Tetrahedron Letters

Editorial board ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37
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Graphical Contents List ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37
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Catalytic asymmetric reactions in alkaloid and terpenoid syntheses ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Tomoyuki Yoshimura Catalytic asymmetric induction is one of the most important methods in current synthetic organic chemistry for designing efficient and attractive synthetic routes. The efficient total synthesis of a natural product can be achieved through the identification of appropriate method and strategy. This Letter introduces the catalytic asymmetric syntheses of alkaloids and terpenoids based on an overview of four recently reported types of asymmetric reaction: (1) asymmetric decarboxylative allylation, (2) organocatalytic cascade reaction, (3) polyene cyclization, and (4) asymmetric [2+2]-photocycloaddition catalyzed by a chiral Lewis acid. Graphical abstract image
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Fluorescent sensor of fluorene derivatives having phosphonic acid as a fluorogenic ionophore: synthesis and static quenched properties for Fe(III) ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Chang Yi , Bo Song , Wenwen Tian , Xia Cui , Qi Qi , Wei Jiang , Zhengjian Qi , Yueming Sun A series of novel fluorene derivatives containing –PO(OH)2 (1, 2), –HS (3), and –N+ (CH3)3 (4) were synthesized and only phosphonic-functionalized fluorene derivatives can detect Fe3+ with high selectivity over other metal ions. The fluorescence quenching of 1 and 2 with titration Fe3+ in water–DMF solution fits the Perrin model of static quenching. Spectral analysis showed that Fe3+ bound with fluorene-based chemosensor through the O-atoms at the phosphonic group to form nonfluorescent complexes. The binding ratio was estimated by the Job plot and the trace levels of iron in samples were successfully monitored. Graphical abstract image
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A new and efficient one-pot synthesis of 2-hydroxy-1,4-dihydrobenzoxazines via a three-component Petasis reaction ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Louisa Chouguiat , Raouf Boulcina , Bertrand Carboni , Albert Demonceau , Abdelmadjid Debache The secondary amines synthesized by the reaction between 2-aminophenols and aromatic aldehydes, via the reduction of the corresponding imines, were employed in the synthesis of new 2-hydroxy-2H-1,4-benzoxazine derivatives through a one-pot Petasis multicomponent reaction in good to excellent yields. Graphical abstract image
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Highly efficient dynamic kinetic resolution of secondary aromatic alcohols at low temperature using a low-cost sulfonated sepiolite as racemization catalyst ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Jian-Ping Wu , Xiao Meng , Liang Wang , Gang Xu , Li-Rong Yang A highly efficient dynamic kinetic resolution system for secondary aromatic alcohol using low-cost sulfonated sepiolite as a racemization catalyst has been developed. The system operates at 25°C, achieves good eep (>99%) and substrate conversion ratio (>99%), is applicable to a variety of substrates and can be reused more than 10 times. Graphical abstract image
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Microwave-promoted efficient synthesis of spiroindenotetrahydropyridine derivatives via a catalyst- and solvent-free pseudo one-pot five-component tandem Knoevenagel/aza-Diels–Alder reaction ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Debajyoti Bhuyan , Manas M. Sarmah , Yuvaraj Dommaraju , Dipak Prajapati A microwave-assisted, one-pot pseudo five-component reaction strategy has been developed for the synthesis of some novel spiroindenotetrahydropyridine derivatives from 1,3-indanedione, an aromatic aldehyde, and ammonium acetate under catalyst- and solvent-free conditions via tandem Knoevenagel/aza-Diels–Alder reaction. Graphical abstract image
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A novel transition metal-free conjugate reduction of α,β-unsaturated ketones with tosylhydrazine as a hydrogen source ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Xiaomeng Zhou , Xiaokang Li , Wei Zhang , Junmin Chen A novel and efficient method has been developed for the chemoselective conjugate reduction of α,β-unsaturated ketones with tosylhydrazine as a hydrogen source to the corresponding saturated ketones in moderate to good yields. The present protocol does not require the use of transition metal, and is efficient being applicable to a wide range of substrates (25 examples). Graphical abstract image
