Tetrahedron Letters

Editorial board ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13
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Electrochemically induced one pot synthesis of 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile derivatives via a four component-tandem strategy ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Abhishek Upadhyay, Laxmi Kant Sharma, Vinay K. Singh, Rahul Dubey, Narendra Kumar, Rana Krishna Pal Singh An efficient one pot, multicomponent-tandem synthesis of highly functionalized 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile is reported by electrochemically induced condensation of ethyl acetoacetate, hydrazine hydrate, malononitrile and various aromatic aldehydes. The reaction is carried out in an undivided cell, at a constant current in the presence of NaBr as a supporting electrolyte and ethanol as solvent. Graphical abstract image
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MeOH or H2O as efficient additive to switch the reactivity of allylSmBr towards carbonyl compounds ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Jianyong Li, Qingsheng Niu, Shanchan Li, Yuehao Sun, Qian Zhou, Xin Lv, Xiaoxia Wang A variety of carbonyl compounds were treated by allylSmBr (allylSmBr) with MeOH as the cosolvent to have further insights on the previously reported reductive coupling of aryl ketones mediated by Sm/alkyl halide/MeOH. The results demonstrate that the real reducing species in Sm/alkyl halide/MeOH system should be allylSmBr, and MeOH has elegantly switched the reactivity of allylSmBr from being nucleophilic to being good reductive coupling reagent. Besides, H2O was also found to be a useful additive to realize the pinacol coupling of aliphatic aldehydes and ketones promoted by allylSmBr. Graphical abstract image
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Novel simple fluorescent sensor for nickel ions ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Zhe Han, Jing Yan, Hou Quan Tang, Yuan He, Ying Zhu, Yan Qing Ge A novel pyrazoline with benzimidazole substituent was conveniently synthesized, starting from a chalcone and 2-hydrazinylpyridine. The addition of Ni2+ to ethanol solution of the synthesized pyrazoline resulted in a rapid color change from blue to green which allows the selective detection of Ni2+ ion over a great number of other metal ions. The association constant for the 1:1 complex was determined to be 2.72×107 M−1. Graphical abstract image
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One-pot facile synthesis of polysubstituted pyridines via tandem reaction of the Blaise reaction intermediates and 3-formylchromones ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Zhiwei Chen, Zhaoran Dai, Zhangxia Zhu, XiaoFeng Yang A novel tandem one-pot method for the synthesis of polysubstituted pyridine derivatives has been developed via Knoevenagel-type reaction and subsequent 6π electrocyclization of the Blaise reaction intermediates and 3-formylchromones. Short reaction time, moderate to good yields and excellent functional group tolerance have been accomplished in this protocol. Graphical abstract image
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Total synthesis of natural fregenedadiol and its diacetate, rearranged labdanes with aromatized B ring ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Satish Chandra Philkhana, D. Srinivasa Reddy Labdane based natural products are most abundant and widely distributed in nature with many compounds exhibiting exceptional biological properties. Fregenedadiol is a bicyclic diterpene isolated from Halimium viscosum and represents a new carbon skeleton fregenedane with its B ring aromatized. Here, we report a total synthesis of this interesting natural product using one-pot Diels-Alder/aromatization sequence and selective hydrogenolysis as key steps. Graphical abstract image
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Non-expensive, open-flask and selective catalytic systems for the synthesis of sulfinate esters and thiosulfonates ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Arisson Tranquilino, Silvia R.C.P. Andrade, Ana Paula M. da Silva, Paulo H. Menezes, Roberta A. Oliveira Two simple and efficient methods for the synthesis of sulfinate esters and thiosulfonates from sodium salts of sulfinic acids are described. Different alcohols were converted into the corresponding sulfinate esters in good yields and purity in an open flask. By the adjustment of the reaction conditions thiosulfonates could also be obtained in a very short reaction time. Graphical abstract image
