- Divergent Carbocatalytic Routes in Oxidative Coupling of Benzofused Heteroaryl Dimers: A Mechanistic Update
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Mildly thermal air or HNO3 oxidized activated carbons catalyse oxidative dehydrogenative couplings of benzo[b]fused heteroaryl 2,2’-dimers, e.g., 2-(benzofuran-2-yl)-1H-indole, to chiral 3,3’-coupled cyclooctatetraenes or carbazole-type migrative products under O2 atmosphere. DFT calculations show that the radical cation and the Scholl-type arenium cation mechanisms lead to different products with 2-(benzofuran-2-yl)-1H-indole, being in accord with experimental product distributions.
- Casadio, David S.,Aikonen, Santeri,Lenarda, Anna,Nieger, Martin,Hu, Tao,Taubert, Stefan,Sundholm, Dage,Muuronen, Mikko,Wirtanen, Tom,Helaja, Juho
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supporting information
p. 5283 - 5291
(2021/02/26)
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- Iodocyclisation of Electronically Resistant Alkynes: Synthesis of 2-Carboxy (and sulfoxy)-3-iodobenzo[ b ]thiophenes
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The iodocyclisation of alkynes bearing tethered nucleophiles is a highly effective method for the construction and diversification of heterocycles. A key limitation to this methodology is the 5-endo-dig iodocyclisation of alkynes that have an unfavourable electronic bias for electrophilic cyclisation. These tend to direct electrophilic attack of the iodonium atom to the wrong carbon for cyclisation, thus favouring competing addition reactions. Using our previously determined reaction conditions for the 5-endo-dig iodocyclisations of electronically resistant alkynes, we have achieved efficient synthetic access to 2-carboxy (and sulfoxy)-3-iodobenzo[b]thiophenes. The corresponding benzo[b]furans and indoles were not accessible under these conditions. This difference may arise due to the availability of a radical mechanism in the case of iodobenzo[b]thiophenes. The 2-carboxy functionality of the iodocyclised products can be further employed in iterative alkyne-coupling iodocyclisation reactions, where the carboxy group or an imine (Schiff base) partakes in a second iodocyclisation to generate a lactone or pyridine ring.
- Chen, Shuqi,Flynn, Bernard L.
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- Biomimetic carbene cascades enabled imine derivative migration from carbene -bearing thiocarbamates
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Inspired by the body circulation of Omeprazole (irreversible proton pump inhibitor), we disclose the carbene-triggered cascades for the synthesis of 2-aminobenzofuran derivatives from N-sulfonyl-1,2,3-triazoles or benzothioazole-bearing thiocarbamates, which represents an unprecedented imine derivative migration process. Furthermore, the desulfurizing reagent-free Barton-Kellogg-type reactions starting from N-sulfonyl-1,2,3-triazoles have also been achieved for the first time, and elemental sulfur is confirmed as a byproduct during this transformation. Both experimental data and DFT calculations further thoroughly explained the unique reactivity.
- Li, Xue,Chen, Haohua,Xuan, Qingqing,Mai, Shaoyu,Lan, Yu,Song, Qiuling
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p. 3518 - 3523
(2021/05/29)
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- Design, synthesis and application of triazole ligands in suzuki miyaura cross coupling reaction of aryl chlorides
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DFT calculations have been demonstrated to be a valuable tool for the mechanistic study of reaction which is difficult to acquire from pure experimental techniques. Structural, electronic and coordination aspects of synthesized triazole ligands were investigated theoretically by structure optimization on Gaussian 09 package by DFT approach at B3LYP/6-31G (d, p). HOMO-LUMO energy gaps correlated to its chemical reactivity and this information applied to interpret the role of ligand in the formation of ligand-metal complex. Electron rich environment around the triazole core stabilized the HOMO orbital and made these electrons available to form complex with Pd centre. The DFT calculations provide a plausible mechanism for the reaction that is consistent with the available experimental facts. A series of triazole ligands have been synthesized via efficient 1,3-dipolar cycloaddition of readily available azide and alkynes for coordination to Pd centre. Characterization of all the synthesized compounds was done by FTIR, 1H NMR, 13C NMR and HRMS. Their ligand-Pd complexes provided excellent yields in the Suzuki-Miyaura coupling reactions (up to 92% yield) of unactivated aryl chlorides. Ligand 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) was found to be most effective ligand because of electron donating 2,6 dimethoxy phenyl moiety attached to triazole ring at 4-position that facilitated the formation of electron rich ligand-catalyst complex. The complex favoured the oxidative addition step of Pd across the aryl chloride substrate and thus allowed for the development of highly active ligand-catalyst system for Suzuki reaction. During computational analysis, 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) also showed lowest band gap due to electron rich distribution pattern on the HOMO that are involve in ligand-Pd complex formation. Conclusively, these triazoles ligands were found to be more competent and attractive for palladium catalyst because of simplistic pathway for the synthesis of triazole motif and the ease of individual tuning of the substituents on triazole core or exocyclic to it.
- Jabeen, Sobia,Khera, Rasheed Ahmad,Iqbal, Javed,Asgher, Muhammad
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- B(C6F5)3-Catalyzed cyclization of alkynes: direct synthesis of 3-silyl heterocyclic compounds
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An efficient one-pot strategy for easy access to 3-silyl heterocyclic compounds was developedviaa B(C6F5)3-catalyzed cycloaddition reaction ofo-(1-alkynyl)(thio)anisoles oro-(1-alkynyl)-N-methylaniline. In this reaction, benzenethiophene, benzofuran or indole skeletons could be constructed by an intermolecular cyclization with diphenylsilane. This protocol elicited moderate-to-good yields with metal-free reaction systems.