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An improved, regioselective synthesis of the radiolabelling precursor for the translocator protein targeting positron emission tomography imaging radiotracer [18F]GE-180 ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Véronique Morisson-Iveson , Harry Wadsworth , Joanna Passmore , Amanda Ewan , Sondre Nilsen , Mikkel Thaning , William Trigg [18F]GE-180 has been demonstrated to be a promising new positron emission tomography radiotracer for targeting translocator protein. PET imaging of TSPO will enable measurement of neuroinflammation and microglia activity in vivo. The synthetic route used in the initial discovery of GE-180, whilst enabling the rapid evaluation of the structure–activity relationships (SAR) in this molecular class, was not high yielding and not suitable for scale-up. Here we present an optimised route towards GE-180 and the radiolabelling precursor of [18F]GE-180 with significantly improved yields due to a strategy which improves the regioselectivity of the key indole formation step of the synthesis. Graphical abstract image
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Benzoxazinone synthesis via Passerini–Smiles couplings ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Elodie Martinand-Lurin , Laurent El Kaïm , Laurence Grimaud Benzoxazinones are easily prepared using Passerini–Smiles couplings of o-nitrophenol derivatives. Palladium-catalyzed flow-hydrogenation of adducts gives aniline derivatives that cyclize into benzoxazinones on treatment with trifluoroacetic acid. Graphical abstract image
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Cycloaddition of keteniminium with terminal alkynes toward cyclobuteniminium and their use in Diels–Alder reactions ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Alexandre Lumbroso , Saron Catak , Sarah Sulzer-Mossé , Alain De Mesmaeker An efficient access to cyclobutanone derivatives has been developed via a ‘one-pot’ [2+2]/[4+2] sequence involving keteniminium and cyclobuteniminium salts as key intermediates. A broad range of novel cyclobuteniminium salts have been prepared via [2+2] cycloaddition of keteniminium salts and alkynes. The resulting [2+2] adducts were then further transformed by Diels–Alder reaction with various dienes to afford cyclobutanone derivatives in good yields. A density functional theory (DFT) based computational study has been performed to obtain insight into the nature of the cycloaddition reactions and to investigate the difference in reactivity of cyclobuteniminium salts. Finally, the usefulness of cyclobutanone derivatives has been demonstrated by ring expansion reactions affording lactone, lactame, and cyclopentanone derivatives. Graphical abstract image
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Iron(III)-catalyzed three-component domino strategy for the synthesis of imidazo[1,2-a]pyridines ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Sougata Santra , Shubhanjan Mitra , Avik Kumar Bagdi , Adinath Majee , Alakananda Hajra An efficient, one-pot, three-component domino strategy has been demonstrated for the synthesis of imidazo[1,2-a]pyridines using a catalytic amount of Fe(III) chloride in high yields in air. A library of imidazo[1,2-a]pyridines was synthesized by the reaction of easily available aldehydes and 2-aminopyridines in a mixture of nitroalkane and DMF (2:1). This transformation presumably occurs by a sequential aza-Henry reaction/cyclization/denitration. The use of readily available chemicals as starting materials, inexpensive metal catalyst, aerobic reaction conditions, tolerance of a wide range of functional groups, and operational simplicity are the notable advantages of this present protocol. Graphical abstract image
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Convenient and chromatography-free partial syntheses of maslinic acid and augustic acid ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Sven Sommerwerk , René Csuk A convenient and chromatography-free 4-step synthesis of analytically pure maslinic acid (1, 41.2%) from oleanolic acid has been developed. Slight variations in the final steps gave an excellent yield of isomeric augustic acid (7, 71.9%). Graphical abstract image
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A new, one-pot, multicomponent synthesis of 5-aza-9-deaza-adenines under microwave irradiation ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Felicia Phei Lin Lim , Giuseppe Luna , Anton V. Dolzhenko A new, practical, three-component method for the synthesis of 5-aza-9-deaza-adenines is developed. Aminopyrazoles react in a one-pot fashion with triethyl orthoformate and cyanamide under microwave irradiation affording 5-aza-9-deaza-adenines in good yields and high purity. The main advantages of this method are the operational simplicity, accessibility, and high efficiency. Graphical abstract image