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New acorane sesquiterpenes isolated from the endophytic fungus Colletotrichum gloeosporioides SNB-GSS07 ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Amandine André, Nathalie Wojtowicz, Kaatio Touré, Didier Stien, Véronique Eparvier Looking for new anti-glycation compounds, four new acorane sesquiterpenes together with seven known molecules were isolated from Colletrotrichum gloeosporioides, an endophytic fungus of Sabicea cinerea. Their structures were established based on mass spectrometry and NMR, together with circular dichroism for their absolute configurations. Graphical abstract image
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Total synthesis of distaminolyne A ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Mohan Dumpala, Srinivas Theegala, Radha Krishna Palakodety Herein we report the stereoselective total synthesis of first occurrence distaminolyne A via aminolytic kinetic resolution, Corey-Fuch’s reaction for alkyne formation and Cardiot-Chodkiewicz cross coupling followed by Wittig olefination as the key steps. Graphical abstract image
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A simple and efficient approach for the synthesis of 2-aminated quinazoline derivatives via metal free oxidative annulation ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Amit N. Pandya, Eric M. Villa, E. Jeffrey North A simple and efficient approach for the synthesis of 2-aminoquinazoline derivatives in moderate to good yields. This reaction employs mild reaction conditions, is metal-free and utilizes readily available starting materials making it a more viable reaction for scale up synthesis and ligand diversity. Notably, this methodology allows for the synthesis of 2-aminoquinazolines using a free amine or cyclic amine enabling structural diversity and good atom economy. Graphical abstract image
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m-Chloroperbenzoic acid-oxchromium (VI)-mediated cleavage of 2,4,5-trisubstituted oxazoles ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Pravin C. Patil, Frederick A. Luzzio An array of 2-substituted-4,5-diphenyloxazoles were found to be cleaved to triacylamines and diacylamines (imides) using a reagent system composed of m-chloroperbenzoic acid (MCPBA) and 2,2′-bipyridinium chlorochromate (BPCC). The 2-alkyl-4,5-diphenyloxazoles give imides (38–60%) as the predominant cleavage product while the 2-aryl-4,5-diphenyloxazoles give triacylamines (44–71%). Two mechanisms involving intermediates such as cyclic endoperoxides or oxachromacycles were proposed. An application of the oxidative cleavage to the multi-step synthesis of (±)-phoracantholide I seco acid is detailed. Graphical abstract image
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Isomerization and functionalization of 2:1 Diels–Alder adducts of cyclopentadiene and p-benzoquinone: Applications to polycycles via ring-closing metathesis and ring-opening metathesis as key steps ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Sambasivarao Kotha, Nalajala Nageswara Rao, Ongolu Ravikumar, Gaddamedi Sreevani Five stereochemically different 2:1 Diels–Alder adducts were prepared starting with cyclopentadiene and p-benzoquinone. Separately, these adducts were treated with an excess amount of base and allyl bromide to deliver two different tetra-allylated products. These allyl derivatives gave the corresponding mono-propellane derivatives on metathesis sequence. Five Diels–Alder adducts on treatment with Grubbs ruthenium catalysts delivered the corresponding mono- and di-ring-opened metathesis products. Structures of three functionalized adducts were determined by single-crystal X-ray diffraction studies. Graphical abstract image
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Theoretical study of Lewis acid activation models for hypervalent fluoroiodane reagent: The generality of “F-coordination” activation model ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Biying Zhou, Xiao-song Xue, Jin-pei Cheng The bench-stable cyclic hypervalent fluoroiodane reagent (1) is receiving increasing attention in fluorine chemistry because of its completely new reactivity. Fluorination mediated by reagent 1 generally requires activation by an exogenous Lewis acid. A more complete understanding of the Lewis acid activation model is thus paramount for the development of new strategies involving this reagent. Density functional theory (DFT) calculations herein demonstrate the generality of the “F-coordination” activation mechanism for reagent 1 that we recently showed to be favored over the commonly accepted “O-coordination” activation mechanism. Graphical abstract image