- Li, Mengxing,Wang, Ting,An, Zhenyu,Yan, Rulong
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p. 11953 - 11956
(2020/10/15)
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- Regioselective Gold-Catalyzed Hydration of CF3- and SF5-alkynes
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The regioselective gold-catalyzed hydration of CF3- and SF5-alkynes is described. The corresponding trifluoromethylated and pentasulfanylated ketones are obtained in up to 91% yield as single regioisomers showcasing the use of CF3 and SF5 as highly efficient directing groups in this reaction. Notably, this transformation represents the first use of CF3- and SF5-alkynes in gold catalysis.
- Cloutier, Mélissa,Roudias, Majdouline,Paquin, Jean-Fran?ois
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supporting information
p. 3866 - 3870
(2019/05/24)
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- Synthesis of Triazole Click Ligands for Suzuki-Miyaura Cross-Coupling of Aryl Chlorides
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A series of new triazole ligands has been synthesized via copper-catalyzed cycloaddition reaction of readily available azides and alkynes. The synthesized compounds were characterized by FTIR, 1H and 13C NMR, and high-resolution mass spectra. The ligands provided excellent yields (up to 92%) in the palladium-catalyzed Suzuki-Miyaura cross coupling of unactivated aryl chlorides with phenylboronic acid. 1-Benzyl-4-(2,6-dimethoxyphenyl)-lH-1,2,3-triazole was found to be the most effective ligand due to the presence of electron-donating 2,6-dimethoxyphenyl substituent, which made it possible to develop a highly active ligand-catalyst system for the Suzuki reaction of aryl chlorides.
- Jabeen,Khera,Iqbal,Asgher
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p. 1416 - 1422
(2019/11/03)
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- DBU-Mediated Synthesis of Aryl Acetylenes or 1-Bromoethynylarenes from Aldehydes
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Two well known synthetic organic reactions Ramirez olefination and Corey-fuchs reactions are integrated in one-pot sequential manner for the synthesis of arylacetylenes and 1,3-enynes starting directly from commercially available aldehydes. The bicyclic amidine 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) along with additive NaOH not only exclusively afforded the terminal alkynes directly from the aldehydes, but also enhanced the reaction rate. The dynamic nature of DBU also facilitated the isolation of 1-bromoalkynes intermediate products. Selection of additive from NaOH and H2O served as a switch for the synthesis of terminal alkyne and 1-bromoalkynes, respectively. (Figure presented.).
- Thummala, Yadagiri,Karunakar, Galla V.,Doddi, Venkata Ramana
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supporting information
p. 611 - 616
(2019/01/04)
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- CO-Free Enantioselective Hydroformylation of Functionalised Alkenes: Using a Dual Catalyst System to Give Improved Selectivity and Yield
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The scope of carbon monoxide-free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2-bis-((2,5)-diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. (Figure presented.).
- Pittaway, Rachael,Dingwall, Paul,Fuentes, José. A.,Clarke, Matthew. L.
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p. 4334 - 4341
(2019/08/21)
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- A Traceless Tether Strategy for Achieving Formal Intermolecular Hexadehydro-Diels-Alder Reactions
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A synthetic strategy formally equivalent to an intermolecular hexadehydro-Diels-Alder (HDDA) reaction is described. Sulfur-based linkers were designed and constructed by joining terminal alkynes or diynes using alkyne thiolate chemistry. The resulting tetraynes and triynes successfully underwent HDDA cyclization and benzyne trapping. Linker removal by reductive desulfurization was uneventful. The strategy was also found suitable for the tetradehydro-Diels-Alder (TDDA) reaction.
- Smela, Merrick Pierson,Hoye, Thomas R.
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p. 5502 - 5505
(2018/09/12)
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- Cascade Annulation of 2-Alkynylthioanisoles with Unsaturated α-Bromocarbonyls Leading to Thio-Benzobicyclic Skeletons
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A protocol of Cu-catalyzed annulation of phenylethynylsulfanes with unsaturated α-bromocarbonyls for the construction of thio-benzobicyclic skeletons is described. In this single reaction, three new bonds and two new rings can be established, highlighting the step-economics and high efficiency of this protocol.
- Gao, Yuzhen,Zhang, Pengbo,Li, Gang,Zhao, Yufen
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p. 13726 - 13733
(2018/11/30)
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- Reaction discovery using acetylene gas as the chemical feedstock accelerated by the stop-flow micro-tubing reactor system
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Acetylene gas has been applied as a feedstock under transition-metal catalysis and photo-redox conditions to produce important chemicals including terminal alkynes, fulvenes, and fluorinated styrene compounds. The reaction discovery process was accelerated through the use of stop-flow micro-tubing reactors. This reactor prototype was developed by joining elements from both continuous micro-flow and conventional batch reactors, which was convenient and effective for gas/liquid reaction screening. Notably, the developed transformations were either inefficient or unsuccessful in conventional batch reactors. Its success relies on the unique advantages provided by this stop-flow micro-tubing reactor system.