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Enormously extended π-electronic conjugation system of dimeric octaethylporphyrin transmitted with anthracene ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Hideto Kempe , Natsuki Kuroda , Junro Yoshino , Naoto Hayashi , Hiroyuki Higuchi Based on the fact that anthracene (Anth) possesses much higher similarity in electron-releasing ability to porphyrin nucleus than the other polyacenes, the dimeric octaethylporphyrin (OEP) derivatives 4 and 5 (OEP–Anth–OEP) were synthesized and their structure–property relationships were examined, as compared with related OEP dimers 1–3. Among them, the derivative 4 showed enormously high electronic communication between two terminal OEP rings, potentially providing a suitable unit of the electronic structure for molecular design of the OEP devices operating with less energy and with higher sensitivity to outside stimuli. Graphical abstract image
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Cycloaddition of cyclohexa-2,4-dienones with β-nitroacrylates: a short and efficient entry into bicyclo[2.2.2]octanes endowed with β-nitro-ester and β-amino ester functionality ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Tarun Kumar Behera , Sk. Nurul Islam , Shaikh M. Mobin , Vishwakarma Singh Regio- and stereoselective cycloaddition of β-nitroacrylates with electron deficient cyclohexa-2,4-dienones leading to highly functionalised bicyclo[2.2.2]octanes having the β-nitroester group and their transformation to bicyclo[2.2.2]octanes having β-aminoester functionality is described. Graphical abstract image
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Solvent control of product diversity in palladium-catalyzed addition of arylboronic acid to aryl aldehydes ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Tuluma Das , Amarnath Chakraborty , Amitabha Sarkar In Pd-catalyzed arylboronic acid addition to aryl aldehydes, the expected carbinol or asymmetrical ether can be obtained as the major product by altering aqueous solvent composition. Exploiting this methodology with 2-formylbiphenyls as reaction partner, a fluorene scaffold can be readily constructed in two steps. Graphical abstract image
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Hybrid material from Zn[aminoacid]2 applied in the thio-Michael synthesis ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Mariana P. Darbem , Aline R. Oliveira , Cristiane R. Winck , Andrelson W. Rinaldi , Nelson Luís C. Domingues Recently, methodologies that are in accordance with green chemistry principles have been garnering increasing attention. One of the most applied methods in this field is heterogeneous catalysis. In this context, many catalysts have been developed, and there is one remarkable class that has emerged: hybrid materials. Such heterogeneous catalysts are developed from organic and inorganic portions, especially from amino acids and metal salts, which are commonly found in the literature. Herein, we introduce Zn[Pro]2 and Zn[Gly]2 as heterogeneous catalysts in thio-Michael reactions via the implementation of two methods: via (1) a magnetic stirrer and (2) via an ultrasound device; the latter method resulted in minimally increased reaction yields in all cases. Graphical abstract image
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In(OTf)3-mediated dehydrative annulation of β-ketothioamides with phenylglyoxal: one-pot access to diversely functionalized pyrrol-2-thiones ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Girijesh Kumar Verma , Gaurav Shukla , Anugula Nagaraju , Abhijeet Srivastava , Maya Shankar Singh Indium triflate mediated first synthesis of diversely functionalized pyrrol-2-thiones has been developed by dehydrative annulation of β-ketothioamides with phenylglyoxal through the domino Knoevenagel condensation/cyclization cascade in one-pot. This new simple strategy not only utilizes readily accessible starting material, but also allows the construction of 5-membered azaheterocycle with one quaternary carbon center as a result of the formation of two new (C–C and C–N) bonds in a single operation. Graphical abstract image
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Preparation of differentially substituted 3,6-diaminopyridazines under mild conditions ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Paul A. Bethel , Bryan Roberts , Andrew Bailey Although desirable from a medicinal chemistry perspective, the differentially substituted 3,6-diaminopyridazine moiety is a highly challenging target using current literature approaches. Recent methods of Ullmann-type couplings are evaluated and a mild route to prepare these structures from iodide precursors is presented. Graphical abstract image
