjith Kumar A facile syntheses of novel poly-substituted pyridine/benzo fused cyclododecane hybrid heterocycles have been achieved through one-pot multi-component tandem strategy employing cyclododecanone, aromatic aldehydes and malononitrile.Graphical abstractImage 1
       
  • Graphical abstract TOC
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s):
       
  • Erratum to “Lycogladines A-H, fawcettimine-type Lycopodium alkaloids
           from Lycopodium complanatum var. glaucum Ching” [Tetrahedron 74 (2018)
           1692–1697]
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Zhi-Jun Zhang, Yan-Yan Qi, Xing-De Wu, Jia Su, Qin-Shi Zhao
       
  • New advances in the synthesis of tripyridinophane macrocycles suitable to
           enhance the luminescence of Ln(III) ions in aqueous solution
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Nadine Leygue, Aritz Perez e Iñiguez De Heredia, Chantal Galaup, Eric Benoist, Laurent Lamarque, Claude Picard A series of four new 18-membered hexaaza macrocyclic ligands bearing three endocyclic pyridine units and acetate or methylenephosphonate pendant arms has been prepared. The new synthetic procedure is based on the use of amine and diamine precursors incorporating masked carboxylate or phosphonate functions and on an efficient sodium template effect which controls the crucial macrocyclization step (yields of macrocyclization reactions: 62–88%). This procedure appears as a suitable alternative compared to the classical Richman-Atkins methodology generally used for the preparation of this class of macrocycles. As demonstrated with the EuIII and TbIII complexes derived from two ligands, these tripyridinophane chelators form luminescent and stable mononuclear LnIII complexes in aqueous solution at physiological pH. In such a medium, TbIII complexes exhibit a brightness of 1700 (λexc = 279 nm) and 3000 (λexc = 268 nm) M−1 cm−1.Graphical abstractImage 1
       
  • Selective aerobic oxidation of benzylic amines to aryl nitriles catalyzed
           by CuBr2/N-methyl imidazole
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Yifan Shen, Yu Zhou, Lili Jiang, Guangni Ding, Luo Luo, Zhaoguo Zhang, Xiaomin Xie A convenient and efficient copper-catalyzed aerobic oxidation of primary amines to aryl nitriles was described. Various benzylic and allylic amines were selectively oxidized to the corresponding nitriles in high yields using CuBr2/NMI as the catalyst and O2 as the oxidant. The oxidation reaction profiles monitored by 1H NMR disclosed the scenario of the reaction path as well as the role of the additives. The addition of NMI increased the rate of reaction and suppressed the hydrolysis and the deamination.Graphical abstractImage 1
       
  • COX-2 and JAK3 inhibitory meroterpenoids from the mushroom Ganoderma
           theaecolum
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Qi Luo, Min-Ke Li, Jing-Feng Luo, Zheng-Chao Tu, Yong-Xian Cheng Ganoderma mushrooms possess antioxidant, anticancer, and immunomodulatory properties. In this study, eleven new meroterpenoids, ganotheaecolumols A-K (1–6, 10,11, 13, 14, and 17), together with nine known ones (7–9, 12, 15, 16, and 18–20) were isolated from the fruiting bodies of G. theaecolum. Their structures were elucidated by spectroscopic and computational methods. All the new compounds and iso-ganotheaecolumol I (12) were tested for their inhibitory activities against COX-2 and JAK3 kinases, and cytotoxic effects. It was found that most meroterpenoids could inhibit COX-2 and JAK3 with compounds 3, 4, 12, 13, and 17 having IC50 values of 1.05 ± 0.10, 1.38 ± 0.11, 2.61 ± 0.79, 3.47 ± 0.58, and 4.84 ± 0.60 μM towards COX-2. Whereas, none of the test compounds exhibited cytotoxic effects against human cancer cells (K562, A549, and Huh-7).Graphical abstractImage 1
       
  • Thioether macrocycles of the microbisporicins via reductive
           desulfurization
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Samuel K. Kutty, Joshua A. Lutz, Simon Felder, Philip Hahn, Carol M. Taylor The microbisporicins are the most potent lantibiotics isolated to-date. Cyclic tetra-, hexa- and octapeptides, inspired by this family of antimicrobial agents, have been synthesized from linear peptides. Generalized reaction conditions are reported for the two-step conversion of linear peptides to thioether macrocycles: formation of a disulfide followed by reductive desulfurization. 1H NMR analysis of the reduction reaction mixture indicated the intermediacy of a dehydroalanine when excess hexamethylphosphorus triamide (HMPT) was employed for the reduction. Maintaining a stoichiometric amount of HMPT, in dilute methanolic solution, gave the corresponding thioethers, retaining stereochemical integrity.Graphical abstractImage 1
       
  • Oxone®-mediated direct arylselenylation of imidazo[2,1-b]thiazoles,
           imidazo[1,2-a]pyridines and 1H-pyrazoles
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Ingrid Rodrigues, Angelita M. Barcellos, Andrei L. Belladona, Juliano A. Roehrs, Roberta Cargnelutti, Diego Alves, Gelson Perin, Ricardo F. Schumacher Oxone mediated reaction of imidazo[2,1-b]thiazole, imidazo[1,2-a]pyridine and 1H-pyrazole derivatives with diaryl diselenides is presented here. The methodology represents an efficient and simple protocol for carrying out the selective synthesis of 5-arylselanyl-imidazo[2,1-b]thiazoles, 3-arylselanyl-imidazo[1,2-a]pyridines and 4-arylselanyl-1H-pyrazoles in high yields using a stable, nontoxic and cheap oxidant. The reactions were conducted at 60 °C in air using acetonitrile as solvent. Alternatively, the use of ultrasound irradiation is presented as a tool for fast and efficient energy transfer that significantly reduced the reaction time.Graphical abstractImage 1
       
  • Chemoselective reduction of aldehydes and ketones by potassium
           diisobutyl-t-butoxy aluminum hydride (PDBBA)
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Joo Yeon Kim, Won Kyu Shin, Ashok Kumar Jaladi, Duk Keun An t-Butoxy derivatives of DIBALH [lithium diisobutyl-t-butoxyaluminum hydride (LDBBA), sodium diisobutyl-t-butoxyaluminum hydride (SDBBA), and potassium diisobutyl-t-butoxyaluminum hydride (PDBBA)] were examined as chemoselective reducing agents of carbonyl compounds. Among them, PDBBA was found to be the most efficient for the reduction of aldehydes and ketones to the corresponding alcohols in the presence of ester, amide, and nitrile substituents at ambient temperature. In addition, the optimal conditions gave higher chemoselectivity for aldehydes in the presence of ketones.Graphical abstractImage 1
       
  • Facile one-pot preparation of 5-aryltetrazoles and 3-arylisoxazoles from
           aryl bromides
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Eiji Kobayashi, Hideo Togo The successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diphenylphosphoryl azide provided efficiently the corresponding 5-aryltetrazoles in good to moderate yields. Similarly, the successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diethyl acetylenedicarboxylate and Oxone® provided efficiently the corresponding diethyl 3-arylisoxazole-4,5-dicarboxylates in good to moderate yields. Aromatic aldoximes are the key intermediates in both reactions, and 5-aryltetrazoles and 3-arylisoxazoles could be obtained from aryl bromides in one pot under transition-metal-free conditions.Graphical abstractImage 1
       