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Synthesis of 2,3-dihydropyrroles by photo rearrangement of Hantzsch 1,4-dihydropyridines with high diastereoselectivity ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Qidi Zhong, Qiangwen Fan, Hong Yan The Hantzsch 1,4-dihydropyridines were found to be transforming to the 2,3-dihydropyrroles by photo rearrangement with air under irradiation of LED light (410nm) with high diastereoselectivity (dr>20:1). This reaction includes tandem photo oxidation/rearrangement. The 2,3-dihydropyrroles were obtained in moderate yields with successfully one-pot process starting from aldehydes, ammonium acetate and ethyl acetoacetate. Graphical abstract image
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Visible light induced decomposition of sulfonyl hydrazides using Pd/ZrO2 nanocomposite photocatalyst ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Xiaoji Li, Chao Zhou, Pinhui Diao, Yanqin Ge, Cheng Guo A new approach to synthesis of thiosulfonates has been developed under mild conditions without any oxidants and promoting reagents through a Pd/ZrO2 nanocomposite photocatalyst catalyzed decomposition of sulfonyl hydrazides. This protocol gave the products in moderate yields, comparable to the best results reported so far. Finally, a plausible reaction mechanism was proposed. Graphical abstract image
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A new ESIPT-based fluorescent probe for highly selective and sensitive detection of HClO in aqueous solution ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Yimin Pan, Jing huang, Yifeng Han A new ESIPT-based fluorescent probe, PHC2, for the detection of hypochlorous acid has been rationally designed and developed. Endowed by the specific reaction between hypochlorous acid and phenyl azo group, PHC2 features high degree of selectivity and sensitivity for HClO with a low detection limit (13.2nM) under physiological conditions in neutral aqueous solution. Graphical abstract image
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Sequential MCR/Fisher indolization strategy for the construction of polycyclic carbazole derivatives ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Esma Lamera, Sofiane Bouacida, Marc Le Borgne, Zouhair Bouaziz, Abdelmalek Bouraiou A one-pot method for the synthesis of novel polycyclic carbazole derivatives from readily available starting materials using a sequential multicomponent reaction/Fisher indolization strategy is described. Graphical abstract image
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CF3S(O)n-containing enaminones as precursors for the synthesis of pyrimidine-4(3H)-ones ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Liubov V. Sokolenko, Yurii L. Yagupolskii, Liliia S. Kumanetska, Jérôme Marrot, Emmanuel Magnier, Volodimir O. Lipetskij, Ihor V. Kalinin Methyl 3-(dimethylamino) acrylates containing trifluoromethylsulfenyl-, trifluoromethylsulfinyl-, and trifluoromethylsulfonyl groups were synthesized and their utility demonstrated by reactions with aliphatic and aromatic amidines to produce 2,5-substituted 4(3H)-pyrimidones. Cyclization reactions of enaminones with urea or thiourea led to 5-substituted uracil or 2-thiouracil derivatives, respectively. Graphical abstract image
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Two new dimmeric xanthanolides isolated from Xanthium mogolium Kitag plant ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Fuwang Xu, Chengqian Xiao, Xue Lv, Min Lei, Lihong Hu Two xanthanolide-type dimmers, namely Mogolide D (4) and Mogolide E (5) are isolated from the aerial parts of Xanthium mogolium Kitag plant collected from Heilongjiang province, China. The dimmers’ relative structures are elucidated on the basis of HRESIMS, IR spectrum and NMR spectroscopy. The absolute configurations of them are assigned with ECD spectra. The biosynthetic pathway of the two dimmers is also proposed. Besides, Mogolide D (4) and Mogolide E (5) are tested against MDA-MB-231 breast cancer cell line with IC50 8.46μM and 19.20μM, respectively. Graphical abstract image
