Tetrahedron

Editorial board ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36
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Palladium-catalyzed regio- and chemoselective direct desulfitative arylation of anilides with arylsulfonyl chlorides ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Ebrahim Kianmehr, Arezoo Tanbakouchian A straightforward and practical palladium-catalyzed regioselective arylation of anilides is described. This method provides a new approach to prepare 2-aminobiaryls, which are valuable precursors for the synthesis of various N-containing heterocycles, using arylsulfonyl chlorides as readily available arylating agents. Graphical abstract image
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A concise enantioselective synthesis of pyrrolidine sedum alkaloids (R)-(R)-(+), (S)-(S)-(−)-pyrrolsedamine and (S)-(R)-(+)-pyrrolallosedamine by using proline catalysed α-amination reaction ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Viraj A. Bhosale, Sachin B. Markad, Suresh B. Waghmode A general approach for the synthesis of pyrolidine member of sedum alkaloids has been developed by employing proline catalysed sequential α-amination and Horner–Wadsworth–Emmons (HWE) olefination of an aldehyde as the key steps. This method can be extended for the synthesis of various bioactive natural products containing pyrolidine skeleton. Graphical abstract image
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Anionic N-heterocyclic carbenes derived from sydnone imines such as molsidomine. Trapping reactions with selenium, palladium, and gold ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Tyll Freese, Ana-Luiza Lücke, Catharina A.S. Schmidt, Mika Polamo, Martin Nieger, Jan C. Namyslo, Andreas Schmidt The sydnone imines Molsidomine and 5-(benzoylimino)-3-(2-methoxyphenyl)-1,2,3-oxadiazolium-2-ide gave anionic N-heterocyclic carbenes on deprotonation at C4 which were trapped as methylated selenium adducts, gold complexes (X-ray analysis) as well as palladium complexes (X-ray analysis). The 13C NMR resonance frequencies of the carbene carbon atom are extremely shifted upfield and appear at δ = 142.1 ppm (Molsidomine carbene) and δ = 159.8 ppm (sydnone imine carbene). The Pd complexes were applied as catalysts in Suzuki-Miyaura and Sonogashira-Hagihara cross-coupling reactions. Graphical abstract image
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An efficient metal-free cascade process for the synthesis of 4-arylpyrimido[1,2-b]indazole-3-carbonitrile derivatives ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Lei Li, Hui Xu, Lei Dai, Junhua Xi, Lingli Gao, Liangce Rong An efficient metal-free cascade reaction to synthesize novel pyrimido[1,2-b]indazole-3-carbonitrile derivatives was reported. The reaction starts from aromatic aldehydes, 1H-indazol-3-amine (4-chloro-1H-indazol-3-amine), and 3-(1H-indol-3-yl)-3-oxopropanenitrile or 3-oxo-3-arylpro-panenitrile in the presence of ethanol and triethylamine under plain laboratory conditions. The reaction was easy to operate with good tolerance to substrates in high yield. Graphical abstract image
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Neoabyssomicins A–C, polycyclic macrolactones from the deep-sea derived Streptomyces koyangensis SCSIO 5802 ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Yongxiang Song, Qinglian Li, Fengxiang Qin, Changli Sun, Hao Liang, Xiaoyi Wei, Nai-Kei Wong, Li Ye, Yun Zhang, Mingwei Shao, Jianhua Ju Neoabyssomicin A (1) possessing a caged 6/6/6 ring system fused with two additional 6/9 lactone rings, neoabyssomicin B (2) featuring a 12-membered macrolactone ring and its seco-form, neoabyssomicin C (3), along with the known abyssomicin 2 (4) and 4 (5), were discovered from the deep-sea derived Streptomyces koyangensis SCSIO 5802. The structures of 1–3 were elucidated on the basis of MS, NMR spectroscopic and X-ray diffraction data analyses. A plausible biogenetic relationship of 1–5 is proposed. Additionally, compound 4 shows antibacterial activities against a panel of Gram-positive pathogens, including clinical MRSA strains, with MICs of 3–15 μg/mL; compounds 1 and 3 also were found to augment HIV-1 virus replication in a human lymphocyte model. Graphical abstract image
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(2S,4R)-Hyp-(S)-Phe-OMe dipeptide supported on imidazolium tagged molecules as recoverable organocatalysts for asymmetric aldol reactions using water as reaction medium ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Arturo Obregón-Zúñiga, Eusebio Juaristi Four novel chiral imidazolium tagged molecules derived from dipeptide (2S,4R)-Hyp-(S)-Phe-OMe were prepared and evaluated as organocatalysts in the asymmetric aldol reaction using water as solvent. It was found that catalysts incorporating the hexanoyl linker are active down to 5 mol% and afford aldol products with up to 94% yield, up to 98:2 dr and up to 97:3 er. This chiral imidazolium catalyst was reused up to 6 times without any loss in the stereoselectivity of asymmetric aldol reactions. By contrast, organocatalysts containing an acetyl linker proved to be highly unstable in protic solvents, and for that reason they could not be recovered and reused. Graphical abstract image
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Reaction of 9-oxabicyclo[4.2.1]non-7-ene-1-ol with tetrazine: An unusually facile intramolecular rearrangement ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Afşin A. Kaya, Emine Salamci, Abdullah Menzek, Safiye S. Erdem, Ertan Şahin, Kadriye Ecer Reaction of (1S*,7R*)-9-oxabicyclo[4.2.1]non-7-en-1-ol (5) with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (6) produced (2R*,4R*)-dimethyl 4-(7-oxooxepan-2-yl)-1,4-dihydropyridazine-3,6-dicarboxylate (11) in a one-pot reaction involving cycloaddition at ambient conditions. The structure of the rearrangement product 11 was determined by X-ray crystallographic analysis. Its formation was discussed based on experimental studies and density functional theory calculations. The driving force of this unusually facile reaction was the stability of the caprolactone product 11 and the extremely exorgenic loss of N2. Structural factors facilitating this rearrangement were also explored employing PCM//M06-2X/6-31G(d, p) calculations. Graphical abstract image