  • Synthesis of chloroboron(III) 3,4,12,13,21,22-
           hexabromosubnaphthalocyanine under high dilution conditions
           and comparative studies of effects of halogenation on
           physicochemical properties of subnaphthalocyanines
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Kaho Shirai, Akuto Takagi, Ryosuke Taniwaki, Masanori Kurata, Kentaro Kinugasa, Koji Yamamoto, Tadashi Mizutani, Yuko Takao, Kazuyuki Moriwaki, Takatoshi Ito, Toshiyuki Iwai, Fukashi Matsumoto, Toshinobu Ohno Chloroboron(III) hexabromosubnaphthalocyanine was prepared by cyclotrimerization of 6,7-dibromo-2,3-naphthalenedicarbonitrile in the presence of BCl3 under high dilution conditions, that is 7.4 mM of dicarbonitrile in o-dichlorobenzene-xylene (1:1). It was converted to fluoroboron(III) hexabromosubnaphthalocyanine by the reaction with AgBF4. Fluorescence quantum yields of chloroboron(III) hexafluoro-, hexachloro-, hexabromo-, and hexaiodosubnaphthalocyanine were 0.22, 0.20, 0.11, 0.05, respectively, indicating that heavy atom effects of Br and I effectively deactivated the singlet excited states. Thermal decomposition temperature (5% weight loss in the TG curve) of fluoroboron(III) hexabromosubnaphthalocyanine was the highest (359 °C) and that of chloroboron(III) hexafluorosubnaphthalocyanine was the lowest (221 °C) among hexahalosubnaphthalocyanines. The hexabromosubnaphthalocyanine served as a substrate of Sonogashira coupling, and proved to be a useful intermediate for further functionalization of subnaphthalocyanines.Graphical abstractImage 1
       
  • Cationic-lanthanide-complex-catalyzed reaction of 2-hydroxychalcones with
           naphthols: Facile synthesis of 2,8-dioxabicyclo[3.3.1]nonanes
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Yanan Zhu, Zhigang Yao, Fan Xu Cationic lanthanide complexes [Ln(CH3CN)9]3+[(AlCl4)3]3–·CH3CN served as efficient catalysts for the tandem Friedel–Crafts alkylation/ketalization reaction of 2-hydroxychalcones with naphthols/substituted phenols to produce diaryl-fused 2,8-dioxabicyclo[3.3.1]nonanes in moderate to high yields. The high catalytic efficiency of the cationic lanthanide complex [Yb(CH3CN)9]3+[(AlCl4)3]3–·CH3CN compared with that of YbCl3 can be attributed to the increased Lewis acidity of the Yb species as a result of cation formation.Graphical abstractImage 1
       
  • Ferrocenophane-based bifunctional organocatalyst for highly
           enantioselective Michael reactions
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Wei Yao, Junchao Zhu, Xiaowei Zhou, Ru Jiang, Pingan Wang, Weiping Chen Highly enantioselective Michael reactions between acetylacetone and trans-β-nitroolefins are achieved by a novel ferrocenophane-based tertiary amine-thiourea organocatalyst to provide the corresponding products in good to excellent yields (up to 95%) and enantioselectivities (up to 99% ee).Graphical abstractImage 1
       
  • Experimental and theoretical investigation of stable diastereomeric
           conformations of biscarboline amides in solution
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Miao-Miao Liang, Yang-Yang Ma, Liang Zhu, Yun-Jing Jia, Hua-Jie Zhu, Wan Li, Bei-Dou Zhou Stable axial conformations generally exist only when the single bond's (axis') rotation was sterically hindered in solution. Herein, we firstly show that two stable conformations could be observed in solution by 1H and 13C NMR experiments when the single bond rotates freely. Its coalescence temperature was measured up to 120 °C when we took compound 13 as an example. The ratio of the two stable conformations was computed using quantum methods. The predicted results matched with the experimental results well. The conversion barrier between two conformers was estimated by potential energy scan (PES) and transition state (TS) calculations at the B3LYP/6-311 + G(d) level. Furthermore, its stereochemistry was also well studied by comparing theoretical electronic circular dichroism (ECD) spectra with the experimental one.Graphical abstractImage 1
       
  • Solvent-free rhodium(III)-catalyzed synthesis of 2-aminoanilides via C−H
           amidation of N-nitrosoanilines under ball-milling conditions
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Liang Li, Guan-Wu Wang A solvent-free rhodium(III)-catalyzed C−H amidation of N-nitrosoanilines with 1,4,2-dioxazol-5-ones has been successfully developed under ball-milling conditions. This protocol provides an efficient and green access to a variety of 2-aminoanilide derivatives with low catalyst loading, remarkable functional group compatibility and excellent yields. In addition, the products allow convenient access to pharmaceutically valuable benzimidazole derivatives through a one-pot two-step synthesis.Graphical abstractImage 1
       
  • Metal-free approach for the ʟ-proline mediated synthesis of nitrones
           from nitrosobenzene
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Minho Choi, Mayavan Viji, Donghwan Kim, Young Hee Lee, Jaeuk Sim, Young-Shin Kwak, Kiho Lee, Heesoon Lee, Jae-Kyung Jung An efficient, and metal-free approach for the ʟ-proline mediated synthesis of nitrones from nitrosobenzene and benzaldehydes has been established. The reaction undergoes very efficiently at room temperature in methanol as a solvent. The reaction is assumed to involve that the initial formation of azomethine ylide and [2 + 3] cycloaddition of nitrosobenzene, followed by the subsequent retro [2 + 3] cycloaddition could offer the desired nitrone.Graphical abstractImage 1
       
  • Efficient PhB(OH)2-catalyzed one-pot synthesis of 3-substituted
           isoindolin-1-ones and isobenzofuran-1(3H)-ones under solvent free
           conditions
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Angel Palillero-Cisneros, Mercedes Bedolla-Medrano, Mario Ordóñez An efficient and practical one-pot synthesis of 3-substituted isoindolin-1-ones and isobenzofuran-1(3H)-ones has been developed under solvent free-conditions using non-toxic and cheap phenylboronic acid as excellent catalyst. This strategy involves the sequential two-step Mannich/lactamization cascade reaction of inexpensive 2-formylbenzoic acid with primary amines and a wide variety of ketones, and an aldol/lactonization cascade reaction of 2-formylbenzoic acid with a broad range of ketones.Graphical abstractImage 1
       
  • Cu(II)-catalyzed one-pot synthesis of fully substituted dihydrothiophenes
           and thiophenes from thioamides and enynones
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Min Wen, Pei-Pei Sun, Xiaoyan Luo, Wei-Ping Deng A facile and direct synthetic method was developed for the construction of fully substituted dihydrothiophenes, which via a copper-catalyzed Michael addition/intramolecular cyclization/protonation cascade reaction of readily available thioamides with enynones under air atmosphere. This approach provides 2,3-dihydrothiophenes with up to 92% yield in a one-pot process. In addition, several fully substituted thiophenes could also be synthesized by changing the substituents of thioamides.Graphical abstractImage 1
       
  • Direct C(sp3)−H difluoroallylation of diarylmethanes with
           α-(trifluoromethyl) styrenes at room temperature
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s): Xinfei Ji, Yisen Liu, Hongyan Shi, Song Cao A rapid and convenient method for the synthesis of 3,3-difluoroallylated diarylmethanes by reactions of diarylmethanes with α-(trifluoromethyl)styrenes in the presence of LiHMDS at room temperature was developed.Graphical abstractImage 1
       
  • Graphical abstract TOC cont'd
    • Abstract: Publication date: 2 August 2018Source: Tetrahedron, Volume 74, Issue 31Author(s):
       
  • One-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones using K10
           montmorillonite clay as heterogeneous catalyst
    • Abstract: Publication date: Available online 10 July 2018Source: TetrahedronAuthor(s): Jin Zhang, Wenhao Xue, Pei Wang, Tao Wang, Yong Liang, Zunting Zhang A facile and efficient one-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones was developed. The reaction of ethyl 3-(2-hydroxyphenyl)-3-oxopropanoates and 2,5-dimethoxy-2,5-dihydrofuran were performed in presence of K10 Montmorillonite Clay heterogeneous catalyst under the solvent-free condition at 80 °C for 1 h, and followed by further converted to 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones via refluxing in the alkaline EtOH solution for 0.5 h. The demonstrate method not only avoided the usage of any expensive transition-metals, but also eliminated the tedious intermediate purification. Moreover, due to the wide functional group tolerance, it could be applied to various substrates and gave product in good to excellent yields.Graphical abstractThe reaction of ethyl 3-(2-hydroxyphenyl)-3-oxopropanoates and 2,5-dimethoxy-2,5- dihydrofuran was performed in presence of K10 Montmorillonite Clay heterogeneous catalyst under the solvent-free condition, and followed by further converted to 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones via refluxing in the alkaline EtOH solution.Image 1
       
