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https://www.readbyqxmd.com/read/28445061/synergistic-visible-light-photoredox-nickel-catalyzed-synthesis-of-aliphatic-ketones-via-n-c-cleavage-of-imides
#1
Javad Amani, Rauful Alam, Shorouk Badir, Gary A Molander
An electrophilic, imide-based, visible-light-promoted photoredox/Ni-catalyzed cross-coupling reaction for the synthesis of aliphatic ketones has been developed. This protocol proceeds through N-C(O) bond activation, made possible through the lower activation energy for metal insertion into this bond due to delocalization of the lone pair of electrons on the nitrogen by electron-withdrawing groups. The operationally simple and mild cross-coupling reaction is performed at ambient temperature and exhibits tolerance for a variety of functional groups...
April 26, 2017: Organic Letters
https://www.readbyqxmd.com/read/28445045/intermediates-and-reactivity-in-iron-catalyzed-cross-couplings-of-alkynyl-grignards-with-alkyl-halides
#2
Jared L Kneebone, William W Brennessel, Michael L Neidig
Iron-catalyzed cross-coupling reactions using alkynyl nucleophiles represent an attractive approach for the incorporation of alkynyl moieties into organic molecules. In the present study, a multi-technique approach combining inorganic spectroscopic methods, inorganic synthesis, and reaction studies is applied to iron-SciOPP catalyzed alkynyl-alkyl cross-couplings, providing the first detailed insight into the effects of variation from sp(2) to sp nucleophiles on iron speciation and reactivity. Reaction studies demonstrate that reaction of FeBr2(SciOPP) with 1 equiv (triisopropylsilyl)ethynylmagnesium bromide (TIPS-CC-MgBr) leads to a distribution of mono-, bis-, and tris-alkynylated iron(II)-SciOPP species due to rapid alkynyl ligand redistribution...
April 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28444956/structural-insights-into-the-recognition-of-n%C3%A2-aryl-and-c8-aryl-dna-lesions-by-the-repair-protein-xpa-rad14
#3
Charlotte Ebert, Nina Simon, Sabine Schneider, Thomas Carell
Aromatic amines are strongly carcinogenic compounds. They are activated in the liver to give reactive nitrenium ions that are known to react with the nucleobases within the DNA duplex. The reaction occurs predominantly at the C8-position of the dG base, which gives C8-acetyl-aryl-, or C8-aryl-dG adducts in an electrophilic aromatic substitution reaction. Alternatively, reaction with the exocyclic 2-NH₂ group is observed. While the C8-adducts retain the base pairing properties, base pairing is strongly compromised in the case of the N²-adducts...
April 26, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/28444826/indium-iii-catalyzed-aza-conia-ene-reaction-for-the-synthesis-of-indolizines
#4
Karl Anker Jørgensen, Marta Meazza, Lars Astrup Leth, Jeremy David Erickson
A novel indium(III)-catalyzed reaction for the synthesis of a series of indolizine scaffolds has been developed. This methodology is highly efficient, allowing a low catalyst loading of 2 mol% (down to 0.5 mol%) and rendering the products in high yields through a 5-exo-dig aza-Conia-ene reaction. Further-more, the possibility of incorporating an electrophile to the generated pyrrolidine-ring in a one-pot synergistic fashion is demonstrated. Finally, based on experimental observations, a mechanism proposal is outlined...
April 26, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28443662/bis-tert-butylimido-bis-n-o-chelate-tungsten-vi-complexes-probing-amidate-and-pyridonate-hemilability
#5
Joseph M Clarkson, Laurel L Schafer
Four new bis(tert-butylimido)bis(N,O-chelate)tungsten(VI) complexes (3-6), in which the N,O-chelate is an amidate or pyridonate ligand, have been synthesized and characterized. Computational analysis has been used to calculate the relative energies of different stereoisomers and shown how the steric demand of each ligand influences coordination and bonding modes. The electronically saturated complexes have been employed to evaluate 1,3-N,O-chelated metal-ligand interactions. Complexes 3-6 were treated with electrophilic reagents, which resulted in strikingly different reactivity patterns between the amidate and the pyridonate ligated complexes...
April 26, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28443502/fe3o4-sio2-kit-6-as-an-efficient-and-reusable-catalyst-for-the-synthesis-of-novel-derivatives-of-3-3-aryl-1-phenyl-1h-pyrazol-4-yl-methylene-bis-1h-indole
#6
Mohammad Nikpassand, Leila Zare Fekri, Mozhdeh Nabatzadeh
Korea advanced institute of science and technology cubic ordered mesoporous silica (KIT-6 mesoporous) silica coated magnetite nanoparticles, is an effective, eco-benign and recyclable catalyst for the electrophilic substitution reactions of indoles with various synthetized aldehydes to afford the corresponding novel diindolylmethanes in high yields and short reaction times. The catalyst can be recovered and reused without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification...
April 25, 2017: Combinatorial Chemistry & High Throughput Screening
https://www.readbyqxmd.com/read/28441020/general-c-h-arylation-strategy-for-the-synthesis-of-tunable-visible-light-emitting-high-stokes-shift-benzo-a-imidazo-2-1-5-c-d-indolizine-fluorophores
#7
Éric Lévesque, William Schulz Bechara, Léa Constantineau-Forget, Guillaume Pelletier, Natalie M Rachel, Joelle N Pelletier, André B Charette
Herein we report the discovery of the benzo[a]imidazo[2,1,5-c,d]indolizine motif displaying tunable emission covering most of the visible spectrum. The polycyclic core is obtained from readily available amides via a chemoselective process involving Tf2O-mediated amide cyclodehydration followed by intramolecular C-H arylation. Additionally, these fluorescent heterocycles are easily functionalized using electrophilic reagents, enabling divergent access to varied substitution. The effects of said substitution on the compounds' photophysical properties were rationalized by DFT calculations...
