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Chemistry: a European Journal

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https://www.readbyqxmd.com/read/30414339/visible-light-photocatalysis-of-the-ketyl-radical-coupling-reaction
#1
Qingmin Wang, Qing Xia, Jianyang Dong, Hongjian Song
Ketyl radical coupling reactions for the construction of diversely functionalised alcohols have been continuously developed for many decades. Based on the widespread application of photocatalysis that is often complementary to the traditional methods, ketyl radical coupling reactions glow the new vigor. This Minireview aims to briefly and concisely summarise the methodologies which construct ketyl radical intermediates through visible light photocatalysis over the past 10 years. The ketyl-radical-generation activators are grouped in Lewis acids, Brønsted acids, in situ-generated Brønsted acids, and others...
November 10, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30414294/spiropyran-based-nanocarrier-a-new-zn2-responsive-delivery-system-with-real-time-intracellular-sensing-capabilities
#2
Sabrina Heng, Xiaozhou Zhang, Jinxin Pei, Alaknanda Adwal, Philipp Reineck, Brant Gibson, Mark Hutchinson, Andrew Abell
A new spiropyran-based stimuli-responsive delivery system is presented that encapsulates and then releases an extraneous compound in response to elevated levels of Zn2+, a critical factor in cell apoptosis. A C12-alkyl substituent on the spiropyran promotes self-assembly into a micelle-like nanocarrier in aqueous media, with nanoprecipitation and encapsulation of added payload. Zn2+ binding occurs to an appended bis(2-pyridylmethyl)amine group at biologically relevant micromolar concentration. This leads to switching of the spiropyran (SP) isomer to the strongly fluorescent ring opened merocyanine-Zn2+ (MC-Zn2+) complex, with associated expansion of the nanocarriers to release the encapsulated payload...
November 10, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30414281/trifluoromethylation-of-allenes-an-expedient-access-to-%C3%AE-trifluoromethylated-enones-at-room-temperature
#3
Massimo Brochetta, Tania Borsari, Andrea Gandini, Sandip Porey, Arghya Deb, Emanuele Casali, Arka Chakraborty, Giuseppe Zanoni, Debabrata Maiti
A silver(I) catalyzed regioselective trifluoromethylation of allenes using Langlois salt NaOSOCF3 is demonstrated. This transformation enables direct expedient access to alpha-trifluoromethylated acroleins which are valuable synthons for a number of pharmaceuticals and agrochemicals containing vinyl-CF3 moieties. Versatility of this trifluoromethylation method has been established with good yield and excellent regioselectivity. Preliminary experiments and computational studies were carried out to elucidate the mechanistic insight of this protocol...
November 10, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30414215/abc-abc-type-meso-meso-directly-linked-porphyrin-dimer
#4
Tomohiro Higashino, Yuma Kurumisawa, Hitomi Iiyama, Hiroshi Imahori
Covalently linked porphyrin oligomers are attractive molecules because of their extended π-conjugated systems. Among various porphyrin oligomers, meso-meso directly linked porphyrin oligomers exhibit unique photophysical properties due to their strong exciton couplings derived from alternative orthogonal geometry of the porphyrins. Although their structural and electronic properties can be greatly altered by substituents at meso-positions, it is still difficult to introduce different substituents at the meso-positions...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30414202/resonance-energy-transfer-in-a-genetically-engineered-polypeptide-results-in-unanticipated-fluorescence-intensity
#5
John T Welch, Jason P Seeley, Mircea Cotlet, Aileen M Eagleton, Seiichiro Higashiya
When β-sheet forming polypeptides bearing tryptophan residues along one edge were irradiated at 280 nm, the tryptophan absorbance maximum, the fluorescence intensity of the C-terminal acceptor chromophore, N-(7-dimethylamino-4-methyl coumarin (DACM), increased proportionally with an increasing number of donor tryptophans. The fluorescence intensity increased even as the length of the β-sheet edge approached 256 Å, well beyond the Förster radius for the tryptophan-acceptor chromophore pair. The folding of the peptides under investigation was verified by circular dichroism (CD) and deep UV resonance Raman experiments...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30412647/hg-ii-mediated-tl-i-to-tl-iii-oxidation-in-dynamic-pb-ii-tl-porphyrin-complexes