  • Synthesis and structures of α-lithiated vinyl ethers
    • Abstract: Publication date: Available online 10 July 2018Source: TetrahedronAuthor(s): Thanh C. Ho, Jonathan Congmon, Zhe Zhou, Marcus A. Tius, Lawrence M. Pratt The structures of α-lithiated vinyl ethers were explored on the basis of a combined computational and NMR study. Calculations (M06/6-31 + G(d)) on free energies of aggregate formation for a series of α-lithiated vinyl ethers indicated that the tetramer is generated preferentially in both the gas phase and THF solution, except for cyclohexylidene derivatives. (1-(Methoxymethoxy)vinyl)lithium, (2,2-difluoro-1-(methoxymethoxy)vinyl)lithium, and (1-butoxyvinyl)lithium were prepared in NMR tubes by the deprotonation of alkyl/alkoxylalkyl vinyl ethers or by the transmetalation of tin compounds. The NMR spectra of these lithium species in THF solution showed that in each species one aggregate is primarily present at 173 K, which is consistent with the preference of the tetramer.Graphical abstractImage 1
       
  • Inorganic base-mediated stereoselective hydroamination of arylalkynes with
           imidazole: An efficient access to N-Vinylimidazoles
    • Abstract: Publication date: Available online 10 July 2018Source: TetrahedronAuthor(s): Lin-Dong Liu, Zhong-Liang Lei, Hong Wang, Ming Bian, Zhen-Jiang Liu, Jin-Tao Liu, Xiao-Jun Hu A metal-free inorganic base-mediated highly stereoselective hydroamination of arylalkynes with imidazoles has been developed, and the corresponding N-vinylimidazoles were obtained in good yields and with moderate to excellent stereoselectivities (up to 99:1). For the electron rich alkynes, the reaction system of CsOH·H2O/NMP/140 °C led to the predominant formation of E-addition products, while the reaction system of KOH/NMP/90 °C afforded the Z-isomers as the major product. The electron deficient alkynes furnished predominantly the E-addition products in both reaction systems. This study essentially provides a general and an efficient protocol for the synthesis of E-isomer of the N-vinylimidazoles.Graphical abstractImage 1
       
  • Rapid solid-phase syntheses of a peptidic-aminoglycoside library
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Casey Kukielski, Krishnagopal Maiti, Sayantan Bhaduri, Sandra Story, Dev P. Arya A library of mono- and di-amino acid peptidic-aminoglycosides (PAs), with kanamycin and neomycin as the model aminoglycosides, was systematically and rapidly synthesized via solid phase peptide synthesis. Aminoglycosides were first converted into N-Boc protected carboxylic acids and fourteen L-amino acids were then used in the diversification of the full library. The approach outlined describes a rapid synthetic procedure where>200 PA compounds can be synthesized in a few months with 85–95% purity. UV thermal denaturation assessed the binding stabilization by PAs to model human and bacterial A-site rRNA sequences. Significant differences were found in thermal melting profiles among PAs that were attributed to specific amino acid sequences. Neomycin PAs lead to a much larger variation in the stabilization of A-site rRNA sequences (ΔTm = 2.6–17.1 °C) as compared to kanamycin PAs (ΔTm = 0.4–4.3 °C). Kanamycin PAs had little activity against Gram-negative and Gram-positive bacteria as compared with neomycin PAs that had significant antibacterial activity with MIC ranging from 2 – 16 μM.Graphical abstractImage 1
       
  • Solvent-controlled dehydration and diastereoselective formation of
           indenone-fused thiazolo[3,2-a]pyridines via a one-pot four-component
           reaction
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Shima Nasri, Fahimeh Sadat Hosseini, Mohammad Bayat A solvent-controlled four-component reaction has been described for the preparation of either hydroxy-tetrahydro-thiaza-cyclopenta[c]fluoren-6-one or dihydro-thiaza-cyclopenta[c]fluoren-6-one from nitroketene dithioacetals, cysteamine hydrochloride, 1,3-indandione and aromatic aldehydes starting materials by changing solvent systems. These reactions proceed under catalyst-free conditions affording a range of two types of skeletally distinct thiazolo[3,2-a]pyridines-based heterocycles. Hydroxy-tetrahydro-thiaza-cyclopenta[c]fluoren-6-one was obtained in H2O/EtOH (3:1, v/v) in high yield and diastereoselectivity but in contrast dihydro-thiaza-cyclopenta[c]fluoren-6-one was synthesized in EtOH in moderate to good yields and in the longer reaction time. The structural diversities have been confirmed spectroscopically, by IR 1H and 13C-NMR, and EI-MS spectra, which agree with the proposed structures.Graphical abstractImage 1
       
  • Anti-pathogens constituents and novel ergosterol derivatives with the
           broad- spectrum germicidal substances from earthworm, Pheretima
           aspergillum
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): H.Q. Liu, J.Y. Gao, B.Y. Lv, Q.Q. Yang, K. Liu, W.P. Yin Antimicrobial activity-guided isolation found a series of new compounds from Pheretima aspergillum. Novel structures were elucidated by NMR spectroscopic and HRMS analyses, whereas their absolute configurations were established by ORD and CD spectrometer. The further evaluation for antipathogens activities showed that broad-spectrum germicidal effects of novel ergosterol derivatives for compound II and III. Our data provide antimicrobial mechanistic insights by molecular docking.Graphical abstractNew natrual products (Compounds I-IV) including one alkaloids (I), two ergosterol derivatives (II-III) and one alkyl oligoglycosides (IV) were isolated for the first time from annulata earthworm, Pheretima aspergillum.Image 1
       
  • Synthesis of 3-sulfonyl coumarins through radical sulfonylation with
           disulfides under catalyst-free conditions
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Hexiang Ren, Ming Zhang, Ai Qin Zhang An efficient and convenient aryl sulfonyl introducing strategy for the synthesis of 3-sulfonyl coumarins via ipso-cyclization/1,2-ester migration from substituted phenyl 3-phenylpropiolates with disulfides and potassium persulfate as sulfonylating reagents was developed, halogen and many other electron-withdrawing or -donating functional groups are tolerated. When naphthalen-1-yl 3-phenylpropiolate was used as a starting material, a spiro compound was obtained via ipso-cyclization.Graphical abstractImage 1
       
  • Oxidation for unsymmetrical bromo-1,10-phenanthrolines and subsequent
           hydroxylation, decarbonylation and chlorination reactions
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Yu-Xin Peng, Bin Hu, Wei Huang A systematic investigation on the oxidation of unsymmetric bromo-phens is presented herein, where the reaction temperature is found to be the key parameter to generate oxidation or oxidation-bromination products. The regioselective C3-brominated compounds are produced in moderate yields in the cases of 2-bromo-phen and 4-bromo-phen. Subsequent hydroxylation and decarbonylation for bromo-phds are also studied, where a series of bromo-diazafluorenones and phen-triones have been isolated. Furthermore, various chlorination products have been obtained by treating bromo-phds or bromo-phts with excess POCl3.Graphical abstractImage 1
       
