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14 March 2018
Editorial Board
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11

14 March 2018
Recent topics of the stereodivergent synthesis of natural products
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Hiroyoshi Takamura A variety of natural products, a valuable source of drug lead compounds, coexist with their stereoisomers as congeners. For pursuing the structural elucidation and the structure–activity relationship study of natural products, it is needed to establish the streamlined synthetic route to supply natural products and their stereoisomers. Divergent pathway is one of the synthetic strategies to deliver more than one target compound. In this digest, selected examples of the stereodivergent approach toward the synthesis of natural products are described. Especially, this digest focuses on common synthetic intermediates and stereodiversification steps from the common intermediates to reach the target compounds.

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14 March 2018
Direct, high-yielding, one-step synthesis of vic-diols from aryl alkynes
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): P. Veeraraghavan Ramachandran, Michael P. Drolet An unprecedented, high yielding, direct, one-step synthesis of vic-diols from alkynes has been developed via metal-free, open-to-air dihydroboration with ammonia borane. The electronics of the alkyne and the reaction stoichiometry are critical for obtaining optimal yields of the 1,2-diol.

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14 March 2018
Organic superbase-induced chemiluminescent decomposition of a hydroxyaryl-substituted dioxetane: Unique effect of a bifunctional guanidine base on the chemiluminescence profile of a bicyclic dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Nobuko Watanabe, Ayu Wakatsuki, Hisako K. Ijuin, Yoshio Kabe, Masakatsu Matsumoto Organic superbases represented by TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) effectively induced the decomposition of hydroxyaryl-substituted dioxetanes in acetonitrile to give bright light. The color of the chemiluminescence from a dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety varied depending on the base used. In addition to this change in the color of emission, TBD increased the chemiluminescence efficiency 2- to 5-fold compared to the results with other base systems and accelerated decomposition of the dioxetane. These unique effects of TBD may be due to its “bifunctional” character, which is different from those of other organic superbases. Chemiluminescent decomposition of the dioxetane was effectively induced by superbases even in apolar p-xylene.

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14 March 2018
20-(N-Methylpyridiniumyl)ethynylated chlorophyll-a derivative with an intense Qx absorption band at a green to orange region
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Yusuke Kamatani, Yuichi Kitagawa, Hitoshi Tamiaki Methyl 20-substituted mesopyropheophorbides-a were prepared by the chemical modification of natural chlorophyll-a via palladium-catalyzed cross-coupling reactions. The 20-ethynylation and further 2-pyridylation showed bathochromic shifts in their visible absorption bands as well as hyperchromic effects of the Qx bands in a diluted chloroform solution. The protonation and methylation at the nitrogen atom of the 202-pyridyl group induced much larger shifts and effects, especially giving red-shifted and intensified Qx bands.

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14 March 2018
A highly efficient reusable homogeneous copper catalyst for the selective aerobic oxygenation sulfides to sulfoxides
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Cheng Ren, Runxing Fang, Xiaochun Yu, Shun Wang Readily available copper showed efficient activity and great selectivity for the homogeneous catalysis of oxidation of sulfides to sulfoxides using molecular oxygen as the oxidant. The reaction proceeds under mild conditions in the presence of a catalytic amount of TEMPO. Importantly, the catalysts could be conveniently recovered and reused. And this methodology was proved to be applicable for the transformation of various aromatic and aliphatic sulfides into the corresponding sulfoxides with high conversion and high selectivity.

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14 March 2018
Synthesis of 2-selenoxo DHPMs by Biginelli reaction with Hf(OTf)4 as catalyst
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Peiran Chen, Mengdi Tu By using Hf(OTf)4 as catalyst, a series of 2-selenoxo DHPMs have been synthesized efficiently in good yields by Biginelli reaction with selenourea as starting material.