- Xue, Fei,Deng, Hongping,Xue, Chengwen,Mohamed, Dara Khairunnisa Binte,Tang, Karen Yuanting,Wu, Jie
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p. 3623 - 3627
(2017/07/11)
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- Control of the Regioselectivity in Cobalt- versus Ruthenium-Catalyzed Alder-ene Reaction of Unsymmetrical 1,3-Diynes
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The Alder-ene reaction of trialkylsilyl-substituted 1,3-butadiynes with terminal alkenes was investigated utilizing a cobalt-based catalyst, and the results were compared with Alder-ene rections catalyzed by the [CpRu(H3CCN)3]PF6 catalyst. Obviously, the two catalysts gave complementary results of yn-dienes differing in the site where the new carbon-carbon bond was formed. Of particular interest are observations concerning the double bond migration within the alkene component. While simple alkenes gave exclusively the E-configuration, the application of 3-buten-1-ol resulted in the corresponding Z-double bond, indicating that the hydroxyl group acts as donor coordinating to the cobalt center and thereby altering the reaction pathway.
- Weber, Sebastian M.,Hilt, Gerhard
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supporting information
p. 564 - 567
(2017/02/10)
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- Halogen-Mediated Cascade Cyclization Reaction of Aryldiynes to Indeno[1,2-c]chromene Derivatives
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The halogen-mediated cyclization reaction of aryldiynes to produce halogenated indeno[1,2-c]chromene derivatives is described. Treatment of aryldiynes 1 with one equivalent of iodine gave iodinated indeno[1,2-c]chromenes 3 in good chemical yields. When two equivalents of iodine were employed into the reaction mixture, dimer 9 was obtained as the major products. On the other hand, reaction of two equivalents of CuBr2 with compounds 1 gave the brominated indeno[1,2-c]chromenes 4. The DFT calculation of the iodine-mediated cyclization reactions for molecules containing methoxy, carboxy, amino, and sulfide substituents were carried out in order to understand how the substituent affects the cyclization pathway.
- Chen, Chin-Chau,Wu, Man-Yun,Chen, Hsing-Yin,Wu, Ming-Jung
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p. 6071 - 6081
(2017/06/23)
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- Iron-Promoted Tandem Cyclization of 1,3-Diynyl Chalcogen Derivatives with Diorganyl Dichalcogenides for the Synthesis of Benzo[b]furan-Fused Selenophenes
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A double intramolecular 5-endo-dig cyclization of butyl[2-(phenylbuta-1,3-diynyl)phenyl]chalcogens has been employed in a selective preparation of benzo[b]chalcogenopheno[2,3-d]furans. Several reaction parameters were studied to determine the best reaction conditions and we observed that the reaction of butyl[2-(phenylbuta-1,3-diynyl)phenyl]chalcogens (0.25 mmol) with iron(III) chloride hexahydrate (2.0 equiv.) and diorganyl diselenides (1.75 equiv.) at reflux of dichloromethane was the most appropriate to give the products in 35–89% yields. These standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, fluorine, methoxy and heteroaryl. This protocol was also efficient for diorganyl diselenides but it was ineffective with diorganyl disulfides and ditellurides. In a competition among selenium, sulfur and oxygen nucleophiles we observed that the nucleophilicity and steric effects of the competing functional groups were determinant factors for the selectivity of the cyclization. The benzo[b]chalcogenopheno[2,3-d]furans had absorptions in the UV region (300–350 nm range) with molar absorptivity coefficient values ascribed to spin and symmetry allowed π–π* electronic transitions. An emission located in the purple region (380–440 nm range), with a Stokes shift of between 65–100 nm, is probably associated to the charge transfer character of the excited state. (Figure presented.).
- Neto, José S. S.,Iglesias, Bernardo A.,Back, Davi F.,Zeni, Gilson
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p. 3572 - 3585
(2016/11/25)
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- Iridium-Catalyzed Intramolecular Methoxy C?H Addition to Carbon–Carbon Triple Bonds: Direct Synthesis of 3-Substituted Benzofurans from o-Methoxyphenylalkynes
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Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C?H bond of a methoxy group in 1-methoxy-2-(arylethynyl)benzenes across a carbon–carbon triple bond took place efficiently either in toluene at 110 °C or in p-xylene at 135 °C in the presence of an iridium catalyst. The initial 5-exo cyclization products underwent double-bond migration during the reaction to give 3-(arylmethyl)benzofurans in high yields.
- Torigoe, Takeru,Ohmura, Toshimichi,Suginome, Michinori
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p. 10415 - 10419
(2016/07/21)
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- Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones
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Allyl, dimethylallyl and prenyl ethers derived from o-acylphenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs.
- Schmidt, Bernd,Riemer, Martin,Schilde, Uwe
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supporting information
p. 7602 - 7611
(2016/01/25)
-
- An efficient method for the production of terminal alkynes from 1,1-dibromo-1-alkenes and its application in the total synthesis of natural product dihydroxerulin
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An efficient method of preparing various terminal alkynes from 1,1-dibromo-1-alkenes by using TBAF (tetra-n-butylammonium fluoride) as a base and triphenylphosphane as a reductant was developed. This method is strong base and low/high temperatures free, and can tolerate a broad range of substrates. These advantages were well demonstrated by the application of this method to the total synthesis of polyene natural product dihydroxerulin.