#6
Stéphane Le Gac, Victoria Ndoyom, Luca Fusaro, Vincent Dorcet, Bernard Boitrel
Compared to their purely organic counterparts, molecular switches based on metal ion translocations have been underexplored and, more particularly, it remains challenging to control the translocation of several particles in multisite receptors. Recently, bimetallic complexes undergoing double translocation processes have been developed with bis-strapped porphyrin ligands and in order to implement a redox control for these systems, we have investigated herein the formation of heteromultimetallic lead/thallium complexes, with thallium stable in the +I and +III oxidation states...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30412336/asymmetric-cyclizative-dimerization-of-ortho-alkynyl-phenyl-methoxymethyl-sulfides-with-palladium-ii-bisoxazoline-catalyst
#7
Cheng Peng Peng, Taichi Kusakabe, Shoko Kikkawa, Tomoyuki Mochida, Isao Azumaya, Yogesh Daulat Dhage, Keisuke Takahashi, Hiroaki Sasai, Keisuke Kato
The first example of an asymmetric cyclizative dimerization of (ortho-alkynylphenyl) (methoxymethyl) sulfides with a palladium(II) bisoxazoline (box) catalyst has been developed. The box ligand enhances the alkynophilicity of benzothienyl palladium(II) intermediate and thus promotes coordination of the second alkyne substrate, leading to the dimerization. The characteristic properties of the box ligand were supported by density functional theory (DFT) calculations of the intermediate. Axially chiral bibenzothiophenes were obtained in good yields with good enantioselectivities...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30412335/porous-core-shell-cuco2s4-nanospheres-as-anode-for-enhanced-lithium-ion-battery
#8
Guangda Li, Tian Zheng, Siyi Li, Manman Ren, Xiangeng Meng
Porous core-shell CuCo2S4 nanospheres that exhibit a large specific surface area, sufficient inner space, and nanoporous shell, have been synthesized through a facile solvothermal method. The diameter of core-shell CuCo2S4 nanospheres is ~800 nm and the radius of the core and the thickness of the shell are ~250 and ~45 nm, respectively. Based on the experimental results, the formation mechanism of core-shell structure is also discussed. These CuCo2S4 show excellent Li storage performance when used as anode for lithium-ion battery...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30412333/a-peptide-backbone-stapling-strategy-enabled-by-the-multicomponent-incorporation-of-amide-n-substituents
#9
Manuel G Ricardo, Javiel F Marrero, Oscar Valdes, Daniel G Rivera, Ludger A Wessjohann
The multicomponent backbone N-modification of peptides on solid-phase is presented as a powerful and general method to enable peptide stapling at the backbone instead of the side chains. We prove that a variety of functionalized N-substituents suitable for backbone stapling can be readily introduced by means of on-resin Ugi multicomponent reactions conducted during solid-phase peptide synthesis. Diverse macrocyclization chemistries were implemented with such backbone N-substituents, including the ring-closing metathesis, lactamization and thiol alkylation...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30412309/asymmetric-difluoroboron-quinazolinone-pyridine-dyes-with-large-stokes-shift-high-emission-efficiencies-both-in-solution-and-in-the-solid-state
#10
Jia Zhou, Lu Liu, Ying Pan, Qiaoyu Zhu, Yajie Lu, Jiacheng Wei, Kang Luo, Yang Fu, Cheng Zhong, Yiyuan Peng, Zhibin Song
Boron difluoroquinazolinone-pyridine (BODIQPy) and substituted derivatives have been designed and synthesized. Strong emission with high fluorescence quantum yield both in solution (up to 0.99) and in solid state (up to 0.60) was achieved in these asymmetric BODIQPys. For 6-halogen substituted BODIQPys, the heavy atomic effect of bromine and iodine was suppressed in solution due to the strong electron-withdrawing ability of the BODIQPy core. As a result, 6-iodine substituted BODIQPy shows the unusual fluorescence quantum yields (>0...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30411821/phosphorus-vs-sulphur-discovery-of-benzenephosphonamidates-as-new-versatile-sulfonamide-mimic-chemotypes-acting-as-carbonic-anhydrase-inhibitors