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Regioselective bromination: Synthesis of brominated methoxyquinolines ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Osman Çakmak, Salih Ökten Simple synthetic methods are described for the synthesis of valuable polyfunctional brominated methoxyquinolines 10–13, 20–21, and 24–25. Three regioselective routes are described for convenient preparation of brominated methoxyquinolines at the C-2, C-3, and C-5 positions with consecutive reaction steps under mild reaction conditions using molecular bromine. While bromination of 6-bromo-8-methoxy-1,2,3,4-tetrahydroquinoline (8) selectively gave 3,6-dibromo-8-methoxyquinoline (10) and 3,5,6-tribromo-8-methoxyquinoline (11), the reaction of 6,8-dimethoxy-1,2,3,4-tetrahydroquinoline (9) resulted in the formation of 3-bromo-6,8-dimethoxyqinoline (12) and tribromide 13. On the other hand, direct bromination of 6-methoxy- 17 and 6,8-dimethoxyquinoline (19) gave 5-bromo derivatives 20 and 21. However, the reaction 3,6-dimethoxyquinoline (8) resulted in dibromination to form 2,5-dibromoquinoline (24). This process selectively led to functionalization of the quinoline ring at both the C-2 and C-5 positions. Graphical abstract image
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Influence of upper rim dibromo-substitution in bis-1,3-diketone calix[4]arenes on spectral properties of ligands and their lanthanide complexes ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Sergey N. Podyachev, Gulnaz Sh. Gimazetdinova, Svetlana N. Sudakova, Nataliya A. Shamsutdinova, Dmitry V. Lapaev, Victor V. Syakaev, Aidar T. Gubaidullin, Rinas N. Nagimov, Asiya R. Mustafina The present work introduces the synthesis and characterization of upper rim dibromo-substituted bis-1,3-diketone calix[4]arenes with hydroxy and propyloxy groups at the lower rim as ligands for Gd3+ and Tb3+ complexes. The dibromo-substitution does not affect 1:1 complex formation with the lanthanide ions arising from their coordination via two 1,3-diketonate groups incorporated at the upper rim of the calix[4]arene. The analysis of the time-resolved luminescence spectra of the Gd3+ complexes clearly demonstrates the notable enhancement of the decay time of the ligand triplet state, while the energy of the triplet state for the new dibromo-bis-1,3-diketones remains practically unchanged versus its non-substituted analogues. The latter tendency points to the heavy-atom effect on the energy transfer from the excited state to vibration levels of the dibromo-substituted ligand resulting in a decreased radiationless decay contribution. Measurements of Tb3+-centered luminescence indicate a better antenna effect (∼1.7) of dibromo-calix[4]arenes compared with its non-substituted counterpart. Graphical abstract image
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Improved biooxidation of Benzyl alcohols catalyzed by the flavoprotein (5-Hydroxymethyl)furfural oxidase in organic solvents ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Mathias Pickl, Etta Jost, Silvia M. Glueck, Kurt Faber The biooxidation of benzylic alcohols catalyzed by (5-hydroxymethyl)furfural oxidase (HMFO) to the corresponding benzaldehydes or benzoic acids was investigated in the presence of various organic (co)solvents. Whereas the enzyme activity decreased at elevated concentrations of water-miscible polar solvents, the presence of (halogenated) hydrocarbons was tolerated up to 90% (v/v), which led to drastically improved conversions of up to >99% in case of hexafluorobenzene. This remarkable effect was correlated with the improved solubility of O2 in the employed solvents. Reaction rates were boosted by O2-saturation of solvents. Graphical abstract image
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Asymmetric ortho-deprotonation of (η6-arene) chromium tricarbonyl complexes substituted with a chiral hydroxylamine ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): M. Rute G. da Costa, M. João M. Curto, Stephen G. Davies, Fátima C. Teixeira, James E. Thomson The use of O-methyl-N-(α-methylbenzyl)hydroxylamine as a novel chiral auxiliary in asymmetric ortho-deprotonation of the (η6-arene) chromium tricarbonyl complexes is described. Upon quenching of the resultant ortho-lithiated complex with an electrophile, 1,2-disubstituted (η6-arene) chromium tricarbonyl complexes were obtained in good yield and excellent levels of diastereoselectivity. Graphical abstract image
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A fluorescence “turn-on” sensor for multiple analytes: OAc− and F− triggered fluorogenic detection of Zn2+ in a co-operative fashion ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Zannatul Kowser, Ummey Rayhan, Shofiur Rahman, Paris E. Georghiou, Takehiko Yamato 7-tert-Butylpyrene-1-azine-salicylaldehyde, L1 has been synthesized as a dual fluorescent chemosensor based on an excited state intramolecular proton transfer (ESIPT) mechanism. Ligand L1 undergoes AcO−/F− triggered sharp fluorescence enhancement towards Zn2+ in a co-operative fashion to form a complex with 2:1 stoichiometry. In order to investigate the influence of the 7-tert-butyl group, pyrene-1-azine-salicylaldehyde, L2 was also prepared. With ligand L1, fluorescence enhancement in acetonitrile solution is found to be twice as large than with ligand L2. The association constants of L1(O−)2 ⊃Zn2+ in the presence of AcO− and F− were determined to be K a2 = 9.2 × 108 M−1 and 1.5 × 106 M−1, respectively using a 2:1 binding model. The results of a DFT interaction study were consistent with the experimental results. Graphical abstract image