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14 March 2018
Continuous flow reaction system for the synthesis of 2,2,2-trichloroacetophenone derivatives and its application
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Byeng Ha Ko, Subeen Yu, Kwang Ho Song, Sunwoo Lee A continuous flow reaction system was developed for the synthesis of 2,2,2-trichloroacetophenone derivatives. When aryl propiolic acids and water were mixed with trichloroisocyanuric acid in DMF at 5
14 March 2018
Two novel iridoid derivatives isolated from Phlomis likiangensis
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Xiao-Hui Li, Li-He Lu, Xu-Hong Li, Yun-Biao Li, Yuan-Chang Duan, De-Huan Fu, Shuang-Xi Mei, Tao Cui, Jing-Kun Wang, Zhao-Yun Zhu The extract of the aerial and underground parts of Phlomis likiangensis afforded two new iridoid derivatives, namely as phloloside H (1) and phloline (2), along with four known compounds (36), and compound 2 was a novel normonoterpene. Their structures were elucidated on the basis of spectroscopic studies and chemical methods. Six compounds were assayed for cytotoxic, antibacterial and antioxidative activities, but were either inactive or very weakly active.

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14 March 2018
d-Mannitol-derived novel chiral thioureas: Synthesis and application in asymmetric Henry reactions
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Miaoxi Liu, Nan Ji, Li Wang, Peng Liu, Wei He Five novel thioureas have been obtained through multi-step reactions from d-Mannitol as starting material and applied as catalysts in the asymmetric Henry reaction. Using catalyst 7a, (1S,2R)-2-nitro-1-phenylpropan-1-ol containing two chiral centers was obtained in high yield and with high selectivity (up to 95% yield, 87% ee, 91:9 dr). This catalyst also retained activity in the presence of water, affording a up to 93% yield, 88% ee, and 94:6 dr.

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14 March 2018
The first synthesis of cis-N,N
14 March 2018
Synthesis and stereochemistry of JBIR-81, a peptide enamide derived from aspergilli
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Ryo Katsuta, Mami Toyoda, Arata Yajima, Ken Ishigami, Tomoo Nukada The absolute stereochemistry of an aspergilli-derived peptide enamide, JBIR-81, was determined to be 12S, 15S by the first synthesis of (12S,15S)-JBIR-81 and its epimer. The overall yield was 56% over six steps from N-methyl-l-leucine. The (Z)-enamide structure was effectively constructed with use of a copper (I) catalyzed coupling reaction between a vinyl halide and a carboxamide.

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14 March 2018
One-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Adisak Thanetchaiyakup, Hassayaporn Rattanarat, Nutthawat Chuanopparat, Paiboon Ngernmeesri A simple and efficient one-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions has been developed. When 2-fluorobenzaldehyde was treated with substituted 2-methylindoles in the presence of Cs2CO3, the desired products were typically obtained in good to excellent yields. This reaction sequence involves a nucleophilic aromatic substitution and a Knoevenagel condensation reaction. Our mechanistic investigation revealed that both reactions could proceed as an intermolecular reaction in the first step.

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14 March 2018
TBHP-promoted oxidative cyclization of o-alkynylquinoline aldehydes: Metal/additive-free domino synthesis of pyrano[4,3-b]quinolin-1-ones
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Jay Bahadur Singh, Kalpana Mishra, Tanu Gupta, Radhey M. Singh TBHP-promoted domino synthesis of pyrano[4,3-b]quinolin-1-ones is described from o-alkynylquinoline aldehydes. The radical reaction proceeded without metal and additive via oxidation of aldehydic C-H bond into C-OH bond followed by intramolecular 6-endo-dig cyclization. The probable mechanism is discussed.

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14 March 2018
Synthesis of star-shaped pyrrole-based C3-symmetric molecules via ring-closing metathesis, Buchwald–Hartwig cross-coupling and Clauson–Kaas pyrrole synthesis as key steps
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Sambasivarao Kotha, Saidulu Todeti, Tarasankar Das, Anindya Datta We have demonstrated three contrasting synthetic strategies to assemble pyrrole-based C 3-symmetric molecule. Here, ring-closing metathesis (RCM), Buchwald–Hartwig cross-coupling and Clauson–Kaas pyrrole synthesis have been used as key steps. Interestingly, readily available starting materials such as 4-aminoacetophenone, 4-bromo acetophenone and 4-nitro acetophenone have been used as starting materials. Grubbs’ first generation catalyst (G-I) is useful for one-pot RCM and aromatization sequence without the involvement of additional reagents. We also report photophysical properties of these star-shaped molecules.

