Tetrahedron Letters

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Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29
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Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29
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Asymmetric phase-transfer reactions under base-free neutral conditions ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Seiji Shirakawa , Keiji Maruoka Although quaternary onium salt-catalyzed phase-transfer reactions are generally believed to require base additives, we discovered even without any base additives conjugate additions of 3-substituted oxindoles proceeded smoothly in the presence of lipophilic quaternary onium bromide under water-organic biphasic conditions. The mechanism of this novel base-free neutral phase-transfer reaction system was investigated, and the assumed catalytic cycle was presented together with interesting effects of water and lipophilicity of the phase-transfer catalyst. The base-free neutral phase-transfer reaction system could be applied to highly enantioselective conjugate additions, aldol reaction, sulfenylation, and chlorination under the influence of chiral bifunctional onium bromides as key catalysts. Graphical abstract image
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A one-pot four-component synthesis of N-arylidene-2-aryl-imidazo[1,2-a]azin-3-amines ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Abbas Rahmati , Ali Moazzam , Zahra Khalesi N-Arylidene-2-aryl-imidazo[1,2-a]azin-3-amines were synthesized via a one-pot, four-component condensation reaction using a 2-aminoazine, toluene-4-sulfonylmethyl isocyanide (TsCH2NC), and two equivalents of readily available aromatic aldehydes. The reaction was performed in diethyl ether as the solvent, with p-toluenesulfonic acid (p-TSA) as the catalyst at reflux temperature. Graphical abstract image
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A solvent-free reaction between acetophenone oximes and epoxy styrenes: an efficient synthesis of 2,4,6-triarylpyridines under neutral conditions ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Shabnam Mahernia , Mehdi Adib , Mohammad Mahdavi , Meisam Nosrati An efficient synthesis of 2,4,6-triarylpyridines is described which involves heating a mixture of an acetophenone oxime and an epoxy styrene under neutral, solvent-free conditions. Kröhnke pyridine products are obtained in excellent yields. Graphical abstract image
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Base-mediated reaction of vinyl bromides with aryl azides: one-pot synthesis of 1,5-disubstituted 1,2,3-triazoles ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Luyong Wu , Yuxue Chen , Jianheng Luo , Qi Sun , Mingsheng Peng , Qiang Lin A one-pot base-mediated reaction of azides and β- or α-vinyl bromides has been reported. The effects of bases and solvents have been investigated in the process. A variety of 1,5-disubstituted triazoles were prepared in low to good yields. Further studies reveal that the corresponding alkynes were produced as intermediates via elimination reaction. Under the same reaction conditions, the reactions of alkyl alkynes with phenyl azide would give 1,5-disubstituted 1,2,3-triazoles. Graphical abstract image
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Expedient synthesis of biologically important sulfonylmethyl pyrimidines ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Kevin Blades , Julie Demeritt , Shaun Fillery , Kevin M. Foote , Ryan Greenwood , Clare Gregson , Lorraine A. Hassall , Thomas M. McGuire , Kurt G. Pike , Emma Williams Two novel synthetic strategies that allow rapid diversification of the sulfone moiety in sulfonylmethyl pyrimidines, a class of compounds with a wide range of biological activity, which are of interest in a wide variety of drug discovery programmes, are described. Graphical abstract image
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Copper-catalyzed direct N-arylation of N-arylsulfonamides using diaryliodonium salts in water ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Xu Geng , Song Mao , Liangshun Chen , Jianjun Yu , Jianwei Han , Jianli Hua , Limin Wang An efficient copper-catalyzed N-arylation of N-arylsulfonamides with diaryliodonium salts is reported. The reaction employs diaryliodonium salts and N-arylsulfonamides in water at room temperature, giving the products in moderate to excellent yields. Graphical abstract image
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Stereoselective synthesis of tetrahydropyran–tetrahydrofuran (THP–THF) core of (+)-muconin via Prins cyclization ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): J.S. Yadav , U.V. Subba Reddy , B.V. Subba Reddy A stereoselective synthesis of tetrahydropyran–tetrahydrofuran (THP–THF) core 2 of (+)-muconin (1) has been achieved using Prins cyclization as a key step to construct tetrahydropyran moiety. Other important transformations such as Wittig olefination, Sharpless epoxidation, regio-, and stereoselective exo-cyclization of the epoxy alcohol, titanocene induced regioselective deoxygenation of 2,3-epoxy alcohol, Grignard reaction, and Barton–McCombie reaction are successfully employed to accomplish the synthesis of THP–THF core 2. Graphical abstract image