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Deprotection of silyl ethers by using SO3H silica gel: Application to sugar, nucleoside, and alkaloid derivatives ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Hideaki Fujii, Naoyuki Shimada, Masaki Ohtawa, Fumika Karaki, Masayoshi Koshizuka, Kohei Hayashida, Mitsuhiro Kamimura, Kazuishi Makino, Tohru Nagamitsu, Hiroshi Nagase We applied a desilylation procedure using SO3H silica gel, with the surface modified by alkylsulfonic acid groups, to silylated sugar, nucleoside, and alkaloid derivatives. The treatment with SO3H silica gel provided desilylated products in good to excellent yield. In the reactions of sugar and nucleoside derivatives, no silyl residue was detected in the crude products, but the crude products of the reaction of alkaloids contained small amounts of silyl residues. Even though the sugar and nucleoside derivatives had a labile glycosyl and CN bond, respectively, these bonds tolerated the reaction conditions. These outcomes suggested that the desilylation procedure using SO3H silica gel would be applicable to the deprotection of a variety of types of compounds protected by silyl groups. In a gram scale experiment, the desilylation procedure successfully proceeded without the observation of any silyl residue in the crude product. Graphical abstract image
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Stereochemical correction and total structure of roridin J ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Manami Matsumoto, Atsushi Ito, Akio Tonouchi, Masaaki Okazaki, Masaru Hashimoto The (2′Z)-configuration of roridin J (1) was revised to the (2′E) form by conducting NOE experiments. Although the configurations with respect to the stereogenic carbons on the macrocyclic ring of 1 had remained unknown, a combination of NMR analysis and molecular modeling calculations revealed the (2′E,5′R,6′S,7′E,9′Z,13′S) form. In addition, the modeling calculations successfully reproduced the 1H and 13C NMR chemical shifts as well as the ECD spectrum. An X-ray crystallographic analysis verified all the relative configurations. Graphical abstract image
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“One-pot” sequential preparation of isoquinoline-1,3(2H,4H)-dione derivatives by reacting N-alkyl(aryl)-N-methacryloyl benzamides with benzyl alcohols and sodium benzenesulfinates ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Qiujie Tang, Ping Xie, Jin Wang, Jiajun Lin, Chunlai Feng, Charles U. Pittman, Aihua Zhou Two cascade coupling reactions were developed between N-alkyl(aryl)-N-methacryloyl benzamides and readily available benzyl alcohols or sodium benzenesulfinates. Through a radical cyclization strategy, these one-pot sequential reactions provided two simple and efficient approaches to the synthesis of a variety of isoquinoline-1,3(2H,4H)-dione derivatives in high yields with a broad substrate scope. These compounds are valuable molecules in drug discovery. Graphical abstract image
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Base-catalyzed bis-sulfenylation of γ-substituted butenolides for the synthesis of α,α-bisthiofunctionalized butenolide derivatives ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Jian-Qiang Zhao, Shu-Wen Luo, Xiao-Mei Zhang, Xiao-Ying Xu, Ming-Qiang Zhou, Wei-Cheng Yuan A method for the synthesis of α,α-bisthiofunctionalized butenolide compounds has been successfully developed. The bis-sulfenylation of γ-substituted butenolides at α-position is promoted by using triethylamine as the catalyst and N-(aryl(alkyl)sulfanyl)succinimides or N-(phenylsulfanyl)phthalimides as sulfenylating reagents under mild reaction conditions. A range of α-sulfenylated butenolide derivatives could be smoothly obtained in moderate to excellent yields. A preliminary attempt at the catalytic asymmetric α-sulfenylation of α-methyl-γ-phenyl-substituted butenolide was also conducted and afforded promising enantioselectivity. Graphical abstract image
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Phenolic polyketides from the marine alga-derived Streptomyces sp. OUCMDZ-3434 ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Haishan Liu, Zhengbo Chen, Guoliang Zhu, Liping Wang, Yuqi Du, Yi Wang, Weiming Zhu Five new phenolic polyketides, namely 3-O-methylwailupemycin G (1), wailupemycin J (2), R- and S-wailupemycin K (3 and 4) and wailupemycin L (5), as well as the known enterocin (6) and 5-deoxyenterocin (7) were isolated and identified from the fermentation broth of Streptomyces sp. OUCMDZ-3434 associated with the marine green algae, Enteromorpha prolifera. Their structures including absolute configurations were elucidated according to the spectroscopic analysis, X-ray single crystal diffraction and the Mosher's experiments. Compound 1 showed comparable α-glucosidase inhibition with an IC50 value of 0.86 mM to acarbose (IC50 1.12 mM), and compound 4 was cytotoxic on the HeLa cell with an IC50 value of 8.2 μM. Compounds 2, 3 and 7 showed anti-H1N1 virus activity with 47.8%, 42.5% and 60.6% inhibitions, respectively at 50 μg/mL (ribavirin, 45.3% inhibition). Graphical abstract image
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Methimazolium-based ionic liquid crystals: Emergence of mesomorphic properties via a sulfur motif ()
Publication date: 7 September 2017 Source:Tetrahedron, Volume 73, Issue 36 Author(s): Stephen T. Nestor, Benoît Heinrich, Richard A. Sykora, Xiaofei Zhang, Gregory J. McManus, Laurent Douce, Arsalan Mirjafari We describe the proficient synthesis and thermotropic mesomorphicity of thioether–functionalized imidazolium–type ionic liquids containing C12 and C18 chains associated with Br− and OTf− anions. The mesomorphic behavior and phase transition temperatures were studied by Polarizing Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Small-Angle X-ray Scattering (SAXS). The ionic liquids with bromide anion display Smectic A lamellar phase giving homeotropic and fan-shaped textures. The layered crystallographic structure is reported by Single-Crystal XRD. The electrochemical characteristics of the ionic liquids with C18 side chain have been determined via Cyclic Voltammetry. Graphical abstract image
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Editorial board ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35