  • TBAI-mediated regioselective 5-exo-dig iodinative oxocyclization of
           2-alkynylbenzamides for the synthesis of isobenzofuran-1-imines and
           isobenzofurans
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Yan-Hua Wang, Jin-Biao Liu, Banlai Ouyang, Hongwei Zhou, Guanyinsheng Qiu Alkyne-based regioselective functionalization is an important transformation method for the synthesis of a wide variety of organic products. In this work, a regioselective TBAI-mediated oxidative 5-exo-dig iodo-oxycyclization of 2-alkynylbenzamide is used for the synthesis of various isobenzofuran derivatives with excellent functional group tolerance and high reaction efficiency. We hypothesized that using water in a mixed solvent could change the reaction pathway and realize a high reaction regioselectivity. Furthermore, the application of the developed procedure was demonstrated by the synthesis of phthalazin-1(2H)-one and aryl-substituted isobenzofurans.Graphical abstractImage 1
       
  • Ozonolysis of 18α-Oleanane triterpenoid with an alkenenitrile moiety in
           the five-membered ring A
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Victoria V. Grishko, Natalia V. Galaiko, Ekaterina V. Igosheva, Maksim V. Dmitriev A novel synthetic protocol of ozonolytic cleavage of 18α-oleanane triterpenoid with the five-membered α,β-alkenenitrile moiety dissolved in dichloromethane to selectively synthesize a 1,3-secotriterpene derivative with 78% yield was developed. Spontaneous condensations of the synthesized 19β,28-epoxy-1,3-seco-2-nor-18α-olean-3-al-1-oic acid followed by formation of unsubstituted 1,3- and 1,4-lactones were registered in reactions with sodium borohydride as a reducing reagent or oxalyl chloride as an activating agent, respectively. α-Methoxy- and α-ethoxy-substituted 1,3-lactones were obtained when the polar protic solvents methanol or ethanol were used for the ozonolysis of the alkenenitrile. Experiments on ozonolysis were carried out in combination with reduction with dimethyl sulfide. Ozonolysis of alkenenitrile in dichloromethane without reductive treatment was found out to have resulted in stable triterpene ozonide.Graphical abstractImage 1
       
  • Comprehensive study towards the desulfonylation/desulfinylation of
           cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams to access novel
           cis-3-monosubstituted-β-lactams
    • Abstract: Publication date: Available online 7 July 2018Source: TetrahedronAuthor(s): Anu Kumari, S.S. Bari, Garima Modi, Shiwani Berry, Sadhika Khullar, Sanjay K. Mandal, Aman Bhalla An inclusive study towards the stereospecific synthesis of novel cis-3-monosubstituted-β-lactams from cis-3-functionalized 3-phenylsulfonyl/sulfinyl-β-lactams is described. 3-Sulfinyl-β-lactams 5/5ʹ successfully furnished stereospecific cis-3-monosubstituted-β-lactams 6, however 3-sulfonyl-β-lactams 2 failed to give the desulfurized product 6ʹ. The final stereochemical and structural conformations of novel β-lactams were established by single crystal X-ray crystallographic study (5c). The cis configuration of the β-lactams 5/5ʹ and 6 was assigned in relevance to E and C4-H and C3-H and C4-H respectively.Graphical abstractImage 1
       
  • Identification and synthesis of new sex-specific components of olive fruit
           fly (Bactrocera oleae) female rectal gland, through original Negishi
           reactions on supported catalysts
    • Abstract: Publication date: Available online 6 July 2018Source: TetrahedronAuthor(s): Graziano Fusini, Davide Barsanti, Gaetano Angelici, Gianluca Casotti, Angelo Canale, Giovanni Benelli, Andrea Lucchi, Adriano Carpita In the present study, eleven new sex-specific components extracted from female rectal gland of olive fruit flies were synthesized and identified. The quantitative determination of those components by GC and GC/EI-MS, at different moments of the insect life span, highlighted the growing trend of their secretion. While for the synthesis of saturated esters, conventional transesterification methods could be adopted, for the synthesis of unsaturated components, a Negishi cross-coupling between organozinc halides and (Z)-1-bromo-1-alkenes was developed. To the extent of our knowledge, this reaction represents the first example of supported-catalyst promoted Negishi coupling, between an alkylzinc reagent and an alkenyl halide.Graphical abstractImage 1
       
  • The Dakin-West reaction: Past, present and future
    • Abstract: Publication date: Available online 6 July 2018Source: TetrahedronAuthor(s): Luciana Dalla Vechia, Rodrigo Octavio Mendonça Alves de Souza, Leandro Soter de Mariz e Miranda The decarboxylation of amino acids in presence of a carboxylic anhydride leading to the corresponding ketones, known as Dakin-West reaction, is about to complete almost one century of discovery. In this review, we firstly present the chronological progress in the mechanistic study of the reaction, with an overview about types of substrates, anhydrides and bases already used in the Dakin-West reaction. And ultimately, the application of the reaction in the synthesis of compounds of pharmaceutical or industrial interest is also discussed.Graphical abstractImage 1
       
  • Extensive effect of π-conjugation in rotatable oligonaphthyl derivatives
           on circularly polarised luminescence in solution and solid films
    • Abstract: Publication date: Available online 6 July 2018Source: TetrahedronAuthor(s): Takuya Sato, Nobuyuki Hara, Keishiro Yoshida, Nobuo Tajima, Kazunori Tsubaki, Yoshitane Imai Extending the π-conjugation of chiral rotatable oligonaphthyl derivatives results in longer circularly polarised luminescence (CPL) wavelengths and increased unpolarised-photoluminescence (PL) quantum yields. The CPL was observed to shift to a significantly longer wavelength and the PL quantum yield was greatly improved when the number of naphthyl units was extended from two (dimer) to four (tetramer). On the other hand, the wavelength and quantum yield increased less in moving from the tetramer to the octamer in solution and solid films.Graphical abstractImage 1
       
  • A highly selective fluorescence switch for Cu2+ and Fe3+ based on a new
           diarylethene with a triazole-linked rhodamine 6G unit
    • Abstract: Publication date: Available online 6 July 2018Source: TetrahedronAuthor(s): Huimin Kang, Congbin Fan, Huittao Xu, Gang Liu, Shouzhi Pu A new diarylethene compound with a triazole-linked rhodamine 6G unit attached to the imino group (1O) was designed and synthesized. According to the test results, the solution color and fluorescence color of diarylethene can be modulated by lights and metal ions. The solution color could change from colorless to light purple when irradiated with UV light. When Cu2+ was added to the diarylethene solution, the color of diarylethene solution became blue, the fluorescence color turned from dark to bright yellow. Although the solution color did not change by adding Fe3+, its fluorescence color varied from dark to yellow. Moreover, it was found that the complex ratio of the diarylethene to Cu2+ was 1:1 and the binding stoichiometry of the diarylethene to Fe3+ was also 1:1 based on the data of NMR, MS, and other experiments. Based on these findings, photochromic figure of the diarylethene with UV/Vis light, Cu2+ and Fe3+ was constructed. Furthermore, the logic circuit was designed by input signals (ultraviolet stimulus, visible light stimulus, Cu2+ (or Fe3+) and EDTA) and an output signal (fluorescent intensity at 566 nm (or 575 nm)).Graphical abstractImage 1
       
  • Decarboxylative nucleophilic difluoromethylation of aldehydes and imines
    • Abstract: Publication date: Available online 2 July 2018Source: TetrahedronAuthor(s): Jia Chen, Jin-Hong Lin, Ji-Chang Xiao The high demand for the biologically active CF2H-molecules has stimulated significant efforts to develop efficient methods for the installation of CF2H functionality. We found that phenylsulfonyl difluoroacetate salt (PhSO2CF2CO2− K+) could directly undergo decarboxylation under warming conditions to produce active anion (PhSO2CF2−) without the need of any base or additive, thus allowing for the subsequent nucleophilic (phenylsulfonyl)difluoromethylation of aldehydes or imines to give PhSO2CF2-alcohols or -amines, respectively. Interestingly, the removal of PhSO2 group was achieved simply by elevating the reaction temperature for the conversion of aldehydes to afford CF2H-ketones.Graphical abstractImage 1
       
