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https://www.readbyqxmd.com/read/30336052/metal-free-triple-annulation-of-ene-yne-ketones-with-isocyanides-domino-access-to-furan-fused-heterocycles-via-furoketenimine
#1
Zhongyan Hu, Jinhuan Dong, Zhaoyang Li, Bo Yuan, Ruyue Wei, Xianxiu Xu
A new furoketenimine intermediate from the coupling of ene-yne-ketones and o-alkenyl arylisocyanides, which enables the efficient synthesis of a wide range of tetracyclic and pentacyclic furan-fused heterocycles in a one-pot domino process under catalyst-free conditions, is disclosed. Based on the control experiments, a cascade of 1,6-addition, cyclization, intramolecular Diels-Alder reaction, and oxidative aromatization was proposed for the mechanism.
October 17, 2018: Organic Letters
https://www.readbyqxmd.com/read/30334562/metal-free-photocatalytic-thiol-ene-thiol-yne-reactions
#2
Sarbjeet Kaur, Gaoyuan Zhao, Evan Busch, Ting Wang
The organic photocatalyst (9-mesityl-10-methylacridinum tetrafluoroborate) in the presence of visible light is used to initiate thiol-ene and thiol-yne reactions. Thiyl radicals are generated upon quenching the photoexcited catalyst with a range of thiols. The highlighted mild nature of the reaction conditions allows a broad substrate scope of the reactants. Relying on this efficient metal-free condition, both thiol-ene and thiol-yne reactions between carbohydrates and peptides could be realized in excellent yields...
October 18, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/30318724/expanding-the-material-space-of-biosustainable-poly-sophorolipids-by-modular-functionalization
#3
Tom Kunde, Worarin Meesorn, Christoph Weder, Hans G Börner
A general strategy to modify the structurally interesting poly(lactonic sophorolipid) (Poly(LSL)), a polymer derived from the biobased sophorolipid monomer, is presented. Effective backbone modification is achieved via a triazolinedione (TAD)-ene-reaction. This enables the straightforward introduction of various functionalities to the double bond in the fatty acid segment of the Poly(LSL). The reaction occurs quantitatively in stoichiometric ratios up to a targeted functionalization degree of 50% and complete functionalization of all double bonds is feasible when three equivalents excess of the TAD moiety with respect to the double bonds are used...
October 15, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/30314332/pretargeted-imaging-with-gallium-68-improving-the-binding-capability-by-increasing-the-number-of-tetrazine-motifs
#4
Dominik Summer, Sonja Mayr, Milos Petrik, Christine Rangger, Katia Schoeler, Lisa Vieider, Barbara Matuszczak, Clemens Decristoforo
The inverse electron-demand Diels-Alder reaction between 1,2,4,5-tetrazine (Tz) and trans -cyclooct-2-ene (TCO) has gained increasing attraction among extensive studies on click chemistry due to its exceptionally fast reaction kinetics and high selectivity for in vivo pretargeting applications including PET imaging. The facile two-step approach utilizing TCO-modified antibodies as targeting structures has not made it into clinics yet. An increase in the blood volume of humans in comparison to mice seems to be the major limitation...
October 11, 2018: Pharmaceuticals
https://www.readbyqxmd.com/read/30310909/umpolung-cyclization-reaction-of-n-cinnamoylthioureas-in-the-presence-of-dbu
#5
Rei Saito, Naohiro Uemura, Hiroki Ishikawa, Akina Magara, Yasushi Yoshida, Takashi Mino, Yoshio Kasashima, Masami Sakamoto
A novel regioselective cyclization reaction of N-cinnamoylthioureas leading to six- or five-membered heterocyclic compounds was developed. N-Cinnamoylthioureas in the presence of trifluoroacetic acid (TFA) underwent the well-established intramolecular cycloaddition reaction to give 2-imino-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones in good yields. On the other hand, the reaction with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proceeded in an unprecedented "umpolung" cyclization fashion to afford five-membered 2-imino-1,3-thiazolidin-4-ones and/or 2-thioxoimidazolidine-4-ones...