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Catechol amide iron chelators produced by a mangrove-derived Bacillus subtilis ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Jingyan Li, Shaowei Liu, Zhongke Jiang, Chenghang Sun A novel triscatecholamide siderophore derivative, linear tribenglthin A (1), together with well known congener, bacillibactin (2) as well as mentioned monomer unit, benglthin were found in the secondary metabolites of a magrove-derived Bacillus subtilis subsp. spizizenii MMB-016. The structure of 1, determined by extensive 1D and 2D NMR studies has an unusual nonproteinogenic amino acid, Z-dehydrobutyrine (Z-Dhb) residue to reveal a putative lantibiotic synthetase function involved in the iterative biosynthesis of non-ribosomal peptide (NRP). Our 1H–15N correlation spectroscopy of 2 resulted in a correction of previous NH assignment of bacillibactin, as well as a new evaluation of DPPH free radical scavenging potential suggested antioxidant activity. Benglthin monomer was isolated as a ferrous complex (3), unveiling an interestingly higher affinity for iron Fe(Ⅱ) than trimers, 1 and 2. No dimeric forms were found. Graphical abstract image
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Self-assembly, AIEE and mechanochromic properties of amphiphilic α-cyanostilbene derivatives ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Yanming Ren, Ruilin Zhang, Chao Yan, Tingyan Wang, Huifang Cheng, Xiaohong Cheng A series of amphiphilic α-cyanostilbene derivatives consisting of an α-cyanostilbene rodlike core with lipophilic and flexible alkyl chains at one end and a polar glycerol group at the opposite end have been synthesized and investigated by polarizing microscopy, DSC, X-ray scattering, SEM, UV-vis spectroscopy and photoluminescence measurements. These compounds can self-assemble into liquid crystalline phase sequence of SmA- Colhex/p6mm- CubI/ P m 3 ¯ n in the bulk states and multistimuli responsive organogels in organic solvents. They have reversible photoresponsive properties in solution, liquid crystalline state and gel state. They also show aggregation-induced enhanced emission (AIEE) property, meanwhile, they present excellent mechanochromic behavior and have a good reversibility of fluorescence conversion upon grinding-fuming process. Graphical abstract image
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Synthesis of pyridines with an amino acid residue by [2+2] cycloadditions of electron-poor acetylenes on enaminone systems derived from N-Boc protected amino acids ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Benjamin Prek, Jure Bezenšek, Branko Stanovnik In this paper we present a pyridine synthesis, starting from N-protected amino acids. Amino acids are firstly converted to an ynone system, which is later converted to an enaminone system. Following a formal [2 + 2] cycloaddition of electron poor acetylenes and subsequent ring closure the final products are pyridines bearing an amino-acid substituent. Graphical abstract image
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Self-assembled organic microfibers and nanofibers of 2,6-diphenyl dihydrodipyrrolopyrazine (DP-DPP) derivatives for optoelectronic applications ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Puttavva Meti, Jung-Won Yang, Young-Dae Gong Microfibers and nanofibers with promising application in optoelectronics are desirable in current material synthesis. Synthetic method has been developed for the preparation of dipyrrolopyrazine derivatives by employing palladium catalysed Buchwald and Sonogashira coupling reactions. A comprehensive study on the synthesis, optical properties, thermal stability and morphology of DP-DPP derivatives 8(a–d) were carried out. Surface morphological analysis showed the formation of microfibers, square facets and nanorods. Electrochemical studies revealed HOMO energy levels in the range of −5.10 to −5.88 eV and LUMO energy levels in the range −2.49 to −3.12 eV. All compounds exhibited a high degree of thermal stability and decomposition temperature of 322–372 °C. The enhanced air durability and thermal stability combined with good morphology makes DPP as a promising candidate for optoelectronic application. Graphical abstract image
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Nitrene insertion into an adjacent o-methoxy group followed by nucleophilic addition to the heterocumulene intermediate: Experimental and computational studies ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Sambasivan V. Eswaran, Divneet Kaur, Kalyanashis Jana, Krishnendu Khamaru, Sripadi Prabhakar, Partha Raghunathan, Bishwajit Ganguly The chemistry of aryl azides and aryl nitrenes is rich and varied in nature with different products being obtained with minor changes in reaction conditions. Thermolysis of azido- dimethylsuccinylosuccinate has been carried out to study the behaviour of this new azide during thermolysis. The products obtained have been studied by various spectroscopic and DFT calculations. These results reveal formation of compound-II and compound-III from the nitrene intermediate (1) generated during the thermolysis process. DFT results rationalized the formation of thermodynamically stable compound-II and compound-III from the stable intermediates 2 and 4 formed during the thermolysis process. Further, DFT results suggest that the reaction between 4 and 2 is thermodynamically more favourable compared to the further thermal degradation of the intermediate 4 to pyridylcarbene (4b) and carbene intermediate (5), which corroborates that such products were not formed during thermolysis. Graphical abstract image
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Polyethylene glycol methacrylate-grafted dicationic imidazolium-based ionic liquid: Heterogeneous catalyst for the synthesis of aryl-benzo[4,5]imidazo[1,2-a]pyrimidine amines under solvent-free conditions ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Mudumala Veeranarayana Reddy, Kang Rok Byeon, Su Hong Park, Dong Wook Kim A novel polyethylene glycol methacrylate-grafted tetra-ethylene glycol-bridged dicationic imidazolium-based ionic liquid (PEGMA-g-TEGBDIM) was prepared by grafting tetra-ethylene glycol-bridged 1-vinyl imidazolium mesylate to the surface of cross-linked polyethylene glycol methacrylate. Its structure was characterized by FT–IR, NMR, TGA, and XPS. Due to the combination of polymer-supports and flexible imidazolium linkers, it acted as a heterogeneous catalyst to exhibit excellent catalytic activity for the efficient synthesis of N-methyl-2-nitro-aryl-benzo[4,5]imidazo[1,2-a]pyrimidine amines via the multicomponent reaction of 1H-benzo[d]imidazol-2-amine (1) and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (3) with a variety of aldehydes under solvent-free conditions. Moreover, PEGMA-g-TEGBDIM was easily reused and it maintained its high catalytic activity and stability even after seven reaction-cycles. This protocol perfectly obeys the features of green chemistry, including having no waste regarding side-products, being solvent-free, and having free from column chromatographic purification. Graphical abstract image