#11
Alessio Nocentini, Paola Gratteri, Claudiu T Supuran
The first zinc binding group (ZBG) to have been identified as inhibitor of the metallo-enzymes carbonic anhydrases (CA, EC 4.2.1.1) was the sulfonamide. From then on several classes of zinc-binders have been described. Herein we propose the benzenephosponamidates as a new chiral aromatic sulfonamide-mimic ZBG able to meet the requirements for effectively binding the enzyme active site. Several low micromolar CA I, II, VII, IX inhibitors were thus detected. Kinetic studies, QM-polarized ligand docking and MM-GBSA in silico methods were used to characterize this newly identified CA inhibitor chemotype...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30411413/ca-ii-yb-ii-and-sm-ii-bis-amido-complexes-coordinated-by-nhc-ligands-efficient-catalysts-for-highly-regio-and-chemoselective-consecutive-hydrophosphinations-with-ph3
#12
Alexander Trifonov, Ivan Lapshin, Ivan Basalov, Konstantin Lyssenko, Anton Cherkasov
The first example of intermolecular hydrophosphination of styrene, 2-vinylpyridine and phenylacetylene with PH3 catalyzed by bis-(amido) complexes [(Me3Si)2N]2M(NHC)2 (M = Ca, Yb, Sm) coordinated by NHC ligands is described. The reactions of styrene with PH3 proceed under mild conditions in quantitative yields to afford only anti-Markovnikov product and allow for the chemoselective synthesis of primary, secondary and tertiary phosphines. Addition of phenylacetylene to PH3 regardless the initial molar substrates ratio results in the exclusive formation of tertiary tris-(Z-styryl)-phosphine...
November 9, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30411410/construction-of-a-dna-based-supramolecular-nanosheet-that-emits-bluish-white-light-from-charge-transfer-excited-states-of-the-nucleobases
#13
Rika Iwaura
1,ω-Inosinic acid-bearing bolaamphiphiles (dI(18), dI(19), and dI(20)) with a 3'-phosphorylated inosine as a universal base connected to each end of an oligomethylene chain were synthesized for the first time. Single-component self-assemblies of these bolaamphiphiles and their binary self-assemblies with salmon sperm DNA were studied by atomic force microscopy; temperature-dependent UV absorption, fluorescence, and circular dichroism spectroscopy; and gel electrophoresis. The binary self-assembly of dI(20) and salmon sperm DNA (dI(20)-DNA) had a nanosheet structure with a homogeneous thickness of ca...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30408250/ce-io3-2f2%C3%A2-h2o-the-first-rare-earth-iodate-fluoride-with-large-second-harmonic-generation-response
#14
Tushagu Abudouwufu, Min Zhang, Shichao Cheng, Zhihua Yang, Shilie Pan
The first rare earth iodate fluoride, Ce(IO3)2F2·H2O, has been synthesized via hydrothermal method. In the structure, the CeO5F4 polyhedra connect with isolated IO3 groups to form one-dimensional infinite 1∞[Ce(IO3)2F2] chains, which interconnect with each other by weak hydrogen bond to construct the whole structure. Ce(IO3)2F2·H2O produces a large second harmonic generation response, which is 3 times that of KDP. Theoretical calculations using density functional theory and dipole moments were executed to illustrate the relationships between the structure and the properties...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30408248/a-high-pressure-praseodymium-fluoride-borate-linking-multiple-structural-features-of-apatite-type-compounds
#15
Matthias Glätzle, Almut Pitscheider, Oliver Oeckler, Klaus Wurst, Hubert Huppertz
Pr5(BO4)3-x(BO3)x(F,OH)2.67O0.28 (x ≈ 1.6), a boron-containing fluoride-oxoapatite-like compound, was obtained by the application of high-pressure/high-temperature synthesis. It exhibits a superstructure of the fluorite type with a tripled c lattice parameter (space group P63/m) and shows complex anion disorder along the 63 screw axis and occupation of distorted octahedral as well as almost trigonal planar sites by oxygen and fluorine atoms. Furthermore, a distinct BO4 / (BO3 + F) group disorder is found, 46% of the sites being occupied by BO4 groups and 54% by BO3 groups with a fluoride ion located near the missing oxygen atom...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30408240/stable-and-persistent-acyclic-diaminocarbenes-with-cycloalkyl-substituents-and-their-transformation-to-%C3%AE-lactams-by-uncatalysed-carbonylation-with-co