October 12, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/30310906/isomerization-barriers-and-resonance-stabilization-for-the-conrotatory-and-disrotatory-isomerizations-of-nitrogen-containing-tricyclo-moieties
#6
Weiwei Yang, Kimberley N Poland, Steven R Davis
The isomerizations of 3,4-diazatricyclo[4.1.0.02,7]hept-3-ene and 3,4-diazatricyclo[4.1.0.02,7]heptane to their corresponding products were studied by ab initio calculations. Structures were determined at the multiconfiguration self-consistent field level and energies calculated at the single state second-order MRMP level. The isomerization of 3,4-diazatricyclo[4.1.0.02,7]hept-3-ene occurs through four unique pathways with barriers of 36.1 and 37.9 kcal mol-1 for the allowed channels, while those for the forbidden channels were 44...
October 12, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30303376/an-approach-to-the-9-oxo-10-oxabicyclo-5-3-0-dec-2-ene-core-of-the-guaianolide-and-pseudoguaianolide-sesquiterpenes-via-a-domino-electrocyclic-ring-opening-carboxylic-acid-trapping-of-a-gem-dibromocyclopropane
#7
Simon J Kim, Alan J Lough, Robert A Batey
A domino silver(I) promoted electrocyclic 2-disrotatory electrocyclic ring-opening / intramolecular nucleophilic trapping of [n.1.0]-dibromocyclopropanes by tethered carboxylic acids results in cyclization to butyrolactones fused to six- and seven-membered carbocycles. In the case of bicyclic [4.3.0] lactones the cis-fused stereoisomer was formed, whereas for the bicyclic [5.3.0] lactones the trans-fused stereoisomer was formed. Optimal conditions for the reaction used silver(I) trifluoroacetate (2.0 eq...
October 10, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30300959/radical-mediated-thiol-ene-strategy-for-photoactivation-of-thiol-containing-drugs-in-cancer-cells
#8
Shuang Sun, Bruno Oliveira, Gonzalo Jiménez-Osés, Gonçalo J L Bernardes
Photo-activated drugs provide an opportunity to improve efficacy alongside reducing side-effects in the treatment of severe diseases, such as cancer. Herein, we describe a photoactivation decaging method of isobutylene-caged thiols through a UV-initiated thiol-ene reaction. The method was demonstrated with an isobutylene-caged cysteine, cyclic disulfide-peptide and thiol-containing drug, all of which were rapidly and efficiently released under mild UV irradiation in the presence of thiol sources and a photoinitiator...
October 9, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30300547/successive-surface-reactions-on-hydrophilic-silica-for-modified-magnetic-nanoparticle-attachment-probed-by-sum-frequency-generation-spectroscopy
#9
Jeeranan Nonkumwong, Uriel Joseph Erasquin, Kurt Waldo E Sy Piecco, Uvinduni I Premadasa, Ahmed M Aboelenen, Andrew A Tangonan, Jixin Chen, David C Ingram, Laongnuan Srisombat, Katherine Leslee Asetre Cimatu
Successive surface reactions on hydrophilic silica substrates were designed and performed to immobilize ethanolamine-modified magnetic ferrite-based nanoparticle (NP) for surface characterization. The various surfaces were monitored using sum-frequency generation (SFG) spectroscopy. The surface of the hydrophilic quartz substrate was first converted to a vinyl-terminated surface by utilizing a silanization reaction, and then, the surface functional groups were converted to carboxylic-terminated groups via a thiol-ene reaction...
October 9, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/30298735/pd-ii-norbornene-catalyzed-meta-c-h-alkylation-of-nosyl-protected-phenylalanines
#10
Jieyu Liu, Qiuping Ding, Wenjun Fang, Wanhui Wu, Yuanguang Zhang, Yiyuan Peng
A Pd/norbornene-catalyzed direct meta-alkylation of nosyl-protected phenylalanine derivatives with alkyl iodides is reported in moderate to good yields. The use of diisopropyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate is identified as a more suitable transient mediator. A simple pyridine ligand is also essential for this reaction to proceed. No racemization was observed in this meta-methylation reaction.
October 18, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30296105/surfaces-with-dual-functionality-through-specific-coimmobilization-of-self-assembled-polymeric-nanostructures
#11
Serena Rigo, Gesine Gunkel-Grabole, Wolfgang Meier, Cornelia G Palivan
Coimmobilization of functional, nanosized assemblies broadens the possibility to engineer dually functionalized active surfaces with a nanostructured texture. Surfaces decorated with different nanoassemblies, such as micelles, polymersomes, or nanoparticles are in high demand for various applications ranging from catalysis, biosensing up to antimicrobial surfaces. Here, we present a combination of bio-orthogonal and catalyst-free strain-promoted azide-alkyne click (SPAAC) and thiol-ene reactions to simultaneously coimmobilize various nanoassemblies; we selected polymersome-polymersome and polymersome-micelle assemblies...
