Tetrahedron Letters

Editorial board ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41
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Graphical Contents List ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41
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N-alkylation of lactams with secondary heterobenzylic bromides ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Ming Yu , Karis Stevenson , Gene Zhou We herein report a general N-alkylation reaction of lactams with secondary heterobenzylic bromides. This methodology features mild reaction condition, moderate to high product isolation yield, and broad substrate scope. Good chemical and structural tolerance has also been demonstrated by both the secondary heterobenzylic bromides and lactam substrates. Graphical abstract image
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Synthesis of N-alkyl-N′-aryl-piperazines via copper-catalyzed C–N bond formation ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Issa Yavari , Mohammad J. Bayat , Majid Ghazanfarpour-Darjani An efficient copper-catalyzed tandem synthesis of N-alkyl-N′-aryl-piperazines from 1,4-diaza-bicyclo[2.2.2]octane, alkyl halides, and aryl halides in the presence of copper(I) iodide and potassium tert-butoxide in DMSO is described. Graphical abstract image
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An efficient solvent-tuning approach for the rapid synthesis of thiazolidinone derivatives and the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Garima Choudhary , Rama Krishna Peddinti Green synthetic approach has been developed for the rapid generation of thiazolidinone derivatives as crystallized products under catalyst-free conditions in water by polarity adjustment with ethyl lactate as a co-solvent in excellent yields. Additionally, interesting findings on the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates have been reported. Graphical abstract image
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Chromeno[2,3-c]pyrroles by one-pot multicomponent domino addition–amination reaction ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Michael A. Terzidis , Vassilios G. Tsiaras , Nicolaos M. Drosos , Paraskevi M. Kasapidou , Julia Stephanidou-Stephanatou , Constantinos A. Tsoleridis , Gernot Buth , George E. Kostakis A new aspect concerning chromone chemistry leading to the one-pot synthesis of chromeno[2,3-c]pyrroles is described. The synthesis involves a multicomponent reaction of 3-formylchromones with isocyanides and azodicarboxylates, whereupon novel chromeno[2,3-c]pyrrole derivatives were formed in good yields. The structures of the products were elucidated by 1D and 2D NMR experiments and were unambiguously confirmed by the use of crystal X-ray diffraction analysis. Full assignment of all 1H and 13C NMR chemical shifts has been achieved. A plausible mechanistic scheme is proposed. Graphical abstract image
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Phosphorus deprotonation by a non-nucleophilic base is critical for the synthesis of nucleoside α-P-boranodiphosphates via a phosphoramidite approach ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Zhihong Xu , Barbara Ramsay Shaw Here we report the synthesis of nucleoside α-P-boranodiphosphate analogs via our improved phosphoramidite approach, where the addition of a non-nucleophilic base, TEA, to deprotonate phosphorus is considered to be critical to improve final product yields. Protonation on trivalent phosphorus might not only have blocked Lewis acid borane modification, but also have promoted byproduct formation through a trans-nucleophile process. Here, based on 31P NMR data, mechanisms are proposed for P(V)P(III) bond cleavage via phosphorus protonation-promoted nucleophile-exchange, and TEA deprotonation of phosphorus in promoting product formation in anhydrous synthetic reaction mixtures. Graphical abstract image
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A facile route for the synthesis of novel S-linked 1,3,5-triazine tethered peptidomimetics ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Muniyappa Krishnamurthy , Basavaprabhu , K.M. Sharanabai , Vommina V. Sureshbabu An efficient one-pot synthesis of Nα-protected S-linked 1,3,5-triazine tethered peptidomimetics is described. The protocol involves a three-component condensation reaction employing Nα-protected amino alkyl isothiouronium salt, formaldehyde and amino acid ester or aryl amine as reactants. Various aryl amines with substitutions and amino acids with simple as well as bifunctional side chains were employed to obtain triazine tethered peptidomimetics in good yield. Graphical abstract image