  • Amidation and esterification of carboxylic acids with amines and phenols
           by N,N′-diisopropylcarbodiimide: A new approach for amide and ester bond
           formation in water
    • Abstract: Publication date: Available online 30 June 2018Source: TetrahedronAuthor(s): Nadia Fattahi, Morteza Ayubi, Ali Ramazani The present study reports the successful synthesis of two important and abundant functional groups "ester and amide" by N,N′-diisopropylcarbodiimide (DIC) in water as a green solvent. A wide range of substrates could be employed with high functional group tolerance. The products were obtained in high yields after short reaction times. This method provides an efficient, economic, simple and very mild protocol for ester and amide bond formation in aqueous media. In addition, this work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water.Graphical abstractImage 1
       
  • Efficient synthesis of tetrazole derivatives of cytisine using the
           azido-Ugi reaction
    • Abstract: Publication date: Available online 30 June 2018Source: TetrahedronAuthor(s): Danil P. Zarezin, Adil M. Kabylda, Valentina I. Vinogradova, Pavel V. Dorovatovskii, Victor N. Khrustalev, Valentine G. Nenajdenko The azido-Ugi reaction with natural alkaloid cytisine was investigated. It was demonstrated that the reaction could be performed with various carbonyls (both aldehydes and ketones) and isocyanides. The transformation proceeded under mild conditions in methanol using TMSN3 as a source of hydrazoic acid to give target tetrazole derivatives of cytisine in up to 98% yield. The diastereoselectivity of this reaction was studied using both aliphatic and aromatic aldehydes. A family of tetrazole derived cytisine compounds was prepared. Selective deprotection of tetrazoles was elaborated to synthesize the corresponding NH-tetrazoles.Graphical abstractImage 1
       
  • Understanding the Diels-Alder reactivity of 1,2-azaborine analogues
    • Abstract: Publication date: Available online 30 June 2018Source: TetrahedronAuthor(s): Jorge Juan Cabrera-Trujillo, Israel Fernández The Diels-Alder reactivity of 1,2-heteroborines (H4C4B(H)X, X = NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB = X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.Graphical abstractImage 1
       
  • Relative stereochemical assignment of C-33 and C-35 in the antibiotic
           gladiolin
    • Abstract: Publication date: Available online 30 June 2018Source: TetrahedronAuthor(s): Christopher Perry, Jacob R. Sargeant, Lijiang Song, Gregory L. Challis Gladiolin is a macrolide antibiotic isolated from Burkholderia gladioli BCC0238 with promising activity against Mycobacterium tuberculosis, including several multidrug resistant strains. The configuration of all but one of the stereogenic centers of gladiolin has previously been elucidated using a combination of NOESY NMR experiments and predictive sequence analysis of the polyketide synthase responsible for its assembly. However, it was not possible to assign the configuration of the C-35 methyl group using such methods. Here we report the synthesis of C-33/C-35-syn and C-33/C-35-anti mimics of the C-30 to C-38 fragment of gladiolin from (R) and (S)-citronellol, respectively. Comparison of HSQC NMR data for the mimics and the natural product showed that the C-35 methyl is anti to the C-33 hydroxyl group, indicating that gladiolin has the 35S configuration.Graphical abstractImage 1
       
  • Formation of meta-arylsulfanyl- and meta-(alkylsulfanyl)phenols from
           cyclohexane-1,3-diones
    • Abstract: Publication date: Available online 30 June 2018Source: TetrahedronAuthor(s): Nhan Do Van Thanh, Subrata Patra, Derrick L.J. Clive Reaction of cyclohexane-1,3-diones with TsCl/Et3N and treatment of the resulting 3-(tosyloxy)cyclohex-2-en-1-ones with aryl- or alkyl thiols and K2CO3 in MeCN gives 3-(arylsulfanyl)cyclohex-2-en-1-ones or 3-(alkylsulfanyl)cyclohex-2-en-1-ones, respectively. These compounds are easily brominated at C-2 by using NBS in MeCN; exposure to DBU in MeCN at room temperature then causes aromatization to afford meta-arylsulfanyl- and meta-(alkylsulfanyl)phenols.Graphical abstractImage 1
       
  • Iodine-promoted five-component reaction using fragment assembly strategy
           to construct dihydrooxepines
    • Abstract: Publication date: Available online 27 June 2018Source: TetrahedronAuthor(s): Peng Zhao, Xia Wu, Xiao Geng, Can Wang, Yan-Dong Wu, An-Xin Wu An iodine-promoted fragment assembly strategy for the synthesis of fused heterocycles has been established. It provides an efficient route to construct pyrazolone-oxepine-pyrazoles from phenylhydrazines, aryl methyl ketones and acetoacetate esters. Notably, acetoacetate esters play two distinct pivotal roles in the five-component reaction by realizing the unique reactivities of methyl, methylene and carbonyl groups to construct 3-methyl-5-pyrazolone skeletons and by the reaction of methyl and carbonyl groups to form a C (sp3)-O bond.Graphical abstractImage 1
       
  • Smart optical probe for ‘equipment-free’ detection of oxalate in
           biological fluids and plant-derived food items
    • Abstract: Publication date: Available online 27 June 2018Source: TetrahedronAuthor(s): Nilanjan Dey, Namita Kumari, Deepa Bhagat, Santanu Bhattacharya A reversible ‘turn-on’ sensor has been designed for ‘naked-eye’ detection of oxalate at nanomolar concentration (∼12.5 nM) at pH 7.4. The sensory system shows a highly specific response towards oxalate among a wide range of antinutrients and biologically relevant anionic species. Mechanistic investigations indicate that oxalate can turn the pink-colored solution colorless by dissociating the preformed metal complex. Additionally, high specificity and good accuracy with recovery values ranging from 93.3 to 105.0% were obtained during oxalate estimation in spiked water and human urine samples, confirming the suitability of the present method in estimating trace-level of oxalate in complex matrices. With these results, quantitative estimations of endogenous oxalate were achieved in more than twenty-five different agricultural crops. Finally, low-cost, portable paper strips were developed for on-site detection of oxalate.Graphical abstractImage 1
       
  • Ultrasound-assisted synthesis of substituted guanidines using
           1H-pyrazole-1-carboxamidine and S-methylisothiouronium sulfate under
           solvent-free conditions
    • Abstract: Publication date: Available online 26 June 2018Source: TetrahedronAuthor(s): Mitsue Fujita, Yoshio Furusho We have investigated ultrasound-assisted synthesis of guanidine derivatives using 1H-Pyrazole-1-carboxamidine (PyzCA) and S-substituted isothiouronium sulfate (MeITU). The guanylations of several amines are promoted by ultrasound sonication under solvent-free conditions, and proceed under mild conditions. It is of particular interest that the guanylations do not require bases in most cases.Graphical abstractImage 1
       
  • CuX2-mediated halocyclization of 1,1-difluoro-2,3-allenylphosphonic acid
           monoesters –synthesis of novel cyclic phosphate mimics
    • Abstract: Publication date: Available online 26 June 2018Source: TetrahedronAuthor(s): Xu Jiang, Xiang Cai, Yun Lin, Jintao Liu Novel six-membered cyclic phosphate mimics (5-halo-3,3-difluoro-3,6-dihydro-2H-1,2-oxaphosphinine 2-oxides) were synthesized via CuX2 (X = Br, Cl)-mediated halocyclization of 1,1-difluoro-2,3-allenylphosphonic acid monoesters in moderate to good yields with high regio-selectivity. This reaction represents the first example of transition metal-mediated intramolecular cyclization of a P-OH moiety to β-allenylphosphonates with a carbon-carbon double bond.Graphical abstractImage 1
       