- Liu, Shihui,Chen, Xiaobei,Hu, Yanwei,Yuan, Laiqi,Chen, Shaohua,Wu, Ping,Wang, Wei,Zhang, Shilei,Zhang, Wei
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p. 553 - 560
(2015/03/05)
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- Visible-Light-Promoted Vinylation of Tetrahydrofuran with Alkynes through Direct C-H Bond Functionalization
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(Chemical Equation Presented) Mild and direct C-H bond functionalizations and vinylations of tetrahydrofuran with alkynes have been accomplished through visible light photocatalysis, yielding a range of vinyl tetrahydrofurans under the synergistic actions of organic dye-type photocatalyst eosin Y, tert-butyl hydroperoxide (t-BuOOH), and a 45 W household lightbulb. A significant kinetic isotope effect (KIE) was recorded, which helps shed light on the mechanistic course.
- Li, Jing,Zhang, Jing,Tan, Haibo,Wang, David Zhigang
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p. 2522 - 2525
(2015/05/27)
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- One-pot synthesis of 1,3-enynes with a CF3 group on the terminal sp2 carbon by an oxidative Sonogashira cross-coupling reaction
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Oxidative Sonogashira cross-coupling reactions of (E)-trimethyl(3,3,3-trifluoroprop-1-enyl)silane with arylacetylene were achieved using silver fluoride and a palladium catalyst, to afford high yields of various 1,3-enynes with a CF3 group on the terminal sp2 carbon. Silver fluoride promoted C-Si bond dissociation and oxidation of palladium, enabling catalytic use of palladium.
- Ikeda, Akari,Omote, Masaaki,Kusumoto, Kana,Tarui, Atsushi,Sato, Kazuyuki,Ando, Akira
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p. 8886 - 8892
(2015/08/24)
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- Practical, modular, and general synthesis of 3-coumaranones through gold-catalyzed intermolecular alkyne oxidation strategy
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A gold-catalyzed intermolecular alkyne oxidation for the preparation of 3-coumaranones has been developed. Using 8-isopropylquinoline N-oxides as oxidants, the reactions of o-ethynylanisoles afford versatile 3-coumaranones in moderate to good isolated yields. The synthetic utility of this chemistry is also indicated by the synthesis of the natural product sulfuretin.
- Shu, Chao,Liu, Rongfu,Liu, Shuang,Li, Jian-Qiao,Yu, Yong-Fei,He, Qiao,Lu, Xin,Ye, Long-Wu
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supporting information
p. 91 - 95
(2015/02/19)
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- Palladium nanoparticles catalyzed Sonogashira reactions for the one-pot synthesis of symmetrical and unsymmetrical diarylacetylenes
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A variety of symmetrical and unsymmetrical diarylacetylenes are synthesized by ligand-free palladium nanoparticles catalyzed copper-free and amine-free Sonogashira cross-coupling reactions between aryl iodides and trimethylsilylacetylene (TMSA) under mild reaction conditions.
- Mandali, Pavan Kumar,Chand, Dillip Kumar
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- Synthesis of thieno-fused heterocycles through reiterative iodocyclization
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Iodocyclization of ethynyl methyl sulfides gives 3-iodo-2-thiomethyl heterocycles, setting up the synthesis of thieno-fused systems through a subsequent iteration of alkyne coupling and iodocylization. This approach can also be exploited in the synthesis of polyfused thiophenes. In developing this protocol it was necessary to address issues associated with unfavourable electronic bias and redox sensitivity in some substrates. The manner in which these have been addressed should prove useful elsewhere in iodocyclization chemisty.
- Aurelio, Luigi,Volpe, Rohan,Halim, Rosliana,Scammells, Peter J.,Flynn, Bernard L.
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p. 1974 - 1978
(2014/07/07)
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- Autotandem catalysis: Synthesis of pyrroles by gold-catalyzed cascade reaction
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A novel synthesis of substituted pyrroles by a gold(I)-catalyzed cascade reaction has been developed. The reaction proceeded with an autotandem catalysis consisting of an initial addition of gold-acetylide to an acetal moiety and was followed by gold-catalyzed 5-endo-dig cyclization and aromatization. Gold catalysts play a dual role in activating nucleophilicity or electrophilicity of terminal acetylenes by forming gold-acetylides or by π-coordination. The formal (3 + 2) annulation of two components provided a variety of substituted pyrroles in a modular fashion.
- Ueda, Hirofumi,Yamaguchi, Minami,Kameya, Hiroshi,Sugimoto, Kenji,Tokuyama, Hidetoshi
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p. 4948 - 4951
(2015/04/27)
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- Triflic acid mediated cascade cyclization of aryldiynes for the synthesis of indeno[1,2-c]chromenes: Application to dye-sensitized solar cells
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A new triflic acid (TfOH)-mediated cascade cyclization of ortho-anisole-substituted aryldiynes is described for the construction of indeno[1,2-c]chromenes. The cascade cyclization proceeds through an unusual TfOH-induced alkyne-alkyne cyclization followed by nucleophilic attack of the methoxy group on the benzylidene cation, which is completely different to the cyclization of ortho-aniline- or ortho-thioanisole-substituted aryldiynes. A new class of organic dyes with the indeno[1,2-c]chromene framework as both donor and π-linker were synthesized. These compounds exhibit high photovoltaic performances in dyesensitized solar cells (DSCs).