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Penioxalamine A, a novel prenylated spiro-oxindole alkaloid from Penicillium oxalicum TW01-1 ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Xiao-Lan Hu , Xi-Qing Bian , Xin Wu , Jian-Yong Li , Hui-Ming Hua , Yue-Hu Pei , Ai-Hong Han , Jiao Bai Penioxalamine A (1), a novel prenylated spiro-oxindole alkaloid having a unique seven-membered nitrogen heterocycle system, was isolated from the fungus Penicillium oxalicum TW01-1. The structure of 1 was elucidated on the basis of the spectral data, single-crystal X-ray diffraction, and CD analysis. Compound 1 showed moderate cytotoxicity against HL-60 cell line. The possible biosynthetic pathway of 1 was also proposed. Graphical abstract image
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The asymmetric addition of malononitrile to α,β-unsaturated ketones catalyzed by RuCl2[(R,R)-DPEN](PPh3)2 as the precatalyst ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Xuefeng Li , Yaping Ma , Zhikui Xing , Ning Tang , Jin Zhu , Jingen Deng Non-borohydride ruthenium complex, RuCl2[(R,R)-DPEN](PPh3)2 (1f), was demonstrated to catalyze asymmetric Michael addition of malononitrile to acyclic enones with weak bases. Michael addition of malononitrile to chalcone and analogues was promoted by combining CsOAc with CsOH in the presence of 1f and gave good yields and up to 82% ee. Graphical abstract image
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Zirconium(IV)-catalyzed one-pot synthesis and oxidation of bis- and tris(indolyl)methanes into conjugated chromophores as new pH indicators or calorimetric chemosensors for transition metals ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Alireza Khorshidi , Neda Mardazad , Zahra Shaabanzadeh Zirconium(IV) oxynitrate hydrate catalyzed efficiently the condensation reactions of indoles and aldehydes in acetonitrile, under ambient conditions. The bis- or tris(indolyl)methane products were then dehydrogenated in one pot by using a stoichiometric amount of DDQ, to give conjugated chromophores that showed feasible applications as new pH indicators with excellent sensitivity in the pH range 8–10. Hypsochromic effects were observed in the presence of transition metal cations in acetonitrile with a significant color change for cobalt(II). Graphical abstract image
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DBU and copper(I) mediated carboxylation of terminal alkynes using supercritical CO2 as a reactant and solvent ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Fa-Wang Li , Quan-Ling Suo , Hai-Long Hong , Ning Zhu , Ya-Qi Wang , Li-Min Han An organic solvent free, DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene)-mediated and copper(I)-catalyzed CH activating carboxylation of terminal alkynes in supercritical CO2 (ScCO2) was developed in this work. Terminal alkynes react with ScCO2 in the presence of CuI/DBU and produce the corresponding functionalized propiolic acids in excellent yields. Under the optimized conditions, carbon dioxide can act as both reactant and solvent for the reaction. DBU serves as a ligand of copper catalyst, nucleophile, and base during the reaction. DBU alone can also mediate the direct CH carboxylation in the absence of transit metal catalyst. But the reaction requires a higher reaction temperature and pressure to obtain desired yields. Graphical abstract image
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Synthesis of highly substituted indene derivatives by Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Xiaoxiang Zhang , Wan Teng Teo , Weidong Rao , Dik-Lung Ma , Chung-Hang Leung , Philip Wai Hong Chan An efficient synthetic method to prepare highly substituted indenes in moderate to excellent yields that relies on Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols under mild conditions is described. Graphical abstract image
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Total synthesis of agomelatine via Friedel–Crafts acylation followed by Willgerodt–Kindler reaction ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Satish Kumar Vujjini , V.R. Krishnam Raju Datla , Krishna Rao Badarla , V.N.K.V. Prasada Raju Vetukuri , Rakeshwar Bandichhor , Mukkanti Kagga , Praveen Cherukupally Total synthesis of antidepressant drug, agomelatine is reported. Regio selective Friedel–Crafts acylation followed by Willgerodt–Kindler reactions is used as the key steps for the synthesis of agomelatine. Graphical abstract image