  • Synthesis of B←N embedded indacenodithiophene chromophores and effects
           of bromine atoms on photophysical properties and energy levels
    • Abstract: Publication date: Available online 26 June 2018Source: TetrahedronAuthor(s): Yongchun Li, Huifeng Meng, Dong Yan, Yuqing Li, Bo Pang, Kai Zhang, Genggeng Luo, Jianhua Huang, Chuanlang Zhan Developing novel fused π-conjugated chromophores has been an energetic research realm and knowing how to adjust their photophysical properties and energy levels through structure tailoring is of pivotal importance. Herein, based on the ladder-type π-conjugated indacenodithiophene (IDT) moiety, four B←N embedded IDT structures, namely, BNIDT, BNIDT-2Br, BNIDT-4Br, and BNIDT-6Br are synthesized and fully characterized. The influences of B←N unit embedded in the IDT backbone and Br atoms anchoring at the periphery on the photophysical properties and energy levels are discussed systematically. From IDT to BNIDT, a new intra-molecular charge transfer (ICT) transition band appears at lower energy (400–600 nm) in the absorption spectra with reduced optical bandgaps (Eg) from 3.25 eV to 2.11 eV and the fluorescence emission peaks red-shift from 390 nm to 565 nm along with remarkably extended fluorescence lifetimes from 1.2 ns to 12.4 ns due to the introduction of electron-deficient B←N into the backbone. Further anchoring Br atoms at the periphery of the backbone gives rise to depressed optical bandgaps, decreased fluorescence quantum yields (Φ), and shortened fluorescence lifetimes (τ) from BNIDT (Eg = 2.11 eV, Φ = 0.46, τ = 12.4 ns), BNIDT-2Br (Eg = 2.08 eV, Φ = 0.18, τ = 4.9 ns), BNIDT-4Br (Eg = 1.67 eV, non-emission) to BNIDT-6Br (Eg = 1.61 eV, non-emission). The HOMO and LUMO levels estimated from ultraviolet photoelectron spectroscopy (UPS) and optical bandgaps also experience synergetic lowering from IDT to BNIDT-6Br. This work indicates that backbone modification with electron-deficient B←N unit and side groups tailoring with halogen atoms are powerful to manipulate the optical properties and energy levels of fused π-conjugated chromophores.Graphical abstractImage 1
       
  • De novo asymmetric synthesis of (−)-nanaomycin A
    • Abstract: Publication date: Available online 22 June 2018Source: TetrahedronAuthor(s): Qi Zhang, George A. O'Doherty The de novo asymmetric total synthesis of (−)-nanaomycin A is described. The entirely linear route required only 13 steps from commercially available starting materials (3% overall yield). Key transformations include a Claisen rearrangement, an asymmetric dihydroxylation, a regioselective tosylation, a diastereoselective intramolecular Friedel-Crafts alkylation and a nitrile hydrolysis. As the route relies on a Sharpless asymmetric dihydroxylation it is equally amenable for the synthesis of (+)-nanaomycin A.Graphical abstractImage 1
       
  • Highly enantioselective allylic alkylation of 5H-oxazol-4-ones with
           Morita-Baylis-Hillman carbonates
    • Abstract: Publication date: Available online 22 June 2018Source: TetrahedronAuthor(s): Han Xu, Feng Sha, Xin-Yan Wu An organocatalytic enantioselective allylic alkylation of 5H-oxazol-4-ones with Morita-Baylis-Hillman carbonates has been developed. With 10 mol% of commercially available cinchonidine, a wide range of substituted 5H-oxazol-4-one derivatives were constructed in good-to-excellent yields with high diastereo- and enantioselectivities. The allylic alkylation adducts obtained are valuable precursors for the synthesis of chiral α-alkyl α-hydroxycarboxylic acid derivatives, which represent a series of versatile building blocks in many biologically active compounds.Graphical abstractImage 1
       
  • Rosellin A and B, two red diketopiperazine alkaloids from the mushroom
           Mycena rosella
    • Abstract: Publication date: Available online 22 June 2018Source: TetrahedronAuthor(s): Julia S. Lohmann, Monika von Nussbaum, Wolfgang Brandt, Julia Mülbradt, Wolfgang Steglich, Peter Spiteller Rosellin A and B, two red diketopiperazine alkaloids with unprecedented structures, have been isolated from the fruiting bodies of the mushroom Mycena rosella. The structures of the rosellins were mainly deduced from their 2D NMR and HRMS (ESI) spectra. Their absolute configuration was determined by comparison of the CD spectra of the rosellins with the corresponding CD spectra obtained by quantum chemical calulations. Root exposure to rosellin A led to bleaching of the leaves of Lepidium sativum plants.Graphical abstractImage 1
       
  • The Dimroth rearrangement as a probable cause for structural
           misassignments in imidazo[1,2-a]pyrimidines: A 15 N-labelling study and
           an easy method for the determination of regiochemistry
    • Abstract: Publication date: Available online 21 June 2018Source: TetrahedronAuthor(s): Maria Chatzopoulou, R. Fernando Martínez, Nicky J. Willis, Timothy D.W. Claridge, Francis X. Wilson, Graham M. Wynne, Stephen G. Davies, Angela J. Russell Structural misassignments are often seen for complex natural products, but this can also be an issue with seemingly simpler structures. In this paper, we describe how, using a 15N-labelled analogue, we established that the Dimroth rearrangement can occur in imidazo[1,2-a]pyrimidines and result in an incorrect regiochemical assignment of such compounds. These studies supported a rearrangement mechanism involving addition of hydroxide ion followed by ring opening. It was also observed that C(2) and C(3) substituted regioisomers could be readily distinguished using 1H NMR spectroscopy.Graphical abstractImage 1
       
  • Highly diastereoselective boron and titanium mediated aldol reactions of a
           mannitol derived 2,3-butanediacetal ethyl ketone
    • Abstract: Publication date: Available online 19 June 2018Source: TetrahedronAuthor(s): Matthew O'Brien, Arne Weber, Gemma Hardy, Steven V. Ley A mannitol derived 2,3-butanediacetal ethyl ketone displays high levels of diastereoselectivity in boron and titanium mediated aldol reactions with a range of aliphatic and aromatic aldehydes to afford syn aldol products in high yield. The stereochemical outcome of the reaction was determined using J-value analysis, NMR analysis of acetoxymandelate derivatives and X-ray crystallography.Graphical abstractImage 1
       
  • Merging metathesis and photochemical Csp3-H activation: Access to masked
           β-formyl hexanolides and their rearrangement to furofuranones
    • Abstract: Publication date: Available online 19 June 2018Source: TetrahedronAuthor(s): Quentin Glenadel, Youssef Nassar, Ludovic Raffier, Sebastiaan Veys, Olivier Piva β-Masked formyl hexanolides were prepared by a three-step sequence including esterification of homoallylic alcohols, ring-closing metathesis and the photochemically induced addition of dioxanyl radical. When treated under oxidative conditions, the adducts underwent cleavage of the ketal group leading after rearrangement to parent furofuranones, structures found in some biological active compounds.Graphical abstractImage 1
       
  • Synthesis, conformational preferences in gas and solution, and molecular
           gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase
           electron diffraction (GED), LT NMR and theoretical calculations
    • Abstract: Publication date: Available online 19 June 2018Source: TetrahedronAuthor(s): Bagrat A. Shainyan, Elena N. Suslova, Tran Dinh Phien, Sergey A. Shlykov, Erich Kleinpeter 1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature 13C NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Phax conformer (1-Pheq:1-Phax ratio of 20:80%, ΔG°(317 K) = −0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of Cipso and C(1,5) carbon signals in 13C NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Pheq conformer was found to be the preferred one [(1-Pheq: 1-Phax = 77%: 23%, K = 77/23 = 2.8; −ΔG° = −RT ln K (at 103 K) = 0.44 ± 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Phax conformer in the gas phase and of the Pheq conformer in solution is confirmed.Graphical abstractImage 1
       