- Jiang, Hua,Ferrara, Giovanni,Zhang, Xuan,Oniwa, Kazuaki,Islam, Ashraful,Han, Liyuan,Sun, Ying-Ji,Bao, Ming,Asao, Naoki,Yamamoto, Yoshinori,Jin, Tienan
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p. 4065 - 4070
(2015/10/19)
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- Regio- and stereoselective dimerization of arylacetylenes and optical and electrochemical studies of (E)-1,3-enynes
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The N-heterocyclic carbene palladium complex (SIPr)Pd(cinnamyl)Cl [SIPr=N,N'-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) promotes regio- and stereospecific dimerization of a variety of arylalkynes to give (E)-1,3-enynes in good to excellent yields. An efficient and practical procedure for their synthesis was developed using a biphasic aqueous alkali/heptane system. Optical and electronic properties of (E)-1,3-enynes are highly tunable. Depending on the nature of the substituents, HOMO energies vary in the range 5.3-6.0eV. (E)-1,3-Enynes can exhibit intense photoluminescence in the spectral region 350-500nm.
- Morozov, Oleg S.,Asachenko, Andrey F.,Antonov, Denis V.,Kochurov, Vitaly S.,Paraschuk, Dmitry Yu.,Nechaev, Mikhail S.
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supporting information
p. 2671 - 2678
(2014/09/29)
-
- Synthesis, DNA-binding abilities and anticancer activities of triazole-pyrrolo[2,1-c][1,4]benzodiazepines hybrid scaffolds
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We synthesized a new series of PBD-hybrid derivatives having tethered triazoles and investigated for their cytotoxicity. The studies indicated that cis-olefin compounds induce higher cytotoxicity with increase in the G1 cell cycle phase compared with the trans-compounds. Quantitative RT-PCR assay indicated that compounds (16a-d) induced G1 phase arrest through down-regulation of cyclin D1 and up-regulation of p21, p27, and p53 mRNA expressions. Compounds 16a-d induced A375 early apoptosis as detected by flow cytometry after double-staining with annexin V and propidium iodide. Moreover, the Western blot analysis showed that A375 treated by compounds (16a-d) resulted in decreased levels of Bcl-2 and Bcl-xL, increased levels of Bax and Bad, and caspase/PARP degradation to identify apoptotic cells.
- Chen, Chung-Yu,Lee, Pei-Hua,Lin, Yong-Yong,Yu, Wen-Ting,Hu, Wan-Ping,Hsu, Chia-Chen,Lin, Ying-Ting,Chang, Long-Sen,Hsiao, Cheng-Tien,Wang, Jeh-Jeng,Chung, Mei-Ing
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p. 6854 - 6859
(2014/01/06)
-
- One-pot, two-step conversion of aldehydes to phosphonyl- and sulfonylpyrazoles using Bestmann-Ohira reagent
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A one-pot, two-step, three-component method for the conversion of commercially available aldehydes to phosphonylpyrazoles has been developed, demonstrating, for the first time, the dual reactivity of the Bestmann-Ohira reagent (BOR) in a single-pot transformation. This method, extended to the synthesis of sulfonylpyrazoles by employing BOR in the first step and a diazomethyl sulfone in the second step, is complementary, with regard to regioselectivity, to the previous methods for the synthesis of such functionalized pyrazoles.
- Kumar, Rahul,Verma, Deepti,Mobin, Shaikh M.,Namboothiri, Irishi N. N.
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supporting information; experimental part
p. 4070 - 4073
(2012/09/21)
-
- Synthesis of aryl alkynyl carboxylic acids and aryl alkynes from propiolic acid and aryl halides by site selective coupling and decarboxylation
-
The coupling of propiolic acid with aryl iodides afforded the aryl alkynyl carboxylic acids and aryl alkynes in generally good yields. Aryl alkynyl carboxylic acids were obtained when the reaction was performed in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %) and DBU (5 equiv) at 50°C. For the synthesis of the terminal aryl alkynes, the reaction was conducted in the presence of Pd(PPh3) 2Cl2 (2.5 mol %), dppb (5.0 mol %), DBU (5.0 equiv), and Cu(acac)2 (10 mol %) at 25°C for 5 h, and further reacted at 60°C for 6 h.
- Park, Kyungho,Palani, Thiruvengadam,Pyo, Ayoung,Lee, Sunwoo
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experimental part
p. 733 - 737
(2012/03/08)
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- Cs2CO3-mediated synthesis of terminal alkynes from 1,1-dibromo-1-alkenes
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An unprecedented route to prepare terminal alkynes from 1,1-dibromo-1-alkenes mediated by Cs2CO3 was proven. 1,1-Dibromo-1-alkenes bearing various functional groups were efficiently converted to corresponding terminal alkynes in moderate to excellent yields.
- Zhao, Ming,Kuang, Chunxiang,Yang, Qing,Cheng, Xuezhi
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scheme or table
p. 992 - 994
(2011/03/22)
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- Simple and practical one-step synthesis of new 1,3-dienic δ-sultones from terminal alkynes and some synthetic applications of these compounds
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1,3-Dienic δ-sultones 4,6-diaryl-[1,2]oxathiine 2,2-dioxides were synthesized via a one-step reaction of arylalkynes with dioxane sulfotrioxide. The reactivity of various alkynes in this reaction was investigated. The resulting sultones were brominated with Br2 or N-bromosuccinimide regioselectively to sulfur and subsequently coupled with phenylacetylene using Sonogashira conditions.
- Gaitzsch, Jens,Rogachev, Victor,Metz, Peter,Filimonov, Victor D.,Zahel, Martin,Kataeva, Olga
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- Three types of products by carbon nucleophiles toward methoxyphenylacetylenic sulfones
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Methoxy-arylacetylenic sulfones were examined to react with various carbanion nucleophiles to result in the three types of products; thus, (i) nucleophiles (MeLi·LiBr, Vinyl MgBr, LiCH2CN) showed the α-addition, however, (ii) Li-CC-TMS afforded β-addition (conjugate addition) products. The (iii) displacement reaction through α-addition/ isomerization/trans-elimination was enhanced by the presence of ortho-methoxy group at high temperature. The heteroatom nucleophiles (nitrogen, oxygen or sulfur atom) in a protic solvent provided only conjugate addition products as reported.