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Synthesis of two epimeric long-term metabolites of oxandrolone ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Nicolas Kratena, Berthold Stöger, Matthias Weil, Valentin S. Enev, Peter Gärtner The goal of the work reported herein, was the synthesis of two C-17-epimeric substances which have been found to be long-term urinary metabolites of the prescription drug and anabolic steroid oxandrolone. These 17-hydroxymethyl-17-methyl-18-nor-2-oxaandrost-13-en-3-ones have been used as markers to trace oxandrolone abuse in professional athletes since 2013. Our synthesis relied on an ozonolysis/lactonisation strategy and acidic rearrangement of a spiroepoxide. To the best of our knowledge, no chemical synthesis of either substance has been published. Graphical abstract image
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New cyclen-cored dendrimers functionalized with pyrene: Synthesis characterization, optical and photophysical properties ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Amanda Cevallos-Vallejo, Mireille Vonlanthen, Pasquale Porcu, Andrea Ruiu, Ernesto Rivera New cyclen (1,4,7,10-teraazacyclododecane) cored dendrimers up to the second generation, functionalized with 4, 8 and 16 pyrene units, respectively, were synthesized following a convergent procedure. All new compounds were characterized by NMR spectroscopies and ESI or MALDI TOF mass spectrometry. The optical and photophysical properties of the new dendrimers were studied in THF solution. Absorption spectra showed the typical absorption bands of pyrene moieties. In the fluorescence spectra, monomer as well as excimer emission were observed for all compounds. An increased proportion of excimer emission was observed in the dendrimer of the highest generation. Graphical abstract image
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Unexpected synthesis of azepino[4,3,2-cd]indoles from 4-aminoindoles ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Olexandr Halaiev, Myroslav Garazd, Andrzej Gzella, Roman Lesyk Unexpected regioselectivity for the Skraup-Doebner-Von Miller reaction was observed during the synthesis of quinolines from 4-aminoindoles and acetone in the presence of hydrochloric acid as a catalyst. The products were unambiguously assigned as 1-alkyl-3,5,5-trimethyl-5,6-dihydro-1H-azepino[4,3,2-cd]indoles instead of 2,2,4-trimethyl-2,7-dihydro-1H-pyrrolo[2,3-h]quinolones based on NMR spectroscopy and X-ray crystallographic analysis. Graphical abstract image
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Xanthate-based microwave-assisted CH radical functionalization of caffeine, 1,3-dimethyluracil, and imidazo[1,2-a]pyridines ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Víctor M. Pérez, Daniela Fregoso-López, Luis D. Miranda Xanthate-based radical chemistry was used for the regioselective direct alkylation of caffeine, uracil, and imidazo[1,2-a]pyridine systems, using dilauroyl peroxide as initiator and oxidant, under microwave irradiation. Under these conditions, several electrophilic radicals (located alpha to a carbonyl function such as esters, amides, ketones, malonates and cyano groups) were added to the title heterocyclic systems. The methodology allows the intermolecular regioselective construction of a sp2-sp3 CC bond via a CH functionalization in an aromatic substitution, from readily available starting materials. Graphical abstract image
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Sphaerialactonam, a γ-lactam–isochromanone from the Hawaiian endophytic fungus Paraphaeosphaeria sp. FT462 ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Peng Huang, Chunshun Li, Ariel M. Sarotti, James Turkson, Shugeng Cao Reinvestigation of the endophytic fungus Paraphaeosphaeria sp. FT462 from the Hawaiian plant Lycopodiella cernua (L.) Pic. Serm led to the isolation and identification of a unique γ-lactam-isochromanone (1). The structure of 1 was determined by NMR, MS spectroscopic analysis, and quantum chemical calculations of NMR. The compound was tested inactive against A2780 and A2780cisR. Graphical abstract image
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Synthesis, chiral resolution and optical properties of amphiphilic oxa[9]helicene derivatives ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Mohammad Shahabuddin, Md Jalil Miah, Ken-ichi Iimura, Takao Kimura, Michinori Karikomi A new class of amphiphilic oxa[9]helicene derivatives were synthesized in excellent-to-fair yields, and successfully characterized by different analytical techniques (e.g., FT-IR, 1H and 13C NMR, and HRMS). The compounds were enantiomerically separated by chiral HPLC and the absolute configurations of the enantiomers were confirmed by circular dichroism spectroscopy. Other optical properties (e.g., UV, photoluminescence, specific optical rotation and molecular optical rotation) of the newly synthesized compounds were also examined. Graphical abstract image