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Hydrated ferric sulfate catalyzed synthesis of 5,6-unsubstituted 1,4-dihydropyridines using three-component reaction ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Kobirul Islam , Deb K. Das , Abu T. Khan A wide variety of 5,6-unsubstituted 1,4-dihydropyridines derivatives (4a–q) were synthesized through a one-pot three-component reaction from α,β-unsaturated aldehydes, amines, and 1,3-diketones at room temperature using hydrated ferric sulfate as a Lewis acid catalyst. The key features of the present protocol are mild and simple reaction procedure, good to excellent yields, and use of inexpensive, recyclable, and environmentally benign catalyst. Graphical abstract image
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I2-mediated C3-formylation of indoles by tertiary amine and H2O ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Bo Zhang , Bin Liu , Jianbin Chen , Jiehui Wang , Miaochang Liu An I2-promoted 3-formylation of free (N–H) and N-substituted indoles with tetramethylethylenediamine (TMEDA) and H2O as the carbonyl source is achieved, providing 3-formylindole in moderate to excellent yields with good functional group tolerance. This procedure represents an exceedingly attractive alternative to the traditional formylation methods. Graphical abstract image
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A new approach to the synthesis of cross-conjugated cyclopentenone prostaglandins. Synthesis of (±)-15-deoxy-Δ12,14-prostaglandin J2 methyl ester ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): N.S. Vostrikov , I.F. Lobko , M.S. Miftakhov A new approach to 15-deoxy-Δ12,14-prostaglandin J2 and related structures based on the (±)-Corey lactone diol has been developed. The key stage of this approach involves building the structure of a prostaglandin (PG) derivative with leaving groups at positions 9, 13, and 15, followed by elimination of these groups by treatment with an organic base. Graphical abstract image
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PhI(OAc)2 and BF3–OEt2 mediated heterocyclization: metal-free synthesis of pyrimidine-annulated oxazolines ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Biplab Mondal , Somjit Hazra , Kishor Naktode , Tarun K. Panda , B. Roy A simple high yielding and highly efficient synthesis of oxazoline ring fused with uracil moiety is reported. Hypervalent iodine (PIDA) in the presence of BF3–OEt2 generates an effective electrophile to activate uracil C5–C6 double bond leading to heterocyclization. Graphical abstract image
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First stereoselective total synthesis of Neocosmosin A: a facile approach ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Soma Shekar Dachavaram , Kondbarao Balasaheb Kalyankar , Saibal Das First stereoselective concise synthesis of Neocosmosin A, with in vitro binding affinity for human opioid and cannabinoid receptors, has been reported using readily available starting materials such as methylacetoacetate, cyclohexanone, and homoallyl alcohol involved in the key transformations. There are three fragments involved in the synthesis of target molecule, bearing acid functionality, (R)-pent-4-en-2-ol, and Weinreb amide which are synthesized in four, eight, and three steps, respectively. Then the fragments were coupled in four steps to yield the target molecule in an overall yield of 28.6%. Graphical abstract image
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Antimicrobial sesquiterpenes from the Chinese medicinal plant, Chloranthus angustifolius ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Xinzhou Yang , Chao Wang , Jing Yang , Dingrong Wan , Qinxiong Lin , Guangzhong Yang , Zhinan Mei , Yunjiang Feng Two new eudesmane-type sesquiterpenes, 9α-hydroxycurcolonol (1) and 3α-hydroxy-4-deoxy-5-dehydrocurcolonol (2), along with nine known sesquiterpenes (3–11), were isolated from the roots of Chloranthus angustifolius. The antimicrobial activities of compounds 1–11 were evaluated against five bacteria and six fungal strains. Compounds 6–11 showed potent activities against Candida albicans with MIC values ranging from 4 to 8μg/mL. The structures of the two new compounds 1 and 2 were established by a detailed analysis of their NMR and mass spectroscopic data. Graphical abstract image