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Concise access to primin, miconidin and related natural resorcinols ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Miroslav Sisa, Marcela Dvorakova, Tomas Vanek An efficient and short synthetic procedures affording the biologically active natural products primin, miconidin, olivetol, grevillol, and cardol (adipostatin A) in high yields are reported. The two strategies involve Sonogashira and Suzuki cross-couplings as the crucial steps for the installation of the alkyl side-chains. Syntheses start from cheap, commercially available 1-bromo-3,5-dimethoxybenezene to obtain 1,3-dimethoxy-5-(alk-1-yn-1-yl)benzene as the key intermediate. This intermediate can be easily and economically oxidized to provide primin in excellent overall yield while avoiding undesired side products by the virtue of its symmetry. The demethylation of the key intermediate affords natural resorcinols olivetol, grevillol, and cardol, respectively. The reduction of primin provides its hydroquinone derivative miconidin. Graphical abstract image
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A comprehensive test of computational approaches for evaluation of cyclodextrin complexes. Self-inclusion in monosubstituted β-cyclodextrins – a case study ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Oleg Lukin, Grygoriy Dolgonos, Jerzy Leszczynski An in-depth theoretical analysis of two monosubstituted cyclodextrins (CDs) has been performed in order to find the appropriate level of theory capable of the correct qualitative description of their experimentally evidenced self-inclusion phenomenon. The correct increased stability of conformations with substituents included into the cavity (‘IN’ conformations) compared with those in which substituents point outside the cavity (‘OUT’ conformations) is qualitatively predicted by molecular mechanics, the dispersion-corrected self-consistent-charge density-functional tight-binding (SCC-DFTB-D), dispersion-corrected density-functional theory (DFT-D), single-point second-order Møller–Plesset (MP2), and domain based local pair natural orbital coupled cluster (DLPNO-CCSD(T)) computations. The latter four approaches provide also quantitative insights into the relative stability of the ‘IN’ and ‘OUT’ conformations. The method of choice for the fast evaluation of the stability order of the CD conformations is the SCC-DFTB-D that yields relative energies with nearly DFT-D and MP2 accuracy. Graphical abstract image
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A novel water soluble self-assembled supramolecular sensor based on pillar[5]arene for fluorescent detection CN− in water ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Qi Lin, Lu Liu, Feng Zheng, Peng-Peng Mao, Juan Liu, You-Ming Zhang, Hong Yao, Tai-Bao Wei Efficiently sensing target ions in water solution is still an intriguing challenge. Herein, we report a novel and efficient approach for high fluorescent detection ions in water by a pillar[5]arene-based supramolecular sensors. This novel approach is illustrated as follows. Firstly, water soluble cationic pillar[5]arene (P5) and acid functionalized naphthalene monoimide derivative (N2) were self-assembled in water and formed supramolecular sensor (P5N2). Then, competitive coordination was rationally introduced into the supramolecular sensor P5N2 by adding Al3+ in suit and formed new supramolecular sensor (P5N2Al). Interestingly, the supramolecular sensor P5N2 could sense Al3+ in water, while the supramolecular sensor P5N2Al could sense CN− in water with high selectivity and sensitivity, respectively. Therefore, it's a novel and facile way for the design of sensor which could efficiently sense ions in water. Graphical abstract image
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Orbital interaction between electron lone pair and carbonyl group in N-trifluoroacetylpiperidine and N-piperidine amides: Planar and non-planar nitrogen bond configurations ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Sergey A. Shlykov, Tran Dinh Phien, Nguyen Hoang Trang Molecular structure of N-trifluoroacetylpiperidine (NFAPi) was studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS), IR spectroscopy and quantum chemical (QC) calculations. Due to the influence of strong conjugation between the electron lone pair on the nitrogen atom and the double bond of the carbonyl group, NFAPi may exist as only one conformer, in which the trifluoroacetyl group is located in an intermediate, between axial and equatorial, position. Nine atoms (two Cα atoms along with their Heq atoms, the nitrogen atom, the carbonyl group and one CF fragment of the trifluoromethyl group) form a single plane. In contrast, partition of the conjugation between the double CO bond and the two lone pairs leads to coexisting intermediate and axial, in 1-piperidinecarboxamide, and axial and equatorial forms in N, N-dimethyl-1-piperidinecarboxamide and 1,1′-carbonyldipiperidine. The conformational ratio for the latter ones is Eq:Ax≈50:50%. The steric effect and conjugation stabilize the axial conformer. Graphical abstract image
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Synthesis and application of a novel asymmetric azo reagent: 1-(tert-butyl)-2-(4-chlorobenzyl) azodicarboxylate (tBCAD) ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Jian Xie, Cai Xu, Qianjin Dai, Xiaozhong Wang, Gang Xu, Yingqi Chen, Liyan Dai A series of novel asymmetric azo reagents, 1-(tert-butyl)-2-(4-substituted benzyl) azodicarboxylate, were prepared. The synthetic process has the advantage of simpleness, easy operation, mild reaction condition and high yield. The 1-(tert-butyl)-2-(4-chlorobenzyl) azodicarboxylate (tBCAD) was selected for its stability and convenience to handle, and its precursor can be recycled by recrystallization with toluene. The tBCAD and DIAD were applied to a wide variety of Mitsunobu reactions. The experimental results showed that the performance of tBCAD in Mitsunobu reaction was comparable to that of DIAD, while the stability of tBCAD was much better than DIAD. Thus, tBCAD can be a novel, stable, effective azo-reagent for the Mitsunobu reaction. Graphical abstract image