- Cheng, Chia-Yi,Isobe, Minoru
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supporting information; experimental part
p. 9957 - 9965
(2012/02/06)
-
- Photochemical behavior of (diphosphine)(η2-tolane)Pt 0 complexes. Part A: Experimental considerations in solution and in the solid state
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A series of various (diphosphine)(η2-tolane)Pt0 complexes exhibiting manifold substitution pattern of the tolane ligand (5a-g) and different rigid diphosphines defining various bite angles at the Pt center (9a-b) have been synthesized. All compounds were isolated and characterized by means of spectroscopic methods and additionally by X-ray structure determination (5a-e, 9a-b). In view of potential Caryl-Cethynyl bond activation, we investigated their photochemical behavior in the solid state as well as in solution by irradiating with sunlight. The reactivity towards C aryl-Cethynyl bond activation in the crystalline state and in solution is discussed in relation to substituents attached to the tolane ligand and on the extent of the torsion of its phenyl rings. Complexes 5a-c and 9a either bearing electron withdrawing bromides or possessing a large dihedral angle of the phenyl rings, showed selective oxidative addition of the C aryl-Cethynyl bond to the Pt center in the solid state, yielding complexes 6a-c and 10a, respectively. In contrast, 5d-f and 9b proved to be unreactive under similar conditions because of their electron donating methoxy groups as well as the reduced twisting of their phenyl or pyridyl moieties of the tolane ligands. Irradiation of complexes 5a and 5b with sunlight in solution revealed the formation of the appropriate C-Br activated compounds 7a and 7b along with 6a and 6b in a 1:1 mixture. The observed photochemical Caryl-Cethynyl bond activation is reversible under thermal conditions, regaining the appropriate Pt0 complexes by reductive elimination.
- Weisheit, Thomas,Escudero, Danie,Petzold, Holm,Goerls, Helmar,Gonzalez, Leticia,Weigand, Wolfgang
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p. 9493 - 9504
(2011/01/11)
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- Synthesis of π-conjugated polymers via regioregular organometallic polymers 2. Transformation of titanacyclopentadienecontaining polymer into poly(ρ-phenylene) derivative
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The transformation of a regioregular organometallic polymer possessing titanacyclopentadiene-2,5-diyl units into a poly(ρ-phenylene) derivative by means of a novel polymer reaction method is described. The organotitianium polymer was prepared by the polymerization of 1,4-diethynyl-2,5- dioctyloxybenzene and a low-valent titanium complex, generated in situ from titanium(IV) isopropoxide and isopropylmagnesium chloride, and was subjected to the reaction with 3-bromo-1-propyne followed by the protonation. Consequently, a polymer consisting of the substituted phenylene-1,4-diyl units could be produced in a high yield,which is soluble in organic solvents such as chloroform. The number-average molecularweight and themolecular weight distribution of the polymer were estimated as 4800 and 1.8, respectively (GPC, polystyrene). The UV-vis absorption spectrum of the polymer exhibited the absorption maximum (λmax) at 329 nm, which was bathochromically shifted by 53 nm compared with that of a model compound, 1,4-bis(2-methoxyphenyl)-2- methylbenzene (λmax = 276 nm). Copyright
- Kino, Tomoko,Nishiyama, Hiroki,Tomita, Ikuyoshi
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experimental part
p. 558 - 562
(2010/11/16)
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- Electrophilic cyclization of 2-chalcogenealkynylanisoles: Versatile access to 2-chalcogen-benzo[b]furans
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An efficient synthesis of 2-ehalcogen-3-substituted-benzo[b]furan compounds has been accomplished via electrophilic cyclization reaction of 2-chalcogenealkynyl anisoles using I2, ICl, Br2, and PhSeBr as electrophile sources. The product distributions were strongly dependent on the nature of substituents in the aromatic ring of anisole and on the chalcogen atom directly bonded to the triple bond. The 2-chalcogen-3-iodo- benzo[b]furans obtained smoothly underwent conversion to more complex structures of benzo-[b]furan derivatives via palladium- or copper-catalyzed cross-coupling reaction with thiols, diphenyl diselenides, and zincates.
- Manarin, Flavia,Roehrs, Juliano A.,Gay, Rafaela Mozzaquatro,Brandao, Ricardo,Menezes, Paulo H.,Nogueira, Cristina W.,Zeni, Gilson
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body text
p. 2153 - 2162
(2009/07/01)
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- Terminal alkynes from aldehydes via dehydrohalogenation of (Z)-1-iodo-1-alkenes with TBAF
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Terminal alkynes were prepared in near quantitative yields via dehydrohalogenation of (Z)-1-iodo-1-alkenes with tetrabutylammonium fluoride (TBAF) under mild conditions. The methodology was expanded to include a one-pot, direct synthesis of terminal alkynes from aldehydes without the necessity of isolating and purifying the intermediate iodoalkene.
- Beshai, Mira,Dhudshia, Bhartesh,Mills, Ryan,Thadani, Avinash N.