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14 March 2018
Enantioselective biomimetic transamination of
14 March 2018
Stirring-controlled mono or double aminocarbonylation of 1,3-bis(2-iodoaryl)propan-2-amines
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Huaanzi Hu, Zeqiang Xie, Shuang Luo, Qiang Zhu A palladium-catalyzed highly selective mono or double aminocarbonylation of 1,3-bis(2-iodoaryl)propan-2-amines under balloon pressure of CO has been developed. Tetracyclic isoquinolino[2,3-b]isoquinolinones were obtained through double aminocarbonylation when the reaction was stirred overnight, as most of organic reactions being operated. We accidentally found that monocarbonylated isoquinolinone products could be formed in good selectivity and chemical yield just without stirring the reaction mixture. The low concentration of CO in the still solution may account for the selectivity.

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14 March 2018
Practical way for the synthesis of 3,3
14 March 2018
Cycloadditions between methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate and various tosylacetamides: Synthesis of trifluoromethylated pyroglutamates and 2-pyridones derivatives
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Hong-Hai Zhang, Wei Shen, Long Lu Cycloaddition reactions between methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate and various 2-tosylacetamides are described. Various 2-tosylacetamides react with methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate in the presence of NaH at room temperature in one step to form trifluoromethylated pyroglutamates as single diastereomers. However, employing the same reactants using t-BuOK as base at
14 March 2018
Catalyst-free Petasis-type reaction: Three-component decarboxylative coupling of boronic acids with proline and salicylaldehyde for the synthesis of alkylaminophenols
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Babak Kaboudin, Ali Zangooei, Foad Kazemi, Tsutomu Yokomatsu A simple method is reported for the synthesis of alkylaminophenols in moderate to good yields via a three-component, catalyst-free decarboxylative coupling of proline with salicylaldehyde and boronic acids.

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14 March 2018
Pd-catalyzed Suzuki/Sonogashira cross-coupling reaction and the direct sp3 arylation of 7-chloro-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Mohammed Loubidi, Ana
14 March 2018
An unusual reaction of a Reissert compound involving alkylation, rearrangement, SNAr and SET processes
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Harry W. Gibson, Zhenbin Niu, Minjae Lee, Terry L. Price, Daniel V. Schoonover, Michael A.G. Berg Reaction of isoquinoline Reissert compound 1 with NaH and then isopropyl iodide in DMF at 22
14 March 2018
Synthesis and characterization of cyclophane: The highly selective recognition of Fe3+ in aqueous solution and H2PO4
14 March 2018
Direct arylation for the synthesis of 2-arylquinolines from N-methoxyquinoline-1-ium tetrafluoroborate salts and arylboronic acids
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Xiaoxiao Ren, Shuaijun Han, Xianying Gao, Jingya Li, Dapeng Zou, Yangjie Wu, Yusheng Wu A rapid and direct arylation reaction of N-methoxyquinoline-1-ium tetrafluoroborate derivatives and arylboronic acids with high regioselectivety at room temperature was discovered. The reaction shows exceptional functional group tolerance and broad substrate scope regarding both the quinoline derivatives and the arylboronic acids.

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14 March 2018
Palladium-catalyzed cyclizative carbonylation of azobenzenes toward 3H-Indazol-3-ones using formic acid as CO source
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11 Author(s): Ning Gu, Song Sun, Jiang Cheng A palladium-catalyzed cyclizative carbonylation of azobenzenes has been developed to access 1-acyl 2-aryl 3H-indazol-3-ones in moderate to good yields with good functional compatibility. This procedure proceeded with the sequential ortho-C–H carbonylation and cyclization, where formic acid served as the CO source. The practicability of this transformation was further increased by the employment of facilely available azobenzenes derivatives as one-handled starting materials.