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7,8,9,10-Tetrahydropyrrolo[2,1-a]isoquinolines in the search for new indolizine derivatives ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Mino R. Caira , Marcel Mirel Popa , Constantin Draghici , Loredana Barbu , Denisa Dumitrescu , Florea Dumitrascu 7,8,9,10-Tetrahydropyrrolo[2,1-a]isoquinolines were obtained by 1,3-dipolar cycloaddition reactions of their corresponding N-ylides with olefinic (acrylonitrile) and symmetrical or non-symmetrical acetylenic dipolarophiles (methyl/ethyl propiolate, dimethyl acetylenedicarboxylate). Also, stable 5,6,7,8-tetrahydroisoquinolinium dicyanomethylide was isolated and characterized by X-ray diffraction analysis. Graphical abstract image
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Synthesis of thieno[3,4-b]pyrrole derivatives based on the reaction of 1-methyl-2-nitromethylenepyrrolidine with isothiocyanates ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Konstantin Shvidenko , Kostiantyn Nazarenko , Tatyana Shvidenko , Yurii Vlasenko , Aleksandr Kostyuk The reaction of 1-methyl-2-nitromethylenepyrrolidine with arylisothiocyanates in the presence of a base was found to proceed at the 3-СН2 group of the nitroenamine followed by further cyclization to afford 4-R-imino-1-methyl-1,2,3,4-tetrahydro-6H-thieno[3,4-b]pyrrol-6-one oximes. Under analogous conditions, alkylisothiocyanates add to 1-methyl-2-nitromethylenepyrrolidine giving 1-methyl-2-nitromethylenepyrrolidine-3-carbothioic acid amides, and no cyclization was observed. A tentative mechanism for the formation of thieno[3,4-b]pyrrolе derivatives is proposed. Graphical abstract image
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Aerobic oxidative α-iodination of carbonyl compounds using molecular iodine activated by a nitrate-based catalytic system ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Rok Prebil , Stojan Stavber The novel reaction system comprising air/NH4NO3(cat.)/I2/H2SO4(cat.) is introduced as a simple, safe, cheap, efficient, and regioselective mediator for direct aerobic oxidative α-iodination of aryl, heteroaryl, alkyl, and cycloalkyl methyl ketones. The reaction system enabled the moderate to quantitative regioselective iodination of a large range of different methyl ketone derivatives including those bearing oxidizable heteroatom (S, N) substituents. Several activated aromatic compounds were also efficiently and selectively iodinated. The practical applicability of the presented reaction system was shown on 20mmol scale under ambient pressure and 100% conversion of substrate was achieved. Graphical abstract image
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Cu(OTf)2-promoted efficient synthetic route towards glycospiro-pyrrolo[2,1-a]isoquinolines ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Piyali Deb Barman , Ishita Sanyal , Sukhendu B. Mandal , Asish Kumar Banerjee A simple, convenient and efficient protocol for the construction of an array of glycospiro-pyrroloisoquinolines using isoquinolinium ylide and a carbohydrate-derived exocyclic olefin in the presence of Cu(OTf)2–Et3N catalytic system is described. Isoquinoline and alkylbromoacetates/2-bromoacetophenones were employed to generate the azomethine ylides in the presence of Et3N in refluxing toluene and subsequent exposure to the olefin led to the desired isoquinoline derivatives. Graphical abstract image
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Direct Michael addition to electron-deficient alkenes using diorganyl dichalcogenides (Te/S) and NaBH4/PEG-400 ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Gelson Perin , Elton L. Borges , Thiago J. Peglow , Eder J. Lenardão Nucleophilic species of tellurium and sulfur were generated in situ from the reaction of the respective diorganyl dichalcogenides with NaBH4 in PEG-400 as solvent and selectively added to electron-deficient alkenes. Chalcogenolate anions were directly added at mild conditions by this simple procedure and in all cases furnished the respective Michael adducts in short reaction times and good yields. Graphical abstract image
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Regioselective synthesis of 3,4,6,7-tetrahydro-3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones through ascorbic acid catalyzed three-component domino reaction ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Ayyakannu Arumugam Napoleon , Fazlur-Rahman Nawaz Khan , Euh Duck Jeong , Eun Hyuk Chung An efficient, three-component domino reaction of dimedone 1, aromatic aldehydes (2a–o), and 1,3-cyclohexanedione 1a in the regio-selective synthesis of 3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones (3a–o) is reported. The desired product, 3 is efficiently promoted by ascorbic acid as an organo catalyst. Graphical abstract image