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Efficient synthesis of isoindoles using supercritical carbon dioxide ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Satoshi Ito, Masayuki Akaki, Yasutaka Shinozaki, Yuuki Iwabe, Masaru Furuya, Marina Tobata, Makoto Roppongi, Takafumi Sato, Naotsugu Itoh, Toru Oba Bicyclopyrroles were efficiently converted to the corresponding isoindoles by a retro Diels-Alder reaction in supercritical carbon dioxide. By adding ethylene gas as an oxygen scavenger, the isoindole yield was further improved. Graphical abstract image
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Synthesis of picolinohydrazides and their evaluation as ligands in the zinc-catalyzed hydrosilylation of ketones ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Vita Surzhko, Thierry Roisnel, Barbara Le Grel, Philippe Le Grel, Claudia Lalli, Gilles Argouarch A set of picolinohydrazides was prepared by reaction between hydrazines and either 2-picolinic acid or ethyl pyridine-2-carboxylate, and characterized. These molecules were evaluated as ligands in the zinc-catalyzed hydrosilylation of ketones. Thus, several aromatic and aliphatic ketones were successfully reduced by diethoxymethylsilane as the hydride source in the presence of a catalytic system made of diethylzinc combined in situ to the picolinohydrazides described herein. Graphical abstract image
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Regiospecific synthesis of 6-halouridine derivatives: An effective method for coupling sterically hindered pyrimidine bases to ribose ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Daniel J. Blackburn, Greggory T. Kent, Weiming Wu 6-Halouridine derivatives were synthesized regiospecifically through the coupling of N3-protected 6-halouracil to a ribose derivative. The combination of the silylating reagent N,O-bis(trimethylsilyl)acetamide and Lewis acid catalyst trimethylsilyl trifluoromethanesulfonate is unique in their ability to facilitate the coupling of sterically hindered pyrimidine bases to ribose to form nucleoside derivatives. Graphical abstract image
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Highly selective fluorescence turn-on determination of fluoride ions via chromogenic aggregation of a silyloxy-functionalized salicylaldehyde azine ()
Publication date: 29 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 13 Author(s): Yun-Hui Zhao, Yubo Li, Yunfei Long, Zhihua Zhou, Zilong Tang, Keqin Deng, Shaowei Zhang A novel fluorescent chemsensor TBS-protected salicylaldehyde azine (TSAA) for fluoride ion was developed based on aggregation-induced emission (AIE). The probe TSAA was prepared by the reaction of salicylaldehyde azine (SAA) with tert-butyldimethylsilyl chloride (TBS-Cl) via an unusual synthetic methodology and shows only non-emission. Upon treatment with fluoride in aqueous MeCN solution, the TBS protective group of probe TSAA was removed readily and the fluorescence of the probe was switched on, which resulted in a new fluorescence peak around 543nm. The fluorescent intensity at 543nm increases linearly with fluoride ion concentration in the range 1–50μmolL−1. This proposed probe shows excellent selectivity toward fluoride ion over other common anions and cations. Graphical abstract image
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Editorial board ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12
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Synthesis, characterization and energetic properties of novel 1-methyl-1,2,4-triazolium N-aryl/N-pyridinyl ylids ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Hong Zhang, Zuoquan Wang, Ion Ghiviriga, Girinath G. Pillai, Farukh Jabeen, Justin A. Arami, Wenfeng Zhou, Peter J. Steel, C. Dennis Hall, Alan R. Katritzky Synthesis, characterization and energetic properties of novel, nitrogen-rich 1-methyl-1,2,4-triazolium N-aryl/N-pyridinyl ylids 3a–m are reported. Graphical abstract image
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Zinc mediated direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones and mechanistic insight ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Prasanta Das, Ashton T. Hamme A Lewis acid catalyzed direct transformation of propargyl N-hydroxylamines to α,β-unsaturated ketones in the presence of aqueous Zn(II)-salts has been described. This investigation also provides a novel observation for the stoichiometric role of Zn-halides over what is known to date for catalytic processes. A thorough mechanistic study has been established based on the experiment using 18O-labeled water in optimized reaction conditions; the incorporation of 18O in the desired product was also substantiated by HRMS. This methodology is also a mild, inexpensive, and an efficient approach for this unusual conversion. Graphical abstract image