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An enantioselective synthesis of a MEM-protected aetheramide A derivative ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Arun K. Ghosh , Kalapala Venkateswara Rao , Siddhartha Akasapu Aetheramides A and B are very potent anti-HIV agents. An enantioselective synthesis of a MEM-protected aetheramide A derivative is described. The synthesis was accomplished in a convergent and stereoselective manner. The key reactions involved asymmetric dihydroxylation, asymmetric allylation, asymmetric syn-aldol reactions, and asymmetric hydrogenation. Graphical abstract image
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Novel 10,13-disubstituted dipyrido[3,2-a:2′,3′-c]phenazines and their platinum(II) complexes: highly luminescent ICT-type fluorophores based on D–A–D structures ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Tatsuya Shigehiro , Shigeyuki Yagi , Takeshi Maeda , Hiroyuki Nakazumi , Hideki Fujiwara , Yoshiaki Sakurai Novel donor–acceptor–donor (D–A–D) π-conjugated molecules based on a dipyrido[3,2-a:2′,3′-c]phenazine (dppz) skeleton were synthesized, and their luminescent properties were investigated. Introduction of various aryl substituents to the 10- and 13-positions of dppz allowed us to tune the emission properties through modulation of the intramolecular charge transfer (ICT) character on the D–A–D chromophores. Coordination of platinum(II) to the diimine site of dppz also gave rise to facilitation of the ICT to induce a significant red shift of the emission. Graphical abstract image
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Prenylation of tyrosine and derivatives by a tryptophan C7-prenyltransferase ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Aili Fan , Shu-Ming Li 7-DMATS from Aspergillus fumigatus and SirD from Leptosphaeria maculans catalyse a C7-prenylation of l-tryptophan and an O-prenylation of l-tyrosine in nature, respectively. SirD was reported to catalyse the C7-prenylation of l-tryptophan and some derivatives thereof in vitro. We report here the O-prenylation of tyrosine and O- or N-prenylation of its derivatives by 7-DMATS. These results provide experimental evidence for the close relationship of tyrosine O- and tryptophan C7-prenyltransferases regarding their substrate and catalytic promiscuity. Graphical abstract image
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Hexaphenylbenzene end-capped tri(p-phenylenevinylenes): synthesis and properties ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Debabrata Jana , Binay K. Ghorai Three new hexaphenylbenzene end-capped tri(p-phenylenevinylenes) were synthesized by the Horner–Wadsworth–Emmons reaction in good yields (86–76%). All compounds have bright fluorescent emissions in the blue to blue–green region in solution (λ max =445–492nm in tetrahydrofuran) and also high emission efficiency (Φ fl =0.51–0.72 in tetrahydrofuran). They exhibit good electrochemical reversibility, high thermal stability, and have high HOMO value. Graphical abstract image
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A concise synthesis of (±)-3-deoxyisoaltholactone ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Stephen Philip Fearnley , Pedro Lory The novel styryl lactone analog (±)-3-deoxyisoaltholactone was synthesized in 5 steps from dihydrofuran. An intramolecular vinylsilane–oxocarbenium condensation thus afforded the central cis-fused bicyclic ether array in near quantitative yield as a single stereoisomer. Graphical abstract image
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Development of a general approach to the synthesis of a library of isoflavonoid derivatives ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Kyle F. Biegasiewicz , James S. Gordon IV , Deana A. Rodriguez , Ronny Priefer Isoflavonoids are a class of organic compounds that act primarily as antioxidants. They are produced almost exclusively by various members of the bean family including soybeans, tofu, peanuts, chick peas, and alfalfa. The antioxidant characteristics that isoflavonoids exhibit help hinder the progression of certain cancers, primarily breast, prostate, and colon cancer. We have developed a three-five step synthesis for obtaining a suite of isoflavonoid derivatives. The synthesis involves an enamine formation, a ring closure and halogenation, a Suzuki coupling, and finally a global deprotection to obtain the respective isoflavonoid derivatives. Graphical abstract image
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Silyl trifluoromethanesulfonate-activated para-methoxybenzyl methyl ether as an alkylating agent for thiols and aryl ketones ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): C. Wade Downey , Sarah E. Covington , Derek C. Obenschain , Evan Halliday , James T. Rague , Danielle N. Confair para-Methoxybenzyl methyl ether acts as an alkylating agent for thiols in the presence of trimethylsilyl trifluoromethanesulfonate and trialkylamine base in good yields (58–96%). Aryl ketones are alkylated under similar conditions, probably through an enol silane intermediate, also in high yields (67–95%). The active alkylating species is likely a p-methoxybenzyl cation. Graphical abstract image