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14 March 2018
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Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11

14 March 2018
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Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11

7 March 2018
Graphical abstract TOC
Publication date: 14 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 11

7 March 2018
Editorial Board
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10

7 March 2018
Transition metal-mediated or catalyzed hydrocarboxylation of olefins with CO2
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Yu-Xin Luan, Mengchun Ye The development of new methods to incorporate carbon dioxide into organic molecules is of special significance and interest as it is an abundantly available and recyclable C1 source. Catalytic hydrocarboxylation of readily available olefins with CO2 represents a highly atom- and step-economic approach toward transformations of CO2 into widely-used aliphatic acids. However, due to relatively lower reactivity of them, this goal has been always a formidable challenge. Herein we review relevant progress on transition metal-mediated or catalyzed methodologies toward the desired hydrocarboxylation, with an emphasis on the development of two main pathways, including transition-metal-catalyzed cyclometallation of olefin and CO2 and direct addition of alkylmetal to CO2.

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7 March 2018
Recent advances in C(sp3)H bond carbonylation by first row transition metals
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Nimmakuri Rajesh, Nagaraju Barsu, Basker Sundararaju Carbonylation is one of the most valuable processes both in academia and industry. Direct functionalization of inert C(sp2)H bond into C(sp2)-carbonyl derivatives was actively pursued over decades using noble metals. But the corresponding C(sp3)H bond carbonylation is a challenging area and only few examples were known till now. Utilization of first row transition metals as an alternative to their noble partners is more sustainable. In this context, use of first row transition metals for direct C(sp3)H bond functionalization is burgeoning as an exciting area. This digest review covers some of the recent achievements in this regard especially using Ni, Co and Cu as first row transition metals. The reported approaches are categorized in two types: directed and non-directed activation/functionalization of C(sp3)H bonds using carbon monoxide gas or its surrogates as a C1 source.

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7 March 2018
Hydrogen bond donor solvents enabled metal and halogen-free Friedel–Crafts acylations with virtually no waste stream
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Guangchang Liu, Bo Xu We have developed a metal and halogen-free Friedel–Crafts acylation protocol with virtually no waste stream generation. We propose a hydrogen bonding donor solvent will form a hydrogen bonding network and may provide significant rate enhancement for Friedel–Crafts reactions. Trifluoroacetic acid is one of the strongest H-bond donor solvents, which is also volatile and can be easily recovered by distillation without need for reaction workup. Our protocol is a ‘green’ Friedel–Crafts acylation process: 1) the catalyst can be recovered and reused; 2) using halogen free starting material (carboxylic acids anhydride or carboxylic acids); 3) no need for aqueous reaction work-up; 4) minimum or no waste steam generation.