October 18, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/30288462/synthesis-of-2-azaadamantan-6-one-a-missing-isomer
#12
Jianbo Wu, Derek A Leas, Yuxiang Dong, Xiaofang Wang, Edward L Ezell, Douglas E Stack, Jonathan L Vennerstrom
2-Azaadamantan-6-one and its Boc and ethylene ketal derivatives were synthesized from 9-oxo endo -bicyclo[3.3.1]non-6-ene-3-carboxylic acid. Similarly, the Cbz, Boc, and ethylene ketal derivatives of 2-azaadamantan-4-one were synthesized from endo -bicyclo[3.3.1]non-6-ene-3-carboxylic acid. Key steps were Curtius rearrangements to form benzyl carbamates, followed by spontaneous intramolecular attack of the carbamate nitrogen on transient bromonium ion or epoxide intermediates to effect ring closure to azaadamantane intermediates...
September 30, 2018: ACS Omega
https://www.readbyqxmd.com/read/30286336/synthesis-of-thiomaltooligosaccharides-by-a-thio-click-approach
#13
László Lázár, Anikó Borbás, László Somsák
Phenyl 2,3,6,2',3',6'-hexa-O-acetyl-4'-S-acetyl-1,4,4'-trithio-β-d-maltoside and its tri-, tetra- and pentasaccharide homologues were prepared by completely regio- and stereoselective photoinitiated thiol-ene coupling reactions of 2-acetoxy-glucal and 4-thioglucose type reaction partners. Complex protecting group strategies could be avoided since all thiols and glucals were prepared from a single starting material, phenyl 2,3,6-tri-O-acetyl-4-S-acetyl-1,4-dithio-β-d-glucopyranoside. The method represents a simple alternative to the known syntheses of similar products...
September 27, 2018: Carbohydrate Research
https://www.readbyqxmd.com/read/30284398/controlled-formation-of-a-main-chain-supramolecular-polymer-based-on-metal-ligand-interactions-and-a-thiol-ene-click-reaction
#14
Feiyi Chen, Yu-Kui Tian, Yulan Chen
Supramolecular polymers with multiple functionalities and hierarchical structures have received considerable attention and become a hot research topic over the past years. Herein, a main-chain supramolecular polymer has been successfully fabricated by using metal-ligand interactions and a thiol-ene click reaction. 1 H NMR, UV/Vis, DOSY, and viscosity measurements were carried out to investigate the molecular recognition and the process of supramolecular polymerization. From the study, the orthogonality between thiol-ene click reactions and the terpyridine-metal ions complexation behavior was testified, and supramolecular polymeric assemblies could be constructed by a one pot method...
October 3, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/30280563/construction-highly-hierarchical-layered-structure-consisting-of-titanate-nanosheets-tungstate-nanosheets-ru-bpy-3-2-and-pt-terpy-for-vectorial-photoinduced-z-scheme-electron-transfer
#15
Fuminao Kishimoto, Dai Mochizuki, Masato M Maitani, Eiichi Suzuki, Yuji Wada
To imitate the precisely ordered structure of the photo-antennas and electron mediators in the natural photosynthesis system, we have constructed the Ru(bpy)3 2+ -intercalated alternate-layered structure of titanate nanosheets and tungstate nanosheets via thiol-ene click reaction. In advance of nanosheets stacking, Pt(terpy) was immobilized at the edge of the titanate nanosheets. The visible-light induced vectorial Z-scheme electron transfer reaction from the valence band of tungstate to the conduction band of titanate via the photoexcited Ru(bpy)3 2+ was demonstrated by the following two evidences: (1) From the results of the fluorescence decay of Ru(bpy)3 2+ , the rate of the forward electron transfer from the photoexcited Ru(bpy)3 2+ to the conduction band of titanate was estimated as 1...