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High enantioselective Michael addition of malonates to β,γ-unsaturated α-ketoesters catalyzed by bifunctional thioureas ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37 Author(s): Swapna Konda , John C.-G. Zhao A highly enantioselective Michael addition of malonates to β,γ-unsaturated α-ketoesters was achieved using cinchona alkaloid-derived thioureas as the bifunctional catalyst. The corresponding Michael addition products were obtained in excellent yields (90–99%) and ee values (up to >99% ee) using a quinidine-derived thiourea as the catalyst under neat conditions. The opposite enantiomer may be obtained using a quinine- or cinchonidine-derived thiourea as the catalyst. Graphical abstract image
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The Nagoya Medal of Organic Chemistry 2014 ()
Publication date: 10 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 37
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Editorial board ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36
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Graphical contents list ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36
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Synthesis of amides via copper-catalyzed amidation of aryl halides using isocyanides ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Issa Yavari , Majid Ghazanfarpour-Darjani , Mohammad J. Bayat An efficient method for intermolecular CC cross-coupling reactions between isocyanides and aryl halides, catalyzed by copper(I) oxide, is developed. This transformation serves as a direct method for the preparation of benzamides in aqueous DMSO, in moderate to good yields. Graphical abstract image
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A highly diastereoselective five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Mehdi Adib , Ehsan Sheikhi , Pouyan Haghshenas , Saideh Rajai-Daryasarei , Hamid Reza Bijanzadeh , Long-Guan Zhu A novel one-pot, five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates is described. A mixture of phenacyl bromide, malononitrile, isocyanide, and two equivalents of a dialkyl acetylenedicarboxylate undergoes a novel 1:1:1:2 addition reaction at ambient temperature in absolute ethanol to produce diastereoselectively the title compounds in good yields. Graphical abstract image
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Facile and efficient preparation of hybrid phenylthiazolyl-1,3,5-triazines and their antidepressant-like effect in mice ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Archana Gahtori , Abhay Kumar , Preeti Kothiyal , Prashant Gahtori High safety, robust efficacy, and rapid onset of action remain the key challenges for improving antidepressant drug discovery. We report a facile and efficient synthetic strategy to structurally encompass mono-, di-, or tri-substituted derivatives using cyanuric chloride and various substituted phenylthiazole-2-amines. The predicted physicochemical property precisely state their specificity as CNS acting agent and antidepressant-like effect of the most promising compound 10 after oral administration significantly reduced immobility in mice behavior models, especially TST from 63s. In addition, good safety features of 10 highlight its ability to modulate hallmarks for antidepressant discovery. These insights are useful in generalization and systematization of CRF1 antagonist design to develop future biological end points. Graphical abstract image
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A green and expedient synthesis of enantiopure diketopiperazines via enzymatic resolution of unnatural amino acids ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Pedro C. Pereira , Isabel W.C.E. Arends , Roger A. Sheldon Dipeptides comprising a d-phenylglycyl moiety coupled to the l-enantiomer of 2-amino butyric acid, norvaline, norleucine, and homocysteine were successfully synthesized from d-phenylglycine amide and the racemate of the corresponding unnatural amino acid. The reaction is catalyzed by an immobilized form of penicillin G acylase in an aqueous medium. The dipeptides were subsequently converted into the corresponding enantiopure diketopiperazines in overall isolated yields of 22–33%. Graphical abstract image
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A tandem synthesis of N-(4-hydroxyquinolin-2-yl)sulfonamides from sulfonoketenimides and isatoic anhydride ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Issa Yavari , Manijeh Nematpour , Mohammad Askarian-Amiri The one-pot synthesis of a novel class of N-(4-hydroxyquinolin-2-yl)sulfonamide derivatives is achieved in moderate to good yields by the sequential copper-catalyzed reaction between sulfonyl azides, terminal alkynes, and isatoic anhydride in N,N-dimethylformamide. Graphical abstract image