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7 March 2018
Cationic ruthenium complex of the formula [RuCl(2,6-diacetylpyridine)(PPh3)2]BArF and its catalytic activity in the formation of enol esters
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Matthew J. Stark, Douglas T. Tang, Nigam P. Rath, Eike B. Bauer A new ruthenium 2,6-diacetylpyridine complex was synthesized and applied in the atom-economic synthesis of enol esters through Markovnikov-directed addition of carboxylic acids to terminal alkynes. The ruthenium complex [RuCl(dap)(PPh3)2]+BArF
7 March 2018
Synthesis and spectral properties of non-symmetrical red and near IR emitter dibenzoBODIPYs
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Mustapha Khelladi, Nicolas Leclerc, Denis Jacquemin, Antoinette De Nicola, Gilles Ulrich New symmetrical and non-symmetrical benzoBODIPYs have been synthesized from diketones. For the two series the 3 and 5 positions have been substituted by different aromatic rings and onto benzo sub-units different groups have been introduced. The methodology of diketones self-condensation provides symmetrical dyes. By cross-condensation reaction, these positions can be differentiated and specific functions connected to the desired positions. These molecules have been fully characterized and their optical properties analyzed by both experimental and theoretical means. They are red to NIR emitters with a range of emission from 679 to 780
7 March 2018
Research on Liebeskind-Srogl coupling/intramolecular Diels-Alder reaction cascade
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Tomohiro Fujii, Yuta Oki, Masahisa Nakada The Liebeskind-Srogl coupling/intramolecular Diels-Alder (IMDA) reaction cascade that stereoselectively affords a tricarbocyclic compound with a transtrans-cis fused ring system including an all-carbon quaternary stereogenic center at the ring junction is described. The cascade reactions proceed quickly and stereoselectively afford the products within 2
7 March 2018
Diastereoselective synthesis of 5,5-disubstituted 3,3-difluorotetrahydrofurans
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Satoru Arimitsu, Makoto Nakasone, Emi Gima The diastereoselective synthesis of 5,5-disubstituted 3,3-difluorotetrahydrofurans 2 was achieved using
7 March 2018
A comparative study using conventional methods, ionic liquids, microwave irradiation and combinations thereof for the synthesis of 5-trifluoroacetyl-1,2,3,4-tetrahydropyridines
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Valquiria P. Andrade, Mateus Mittersteiner, M
7 March 2018
Palladium-catalyzed coupling of 2-en-4-yne carbonates with terminal alkynes
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Do
7 March 2018
Graphene oxide (GO) catalyzed transamidation of aliphatic amides: An efficient metal-free procedure
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Suchandra Bhattacharya, Pranab Ghosh, Basudeb Basu Transamidation involves direct interconversion of an amide with amine, and represents an alternative to the common method of amide formation from the reaction of carboxylic acid with an amine. While the carboxamides have huge potential in biological systems and polymer industries, their formation from carboxylic acids requires activation by a suitable catalyst. A metal-free transamidation of aliphatic amide with aromatic amine catalyzed by graphene oxide (GO) has been developed and established as a general, synthetically useful and selective procedure. Graphene oxide bearing several carboxylic acids on the edges and having large surface area acts as an efficient and recyclable catalyst for transamidation.

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7 March 2018
The facile and efficient organocatalytic platform for accessing 1,2,4-selenadiazoles and thiadiazoles under aerobic conditions
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): V.P. Rama Kishore Putta, Raghuram Gujjarappa, Nagaraju Vodnala, Richa Gupta, Prasad P. Pujar, Chandi C. Malakar The first organocatalytic approach towards synthesis of rarely explored 1,2,4-selenadiazole and thiadiazole scaffolds have been devised using corresponding carboxamides as substrates. The transformations were realized using two distinct conditions in the presence of catalytic vitamin B3 or thiourea under aerobic conditions. Developed methods overcome the associated limitations of previous reported approaches and the desired products were obtained in high yields and selectivity without the formation of toxic side-products.

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7 March 2018
Regioselective intramolecular annulations of ambident
7 March 2018
Synthesis of 2-unsubstituted imidazolones from bisamides via a one-pot, domino dehydration/base promoted cyclisation process
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Dimitrije Djukanovic, Milos Petkovic, Milena Simic, Predrag Jovanovic, Gordana Tasic, Vladimir Savic A one-pot, domino process was developed as an alternative approach for the preparation of 2-unsubstituted imidazolones. The methodology utilizes readily accessible bisamides, which upon a dehydration/cyclisation sequence produced imidazolones in good yields. The transformation relies on the compatibility of the dehydrating agent and base, and the reaction conditions tolerate various functional groups.

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7 March 2018
Charge-tagged polar phosphine ligands in Pd-catalysed reactions in aqueous and ionic media
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Vivien L. van Zyl, Alfred Muller, D. Bradley G. Williams A new range of polar imidazolium and phosphate-containing ligands was synthesised from readily available starting materials in high yielding multi-step transformations. These ligands were used to generate Pd catalysts for Suzuki and Heck C–C coupling reactions in organic and organic/aqueous media. The catalysts performed well in aqueous media in the Suzuki reaction and less well in the Heck reaction, related to substrate solubility in the aqueous media. When moving to ionic liquids, the Heck reaction dramatically improved, especially in media compatible with the polar catalysts and the non-polar reagents. In all cases, the catalysts were stable to the formation of Pd black, a form of degradation that frequently befalls Pd catalysts. The catalysts could be successfully recycled without loss of activity.