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Highly efficient organocatalytic asymmetric Michael addition of homoserine lactone derived cyclic imino esters to nitroolefins ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Xin Fang , Xiu-Qin Dong , Chun-Jiang Wang An efficient stereoselective Michael addition reaction of homoserine lactone derived cyclic imino esters to nitroolefins promoted by a bis(cinchona alkaloid) (DHQD)2AQN was achieved. This catalytic system features a wide substrate scope, furnishing the corresponding products with excellent diastereoselectivity (>95:5 dr) and good enantioselectivity (up to 87% ee) under mild conditions, and the Michael adducts could be easily transformed into highly functionalized spirocyclic γ-butyrolactone-pyrrolidines through a sequential nitro-Mannich reaction. Graphical abstract image
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Synthesis and characterization of π-extended thienoacenes with up to 13 fused aromatic rings ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Jing Shao , Xiaoli Zhao , Li Wang , Qingxin Tang , Weili Li , Han Yu , Hongkun Tian , Xiaojie Zhang , Yanhou Geng , Fosong Wang π-Extended thienoacenes that comprise alternatively arranged anthracene and thieno[3,2-b]thiophene moieties and have 8 or 13 aromatic rings were synthesized. The delocalization of their HOMO and LUMO orbitals is over the entire molecules, and low-lying HOMO levels endow them good stability. Graphical abstract image
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A sequential synthesis of substituted furans from aryl alkynes and ketones involving a cerium(IV) ammonium nitrate (CAN)-mediated oxidative cyclization ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Sridhar Undeela , Joshi P. Ramchandra , Rajeev S. Menon A convenient, two-step synthesis of substituted furans from readily available aryl alkynes and ketones is reported. The furan-forming oxidative cyclization is mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide and can be carried out in an open flask. Graphical abstract image
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Copper-catalyzed synthesis of aromatic carboxylic acids from arylboronic acids and acetyl acetate ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Rui Zheng , Qizhong Zhou , Haining Gu , Huajiang Jiang , Jiashou Wu , Zhengneng Jin , Deman Han , Guoliang Dai , Rener Chen A simple and efficient copper-catalyzed method for the synthesis of aromatic carboxylic acids in moderate to high yields with great functional-group compatibility in the substrates has been developed. The new method uses readily available arylboronic acids and acetyl acetate as the starting materials and inexpensive CuI as the catalyst. Graphical abstract image
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Synthesis of 2-pyrolyl-2-hydroxy-2-cyanoacetamide through FeCl3–TBHP mediated hydroxylation of captodative stabilized radical intermediate ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Subhendu Maity , Animesh Pramanik A series of 2-hydroxy-2-(4-oxo-1,2-diaryl-4,5,6,7-tetrahydro-1H-3-indolyl)-2-cyanoacetamides have been synthesized through selective CH oxidation of active methylene carbon of cyanoacetamide derivatives using tert-butyl hydroperoxide as oxidant and ferric chloride as radical initiator. In this reaction the tert-butyl oxo radical abstracts hydrogen from the active methylene group of 2-pyrolyl-2-cyanoacetamides to generate a stable captodative radical intermediate. Then recombination of this radical intermediate with tert-butyl oxo radical followed by acid catalysed thermal elimination of the tert-butyl group produces the quaternary hydroxyl cyanoacetamide derivatives in good yield. Graphical abstract image
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Bromolactonization of alkenoic acids mediated by V2O5 via bromide to bromenium in situ oxidation ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): McKenzie L. Campbell , Samuel A. Rackley , Lauren N. Giambalvo , Daniel C. Whitehead An efficient protocol for the bromolactonization of alkenoic acids is presented that obviates the use of molecular bromine or exogenous bromenium sources. Vanadium (V) oxide catalyzes the in situ oxidation of bromide salts to bromenium (Br+) in a process mediated by urea–hydrogen peroxide complex. Initial mechanistic investigations indicate that the presence of urea does not accelerate the halolactonization reaction. Graphical abstract image