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Copper-catalyzed tandem reactions of 2-bromobenzaldehydes/ketones with aminopyrazoles toward the synthesis of pyrazolo[1,5-a]quinazolines ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Lin Gao , Yunping Song , Xinying Zhang , Shenghai Guo , Xuesen Fan An efficient and straightforward synthesis of pyrazolo[1,5-a]quinazolines through copper-catalyzed tandem reactions of 2-bromobenzaldehydes or 2-bromophenyl alkyl/aryl ketones with 5-aminopyrazoles is presented. Graphical abstract image
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A new reaction of [60]fullerene with nitriles and EtMgBr in the presence of Ti(Oi-Pr)4 ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Airat R. Tuktarov , Artur A. Khuzin , Zulfiya R. Shakirova , Natal’ya R. Popod’ko , Usein M. Dzhemilev The reaction of C60 with EtMgBr and different nitriles in the presence of Ti(Oi-Pr)4 as the catalyst was performed for the first time to give novel fullerotetrahydropyridines. Graphical abstract image
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Efficient cyclopropanation of [60]fullerene starting from bromo-substituted active methylene compounds without using a basic catalyst ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Bo Jin , Juan Shen , Rufang Peng , Rongzong Zheng , Shijin Chu Methanofullerene was synthesized via cyclopropanation of [60]fullerene with bromo-substituted active methylene compounds in the presence of amino acid and dimethyl sulfoxide without the use of a basic catalyst. This synthesis is a variation of the Bingel reaction that can be used for base-sensitive substrates. This method allows the cyclopropanation of [60]fullerene with various bromomalonates and bromoacetoacetates at room temperature. Graphical abstract image
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A novel Prins reaction for the synthesis of hexahydro-8,8-dimethyl-1H-isochromen-7-ol derivatives ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): B.V. Subba Reddy , S. Rehana Anjum , G. Madhusudhan Reddy , B. Sridhar Various aldehydes undergo smooth coupling with 5-(hydroxymethyl)-4,6,6-trimethylcyclohex-3-enol in the presence of p-TSA at ambient temperature to afford a novel series of hexahydro-8,8-dimethyl-1H-isochromen-7-ol derivatives in good yields with high selectivity. This is the first report on the synthesis of isochromen-7-ol derivatives via the Prins reaction. Graphical abstract image
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Design, synthesis, and biological evaluation of indolylidinepyrazolones as potential anti-bacterial agents ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): A. Indrasena , Sd. Riyaz , Prema L. Mallipeddi , P. Padmaja , B. Sridhar , P.K. Dubey A series of indolylidinepyrazolones were synthesized using a simple, green, and effective route and evaluated as anti-bacterial agents. The compounds were further studied via structure-guided docking study. One of the compounds exhibiting H-bonding interactions with conserved residue Arg144 turned out to be the most potent compound of the series. The minimum inhibitory concentration values ranged from 50 to 25μg/mL against Staphylococcus aureus in their anti microbial evaluation. Graphical abstract image
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Cyanuric chloride–dimethylformamide mediated cleavage of cyclopropylcarbinols-synthesis of phenolic antioxidant and construction of a new vinylcyclopropane skeleton ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Sagar Khan , Sanchita Roy , Rimi Roy , Avishek Ghatak , Amit Pramanik , Sanjay Bhar Differently substituted cyclopropylcarbinols underwent ring cleavage with easily accessible cyanuric chloride–N,N-dimethylformamide adduct to produce homoallylic chlorides or dienes depending on the nature and location of the substituents. A mechanistic explanation of the aforesaid observations has been provided. A promising antioxidant compound was prepared following this protocol and studied against Fenton’s reagent. This methodology was utilized to construct hitherto unreported vinylcyclopropane frameworks bearing homoallylic chloride and diene moieties. Graphical abstract image
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Titanocene-catalyzed metallation of propargylic acetates in homopropargyl alcohol synthesis ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Jennifer L. Meloche , Peter T. Vednor , Joseph B. Gianino , Allen G. Oliver , Brandon L. Ashfeld The titanium-catalyzed metallation and subsequent carbonyl addition of propargylic acetates enable the direct formation of homopropargylic alcohols in good yields. The corresponding products were obtained as single regioisomers without the corresponding allene adducts observed. Graphical abstract image