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A Re2O7 catalyzed cycloetherification of monoallylic diols ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Xiaolong Wan, Jiadong Hu, Dongyang Xu, Yang Shang, Yanxia Zhen, Chenchen Hu, Fan Xiao, Yu-Peng He, Yisheng Lai, Weiqing Xie A Re2O7 catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture. Graphical abstract image
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Construction of chiral 3,3-disubstituted oxindoles by a thiourea-catalyzed substitution of phenylsulfonyl with 2-naphthol ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Zhen-Hua Xing, Ying Zhang, Yong Wang, Xiao-Ping Xu, Shun-Jun Ji An organocatalytic asymmetric functionalization of C(3)S bond of indolone by naphthol is described. It provided a new and simple method for the construction of 3,3-disubstituted indolones containing a fresh-formed chiral quaternary carbon center with high yield and good enantioselectivity. Graphical abstract image
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Ruthenium-catalyzed selective synthesis of monoalkylated barbituric acids through “borrowing hydrogen” methodology ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Anggi Eka Putra, Yohei Oe, Tetsuo Ohta An environmentally benign alkylation of barbituric acids via “borrowing hydrogen” process with ruthenium catalysis has been established. The corresponding 5-(alkyl)barubituric acids were obtained in good to excellent yields with low catalyst loading. Various substrates including aliphatic alcohols were tolerated in the present catalytic system. A novel method for construction of barbituric acid-fused benzopyrane derivatives was also demonstrated. Graphical abstract image
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Octahedral iridium complex catalyzed α-chlorination of 2-acyl imidazoles with tosyl chloride ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Tao Deng, Pranjal P. Bora, Shao-Xia Lin, Yi Li, Qiang Kang An efficient and catalytic α-chlorination of 2-acyl imidazoles with readily available tosyl chloride catalyzed by an octahedral iridium complex under mild condition was reported. A range of 2-acyl imidazoles were converted to their corresponding α-chlorination products in good to excellent yields. Graphical abstract image
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Synthesis of functionalized 3-arylpyridazines via Pd-catalyzed decarboxylative cross-coupling of pyridazine-3-carboxylic acids ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Shengqiang Wang, Hongtao Lu, Jingya Li, Dapeng Zou, Yusheng Wu, Yangjie Wu An efficient and general protocol for the decarboxylative cross-coupling of pyridazine-3-carboxylic acids with aryl-bromides has been described. This method provides a new avenue for the synthesis of 3-arylpyridazines via decarboxylative cross-coupling strategy by employing the dual-catalyst system of Pd(PPh3)4/Cu2O in the presence of Li2CO3 at 160°C in DMA. Graphical abstract image
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Facile synthesis and structural characterization of μ4-oxo tetrazinc clusters of beyerenoic and kaurenoic acids ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Mario A. Gómez-Hurtado, Karina Nava-Andrade, Ana K. Villagómez-Guzmán, Rosa E. del Río, Noemí Andrade-López, José G. Alvarado-Rodríguez, Diego Martínez-Otero, David Morales-Morales, Gabriela Rodríguez-García The naturally occurring diterpenoids beyerenoic (1) and kaurenoic acids (2) extracted from Perymenium buphthalmoides DC., were treated with NaOH and reacted with ZnCl2 to afford two μ 4-Oxo tetrazinc clusters (μ 4-oxo)-hexakis(μ 2-beyerenate)-tetra-zinc(II) (5) and (μ 4-oxo)-hexakis(μ 2-kaurenate)-tetra-zinc(II) (6). Both species were unequivocally characterized and their structures in the solid state determined by single crystal X-ray diffraction techniques. Graphical abstract image