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Concise synthesis of aromatic tertiary amines via a double Petasis–borono Mannich reaction of aromatic amines, formaldehyde, and organoboronic acids ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Jiayi Wang , Pinzhen Li , Qiaoying Shen , Gonghua Song A simple and efficient strategy to construct aromatic tertiary amines via a double Petasis–borono Mannich reaction of aromatic amines, formaldehyde, and organoboronic acids has been developed. The transformation provides a useful method for the synthesis of amine derivatives. Graphical abstract image
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Microwave-assisted α-halogenation of 2-methylquinolines with tetrabutylammonium iodide and 1,2-dichloroethane (1,2-dibromoethane) ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Yuanyuan Xie , Lehuan Li A simple and efficient methodology permitting the halogenation of 2-methylquinolines into 2-(chloromethyl)quinolines or 2-(bromomethyl)quinolines in the tetrabutylammonium iodide and 1,2-dichloroethane (1,2-dibromoethane) system has been developed for the first time. The halogenation can be rapidly completed with good to excellent yields and high selectivity under microwave irradiation. Graphical abstract image
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A facile one-pot synthesis of 7-substituted pyrazolo[1,5-a]pyrimidines by base induced three-component reaction ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Pallabi Saikia , Partha Pratim Kaishap , Rashmi Prakash , Kommuri Shekarrao , Sanjib Gogoi , Romesh C. Boruah The preparation of steroid/nonsteroid fused 7-substituted pyrazolo[1,5-a]pyrimidines is described by a one-pot reaction of steroidal/nonsteroidal ketones, aromatic aldehydes and 3-amino-1H-pyrazoles/5-amino-1H-pyrazoles in the presence of potassium tert-butoxide in good yield under reflux condition in ethanol. Graphical abstract image
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Alternative synthetic route to annulated diaminopyrimidines ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Alexandre Erdmann , Ludovic Halby , Frédéric Cantagrel , François Sautel , Georges Massiot , Paola B. Arimondo We report an alternative synthetic approach to annulated diaminopyrimidines based on a one-pot process, in which a Thorpe–Ziegler cyclization of a dinitrile is followed by in situ reaction with a cyanamide under highly concentrated and basic conditions. The total reaction can be carried out as fast as 30min. The reaction mechanism is discussed. This one-pot synthetic route is universally applicable to a large variety of cyanamides and dinitriles, even natural products, to afford complex annulated diaminopyrimidines. Graphical abstract image
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Selective oxidation of sulfides to sulfoxides with cyanuric chloride and urea–hydrogen peroxide adduct ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Heung Bae Jeon , Kyoung Tae Kim , Sang Hyun Kim Although a number of methods have been developed for the selective oxidation of sulfides to sulfoxides, the need remains for alternative efficient, reliable strategies that can be generally applied to various sulfides and that use readily available reagents under mild reaction conditions. Herein, we report the use of urea–hydrogen peroxide adduct (UHP) and cyanuric chloride in CH3CN at room temperature to convert sulfides to sulfoxides in excellent yields. In particular, this protocol produced sulfoxides with aromatic rings bearing electron-withdrawing groups in excellent yields. Graphical abstract image
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Silica-supported ceric ammonium nitrate catalyzed chemoselective formylation of indoles ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Sukanya Tongkhan , Widchaya Radchatawedchakoon , Senee Kruanetr , Uthai Sakee Selective formylation of free (N–H) indoles at C3 can be achieved by using formylating species generated from hexamethylenetetramine (HMTA) and silica-supported ceric ammonium nitrate (CAN–SiO2). The use of a catalytic amount of this solid-supported reagent was found to be compatible with a range of substituents on the indoles and generated the corresponding products with good yields. A plausible mechanism for the formylation involving an electron transfer process is discussed. Graphical abstract image
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Targeted synthesis of 2,3-disubstituted 2-phospholenes using catalytic cycloalumination of acetylenes ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Vladimir A. D’yakonov , Alevtina L. Makhamatkhanova , Rina A. Agliullina , Tat’yana V. Tyumkina , Usein M. Dzhemilev A preparative one-pot method for the synthesis of 2,3-dialkyl-substituted phosphol-2-enes by catalytic cycloalumination of symmetric acetylenes with AlEt3 catalyzed by Cp2ZrCl2 is developed. The reaction gives the corresponding aluminacyclopentenes, which then react in situ with phosphorus dihalides. Graphical abstract image