October 3, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/30278903/macro-mesoporous-organosilica-monoliths-with-bridged-ethylene-and-terminal-vinyl-high-density-click-functionalization-for-chromatographic-separation
#16
Ci Wu, Yu Liang, Xudong Zhu, Qun Zhao, Fei Fang, Xiaodan Zhang, Zhen Liang, Lihua Zhang, Yukui Zhang
A novel kind of macro-mesoporous organosilica monolith, with not only bridged-ethylene groups incorporated into the skeleton but also terminal-vinyl groups protruded from the pore-wall, was prepared so that high-loaded double bonds were achieved. Via highly efficient "thiol-ene" click reaction of such high-loaded double bonds, the surface coverage of C18 groups on monolith could be 5.54 μmol m-2 , significantly larger than that of the reported separation materials, beneficial to improvement of separation resolution, especially for peptide separation...
December 14, 2018: Analytica Chimica Acta
https://www.readbyqxmd.com/read/30277766/computational-mechanism-study-on-allylic-oxidation-of-cis-internal-alkenes-insight-into-the-lewis-acid-assisted-br%C3%A3-nsted-acid-lba-catalysis-in-hetero-ene-reactions
#17
Yongsheng Yang, Xin Yang, Yan Zhang, Ying Xue
The catalytic allylic C-H oxidation of alkenes plays an important role in the field of medicine chemistry. Recently, Tambar et al. improved this transformation via a hetero-ene reaction with the assistance of Lewis acid-assisted chiral Brønsted acid (LBA), and achieved a selective allylic oxidation of unactived cis-internal alkenes to versatile oxidation products. By means of density functional theory (DFT) calculations, we provided a detailed investigation on mechanism of the hetero-ene reaction, and successfully located a new catalytic process, which is able to explain the experimental observations very well...
October 2, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/30276958/furfuryl-and-maleimido-polysaccharides-synthetic-strategies-toward-functional-biomaterials
#18
REVIEW
Thomas Elschner, Franziska Obst, Thomas Heinze
In context with facile and efficient syntheses of functional polymeric materials, the combination of polysaccharides and functional moieties based on renewable resources is a sustainable and valuable approach. This review presents alternatives to prominent click reactions utilizing biopolymer derivatives with furfuryl and maleimide groups. On the one hand, the cross-linking by Diels-Alder reaction of these polymers enables the synthesis of novel materials in the fields of self-healing polymers, tissue engineering, and drug delivery...
October 1, 2018: Macromolecular Bioscience
https://www.readbyqxmd.com/read/30270384/interfacing-enzymes-with-silicon-nanocrystals-through-the-thiol-ene-reaction
#19
Christopher Jay T Robidillo, Maryam Aghajamali, Angelique Faramus, Regina Sinelnikov, Jonathan G C Veinot
This study reports the preparation of functional bioinorganic hybrids, through application of the thiol-ene reaction, that exhibit catalytic activity and photoluminescent properties from enzymes and freestanding silicon nanocrystals. Thermal hydrosilylation of 1,7-octadiene and alkene-terminated poly(ethylene oxide)methyl ether with hydride-terminated silicon nanocrystals afforded nanocrystals functionalized with alkene residues and poly(ethylene oxide) moieties. These silicon nanocrystals were conjugated with representative enzymes through the photochemical thiol-ene reaction to afford bioinorganic hybrids that are dispersible and photostable in buffer, and that exhibit photoluminescence (λmax = 630 nm) and catalytic activity...
October 21, 2018: Nanoscale
https://www.readbyqxmd.com/read/30262500/interrupted-carbonyl-olefin-metathesis-via-oxygen-atom-transfer
#20
Jacob R Ludwig, Rebecca B Watson, Daniel J Nasrallah, Joseph B Gianino, Paul M Zimmerman, Ren A Wiscons, Corinna S Schindler
Some of the simplest and most powerful carbon-carbon bond forming strategies take advantage of readily accessible ubiquitous motifs: carbonyls and olefins. Here we report a fundamentally distinct mode of reactivity between carbonyls and olefins that differs from established acid-catalyzed carbonyl-ene, Prins, and carbonyl-olefin metathesis reaction paths. A range of epsilon, zeta-unsaturated ketones undergo Brønsted acid-catalyzed intramolecular cyclization to provide tetrahydrofluorene products via the formation of two new carbon-carbon bonds...
September 28, 2018: Science
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