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Synthesis of phthalan and phenethylamine derivatives via addition of alcohols to rhodium(II)-azavinyl carbenoids ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): John M. Bennett, Jonathan D. Shapiro, Krystina N. Choinski, Yingbin Mei, Sky M. Aulita, Eric W. Reinheimer, Max M. Majireck 1-Sulfonyl-1,2,3-triazoles undergo inter- and intramolecular 1,3-OH insertion with rhodium(II)-azavinyl carbenoid intermediates upon treatment with a rhodium(II) catalyst. Products of this transformation contain a synthetically versatile N-(2-alkoxyvinyl)sulfonamide, enabling divergent reactivity toward several N-protected phenethylamine derivatives under various conditions. Notably, products with a phthalan framework can be accessed directly from 4-aryl-1-sulfonyl-1,2,3-triazoles bearing a pendant alcohol. Graphical abstract image
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Synthesis of novel HIV-1 protease inhibitors via diastereoselective Henry reaction with nitrocyclopropane ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Michael L. Mitchell, Lianhong Xu, Zachary E. Newby, Manoj C. Desai Novel reaction and work-up conditions were developed for the unprecedented Henry reaction using nitrocyclopropane in the key step towards the synthesis of HIV-1 protease inhibitors. This procedure may find application in the preparation of diverse compounds of potential biological interest. Graphical abstract image
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Palladium-catalyzed domino sequence for the synthesis of N-aryl quinolinone-3-carboxylate derivatives and their anti-proliferative activity ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Konidena Lakshmi Narayana Sharma, Chettu Suresh Kumar, Sorra Kumaraswamy, Valluru Krishna Reddy, N.S. Kameswara Rao, Korupolu Raghu Babu, Guduru Ramakrishna An efficient and an operationally simple Palladium-catalyzed domino reaction for the synthesis of N-aryl quinolinone-3-carboxylate derivatives has been developed via the reaction between diethyl 2-(2-bromobenzylidine) malonate and anilines. These newly synthesized compounds exhibited good to moderate anti-proliferative activity with GI50 values ranging from 0.41µM to 45.77µM. Among them, compounds 6j, 6k and 6m demonstrated potential activity particularly against MCF-7 (breast) and KB (oral) cancer cell lines. Graphical abstract image
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Transition metal and base free coupling of N-tosylhydrazones with 1,3-dicarbonyl compound ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Deepika Choudhary, Chanchal Agrawal, Vineeta Khatri, Ranjit Thakuria, Ashok K. Basak N-tosylhydrazones derived from a wide variety of aryl, alkyl and heteroaryl aldehydes undergo smooth coupling with 5,5-dimethylcyclohexane-1,3-dione under transition metal and base free conditions to generate tetraketo compounds in high yields. In presence of a base, the coupling reaction generates β-keto enol ether as the major product in a polar aprotic solvent. N-Tosylhydrazone can also be converted to xanthenedione in high yields in one-pot operation under mild acidic conditions. Graphical abstract image
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Construction of 9-functionalized xanthenes via Diels-Alder reaction of stable ortho-quinone methides and arynes ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Hui Jian, Kai Liu, Wei-Hua Wang, Zhi-Juan Li, Bin Dai, Lin He Diels-Alder reaction of stable o–quinone methides and arynes has been developed, providing 9–aryl and 9–cinnamyl substituted xanthenes in moderate to high yields. Graphical abstract image
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Palladium nanoparticles stabilized by phosphine ligand for aqueous phase room temperature suzuki-Miyaura coupling ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Jiyuan Ge, Jian Jiang, Chenhuan Yuan, Chaozhi Zhang, Minghua Liu Water soluble phosphine ligand triphenylphosphine-3,3′,3″-trisulfonic acid trisodium salt (TPPTS) was used as the stabilizer as well as the activator to the palladium nanoparticles, which showed a high catalytic performance for aqueous phase Suzuki-Miyaura coupling reaction at room temperature. Graphical abstract image
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Palladium-catalysed α-allylation of chiral sulfinimines derived from symmetric cyclic ketones ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Jiangnan Li, Rafid S. Dawood, Shuanglin Qin, Tongtong Liu, Shuangwei Liu, Robert A. Stockman, Shende Jiang, Guang Yang A diastereoselective mono-allylation reaction at the α-position of symmetric cyclic ketones by using tert-butanesulfinamide as a chiral auxiliary is explored. Excellent yields and high diastereomeric ratios were achieved under palladium(0) catalysis in the presence of a readily available achiral phosphine ligand. Graphical abstract image