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An unusual synthesis and crystal interaction studies of a highly functionalised thiophene system ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Samuel K. Kutty , Mohan M. Bhadbhade , George Iskander , David StC. Black , Naresh Kumar Several novel functionalised thiophenes have been synthesised via an unusual acid catalysed reaction of S-acetyl fimbrolides. The crystal structure analysis of one of the thiophene products reveals interesting intermolecular hydrogen bonding and carbonyl–carbonyl (CO⋯CO) dipolar interactions. Graphical abstract image
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Lipase catalyzed Cannizzaro-type reaction with substituted benzaldehydes in water ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Benu Arora , Pramod S. Pandey , Munishwar N. Gupta Lipases were found to catalyze Cannizzaro-type reaction of substituted benzaldehydes in aqueous medium at 30°C without the addition of any external redox reagent. The ratio of alcohol product to acid product varied with nature of the substituted benzaldehyde, enzyme, and the presence of organic co-solvent. Graphical abstract image
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Highly selective and efficient oxidation of sulfides with hydrogen peroxide catalyzed by a chromium substituted Keggin type polyoxometalate ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Roozbeh Afrasiabi , Mostafa Riahi Farsani , Bahram Yadollahi The catalytic oxidation of sulfides into the corresponding sulfones by a chromium substituted Keggin type polyoxometalate, (TBA)4[PW11CrO39]·3H2O, was achieved using mild reaction conditions. Excellent yields were obtained using four equivalents of 30% H2O2. Under these reaction conditions, the sulfide group was highly reactive and other functional groups such as hydroxyl or a double bond were unaffected. Using a commercially available, eco-friendly, and cheap oxidant, mild reaction conditions, operational simplicity, practicality, short reaction times, high to excellent yields, and excellent chemoselectivity are some of the advantages of this catalytic system. Graphical abstract image
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A simple and facile method for regio- and stereoselective bromoformyloxylation and bromoacetoxylation of olefins using NH4Br and oxone® ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Mameda Naresh , Peraka Swamy , Macharla Arun Kumar , Marri Mahender Reddy , Kodumuri Srujana , Nama Narender A mild and efficient protocol for the preparation of bromoformates as well as bromoacetates from olefins using NH4Br and oxone® in nucleophile sources (DMF or DMA) without employing catalyst at room temperature is described. This method is facile, environmentally friendly and cost effective. A variety of terminal, internal and cyclic alkenes reacted smoothly to give the corresponding bromoformate and acetate products in good to excellent yields. Moreover, 1,2-disubstituted olefins provided moderate to excellent diastereoselectivity. Graphical abstract image
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Garratt–Braverman cyclization on basic alumina: a green protocol with improved selectivity ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Debaki Ghosh , Subhanip Biswas , Koena Ghosh , Amit Basak A green protocol (compared to the existing methodology) for carrying out Garratt–Braverman cyclization has been developed. The method involves stirring a pre-absorbed bispropargyl sulfone/ether/sulfonamide over basic alumina. The reaction with sulfones was over within 10–15min at room temperature whereas for the ether/sulfonamide the reaction took 6–8h at 130°C. The products, aryl naphthalene derivatives, are obtained by simple filtration through Celite, in excellent yields. Graphical abstract image
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A novel and convenient route for the construction of 5-((1H-1,2,4-triazol-1-yl)methyl)-1H-indoles and its application in the synthesis of Rizatriptan ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Yi He , Xiaolong Li , Jue Li , Xiaocen Li , Li Guo , Li Hai , Yong Wu In this study, a novel and convenient route for the construction of 5-((1H-1,2,4-triazol-1-yl)methyl)-1H-indoles (8) is presented starting from (1H-1,2,4-triazol-1-yl)methanol (5) and indolines (6) under 98% H2SO4 at room temperature for 4–24h, followed by deacetylation and dehydrogenation. Based on this finding, a novel route to synthesize Rizatriptan starting from tryptamine was designed and accomplished with 48.5% overall yield in 6steps. Compared with operational art, the new route afforded higher yield and more pure products requiring no chromatographic purification, which may further be applied in industrialization. Graphical abstract image