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Discovery of highly functionalized scaffolds: Pyrroloimidazolediones as P2X7 receptor antagonists ()
Publication date: 31 August 2017 Source:Tetrahedron, Volume 73, Issue 35 Author(s): Germain Homerin, Emmanuelle Lipka, Benoît Rigo, Régis Millet, Xavier Dezitter, Christophe Furman, Alina Ghinet A broad range of pyrroloimidazolediones, new highly functionalized bicyclic heterocycles, was obtained by a cycloaddition reaction between l-pyroglutamide derivatives and Bredereck's reagent. Methanolysis of subsequent pyrroloimidazolediones provided antagonists of P2X7 receptor, with retention of initial stereoconfiguration, with potential applications in the treatment of inflammatory and neurological diseases. We have thus developed a new synthesis of lactamic nitrogen free enaminones which is currently the easiest method cited in the literature to access these compounds. Graphical abstract image
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Editorial board ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34
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Enantioselective β-hydroxy thioesters formation via decarboxylative aldol reactions of malonic acid half thioesters with aldehydes promoted by chloramphenicol derived sulfonamides1 ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Yafeng Wang, Guanxin Huang, Sha Hu, Kaijun Jin, Yan Wu, Fener Chen A highly enantioselective synthesis of chiral β-hydroxy thioesters that uses a decarboxylative aldol reaction of malonic acid half thioesters and aldehydes catalyzed by a chloramphenicol base-derived bifunctional organocatalyst is reported. The resulting chiral β-hydroxy thioesters were obtained in high yields (up to 82%) with good to excellent enantioselectivities (up to 94% ee). The synthetic application of the methodology is illustrated by the asymmetric synthesis of the selective serotonin reuptake inhibitor dapoxetine. Graphical abstract image
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Asymmetric total syntheses of teretifolione B and methylteretifolione B via Diels-Alder reaction of optically active pyranobenzyne and substituted furans ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Kazuaki Katakawa, Mika Kainuma, Katsuya Suzuki, Saori Tanaka, Takuya Kumamoto We report the asymmetric total syntheses of teretifolione B and methylteretifolione B, which are benzochromenes originally isolated from Conospermum plants. The synthesis involves enzymatic asymmetric transesterification of racemic acetoxychromene and construction of the basic framework via Diels-Alder reaction of optically active pyranobenzyne and substituted furans. The absolute configuration of the chiral chromene was unambiguously determined by asymmetric total synthesis of teretifolione B and its characterization. The first asymmetric total synthesis of methylteretifolione B was achieved in a similar manner and its absolute configuration, for which direct proof has not been reported, was established. Graphical abstract image
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A new regiospecific synthesis method of 1H-pyrazolo[3,4-b]quinoxalines – Potential materials for organic optoelectronic devices, and a revision of an old scheme ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Andrzej Danel, Katarzyna Wojtasik, Paweł Szlachcic, Marlena Gryl, Katarzyna Stadnicka A series of 6-substituted-1,3-diphenyl-1H-pyrazolo[3,4-b]quinoxalines were prepared using a new synthetic pathway: reductive cyclization of appropriate 5-(o-nitrophenyl)-pyrazoles with ferrous oxalate or triphenylphosphine. The main advantage of this procedure is that, contrary to the older protocols of pyrazolo[3,4-b]quinoxaline synthesis, this method allows for a substituent to be introduced to the carbocyclic ring without the formation of isomers. The pyrazole ring can also be modified to some extent. Furthermore, we propose a new mechanism for the oldest reported pyrazolo[3,4-b]quinoxaline synthesis, based on the condensation between o-phenylenediamine and 3,4-pyrazolin-5-diones. Graphical abstract image
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Simple synthesis of 3-hydroxyquinolines via Na2S2O4-mediated reductive cyclization of (2-(2-nitrophenyl)oxiran-1-yl)(aryl)methanones (o-nitrobenzalacetophenone oxides) ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Vakhid A. Mamedov, Vera L. Mamedova, Victor V. Syakaev, Dmitry E. Korshin, Gul'naz Z. Khikmatova, Ekaterina V. Mironova, Olga B. Bazanova, Il'dar Kh. Rizvanov, Shamil K. Latypov An efficient sodium dithionite (Na2S2O4)-mediated method for construction of 3-hydroxyquinolines via in situ Meinwald rearrangement/intramolecular reductive cyclization of o-nitrobenzalacetophenone oxides has been developed. The practical approach is of excellent functional group compatibility with as high as 98% yield under mild reaction conditions. Moreover, further manipulation successfully furnished 4-bromo substituted derivatives which may provide a promising potential application in exploring biologically active analogs of 3-hydroxyquinolines. Graphical abstract image
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Highly efficient and selective red-emitting Ca2+ probe based on a BODIPY fluorophore ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Rui Liu, Xiao Cai, Yang Li, Senqiang Zhu, Jinyang Hu, Hongjun Zhu A red-emitting Ca2+ probe based on difluoro-boron-dipyrromethene (BODIPY) fluorophore and 1,2-bis(o-aminophenoxy)ethane-N,N,-N′,N'-tetra acetic acid (BAPTA) moiety was designed and synthesized. Four electron-donating 4-methoxyphenyl groups were introduced on BODIPY to make the emission of probe more bathochromic-shifted. Upon Ca2+ binding, the probe exhibits a significant increase of red fluorescence intensity (λ max = 631 nm, Φ F = 0.18), an excellent luminescence ON/OFF ratio (43-fold) and a detection limit of 39 μM. Furthermore, this probe shows desirable sensitivity and selectivity for Ca2+ over other metal ions, which could be potentially applied for Ca2+ detection. Graphical abstract image