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Antiviral peptides from marine gorgonian-derived fungus Aspergillus sp. SCSIO 41501 ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Xuan Ma, Xu-Hua Nong, Zhe Ren, Jie Wang, Xiao Liang, Lu Wang, Shu-Hua Qi A new cyclic pentapeptide and three new linear peptides, namely, aspergillipeptides D–G (1–4), were isolated from a culture broth of marine gorgonian-derived fungus Aspergillus sp. SCSIO 41501. Their structures were elucidated by spectroscopic analysis, and their absolute configurations were confirmed by Marfey’s method. Compounds 1 and 2 showed evident antiviral activity against herpes simplex virus type 1 (HSV-1) with IC50 values of 9.5 and 19.8µM under their non-cytotoxic concentrations against a Vero cell line, respectively, and 1 also had antiviral activity against acyclovir-resistant clinical isolates of HSV-1. Graphical abstract image
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Visible light promoted copper-catalyzed Markovnikov hydration of alkynes at room temperature ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Teng-fei Niu, Ding-yun Jiang, Si-yuan Li, Xing-ge Shu, Huan Li, Ai-ling Zhang, Jia-yu Xu, Bang-qing Ni A new and efficient method for the hydration of alkynes to the corresponding ketones was successfully developed. The hydration process proceeds smoothly at room temperature with 1% mol of CuCl as catalyst under visible light irradiation. This protocol is applicable to various alkynes, including aromatic alkynes, polycyclic aromatic and heterocyclic aromatic excellent regioselectivity in good to excellent yields. Graphical abstract image
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Stereoselective synthesis of novel C-3 functionalized 3-sulfonyl-β-lactams: Promising biologically active heterocyclic scaffolds ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Aman Bhalla, Garima Modi, Shamsher S. Bari, Anu Kumari, Shiwani Berry, Geeta Hundal An efficient and operationally simple strategy for the stereoselective synthesis of novel C-3 functionalized 3-sulfonyl-β-lactam heterocycles is described. The C-3 functionalized 3-phenyl/benzylsulfonyl-β-lactams 3/3′, 5/5′ has been synthesized via Michael addition using different Michael acceptors on trans-3-phenyl/benzylsulfonyl-β-lactams 2(a–f) using K2CO3 as a base and acetonitrile/DMF as solvents. The reaction furnished exclusively cis-β-lactam adducts 3(a–r) using sterically less hindered Michael acceptors. Further, the effect of steric bulk and chiralilty of Michael acceptors was explored to achieve target C-3 functionalized β-lactams 3(s-u)/3′(s-u) and 5(a–c)/5′(a–c). The structural and stereochemical analysis of novel β-lactams were carried out using FT-IR, NMR (1H, 13C, 1H-1H COSY, 1H-13C COSY and 13C DEPT-135), elemental analysis (CHNS), mass spectrometry (EIMS and LCMS) in representative cases and single crystal X-ray crystallographic studies (3e). The cis or trans configuration of the Michael acceptor (E) at C-3 was assigned with respect to C4-H. Graphical abstract image
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Synthesis of cytotoxic cyanobactin, Wewakazole B ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Kiranmai Nayani, SD. Anwar Hussaini We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings. Graphical abstract image
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Ag NPs decked GO composite as a competent and reusable catalyst for ‘ON WATER’ chemoselective synthesis of pyrano[2,3-c:6,5-c′]dipyrazol]-2-ones ()
Publication date: 22 March 2017 Source:Tetrahedron Letters, Volume 58, Issue 12 Author(s): Anshu Dandia, Shyam L. Gupta, Aayushi Indora, Pratibha Saini, Vijay Parewa, Kuldeep S. Rathore We have synthesized and characterized Ag NPs decked GO composite and studied its role as reusable catalyst for the ‘ON WATER’ chemoselective synthesis of pyranodipyrazolones via the reaction of different carbonyl compounds with 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one. This method illustrates significant selectivity for pyranodipyrazolones over arylmethylene bispyrazolols and arylmethylenepyrazolones. Synergistic effect of heterogenic nature of water with reactants and Ag NPs/GO had profuse outcome on reaction as indicated by high TOF (18.03×10−5 molg−1 min−1). Furthermore, catalyst was recycled for 7-times without significant loss of activity. Graphical abstract image
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