  • Trapping rhodium carbenoids with aminoalkynes for the synthesis of diverse
           N-heterocycles
    • Abstract: Publication date: Available online 19 June 2018Source: TetrahedronAuthor(s): Arianne C. Hunter, Bilal Almutwalli, Anae I. Bain, Indrajeet Sharma A convergent approach for the synthesis of diverse N-heterocycles is described. The reaction involves trapping of diazo-derived rhodium carbenoids with gold activated aminoalkynes, and accommodates both the donor/acceptor (D/A) as well as acceptor/acceptor (A/A) diazo carbonyls. Mechanistic investigations indicate that the Rh(II)/Au(I) catalyzed reaction of aminoalkynes with D/A diazos is concerted, while the reaction with A/A diazo is stepwise and proceeds with carbene N–H insertion and a subsequent Conia-ene cyclization.Graphical abstractImage 1
       
  • A new approach for the total synthesis of spilanthol and analogue with
           improved anesthetic activity
    • Abstract: Publication date: Available online 18 June 2018Source: TetrahedronAuthor(s): Isabella G. Alonso, Lais T. Yamane, Verônica S. de Freitas-Blanco, Luiz F.T. Novaes, Michelle Franz-Montan, Eneida de Paula, Marili V.N. Rodrigues, Rodney A.F. Rodrigues, Julio C. Pastre A 5-step synthesis of spilanthol (affinin) is reported, where the route features complete control of alkene geometry during the assembling of the double bonds, with the use of a Sonogashira cross-coupling reaction, a Z-selective alkyne semi-reduction and a HWE olefination reaction as the key steps. A simplified analogue was also prepared in 4 steps. Both compounds were found to permeate dermatomed pig ear skin through an in vitro Franz-type diffusion cell. The simplified analogue presented a superior anesthetic effect in vivo, using the tail flick model, when compared to spilanthol and to the commercial standard EMLA®. These results suggest that both spilanthol and its analogue could be useful as a topical anesthetic in clinical practice.Graphical abstractImage 1
       
  • Synthesis and characterization of a photoaffinity labelling probe based on
           the structure of the cystic fibrosis drug ivacaftor
    • Abstract: Publication date: Available online 15 June 2018Source: TetrahedronAuthor(s): C. Michael Hamilton, Maurita Hung, Gang Chen, Zafar Qureshi, John R. Thompson, Bingyun Sun, Christine E. Bear, Robert N. Young Cystic Fibrosis (CF) is a genetic disorder caused by loss-of-function mutations to the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Ivacaftor (1) was the first therapeutic approved for the treatment of CF that is able to restore gating activity to certain CFTR variants although the mechanism of action is poorly understood. Herein we describe the synthesis of a photoaffinity labelling (PAL) probe (2) based on the structure of ivacaftor incorporating a photoreactive diazirine moiety for use in labelling studies designed to identify the binding site for ivacaftor on mutant CFTR. The PAL probe 2 retained potentiation activity, with a potency similar to 1, using a Fluorescent Imaging Plate Reader (FLIPR®) assay measuring ion conductance potentiation of wild type (Wt)-CFTR. Photolabelling experiments with human serum albumin (HSA) as a model protein have shown that probe 2 can label HSA in a manner consistent with observed and predicted binding.Graphical abstractImage 1
       
  • Studies on the synthesis of the lasubine alkaloids
    • Abstract: Publication date: Available online 15 June 2018Source: TetrahedronAuthor(s): Nur Filza bte Mohamed Aslam, Oliver Simon, Roderick W. Bates Formal syntheses of lasubine II and subcosine II have been completed by the synthesis of epi-lasubine II. The synthesis involves diastereoselective allylation of a methoxy isoxazolidine and a tandem hydrogenation process leading stereoselectively to a trisubstituted piperidine.Graphical abstractImage 1
       
  • Total synthesis 2-epi-α-cedren-3-one via a cobalt-catalysed Pauson-Khand
           reaction
    • Abstract: Publication date: Available online 15 June 2018Source: TetrahedronAuthor(s): William J. Kerr, Mark McLaughlin, Laura C. Paterson, Colin M. Pearson Herein we target the total synthesis of 2-epi-α-cedren-3-one, a natural compound isolated from the essential oil of Juniperus thurifera. Overall, our synthetic sequence presents an optimised and robust series of chemical transformations, with prominent features including a low temperature and highly (Z)-selective Wittig olefination reaction, which is vital for the establishment of the relative stereochemistry within the final natural product, and a microwave-assisted, catalytic, intramolecular Pauson-Khand cyclisation reaction, which is used to construct the intriguing tricyclic core of the target molecule. Our optimum cyclisation protocol utilises only 20 mol% of transition metal, and delivers the complex tricyclic structure in just 10 min. Further manipulations of the annulation product culminate in the first total synthesis of the described natural target.Graphical abstractImage 1
       
  • Short total syntheses of the avenaciolide family of natural products
    • Abstract: Publication date: Available online 14 June 2018Source: TetrahedronAuthor(s): Sandra Ainsua Martinez, Martin Gillard, Anne-Caroline Chany, Jonathan W. Burton The avenaciolide family of natural products are small α-methylene bis-γ-lactones that exhibit a wide variety of biological activities. Herein we report concise syntheses of five members of this family of natural products along with the synthesis of one non-natural analogue. The syntheses proceed in five or six steps from simple, commercially available compounds and feature a key oxidative cyclization/lactonization reaction that likely occurs via a radical mechanism.Graphical abstractImage 1
       
  • Bifunctional iminophosphorane superbases: Potent organocatalysts for
           enantio- and diastereoselective Michael addition reactions
    • Abstract: Publication date: Available online 12 June 2018Source: TetrahedronAuthor(s): Alistair J.M. Farley, Pavol Jakubec, Anna M. Goldys, Darren J. Dixon Bifunctional iminophosphorane (BIMP) organocatalysts catalyze the enantio- and diastereoselective Michael additions of high pKa cyclic malonamate ester pro-nucleophiles to nitroalkenes with reactivity profiles of up to 3 orders of magnitude greater than tertiary amine bifunctional Brønsted base/(thio)urea organocatalysts. The unrivalled performance of the BIMPs allows reaction times of challenging reactions to be slashed from weeks to minutes and has enabled new flow chemistry applications using polystyrene-supported versions contained within a flow reactor.Graphical abstractImage 1
       
  • Radical cyclisation studies of β-nitroamines from the nitro-Mannich
           reaction
    • Abstract: Publication date: Available online 12 June 2018Source: TetrahedronAuthor(s): Abil Aliev, James C. Anderson, Mérina K. Corpinot, Emily S.J. Gascoigne A range of novel β-nitroacetamides with an alkenyl- or alkynyl tether were synthesized using the deprotonative or conjugate addition nitro-Mannich reaction. They were subjected to radical denitration-cyclisation with a 10 equivalent excess of tributyltin hydride, catalytic AIBN in refluxing benzene to explore the structural and electronic requirements for efficient cyclisation. Cyclisations of the β-nitroacetamides were successful in most cases, undergoing 5-exo-trig cyclisation to give the desired cyclopentyl or indanyl structures. Radical 1,4-translocation of a phenyl group was observed in several cases. Diastereoselectivity was low, with 2 or 3 of 4 possible diastereoisomers observed in most cases. Further purification by crystallisation allowed the isolation of some as single diastereoisomers. It was found that higher yields were obtained by increasing the substitution or reducing the degrees of freedom of the tether between the nitro group and the radical acceptor.Graphical abstractImage 1
       
  • Recent advances in the asymmetric catalytic synthesis of chiral 3-hydroxy
           and 3-aminooxindoles and derivatives: Medicinally relevant compounds
    • Abstract: Publication date: Available online 11 June 2018Source: TetrahedronAuthor(s): Pedro Brandão, Anthony J. Burke Several oxindole derivatives, of natural or synthetic origin, have been identified as medicinally appealing compounds, with a plethora of bioactivities reported. Chiral 3-hydroxy and 3-aminooxindole scaffolds have captured the attention of several research groups, due to their importance in drug discovery. In this review, we systematically address the wide variety of asymmetric catalytic methodologies employed in the preparation of these relevant chiral scaffolds, present in many biologically active compounds and/or natural products. Special focus will be given to the nature of the catalyst used.Graphical abstractImage 1
       