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Synthesis of 5-substituted 1H-tetrazoles catalyzed by ceric ammonium nitrate supported HY-zeolite ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Paramasivam Sivaguru , Kaliyan Bhuvaneswari , Rangasamy Ramkumar , Appaswami Lalitha In this Letter we wish to report a simple and efficient synthetic protocol for the synthesis of 5-substituted 1H-tetrazole derivatives through the [2+3] cycloaddition of nitriles with sodium azide using ceric ammonium nitrate supported HY-zeolite as a novel catalyst. Excellent yields of the corresponding tetrazoles were obtained through this cost-effective protocol under aerobic conditions with shorter reaction time under mild reaction conditions. Graphical abstract image
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Binuclear iron(III) octakis(perfluorophenyl)tetraazaporphyrin μ-oxodimer: a highly efficient catalyst for biomimetic oxygenation reactions ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Mekhman S. Yusubov , Cumali Celik , Margarita R. Geraskina , Akira Yoshimura , Viktor V. Zhdankin , Victor N. Nemykin Binuclear iron(III) octakis(perfluorophenyl)tetraazaporphyrin μ-oxodimer complex was prepared by the reaction of bis(perfluorophenyl)maleonitrile and Fe(CO)5 and tested in catalytic oxygenation reactions of several hydrocarbons in comparison with the analogous non-fluorinated phthalocyanine complexes. Results of the study demonstrate that this complex is a highly efficient catalyst for the oxygenation of anthracene, 2-tert-butylanthracene, naphthalene, 2-methylnaphthalene, phenanthrene, adamantane, and toluene using iodosylbenzene, oligomeric iodosylbenzene sulfate, or Oxone as stoichiometric oxidants. Graphical abstract image
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A new route to the versatile synthesis of thiopyrano[2,3-b:6,5-b′]diindoles via 2-(alkylthio)-indole-3-carbaldehydes ()
Publication date: 8 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 41 Author(s): Mukund Jha , Michael Edmunds , Kate-lyn Lund , Ashley Ryan A versatile synthesis of symmetrically and unsymmetrically substituted thiopyrano[2,3-b:6,5-b′]diindoles has been developed by the condensation of 2-(alkylthio)-indole-3-carbaldehydes with indoline-2-thiones in the presence of catalytic amount of ethylenediamine diacetate (EDDA). The EDDA mediated condensation leads to a spontaneous cyclization followed by aromatization to form thiopyrano[2,3-b:6,5-b′]diindoles in quantitative yields. Graphical abstract image
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Editorial board ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40
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Graphical Contents List ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40
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1-Methylimidazolium tetrafluoroborate [Hmim][BF4]: an efficient acidic ionic liquid catalyst for insertion of α-diazo compounds into the N–H bonds of amines ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Jafar Akbari , Ali Ebrahimi , Akbar Heydari The reusable acidic ionic liquid, 1-methylimidazolium tetrafluoroborate [Hmim][BF4], was found to be an effective catalyst for the insertion of α-diazoacetate into the N–H bonds of amines. The corresponding products were obtained in good yields and short reaction times via a simple procedure. The catalyst could be recycled and reused without any noticeable decrease in its activity. Graphical abstract image
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A concise and stereoselective total synthesis of L-783,290 ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): A. Srinivas Reddy , Ch. Kishore , B.V. Subba Reddy A stereoselective total synthesis of L-783,290 has been achieved involving Alder–Rickert reaction, ring closing metathesis, and chemoselective oxidation as key steps. This approach has successfully demonstrated a linear sequence of reactions, which are highly stereoselective for the construction of the resorcylic acid unit. Graphical abstract image
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N-Chlorophthalimide as a mild and efficient chlorination reagent in the Gassman ortho alkylation of aromatic amines. Synthesis of 3-(methylthio)oxindoles ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Marcin Cybulski , Adam Formela , Izabela Fokt A practical modification of the Gassman 3-(methylthio)oxindole synthesis is reported. In our method, substituted anilines and 2-(methylthio)acetamide were reacted under mild reaction conditions, in the presence of N-chlorophthalimide as a chlorinating agent to give α-amidosulfides, which, in the next step of the process, were cyclized to give 3-(methylthio)oxindoles. The method was successfully applied for the synthesis of the key intermediate, 2-(2-amino-3-benzoylphenyl)-2-(methylthio)acetamide, in the process of the preparation of nepafenac, a commonly used ophthalmic drug. Graphical abstract image