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Solid-phase synthesis of polyfunctional polylysine dendrons using aldehyde linkers ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Daniel K. Svenssen , Sahar Mirsharghi , Ulrik Boas A straightforward method for the solid-phase synthesis of C-terminally modified polylysine dendrons has been developed by applying bisalkoxybenzaldehyde and trisalkoxybenzaldehyde linkers. The method has been used for the synthesis of polylysine dendrons with a variety of C-terminal ‘tail groups’ such as alkyl, propargyl, and dansyl to give dendrons in high crude purity. Furthermore, the method was successful for the synthesis of dendrons with multiple N-terminal pentapeptide groups together with C-terminal alkyl and propargyl tail groups. Finally, the method was shown to be well-suited for automated synthesis. Graphical abstract image
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FRET based selective and ratiometric ‘naked-eye’ detection of CN− in aqueous solution on fluorescein–Zn–naphthalene ensemble platform ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Shyamaprosad Goswami , Sima Paul , Abhishek Manna We have developed a FRET-based ratiometric fluorescent probe for the detection of CN− using a fluorescein–Zn–naphthalene ensemble (NFH·Zn2+). The sensing mechanism was ascribed by displacement approach. The chemosensor exhibits high selectivity and sensibility for CN−. The speculation was supported by fluorescence emission spectra, UV–vis spectrum, 1H NMR titration experiments, and mass spectra. The interconversion of probe NFH and NFH·Zn2+ via the complexation/decomplexation by the modulation of Zn2+/CN− mimics INHIBIT gate. In addition, it also shows an excellent performance in ‘dip stick’ method. Graphical abstract image
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Improved synthesis of pyridyl–biaryl ring systems via benzidine rearrangements ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Gulice Y.C. Leung , Anthony D. William , Charles W. Johannes The acid-catalyzed benzidine rearrangement of diazo compounds is known to involve several rearrangements with the major pathway being a [5,5] sigmatropic rearrangement to provide 4,4′-diaminobiaryls. A limitation of this rearrangement has been poor conversions with pyridyl systems. Herein, we address this long standing issue to furnish hetero-biaryls via a pyridinium salt in the presence of trimethylsilyl iodide. Graphical abstract image
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The sila-Pummerer reaction of γ-silyl substituted cycloalkanoyl sulfoxides: the first examples and a new approach to 3-substituted cycloalk-2-enones ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Maciej Mikina , Marian Mikołajczyk The thermal decomposition of 3-(α-trimethylsilyl)alkyl substituted 2-(phenylsulfinyl)cycloalkanones occurs via the γ-sila-Pummerer reaction, affording 3-substituted cycloalk-2-enones and unstable trimethylsilyl benzenesulfenate as an elimination by-product. The starting γ-silyl substituted cycloalkanoyl sulfoxides were obtained through the conjugate addition reaction of nucleophilic reagents to 2-(phenylsulfinyl)cycloalk-2-enones. The tandem conjugate addition/γ-sila-Pummerer reaction investigated here provides a new route to 3-substituted cycloalk-2-enones. Graphical abstract image
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Cu-promoted single-pot intramolecular esterification of C-3 functionalized azetidin-2-one: an efficient diastereoselective access to azido-/amino-aza-lactones ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Kewal Kumar , Sumit Kumar , Tejinder Singh , Amit Anand , Vipan Kumar A facile, single pot diastereoselective access to seven and eight membered aza-heterocycles was developed by using β-lactam-synthon approach. The developed protocol does not involve the typical intricacies viz. the use of expensive transition metal catalysts and high boiling solvents, associated with the convenient protocols. Graphical abstract image
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Facile synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones using monobromomalononitrile (MBM) as an efficient organo-brominating agent ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Ashis Kundu , Sudipta Pathak , Kamalesh Debnath , Animesh Pramanik An efficient methodology for the synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones has been developed where monobromomalononitrile (MBM) has been employed as a non-hazardous brominating agent under ambient reaction condition. The intrinsic advantages of the methodology are the utilization of simple and easily available starting materials and non-toxic reagents, operational simplicity, and good yields of the products with high atom-economy. Graphical abstract image