#16
Ulrich Siemeling, Lars Wallbaum, Daniel Weismann, Dennis Löber, Clemens Bruhn, Pascal Prochnow, Julia E Bandow
Four new acyclic diaminocarbenes (ADACs), viz. [(cyclo-CnH2n - 1)2N]2C (n = 5 - 7) and iPr2N-C-N(cyclo-C6H11)2, were synthesised by reacting the corresponding formamidinium hexafluorophosphates with NaN(SiMe3)2. Their nucleophilicities and electrophilicities were respectively judged from the 1JCH values determined for the N2CH unit of the corresponding formamidinium cations and from the 77Se NMR chemical shifts of the selenourea derivatives obtained from the reaction of elemental selenium with the corresponding ADACs...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30407673/tmsotf-catalyzed-koenigs-knorr-glycosylation-reaction
#17
Yahsapal Singh, Alexei V Demchenko
Presented herein is our discovery that traditional silver(I) oxide-promoted glycosidations of glycosyl bromides (Koenigs-Knorr reaction) can be greatly accelerated in the presence of catalytic TMSOTf. These reaction conditions are very mild and allow for maintaining a practically neutral pH while providing high rates and excellent glycosylation yields. In addition, unusual reactivity trends among a series of differentially protected glycosyl bromides have been documented. Also revealed is an unusual reactivity trend according to which benzoylated α-bromides are much more reactive than their benzylated counterparts under these con-ditions...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30407668/structural-and-kinetic-profiling-of-allosteric-modulation-of-duplex-dna-induced-by-dna-binding-polyamide-analogues
#18
Glenn Burley, Giacomo Padroni, John Parkinson, Thomas Welte
A structural and quantitative biophysical profile of the DNA binding affinity, kinetics and sequence-selectivity of minor-groove binding polyamides (PAs) incorporating N-terminal 5-alkyl thiazole (Nt) and 1-alkyl imidazole (Im) units is described. DNA duplexes containing either target binding sites or mismatch sequences for a suite of hairpin PAs are immobilized on a microelectrode surface. Quantitation of the binding kinetics (i.e., kon, koff), dissociation constant (KD) and melting temperatures show that PAs exhibit picomolar to low nanomolar binding affinities for their target dsDNA sequences...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30407667/single-sided-competitive-axial-coordination-of-g-quadruplex-hemin-as-molecular-switch-for-imaging-intracellular-nitric-oxide
#19
Lei Zhang, Jun Zhou, Fengjiao Ma, Quanbo Wang, Hui Xu, Huangxian Ju, Jianping Lei
Axial coordination is a crucial biological process to regulate biomolecules' functions in natural enzymes. However, it is a great challenge to determine the single or dual axial interaction between the metal center of enzymes and the ligand. In this work, a controllable axial coordination system was developed based on G-quadruplex/hemin complex by designing a series of fluorescent derivatives. The mechanism on axial coordination of G-quadruplex/hemin with coumarin-imidazole ligands was identified to be single-sided, and led to fluorescence quenching of ligands...
November 8, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30407666/catalytic-generation-and-chemoselective-transfer-of-nucleophilic-hydrides-from-dihydrogen
#20
Felix Pape, Lea Brechmann, Johannes F Teichert
Copper(I)/N-heterocyclic carbene (NHC) complexes enable the catalytic generation of nucleophilic hydrides from dihydrogen (H2) and their subsequent transfer to allylic chlorides. The highly chemoselective catalyst displays no concomitant hydrogenation reactivity, as the terminal double bond formed in the hydride transfer remains intact. Switching to deuterium gas (D2) allows for regioselective monodeuteration with excellent isotope incorporation.
November 8, 2018: Chemistry: a European Journal
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