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supporting information; experimental part
p. 6794 - 6796
(2009/04/07)
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- Block modification of rod-shaped π conjugated carbon frameworks with donor and acceptor groups toward highly fluorescent molecules: Synthesis and emission characteristics
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To create organic molecules that are highly fluorescent at a longer wavelength region, we investigated the synthesis (using Pd-catalyzed cross-coupling) and photophysical properties (Φ f, λ em, τ , λ abs, and ε ) of the following π conjugated molecular rods consisting of p-phenyleneethynylene units modified by donor (OMe) and/or acceptor (CN) groups: (1) side-donor modification systems (SD systems), (2) side-acceptor modification systems (SA systems), and (3) systems consisting of a donor block and an acceptor block (BL systems). As a consequence, very high Φ f values (>0.95) were obtained for BL systems. Bathochromic shifts of λ em for the same π conjugation length were largest for BL systems. Thus we succeeded in creating highly efficient light emitters at a longer wavelength region by block modification (e.g., Φ f = 0.97, λ em = 464 nm for BL-9). Considerably intense solid emission (Φ f ~ 0.5) at a longer wavelength region (500- 560 nm) was also found for BL systems. It has been found that BL-6 and BL-8 exhibit interesting two photon absorption characteristics. This journal is The Royal Society of Chemistry.
- Ochi, Takanori,Yamaguchi, Yoshihiro,Wakamiya, Tateaki,Matsubara, Yoshio,Yoshida, Zen-Ichi
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supporting information; scheme or table
p. 1222 - 1231
(2008/10/09)
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- Synthesis of the benzo[b]fluorene core of the kinamycins by arylalkyne-allene and arylalkyne-alkyne cycloadditions
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Arylalkyne-allene and arylalkyne-alkyne cycloadditions yields benzo[a]fluorenones, which are related to the tetracyclic core of the kinamycins. In the arylalkyne-alkyne cycloadditions, we found a rearrangement that produces benzo-[a]fluorenones, in addition to the expected benzo[b]fluorenones. This rearrangement could be suppressed in the presence of phenol, which allowed the synthesis of 4,9-dimeth-oxy-2-methyl-11H-benzo[b] fluoren-11-one in excellent yield. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Gonzalez-Cantalapiedra, Esther,De Frutos, Oscar,Atienza, Carmen,Mateo, Cristina,Echavarren, Antonio M.
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p. 1430 - 1443
(2007/10/03)
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- 4-Aryl-1,2,3-triazole: A novel template for a reversible methionine aminopeptidase 2 inhibitor, optimized to inhibit angiogenesis in vivo
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Inhibitors of human methionine aminopeptidase type 2 (hMetAP2) are of interest as potential treatments for cancer. A new class of small molecule reversible inhibitors of hMetAP2 was discovered and optimized, the 4-aryl-1,2,3-triazoles. Compound 24, a potent inhibitor of cobalt-activated hMetAP2, also inhibits human and mouse endothelial cell growth. Using a mouse matrigel model, this reversible hMetAP2 inhibitor was also shown to inhibit angiogenesis in vivo.
- Kallander, Lara S.,Lu, Qing,Chen, Wenfang,Tomaszek, Thaddeus,Yang, Guang,Tew, David,Meek, Thomas D.,Hofmann, Glenn A.,Schulz-Pritchard, Christina K.,Smith, Ward W.,Janson, Cheryl A.,Ryan, M. Dominic,Zhang, Gui-Feng,Johanson, Kyung O.,Kirkpatrick, Robert B.,Ho, Thau F.,Fisher, Paul W.,Mattern, Michael R.,Johnson, Randall K.,Hansbury, Michael J.,Winkler, James D.,Ward, Keith W.,Veber, Daniel F.,Thompson, Scott K.
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p. 5644 - 5647
(2007/10/03)
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- COMPOUNDS, METHODS AND FORMULATIONS FOR THE ORAL DELIVERY OF A GLUCAGON LIKE PEPTIDE (GLP)-1 COMPOUND OR AN MELANOCORTIN 4 RECEPTOR (MC4) AGONIST PEPTIDE
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The present invention relates to novel compounds, methods, and formulations useful for the oral delivery of a GLP-1 compound or an MC4 agonist peptide.
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Page/Page column 50
(2008/06/13)
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- ANTIBACTERIAL BENZOIC ACID DERIVATIVES
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The invention provides antimicrobial agents and methods of using the agents for sterilization, sanitation, antisepsis, disinfection, and treatment of infections in mammals.
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- Synthesis of 4-(1-alkenyl)isoquinolines by palladium(II)-catalyzed cyclization/olefination
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A variety of 4-(1-alkenyl)-3-arylisoquinolines have been prepared in moderate to excellent yields by the Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes. The introduction of an o-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Ketone-containing isoquinolines 36 and 49-51 have also been prepared by this process when unsaturated alcohols are employed as the alkenes.
- Huang, Qinhua,Larock, Richard C.
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p. 980 - 988
(2007/10/03)
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- Fused pyridine derivatives
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The present provides a condensed pyridine compound (I) represented by the following formula: (wherein, R2represents ring A represents benzene ring, pyridine ring, thiophene ring or furan ring; and B represents its pharmaceutically acceptable salt or hydrates thereof, which is a clinically useful medicament having a serotonin antagonism, in particular, that for treating, ameliorating or preventing spastic paralysis or central muscle relaxants for ameliorating myotonia.
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- Formation of benzo[b]fluorenes and the benzo[a]fluorene core of the fluostatins by cyclization of diaryldiynones.