  • Frozen aryldiazonium chlorides in radical reactions with alkenes and
           arenes
    • Abstract: Publication date: Available online 7 June 2018Source: TetrahedronAuthor(s): Daniel Thon, Michael C.D. Fürst, Lisa-Marie Altmann, Markus R. Heinrich Frozen aryldiazonium chlorides have been investigated in radical alkene and arene functionalizations. Through freezing at – 84 °C, aryldiazonium chlorides, which otherwise show significant decomposition in aqueous solution after several hours at room temperature, can be stored for at least 20 days. In addition, the slow melting of aryldiazonium-containing ice cubes can serve as an alternative to syringe pumps that are commonly used if a controlled addition of the diazonium salt to the reaction mixture is required.Graphical abstractImage 1
       
  • NMR characterization of α- and β-mannopyranurono-2,6-lactones
    • Abstract: Publication date: Available online 6 June 2018Source: TetrahedronAuthor(s): Kazuki Tohda, Masashi Saito, Hiroaki Sakai, Daisuke Ishikura, Ryota Saito, Kaname Sasaki Determining the stereochemistry at the anomeric position of glycosides is imperative in chemical synthesis. As for 1,2-cis-β-glycosides such as β-mannosides, 13C-1H coupling constants, 1JCHs, are conventionally used when glycosides are in an ordinary chair conformation. In this work, we searched for appropriate criteria to determine the stereochemistry of products in a recently developed glycosylation reaction using 2,6-lactones. As a result, we found that α-glycosides exhibited vicinal coupling constants of around 3.0 Hz at the anomeric proton, as well as a long-range coupling between protons at C-1 and C-5, whereas β-glycosides had coupling constants of 1.2 Hz at most. These figures are expected to be useful for future assignments. In addition, the observations obtained from this study revealed the conformation of glycosides with a 2,6-lactone moiety.Graphical abstractImage 1
       
  • Synthesis of the C1 to C13 tetrahydropyranyl-resorcylate core of
           paecilomycin B
    • Abstract: Publication date: Available online 5 June 2018Source: TetrahedronAuthor(s): Rosa Cookson, Andrew J.P. White, Anthony G.M. Barrett A d-Glucose derived tetrahydropyran was converted into the C1 to C13 tetrahydropyranyl-resorcylate core of paecilomycin B in seven steps. Key transformations included the synthesis of a diketo-ester dioxinone, which upon thermolysis underwent a retro-hetero-Diels-Alder fragmentation to generate an acyl ketene. This was subsequently trapped by a secondary alcohol affording a triketo-ester, which was efficiently aromatized to produce the advanced resorcylate intermediate.Graphical abstractImage 1
       
  • 1,3-Dipolar cycloadditions with azomethine ylide species generated from
           aminocyclopropanes
    • Abstract: Publication date: Available online 31 May 2018Source: TetrahedronAuthor(s): Andrzej Wolan, Justyna A. Kowalska-Six, Holisoa Rajerison, Michèle Césario, Marie Cordier, Yvan Six Two types of bicyclic N-cyclopropyl glycine ester derivatives have been prepared and put under scrutiny as possible precursors of azomethine ylides. The results demonstrate that they can indeed participate in 1,3-dipolar cycloaddition reactions with dipolarophiles, as illustrated in the cases of phenyl vinyl sulfone, N-phenylmaleimide, diethyl fumarate and diethyl maleate. The relative configurations of the major diastereoisomers produced are consistent with the predicted generation of azomethine ylide species, reacting in concerted cycloaddition processes. This unprecedented way of generating such 1,3-dipoles provides access to functionalised pyrrolizidine and pyrrolidine derivatives, that would be difficult to make directly by more classic methods. It was also found that using phenyl vinyl sulfone or N-phenylmaleimide as the dipolarophile reactant, a domino nucleophilic conjugate addition/1,3-dipolar cycloaddition process may operate competitively.Graphical abstractImage 1
       
  • Aminolithiation–arylation consecutive cyclization of
           N-(2-fluorophenyl)methylaminoalkylstyryls giving aryl-substituted
           pyrido[1,2-b]isoquinolines
    • Abstract: Publication date: Available online 30 May 2018Source: TetrahedronAuthor(s): Yasutomo Yamamoto, Yasue Nakanishi, Ken-ichi Yamada, Kiyoshi Tomioka Aminolithiation–arylation tandem cyclization of N-(2-fluorophenyl)methylaminoalkylstyryls proceeded smoothly to give hexahydro-2H-pyrido[1,2-b]isoquinoline using a stoichiometric amount of n-BuLi with high trans selectivity. The arylation reaction was highly accelerated by the addition of HMPA. Both pyrido- and pyrrolo-[1,2-b]isoquinoline were successfully constructed by this tandem reaction.Graphical abstractImage 1
       
  • One-pot solvent-free synthesis of triaryl- and triheteroarylmethanes by
           Bi(OTf)3-catalyzed Friedel-Crafts reaction of arenes/heteroarenes with
           trialkyl orthoformates
    • Abstract: Publication date: Available online 29 May 2018Source: TetrahedronAuthor(s): Surisa Tuengpanya, Chayamon Chantana, Uthaiwan Sirion, Wipada Siritanyong, Klaokwan Srisook, Jaray Jaratjaroonphong A convenient, practical and highly efficient one-pot method has been developed for the synthesis of triaryl- and triheteroarylmethane derivatives by Bi(OTf)3-catalyzed Friedel-Crafts alkylation of trialkyl orthoformates in combination with a wide variety of arenes/heteroarenes at room temperature under solvent-free conditions and in an air atmosphere. The methodology offers an operational simplicity, high atom economy and environmentally benign procedure. Furthermore, selected compound 3k showed promising anti-inflammatory activity with inhibition nitric oxide and did not exhibit significant cytotoxic effects on macrophage cells.Graphical abstractImage 1
       
  • An efficient one-pot synthesis of N,N′-disubstituted phenylureas and
           N-aryl carbamates using hydroxylamine-O-sulfonic acid
    • Abstract: Publication date: Available online 29 May 2018Source: TetrahedronAuthor(s): Jennifer Bao, Dale Kuik, Geoffrey K. Tranmer We have developed an efficient one-pot method for the microwave-assisted synthesis of ureas and carbamates via a proposed Lossen rearrangement. Herein we report the first examples of the direct conversion of benzoyl chlorides into N,N′-disubstituted ureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid as reagent. Using our general method, we have produced 11 examples of N,N′-disubstituted phenylureas in yields up to 95% using various substituted anilines, and primary and secondary amines. Additionally, we were able to generate a series of N-aryl carbamates in moderate yields using primary, secondary and tertiary alcohols.Graphical abstractImage 1
       
  • Practical synthesis of four different pseudoenantiomeric organocatalysts
           with both cis- and trans-substituted 1,2-cis-cyclohexanediamine structures
           from a common intermediate
    • Abstract: Publication date: Available online 26 May 2018Source: TetrahedronAuthor(s): Hyo-Jun Lee, Natarajan Arumugam, Abdulrahman I. Almansour, Raju Suresh Kumar, Keiji Maruoka A new and convenient approach has been deviced for the practical synthesis of structurally robust, four different pseudoenantiomeric amino Tf-amido organocatalysts with the unique cis- and trans-substituted 1,2-cis-cyclohexanediamine structures. These pseudoenantiomeric organocatalysts are easily prepared by the Diels-Alder strategy of 2-phenyl-1,3-butadiene and maleic anhydride, and their chemical behavior was investigated by their application to asymmetric aldol synthesis for the practical synthesis of both enantiomeric aldols.Graphical abstractImage 1
       
 
 
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