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Modification of guanosine with cyanopropargylic alcohols ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Valentina V. Nosyreva , Anastasiya G. Mal’kina , Alexander I. Albanov , Boris A. Trofimov Guanosine has been modified with tertiary cyanopropargylic alcohols under mild conditions (1:1.1–2molar ratio, K2CO3, DMF, 20–25°C, 19–50h) to simultaneously give two modifications. The first product (1:1 adduct) is formed by the stereoselective addition of the amide function of the purine ring to the triple bond (38–43% yields), and the second product is the 1:2 adduct, with a second molecule of cyanopropargylic alcohol having reacted with the two vicinal hydroxy groups of the ribose moiety to give a functionalized 1,3-dioxolane ring (29–50% yields). Graphical abstract image
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Chemoselective synthesis of quinoxalines and benzimidazoles by silica gel catalysis ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Chunmei Li , Furen Zhang , Zhen Yang , Chenze Qi Treatment of nitroolefins and o-phenylenediamine with silica gel catalyst produced quinoxalines mainly in THF, but gave benzimidazoles efficiently in water. Such a solvent-dependent chemoselective reaction has prominent features of affording two cyclized products selectively with the same substrate, short reaction time, operational simplicity, as well as available starting materials and nontoxic catalysts. In addition, the scope and limitations were explored and a plausible reaction mechanism is proposed. Graphical abstract image
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Efficient construction of highly functionalized endo′-selective spiro[pyrrolidin-2,3′-oxindoles] via a regioselective 1,3-dipolar cycloaddition reaction between 3-amino oxindoles as azomethine ylide precursors and nitroalkenes ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Hongbao Sun , Xiaoyan Wang , Yi chen , Liang Ouyang , Jie Liu , Yiwen Zhang An efficient synthesis of novel endo′-selective spiro[pyrrolidin-2,3′-oxindoles] has been achieved via a three component regioselective 1,3-dipolar cycloaddition reaction. The azomethine ylides generated in situ from 3-amino oxindoles and aldehydes reacted with the nitroalkenes to furnish novel pyrrolidine–spirooxindole derivatives bearing one spiro quaternary center and multiple chiral centers in moderate to high yields (up to 99%) with high diastereoselectivities (up to 99:1). The structure and relative stereochemistry of cycloadducts were confirmed by NMR spectra and single crystal X-ray diffraction. The possible mechanism was proposed and the cycloaddition proceeded via endo′-transition state. Graphical abstract image
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Rhodium catalyzed three-component reaction of aldehyde, boronic acid, and sulfonamides: a facile one-pot synthesis of diarylmethylamines ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Ponnam Satyanarayana , Ganapam Manohar Reddy , Hariharasarma Maheswaran , Mannepalli Lakshmi Kantam Rhodium(I) catalyzed three-component reaction for the one pot synthesis of diarylmethylamines in excellent yields were achieved by using aldehyde, boronic acid, and sulfonamides. The use of hyper-valent bis(trifluoroacetoxy)iodobenzene as an additive plays a key role in the chemo selective formation of amines instead of alcohols. Graphical abstract image
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Synthesis of arylsulfonyl-quinones and arylsulfonyl-1,4-diols as FabH inhibitors: Pd-catalyzed direct C-sulfone formation by CS coupling of quinones with arylsulfonyl chloride ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Bingyang Ge , Dawei Wang , Weifu Dong , Piming Ma , Yongliang Li , Yuqiang Ding The Pd-catalyzed direct C-sulfone formation by CS coupling of quinones with arylsulfonyl chloride has been developed. This methodology provides an effective, convenient method for the synthesis of arylsulfonyl-quinones and arylsulfonyl-1,4-diols, which are potent inhibitors of FabH. Graphical abstract image
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Isolation and structure elucidation of (−)-idescarparide, a new spiro compound from Idesia polycarpa ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Tae Bum Kim , Hyeon Woo Kim , Mina Lee , Hyang Hwa Lee , Seung Hyun Kim , Sung Kwon Kang , Sang Hyun Sung (−)-Idescarparide, a new spiro compound possessing a tetrahydrobenzodioxole structure from the fruit of Idesia polycarpa Maxim. was identified to be a dimer of (−)-idescarpin by spectroscopic analysis. The absolute configuration of (−)-idescarpin was firstly determined to be of S form by using single-crystal X-ray diffraction. The absolute configuration of (−)-idescarparide was confirmed by comparison with semi-synthetic (−)-idescarparide, achieved via triethylamine-catalyzed dimerization of (−)-idescarpin. (−)-Idescarparide significantly reduced lipid production in 3T3-L1 cells. Graphical abstract image