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[figure: see text] Thermal cyclization of 1-[2-(trimethylsilylethynyl)phenyl]-3-arylpropinones was expected to give benzo[b]fluorenones. However, benzo[a]-fluorenones were also formed as a result of a new rearrangement. These tetracycles possess the core structure of the fluostatins and isoprekinamycin.
- Atienza,Mateo,de Frutos,Echavarren
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p. 153 - 155
(2007/10/03)
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- Dicarba-closo-dodecaboranes as a pharmacophore. Retinoidal antagonists and potential agonists
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Synthesis and biological evaluation of the first dicarba-closo- dodecaborane (carborane) derivatives of retinoids are described. Their retinoidal activity were examined in terms of the differentiation-inducing ability toward human promyelocytic leukemia HL-60 cells. High retinoidal activity (agonist or antagonist for retinoic acid receptor (RAR)) requires a carboxylic acid moiety and an appropriate hydrophobic group located at a suitable position on the molecule. The 4-carboranyl-substituted compounds (7, 11) showed antagonistic activity but no agonistic activity even in the presence of the potent synergist HX630. On the other hand, the 3-carboranyl- substituted compounds (8, 12) showed potential agonistic activity, but no antagonistic activity. The results indicates that carboranes are applicable as the hydrophobic moiety of biologically active molecules.
- Iijima, Toru,Endo, Yasuyuki,Tsuji, Motonori,Kawachi, Emiko,Kagechika, Hiroyuki,Shudo, Koichi
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p. 398 - 404
(2007/10/03)
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- State in solution, structure, and regioselectivity of reactions of the lithium 1-(2-methoxyphenyl)-3,3-diphenylpropyne derivative
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According to the spectrophotometric data, the lithium 1-(2-methoxyphenyl)-3,3-diphenylpropyne derivative in diethyl ether exists as contact ion pairs, while in THF, according to the spectrophotometric and 13C NMR data, solvent-separated ion pairs are predominantly formed. According to the 13C NMR data, the carbanion in the solvent-separated ion pairs has a structure close to the propargylic type. The regioselectivity of reactions of the lithium derivative with ethyl halides in diethyl ether, THF, and hexamethyphosphoramide, with benzyl chloride in the first two solvents, and with methanol in THF were studied. The protonation with methanol proceeds exclusively at the allenylic center (C-1) while the ethylation and especially benzylation proceed predominantly at the propargylic center (C-3). The selectivity of ethylation of the propargylic center of both solvent-separated ion pairs in THF and contact ion pairs in diethyl ether increases as the hardness of the ethylating agent increases, and in the case of the same ethyl halide, the selectivity increases from the solvent-separated ion pairs to the contact ion pairs. The spectral data obtained and the data on changes in the regioselectivity do not allow one to believe that the contact ion pairs of the lithium derivative in ether exhibit the intramolecular coordination of the lithium cation to the methoxy group, which might lead to the allenylic structure of contact ion pairs of this derivative.
- Dem'yanov,Krut'ko,Borzov,Luk'yanov,Petrosyan
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p. 1939 - 1947
(2007/10/03)
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- Enantioselective catalysis 107: new optically active deltacyclenes as building blocks for the synthesis of expanded phosphanes
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The cobalt-catalyzed homo Diels-Alder reaction of norbornadiene and terminal acetylenes yields chiral deltacyclenes.We tried to extend the scope of this reaction to acetylenes containing a heteroatom (i) in the propargylic position, (ii) in the ortho position of phenylacetylene or (iii) directly bonded to the triple bond.The synthesis of nine new substituted deltacyclenes with cobalt cytalysts derived from CoI2 and zinc powder or Co(acac)3 and Et2AlCl is described.Using Norphos as a cocatalyst, the products are obtained in high enantiomeric excess. - Keywords: enantioselective homogeneous catalysis; homo Diels-Alder reaction; deltacyclene; terminal acetylene
- Brunner, Henri,Reimer, Alfred
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p. 307 - 314
(2007/10/03)
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- Derivatives of 2-arylcyclopropylamine: Synthesis and interactions with 5-HT1A receptors
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A series of cis- and trans-derivatives of 2-aryl-N,N-dipropylcyclopropylamines and 1-(2-arylcyclopropyl)-N,N-dipropylmethylamines were synthesized and evaluated for affinity at the 5-HT1A receptor. The key step in the syntheses was a cyclopropanation of cis- and trans-3-arylpropenoic esters with diazomethane which proceeds with retention of the stereochemistry. cis-1-[2-(3-Methoxyphenyl)cyclopropyl]-N,N-dipropylmethylamine (32) had the highest 5-HT1A-receptor affinity (Ki= 58 nM) of the novel derivatives.
- Appelberg, Ulf,Mohell, Nina,Hacksell, Uli
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p. 415 - 420
(2007/10/03)
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- An improved synthesis of dichloroalkylphosphonates, chloroalkynes and terminal alkynes via diethyl dichloromethylphosphonate
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Diethyl 1,1-dichloromethylphosphonate (2) was synthesised in good yield from the reduction of 1,1,1-trichloromethylphosphonate (1) with i-C3H7MgCl and subsequent hydrolysis. The reactivity of 2 towards α-alkylation and its utility in the synthesis of chloroalkynes and terminal alkynes was investigated.
- Carran, John,Waschbuesch, Rachel,Marinetti, Angela,Savignac, Philippe
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p. 1494 - 1498
(2007/10/03)
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