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7 March 2018
Substituent effect on the reaction pathway of Au(I)-catalyzed ene-yne cycloisomerization
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Yuta Oki, Masahisa Nakada The Au(I)-catalyzed ene-yne cycloisomerization pathway which is highly dependent on the substrate structures is described. The steric and electronic effects of substrate substituents could be important factors inducing the formation of the desired and undesired products. Comparison between the Au(I)-catalyzed reactions of substrates bearing the substituted phenyl moiety with and without methoxy group suggests that the methoxy group would direct the formation of undesired products through a cationic intermediate. This intermediate could be formed via aryl moiety attack presumably induced by the methoxy group at the para position. The use of nitrile groups instead of ester groups in the substrate effectively leads to the preferential formation of the desired product. This is probably because 1,3-diaxial interactions in the transition state of the Au(I)-catalyzed ene-yne cycloisomerization would be reduced by the use of the relatively small nitrile group. This steric effect is different from the electronic effect of the methoxy group of the aryl moiety, which makes the undesired reaction pathway favorable.

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7 March 2018
Research on Au(I)-catalyzed ene-yne cycloisomerization for construction of quassinoid scaffold
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Yuta Oki, Masahisa Nakada Compounds that undergo Au(I)-catalyzed cycloisomerizations affording tetracyclic products that can be converted into compounds with the skeleton of bruceantin are described. The Au(I)-catalyzed cycloisomerizations reported herein are hindered by a 1,3-diaxial interaction between the substituent and the methyl group in the transition state. The use of small substituents was found to increase the yield of the desired product, while the reaction of substrates with large substituents afford undesired constitutional isomers.

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7 March 2018
An alternative route to tethered Ru(II) transfer hydrogenation catalysts
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Roy Hodgkinson, V
7 March 2018
Identification of the new chymotrypsin inhibitor micropeptin 996 by metabolomics-guided analysis
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Wendy K. Strangman, Allison K. Stewart, Megan C. Herring, Jeffrey L.C. Wright An untargeted metabolomics approach was used to investigate a cultured strain of Microcystis aeruginosa (UTEX LB2386) known to be a prolific producer of a diverse class of cyanopeptides. Identification of a putative new compound with a molecular weight of 996 led to the purification and structure elucidation of this new member of the micropeptin class of cyanopeptides. Micropeptin 996 displayed potent inhibition of the serine protease enzyme chymotrypisin relative to structurally related members of this class.

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7 March 2018
Thermolysis reactions of N-alkyl-N
7 March 2018
Base-catalyzed cascade 1,6-sulfur-Michael/Henry reaction of trifluoromethyl-substituted styrylisoxazoles: Diastereoselective synthesis of tetrahydrothiophenes with a trifluoromethylated quaternary center
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Yong Zhang, Yu-Ping Wang, Jin Ge, Guo-Wei Lai, Dong-Liang Lu, Jin-Xiang Liu, Xun Li An effective diastereoselective [3+2] annulation of 1,4-dithiane-2,5-diol to trifluoromethyl-substituted styrylisoxazoles catalyzed by DABCO is described, giving highly functionalized tetrahydrothiophenes containing trifluoromethylated quaternary center in excellent yields and diastereoselectivities.

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A six-step synthetic approach to marine natural product (+)-aureol
Publication date: 7 March 2018
Source:Tetrahedron Letters, Volume 59, Issue 10 Author(s): Jun-Li Wang, Hui-Jing Li, Meirong Wang, Jun-Hu Wang, Yan-Chao Wu A concise synthetic approach to the marine natural product (+)-aureol has been achieved from readily available starting materials using obviously fewer steps in comparison to the related report in literature (6 steps versus 12 steps from (+)-sclareolide). Key steps of this protocol include a boron trifluoride-catalyzed domino 1,2-H and 1,2-methyl shifts and a nickel(II)-catalyzed cross-coupling reaction between an alkyl iodide and an aryl Grignard reagent.

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