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Using pure shift HSQC to characterize microgram samples of drug metabolites ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Yong Liu , Mitchell D. Green , Rosemary Marques , Tony Pereira , Roy Helmy , R. Thomas Williamson , Wolfgang Bermel , Gary E. Martin Difficulties in isolating samples from complex biological matrices and sensitivity limitations have long stymied the utilization of heteronuclear 2D NMR for the characterization of drug metabolites. Small diameter cryogenic NMR probes have largely ameliorated sensitivity limitations and the recently reported pure shift HSQC 2D NMR pulse sequence offers a further and marked improvement in both resolution and sensitivity. Using a 7.4μg sample of the commercially available metabolite 3-hydroxy carbamazepine dissolved in 30μL of deuterated solvent and a 600MHz NMR equipped with a 1.7mm cryogenic NMR probe, it was possible to acquire high signal-to-noise pure shift HSQC data in just over 30min. A conventional HSQC spectrum acquired with identical parameters had approximately half the signal-to-noise of the pure shift HSQC spectrum. Collapsing the vicinal homonuclear couplings in the pure shift HSQC spectrum also significantly improves resolution. A practical, real world application of the technique is illustrated with the chromatographically isolated metabolite 3-hydroxy amiodarone from incubation with CYP2J2 recombinant enzyme. High quality pure shift HSQC data were recorded in slightly over 14h for a 3μg sample of the metabolite. Graphical abstract image
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Synthesis of α-phthalimido-α′-dithiocarbamato propan-2-ols via a one-pot, three-component epoxide ring-opening in water ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Azim Ziyaei Halimehjani , Seyyed Emad Hooshmand , Elham Vali Shamiri Regioselective ring-opening of the N-(2,3-epoxypropyl)phthalimide with in situ prepared dithiocarbamic acid in water is reported for the synthesis of a new family of α-phthalimido-α′-dithiocarbamato propan-2-ols. The present method is simple, EtOAc is used for work-ups and affords excellent yield of products. Graphical abstract image
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Catalyst- and chromatography-free synthesis of pyrrole-substituted indolinone derivatives in water ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Nazim A.A. Ahmad , Sunil M. Rokade , Ashok M. Garande , Prakash M. Bhate Pyrrole-substituted indolinone derivatives were synthesized by the reaction of 4-hydroxyproline and isatin derivatives in water under catalyst-free conditions. The main advantages of this protocol besides the use of water as a solvent include short reaction time, practical simplicity, and high yield. Graphical abstract image
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Acid ionic liquid promoted addition of C(sp3)–H bond to aldehyde ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Xue-Yan Zhang , Dao-Qing Dong , Tao Yue , Shuang-Hong Hao , Zu-Li Wang A novel protocol for acid ionic liquid promoted C(sp3)–H bond functionalization of alkyl azaarenes and nucleophilic addition to aldehydes was developed in good to excellent yields, which provides an efficient approach for the synthesis of alkyl-substituted azaarene derivatives. It is worthwhile to note that acid ionic liquid used for this reaction can be recycled and reused six times without a significant decrease in activity. Graphical abstract image
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One-pot four-component synthesis of 4-hydrazinothiazoles: novel scaffolds for drug discovery ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Sarah Titus , Kumaran G. Sreejalekshmi One pot ring synthesis of novel 4-hydrazinothiazoles through sequential four-component route employing carbonyl compounds, aminoguanidine, isothiocyanates, and α-haloketones was accomplished under mild reaction conditions. Base-assisted eliminative aromatization in the [4+1] ring synthesis shed light on interesting leaving group propensities of amine versus hydrazine resulting in the exclusive formation of the title compounds with immense potential as scaffolds for drug discovery. Hydrazone deprotection was effected by acylation which subsequently provided a new set of diacylated molecular systems with a wider scope as chemical handles in the design of thiazolyl drug candidates. Graphical abstract image