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Synthesis of 2-carboxylated aza-ring derivatives through α-monohalogenation/ring-contraction of N-sulfonyl lactams ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Fatih Sirindil, Solène Miaskiewicz, Nicolas Kern, Arno Lalaut, Anne-Sophie Felten, Jean-Marc Weibel, Patrick Pale, Aurélien Blanc 2-Carboxylated aza-rings have been synthesized in two steps through a highly selective monohalogenation of N-sulfonylated lactams of various ring sizes (from 5- to 8-membered rings) followed by a ring contraction reaction. The selective monohalogenation of N-sulfonyl lactams has been achieved in modest to excellent yields (9 examples, 39–96%) using N-halogenosuccinimides via the in situ generation of trimethylsilyl ketene aminal derivatives. The so-obtained α-halogeno N-sulfonyl lactams were engaged in a ring opening/ring closing reaction in the presence of various alcohols or anilines under basic conditions affording 2-carboxylated aza-rings, such as azetidine, pyrrolidine or piperidine derivatives in high yields (24 examples, 61–99%). Graphical abstract image
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Construction and single crystal structures of pseudo[1]rotaxanes based on pillar[5]arene mono-pyridylimine derivatives ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Shuo Jiang, Ying Han, Jing Sun, Chao-Guo Yan A series of functionalized pillar[5]arenes mono-pyridylimine derivatives with different lengths of diaminoalkylene units as the side chains on the pillar[5]arene's rim were conveniently synthesized. The investigation of 1H NMR spectra and single crystal structures indicated that the formation of free forms or pseudo[1]rotaxanes turned out to be controlled by both the axle lengths of diaminoalkylene chains and the solvent effect. The pillar[5]arene mono-pyridylimines with short hydrazinyl and diaminoethylene chains exist in free form. On the other hand, pillar[5]arene mono-pyridylimines with longer than diaminopropylene chains formed stable pseudo[1]rotaxanes both in solution and in the crystal state. Graphical abstract image
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Novel quinoxaline derivative: Solubilization by surfactant solutions and membranotropic properties ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Alla B. Mirgorodskaya, Farida G. Valeeva, Dinar R. Gabdrakhmanov, Liliya V. Mustakimova, Lucia Ya. Zakharova, Oleg G. Sinyashin, Vakhid A. Mamedov Novel compound, (E)-3-([1,2,4]triazolo[4,3-a]quinoxalin-4(5H)-on-1-yl)acrylic acid, containing triazole and quinoxaline moieties has been synthesized and characterized. The solubility of the compound in water and surfactant solutions has been estimated at different pH. It has been shown that the increase in solubility is due to hydrophobic effect as well as electrostatic interactions. The capability of this compound to integrate within dipalmitoylphosphocholine lipid bilayer has been evaluated. An increase in membranotropic properties after encapsulation of this compound in nanocontainers based on dicationic surfactant has been exhibited. Graphical abstract image
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Highly diastereoselective synthesis of novel 2,3,4-trisubstituted chromanes via the reaction of 3-nitro-2-(trihalomethyl)- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Vladislav Y. Korotaev, Igor B. Kutyashev, Alexey Y. Barkov, Vyacheslav Y. Sosnovskikh The reaction of 3-nitro-2-trifluoro(trichloro)methyl- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene under the conditions of kinetic or thermodynamic control led to the formation of products due to enamine addition at the C-4 atom of chromene as individual cis,trans- or trans,trans-isomers, differing by the position of double bond in the enamine moiety. Hydrolysis of these compounds in dilute HCl did not cause changes of pyran ring configuration and provided the respective 4-(cyclopentanon-2-yl)chromanes with anti-configuration of hydrogen atoms at the С-4 and С-2′ atoms. Stereochemistry of the obtained compounds was confirmed by X-ray structural analysis. Graphical abstract image
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New generation of tetrapyrazolic macrocycles: Synthesis and examination of their complexation properties and antibacterial activity ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Tarik Harit, Reda Bellaouchi, Chakib Mokhtari, Brahim El Bali, Abdeslam Asehraou, Fouad Malek The synthesis of three macrocycles, containing four pyrazolic units, with different side arms is described and the crystal structure of one of the intermediate compounds is also presented. The complexing properties of these compounds towards alkaline metal ions (Cs+, K+, Na+ and Li+) was studied by the liquid–liquid extraction process. The percentage values of extraction were determined by atomic absorption measurements and UV spectroscopy. These macrocycles extract selectively K+ and highlight the good effect of using a long side chain bearing a donor group, on the percentage of extraction of the alkali cations K+, Na+ and Li+. They also showed a good antibacterial against Gram-positive and Gram-negative microorganisms with minimum inhibitory concentrations at the range of 32–64 μg/mL. Graphical abstract image
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One-pot, four-component synthesis of spiroindoloquinazoline derivatives as phospholipase inhibitors ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Maryam Beyrati, Maryam Forutan, Alireza Hasaninejad, Erik Rakovský, Somayyeh Babaei, Ammar Maryamabadi, Gholamhossein Mohebbi An efficient, one-pot, two-step, four-component reaction for the synthesis of spiroindoloquinazoline derivatives in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) is described. The syntheses are achieved by the condensation reaction of isatin derivatives, isatoic anhydride, malononitrile and carbonyl compounds under reflux in acetonitrile. Several of the resulting compounds showed moderate activity as phospholipase A2 inhibitors. Graphical abstract image