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Synthesis and characterization of new benzimidazole derivatives using 2-substituted 1,3-bis(dimethylamino)-trimethinium salts ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): A.M. Mehranpour , M. Zahiri Novel benzimidazole derivatives are synthesized by the reaction of 2-substituted 1,3-bis(dimethylamino)-trimethinium salts with 2-aminobenzimidazole in the presence of acetic acid or triethylamine in acetonitrile as the solvent. The ultraviolet spectral behavior of these compounds is examined in DMSO. Graphical abstract image
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Phenyliodonium diacetate mediated arylation of benzothiazoles with substituted styrenes ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Ahmed Kamal , N.V. Subba Reddy , B. Prasad A metal-free synthesis of 2-arylbenzothiazoles was achieved using phenyliodonium diacetate (PIDA) from benzothiazoles and styrenes or β-nitrostyrenes. This transformation tolerates various functional groups such as methoxy, hydroxy, fluoro, chloro, and nitro groups. Graphical abstract image
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Synthesis of self-doped conducting polyaniline bearing phosphonic acid ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Toru Amaya , Yasushi Abe , Yuhi Inada , Toshikazu Hirao As a self-doped conducting polyaniline bearing phosphonic acid, poly(2-methoxyaniline-5-phosphonic acid) (PMAP) was synthesized via oxidative polymerization of 2-methoxyaniline-5-phosphonic acid. The pyridinium salt of thus-obtained PMAP was water-soluble and its film exhibited conductivity. Graphical abstract image
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Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Geeta Devi Yadav , Surendra Singh Fe(Cp)2BF4 is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)2BF4 as a catalyst (5mol%) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol. Graphical abstract image
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Cytotoxic cembranoids from the Red Sea soft coral, Sarcophyton auritum ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Nermeen A. Eltahawy , Amany K. Ibrahim , Mohamed M. Radwan , Mahmoud A. ElSohly , Hashim A. Hassanean , Safwat A. Ahmed Chemical investigation of the Red Sea soft coral Sarcophyton auritum led to the isolation and structure elucidation of two new diterpene cembranoids; 2-epi-sarcophine (2) and (1R,2E,4S,6E,8R,11R,12R)-2,6-cembradiene-4,8,11,12-tetrol (4), as well as two known diterpene cembranoids, reported for the first time from this species, namely sarcophine (1) and (+)-7α,8β-dihydroxydeepoxysarcophine (3). Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The isolated cembranoids were found to display high cytotoxicity against HepG2 (liver cancer cell line) and MCF-7 (breast cancer cell line). Graphical abstract image
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A potent antimalarial trichothecene from hyphomycete species ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Carrie Waterman , Laurent Calcul , Tina Mutka , Dennis E. Kyle , Cedric J. Pearce , Bill J. Baker Antimalarial screening of diverse fungal samples resulted in the isolation and identification of a new sesquiterpene, trichothecinol D (1), which exhibited potent in vitro activity against Plasmodium falciparum with a 200-fold selectivity for parasite versus mammalian cytotoxicity. Trichothecinol D was obtained by bioassay-guided fractionation of two hyphomycete species. Its chemical characterization was performed by detailed NMR spectroscopy and high resolution mass spectrometry. The absolute configuration of trichothecinol D was determined by X-ray crystallography. Graphical abstract image
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A facile synthesis of isoindoline and Δ1-pyrrolines from chalcone and glycine by a cascade of process involving addition, in situ decarboxylation, and cyclization ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Elangovan Elamparuthi , Subramaniayan Sarathkumar , Swaminathan Girija , Veerappan Anbazhagan In this Letter, we report a rapid one-step entry into isoindoline and Δ1-pyrrolines from chalcone. The key step in the synthesis is the addition of glycine to chalcone. In acidic medium the reaction presumably goes through aza-Michael addition, whereas in basic medium the reaction proceeds through condensation followed by cyclization. Graphical abstract image
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Application of oxetane ring opening toward stereoselective synthesis of zincophorin fragment ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Jhillu Singh Yadav , Eppa Gyanchander , Saibal Das A stereoselective synthesis of the C1–C11 fragment of zincophorin was achieved by using an intramolecular oxetane ring opening reaction as the key step. The oxetane moiety was synthesized by employing a desymmetrization protocol developed at our group and a non-Evans syn aldol as the key steps toward the synthesis. Graphical abstract image