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Reduction of nitrobenzene derivatives using sodium borohydride and transition metal sulfides ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Samuel Piña Jr. , Diana M. Cedillo , Carlos Tamez , Nezhueyotl Izquierdo , Jason G. Parsons , Jose J. Gutierrez Reported here is the reduction of aromatic nitro compounds using sodium borohydride and transition metal sulfides as catalysts. The reaction conditions were optimized using the reduction of nitrobenzene as a model reaction. The catalysts studied were iron sulfide (Fe3S4), copper sulfide (CuS), zinc sulfide (ZnS), cobalt sulfide (Co3S4), and nickel sulfide (NiS). The reduction was monitored using gas chromatography. Quantitative conversions were achieved using Co3S4 and NiS, representing a ten-fold increase in reactivity compared to the non-catalyzed reaction. Fe3S4 and ZnS had no apparent effect on the reduction of nitrobenzene while the reduction using CuS showed a marginal increase. The reduction method was applied to several aryl-nitro derivatives containing either electron-withdrawing or electron-donating groups. Halogen containing aryl-nitro compounds were reduced without dehalogenation. The reduction had no effect on other functional groups such as carboxylic acids, esters, amides, or alkenes, indicating that the reduction is highly chemoselective. Graphical abstract image
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Direct oxidative synthesis of nitrones from aldehydes and primary anilines using graphite oxide and Oxone ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Maryam Mirza-Aghayan , Mahdieh Molaee Tavana , Rabah Boukherroub One-pot condensation/oxidation of aldehydes and primary anilines into nitrones using graphite oxide (GO) and Oxone as the oxidant under very mild reaction conditions is described. The proposed method provides a direct oxidative synthesis of various nitrones in good to excellent yields under metal-free conditions in short reaction times. Graphical abstract image
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A facile regioselective 1,3-dipolar cycloaddition protocol for the synthesis of new class of quinolinyl dispiro heterocycles ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Gopal Senthil Kumar , Rajendran Satheeshkumar , Werner Kaminsky , James Platts , Karnam Jayarampillai Rajendra Prasad The 1,3-dipolar cycloaddition reaction of azomethine ylides generated in situ from isatin and secondary amino acids with quinolinyl dipolarophiles in refluxing methanol afforded new class of quinolinyl dispiro heterocycles with multi hetero core units. The regio and stereochemistry of the product was unambiguously assigned by 1H, 13C, 2D NMR techniques and single crystal X-ray analysis. The structures of the compounds are stabilized through the presence of intermolecular hydrogen bonding and intramolecular non-covalent interactions. Graphical abstract image
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Synthesis of novel 14-membered cyclic bis-semicarbazones ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Anatoly D. Shutalev , Anastasia A. Fesenko , Olesya M. Kuzmina , Alexander N. Volov , Dmitry V. Albov , Vladimir V. Chernyshev , Ilia A. Zamilatskov An efficient method for the stereoselective synthesis of novel 14-membered cyclic bis-semicarbazones based on acid-catalyzed cyclization of the hydrazones of 3-(3-oxobutyl)semicarbazides has been developed. The starting semicarbazides were prepared according to a four-step strategy involving amidoalkylation of the sodium enolate of acetylacetone with N-(α-tosylbenzyl)carbamates followed by base-promoted retro-Claisen reaction and treatment of the obtained N-(3-oxobutyl)carbamates with hydrazine. Graphical abstract image
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Facile four-component domino reactions for the synthesis of 2,6-diaryl-4-(1H-indol-3-yl)-3-cyanopyridines ()
Publication date: 1 October 2014 Source:Tetrahedron Letters, Volume 55, Issue 40 Author(s): Chelliah Bharkavi , Pethaiah Gunasekaran , Sundaravel Vivek Kumar , Marimuthu Sakthi , Subbu Perumal A series of novel 2,6-diaryl-4-(1H-indol-3-yl)-3-cyanopyridines was obtained in good yields from the domino reactions of 3-(1H-indol-3-yl)-3-oxopropanenitrile, 4,4,4-trifluoro-1-phenylbutane-1,3-dione, and aromatic aldehydes in the presence of ammonium acetate under solvent-free condition. This transformation involves the formation of two CC and two CN bonds leading to the creation of a six-membered ring in a one-pot operation. Graphical abstract image
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