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The reactivity of arylphosphine oxides under Bouveault-Blanc reaction conditions ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Ewelina Korzeniowska, Anna E. Kozioł, Elżbieta Łastawiecka, Anna Flis, Marek Stankevič Treatment of tertiary arylphosphine oxides with alkali metal/alcohol reagent system lead to the corresponding cyclohexyl-substituted phosphine oxides. This transformation makes use of the inexpensive sodium as the electron donor and an alcohol as the proton source, and provides an attractive alternative to reactions mediated by expensive transition metals. Under optimized conditions numerous mono- and diaryl substituted phosphine oxides were transformed into the corresponding mono- and dicyclohexyl-substituted phosphine oxides in good yields. Furthermore, the formation of 1,2-bis(phosphinoyl)cyclohexanes or unknown 5,10-dialkyltetradecahydrophosphanthrene 5,10-dioxides as side products was observed, which are hardly accessible by other procedures. Graphical abstract image
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A highly efficient and recyclable silica-supported tungstic acid (STA) catalyst for the synthesis of pyrano[3,2-c]chromen-5-ones under solvent free conditions ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Amol Maruti Jadhav, Suresh Kumar Krishnammagari, Jong Tae Kim, Yeon Tae Jeong A simple, efficient, green and solvent-free procedure for the synthesis of pyrano[3,2-c]chromen-5-ones has been developed by multi-component condensation of 4-hydroxycoumarin, aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine in the presence of a catalytic amount of silica-supported tungstic acid (STA). The reaction transformation presumably occurs via Knoevenagel condensation, Michael addition, imine-enamine tautomerism intramolecular, O-cyclization, elimination of MeSH. The present environmentally benign protocol offers several advantages such as shorter reaction times, a wide range of functional group tolerance, use of an inexpensive heterogeneous catalyst, and high yield of products via a simple experimental and work-up procedure. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields. Graphical abstract image
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Bafilomycins N and O, novel cytotoxic bafilomycin analogues produced by Streptomyces sp. GIC10-1 isolated from marine sponge Theonella sp. ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Yu-Hsin Chen, Juan-Cheng Yang, Mei-Chin Lu, Ching-Feng Weng, Yin-Di Su, Jimmy Kuo, Yang-Chang Wu, Ping-Jyun Sung Two novel 16-membered tetraene marcolides, bafilomycins N (1) and O (2), along with two known analogues, JBIR-100 (3) and bafilomycin K (4) were produced from isolate GIC10-1, a Streptomyces sp. strain that was originally cloned from bacterial communities associated with marine sponge Theonella sp. The structures of new bafilomycins 1 and 2 were established by using spectroscopic methods and comparing the spectroscopic data with those of known related metabolites. Compounds 1 and 2 were proven to be the first 14-methylbafilomycins to be isolated. Cytotoxicity of these compounds toward various cancer cell lines also is described. Graphical abstract image
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3-Methyl-4-nitro-5-isatylidenyl-isoxazoles as 1,3-dipolarophiles for synthesis of polycyclic 3,3′-pyrrolidinyl-dispirooxindoles and their biological evaluation for anticancer activities ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Bing Lin, Wen-Hui Zhang, Dan-Dan Wang, Yi Gong, Qi-Di Wei, Xiong-Li Liu, Ting-Ting Feng, Ying Zhou, Wei-Cheng Yuan Developed herein is a diversity-oriented one-pot multicomponent synthesis of polycyclic 3,3′- pyrrolidinyl-dispirooxindoles 3 via a multicomponent 1,3-dipolar cycloaddition event of 3-methyl-4-nitro-5-isatylidenyl-isoxazoles 2 with azomethine ylides (thermally generated in situ from isatins and proline or thioproline). Products bearing four consecutive stereocenters consist of two oxindole moieties and a polycyclic pyrrolidinyl core, including vicinal spiroquaternary stereocenters fused in one ring structure were smoothly obtained in high yields (up to 85% yield) with good diastereoselectivity (up to >20:1). Valuable features of this method were application of 3-methyl-4-nitro-5-isatylidenyl-isoxazoles as 1,3-dipolarophiles and the design of new hybrid architectures for biological screenings through the adequate fusion of these sub-units of isoxazole and 3,3′-pyrrolidinyl-dispirooxindole, generating drug-like molecules. Graphical abstract image
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Rhodamine based turn-on fluorescent sensor for Hg2+ and its application of microfluidic system and bioimaging ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Chuantao Liu, Ting Xiao, Yuchen Wang, Fang Wang, Xiaoqiang Chen In this paper, a new rhodamine derivative bearing thiazole and thiocarbonyl moieties 1 was synthesized and its sensing behaviors toward various metal ions were investigated by fluorescence spectroscopies and UV/Vis. The ring-opening process of spirolactam enables the selective fluorescence enhancement and colorimetric change for Hg2+ in CH3CN-HEPES buffer (0.01 M, pH 7.4) (3:7, v/v). The selectivity and sensitivity of 1 towards Hg2+ lead to sensor 1 applied to microfluidic device and even used to functions Hg2+ sensing in Hela cells. Graphical abstract image
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Elemental sulfur mediated cyclization via redox strategy: Synthesis of benzothiazoles from o-chloronitrobenzenes and benzyl chlorides ()
Publication date: 24 August 2017 Source:Tetrahedron, Volume 73, Issue 34 Author(s): Xin Wang, Dazhuang Miao, Xiaotong Li, Renhe Hu, Zhao Yang, Ren Gu, Shiqing Han A novel metal-free synthesis of 2-substituted benzothiazoles from easily available o-chloronitrobenzenes and benzyl chlorides using elemental sulfur as traceless oxidizing agent has been developed. The protocol provides a simple, efficient, and atom-economic way to access to benzothiazoles in moderate to excellent yields. And the approach exhibited good functional group tolerance. Graphical abstract image
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