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A convenient strategy for synthesizing the Agelas alkaloids clathrodin, oroidin, and hymenidin and their (un)saturated linker analogs ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Aleš Žula , Danijel Kikelj , Janez Ilaš A convenient strategy for the scalable synthesis of the 2-aminoimidazole alkaloids, clathrodin, oroidin, and hymenidin derived from marine Agelas species and their analogs possessing a saturated or unsaturated linker moiety is described. The key intermediates, 4-(3-aminopropyl)-1H-imidazol-2-amine and (E)-4-(3-aminoprop-1-en-1-yl)-1H-imidazol-2-amine were obtained through two different synthetic pathways starting from l-ornithine and benzyl 1,2-dihydropyridine-1-carboxylate respectively, using (i) an innovative combination of Weinreb amide strategy with di-Boc protection, and (ii) a modified pyridine-1(2H)-carboxylate based strategy. Convenient access to these 2-aminoimidazole amines is crucial for the synthesis of libraries of clathrodin, oroidin, and hymenidin analogs. Graphical abstract image
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Synthesis of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes via cross-coupling reactions and sequential Lewis acid-catalyzed regioselective cycloaromatization of epoxide ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Keita Hyodo , Hikaru Nonobe , Shuhei Nishinaga , Yasushi Nishihara Phenanthro[1,2-b:8,7-b′]dithiophene (PDT) was prepared via Suzuki–Miyaura or Negishi cross-coupling of a 2-thienylboron or -zinc compound with 1,4-dibromobenzene, followed by Lewis acid-catalyzed regioselective cycloaromatization of the epoxide. A series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene (PDT) derivatives could also be synthesized in good yields by Suzuki–Miyaura coupling of the brominated PDT with alkylboranes by introducing linear alkyl substituents. Graphical abstract image
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An efficient method for the multicomponent synthesis of multisubstituted pyridines, a rapid procedure using Au/MgO as the catalyst ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Ramakanth Pagadala , Suresh Maddila , Vashen Moodley , Werner E. van Zyl , Sreekantha B. Jonnalagadda Au/MgO proved to be a highly efficient and reusable catalyst for multicomponent coupling reactions at 70°C. The synthesized multisubstituted pyridines were obtained in high yields and in short reaction times. With facile work-up, the novel catalyst can be readily recovered after the reaction and reused without any loss of its catalytic activity. Graphical abstract image
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Synthesis of new 10,11-dihydrodibenzo[a,d]cycloheptene S-thiocarbamate derivatives via a benzylic Newman–Kwart rearrangement ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Miron Teodor Căproiu , Florea Dumitrascu , Sergiu Shova , Ileana Cornelia Chirită , Alexandru Vasile Missir , Dana-Mihaela Cioroianu New S-thiocarbamates possessing a 10,11-dihydro-5H-dibenzo[a,d]cycloheptene moiety were obtained unexpectedly in the process of preparing new O-thiocarbamates starting from 5-dibenzosuberol (10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ol) and aroyl-isothiocyanates. These compounds were obtained via a benzylic Newman–Kwart rearrangement mechanism. The structures of the new thiocarbamates were confirmed by elemental analysis, IR, and NMR spectroscopy and by X-ray crystallography. Graphical abstract image
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Synthesis of a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[b]furo[3,2-d]pyridine derivative, the 5-aza analog of ramelteon ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Yasutaka Hoashi , Takafumi Takai , Tatsuki Koike , Osamu Uchikawa The 5-aza analog of ramelteon 3, a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[b]furo[3,2-d]pyridine derivative, was synthesized by hetero-Diels–Alder reaction and chemoselective Dieckmann condensation. Graphical abstract image
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Corrigendum to “Synthetic exploitation of halogenated alkenes containing an electron-withdrawing group: synthesis of α-chlorohydrazones and ketene aminals by regiospecific reactions of in situ generated imide chlorides” [Tetrahedron Lett. 55 (2014) 2085–2089] ()
Publication date: 16 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 29 Author(s): Amac Fatih Tuyun
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Editorial board ()
Publication date: 9 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 28
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Graphical Contents List ()
Publication date: 9 July 2014 Source:Tetrahedron Letters, Volume 55, Issue 28
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