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An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Gayatri Sarmah , Saitanya K. Bharadwaj , Anindita Dewan , Ankur Gogoi , Utpal Bora A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates. Graphical abstract image
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Highly selective synthesis of 1-polyfluoroaryl-1,2,3-triazoles via a one-pot three-component reaction ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Liming Cao , Cuibo Liu , Xiangyang Tang , Xuguang Yin , Bin Zhang A series of 1-polyfluoroaryl-1,2,3-triazoles were synthesized in moderate to good yields by an efficient copper-catalyzed one-pot three-component reaction of polyfluoroarenes, sodium azide, and terminal alkynes. The method involves a polyfluoroarylated azide intermediate produced in situ by the selective CF bond cleavage of polyfluoroarene with sodium azide. Graphical abstract image
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Synthesis of theaflavins with Camellia sinensis cell culture and inhibition of increase in blood sugar values in high-fat diet mice subjected to sucrose or glucose loading ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Masumi Takemoto , Hiroaki Takemoto , Asuka Sakurada Theaflavin and its galloyl esters are major polyphenolic pigments of black tea. We compared the efficiency of a variety of oxidizing enzyme systems to synthesize theaflavin and its galloyl esters. Camellia sinensis cell culture efficiently synthesized theaflavin from epicatechin and epigallocatechin with 70% yield and 100% conversion in 4min. In an administration experiment performed in mice, theaflavin inhibited the increase blood glucose levels in mice that were fed a high-fat diet and subjected to glucose or sucrose loading in mice. Graphical abstract image
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An efficient synthesis of a novel analog of octreotide with an unnatural l-lysine-like tetrazolyl amino acid ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Elena A. Popova , Sofia K. Nikolskaia , Ivan A. Gluzdikov , Rostislav E. Trifonov A new cyclic octreotide-like octapeptide was prepared by incorporation of an unnatural tetrazolyl amino acid, an analog of Fmoc-l-lysine, into the peptide chain. The new tetrazolyl amino acid, (S)-2-{[2-(9H-fluoren-9-yl)acetoxy]amino}-6-(1H-tetrazol-1-yl)hexanoic acid, was obtained by azidation of Fmoc-l-lysine trifluoroacetate with sodium azide in the presence of triethyl orthoformate in glacial acetic acid. The linear peptide sequence was prepared using efficient Fmoc/t-Bu solid-phase peptide synthesis (SPPS). Cyclization of the octapeptide was carried out via oxidation with iodine. The structure and purity of the cyclic octapeptide were confirmed by LC–MS, MALDI-TOF MS/MS analysis as well as 1D/2D 1H and 13C NMR spectroscopy. Graphical abstract image
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Facile one-pot synthesis of tetrahydroisoquinolines from amino acids via hypochlorite-mediated decarboxylation and Pictet–Spengler condensation ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Justin J. Maresh , Sean O. Crowe , Arthur A. Ralko , Mark D. Aparece , Casey M. Murphy , Mark Krzeszowiec , Michael W. Mullowney A convenient method for oxidative decarboxylation of α-amino acids is presented. The aldehyde products may be isolated or converted to tetrahydroisoquinolines by addition of dopamine via Pictet–Spengler reaction. Racemic products are generated by phosphate buffer >300mM to maximize regioselectivity. (S)-Enantiomer products are generated by norcoclaurine synthase reaction in maleic acid buffer to minimize chemical background reaction. Graphical abstract image
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One-pot preparation of 2-(alkyl)arylbenzoselenazoles from the corresponding N-(acetyl)benzoyl-2-iodoanilines via a microwave-assisted methodology ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Sébastien Redon , Youssef Kabri , Maxime D. Crozet , Patrice Vanelle We report here the first example of a one-pot synthesis of 2-(alkyl)arylbenzoselenazoles from N-(acetyl)benzoyl-2-iodoanilines. The reaction was carried out in the presence of Woollins’ reagent under microwave irradiation and resulted in moderate to good yields. Graphical abstract image
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3-Quinuclidinol as a nucleophilic catalyst for the cyanation of 2-chloropyrimidines ()
Publication date: 3 September 2014 Source:Tetrahedron Letters, Volume 55, Issue 36 Author(s): Hong-Yong Kim , Wen-Chung Shieh , Mahavir Prashad 3-Quinuclidinol serves as an effective nucleophilic catalyst for the preparation of 2-cyanopyrimidines by cyanation of 2-chloropyrimidines with potassium cyanide in good yields. Graphical abstract image
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