April 25, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28440951/concluding-the-trilogy-the-interaction-of-2-2-dihydroxy-benzophenones-and-their-carbonyl-n-analogues-with-human-glutathione-transferase-m1-1-face-to-face-with-the-p1-1-and-a1-1-isoenzymes-involved-in-mdr
#8
Nikolaos D Georgakis, Dionisis A Karagiannopoulos, Trias N Thireou, Elias E Eliopoulos, Nikolaos E Labrou, Petros G Tsoungas, Michael N Koutsilieris, Yannis D Clonis
The conjugation of intracellular glutathione (GSH) with several electrophilic, predominantly hydrophobic, endogenous and xenobiotic compounds, such as chemotherapeutics and carcinogenics, agrochemicals and other drugs, is catalyzed by the multigene enzyme family of glutathione transferases (GSTs). The mammalian family of GSTs comprises three groups: cytosolic, mitochondrial and microsomal. Human cytosolic GSTs constitute the largest family, which is classified in seven distinct classes named Alpha (Α), Mu (M), Pi (P), Theta (T), Sigma (S), Zeta (Z) and Omega (O)...
April 25, 2017: Chemical Biology & Drug Design
https://www.readbyqxmd.com/read/28440636/probing-and-comparing-the-photobromination-and-photoiodination-of-dissolved-organic-matter-by-using-ultrahigh-resolution-mass-spectrometry
#9
Zhineng Hao, Yongguang Yin, Dong Cao, Jing-Fu Liu
Photochemical halogenation of dissolved organic matter (DOM) may represent an important abiotic source of natural organobromine compounds (OBCs) and natural organoiodine compounds (OICs) within surface waters. Here we report the significantly enhanced formation of OBCs and OICs by photohalogenating DOM in freshwater and seawater, as well as the noticeable difference in distribution and composition pattern of newly formed OBCs and OICs. By using the negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry, numerous OBCs and OICs were identified during the photo halogenation processes in sunlit waters...
April 25, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28440635/enantioselective-multicomponent-reaction-for-rapid-construction-of-1-2-5-triol-derivatives-with-vicinal-chiral-centers
#10
Mingfeng Li, Xin Guo, Qing Zheng, Wenhao Hu, Shunying Liu
1,2,5-triol derivatives with vicinal chiral centers have been synthesized from simple starting materials by one-pot method in good yields and with an excellent enantioselectivity. This process was promoted by a chiral secondary amine and iridium(I) co-catalyzed three-component reaction of aryldiazoacetates and alcohols with enals as electrophiles followed by a reduction with NaBH4.. Iridium(I)-associated oxonium ylide intermediates were efficiently generated and successfully trapped by the amine-activated enals via a selective 1,4-addtition manner, generating enantioselective three-component coupling products...
April 25, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28437118/blue-light-photocatalytic-glycosylation-without-electrophilic-additives
#11
Peng Wen, David Crich
Photocatalytic formation of glycosidic bonds employing stable and readily accessible O-glycosyl derivatives of 2,2,6,6-tetramethylpiperidin-1-ol is presented that employs an iridium-based photocatalyst and blue LEDs. The reaction proceeds at room temperature and in the absence of additives other than 4 Å molecular sieves. Stereoselectivities are modest but nevertheless dependent on the anomeric configuration of the donor, suggesting a substantial degree of concerted character.
April 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28437089/%C3%AF-n-c-bond-difunctionalization-in-bridged-twisted-amides-sew-and-cut-activation-approach-to-functionalized-isoquinolines
#12
Feng Hu, Pradeep Nareddy, Roger Lalancette, Frank Jordan, Michal Szostak
A rare example of highly selective σ N-C bond difunctionalization in bridged twisted lactams through N-C cleavage has been achieved. In combination with the intramolecular Heck cyclization, this method affords a two-step bond reorganization event ("sew-and-cut") to access functionalized isoquinoline ring systems directly with high atom economy. C-H bond functionalizations directed by a weakly coordinating bridged amide bond increase scaffold diversity. Preliminary mechanistic studies on the effect of amide distortion and the role of electrophile in this unusual σ N-C amide difunctionalization are described...
April 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28436079/-l-2-c2-p2-dicarbondiphosphide-stabilized-by-n-heterocyclic-carbenes-or-cyclic-diamido-carbenes
#13
Zhongshu Li, Xiaodan Chen, Diego M Andrada, Gernot Frenking, Zoltán Benkö, Yaqi Li, Jeffrey R Harmer, Cheng-Yong Su, Hansjörg Grützmacher
Carbon phosphides, Cn Pm , may have highly promising electronic, optical, and mechanical properties, but they are experimentally almost unexplored materials. Phosphaheteroallenes stabilized by N-heterocyclic carbenes undergo a one-electron reduction to yield compounds of the type (L)2 C2 P2 with diverse structures. The use of imidazolylidenes as ligands L give complexes with a central four-membered ring C2 P2 , while more electrophilic cyclic diamidocarbenes (DAC) give a compound with an acyclic π-conjugated CP-PC unit...
April 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28435948/diversification-reactions-of-%C3%AE-silyl-allenyl-esters-selective-conversion-to-all-carbon-quaternary-centers-and-%C3%AE-allene-dicarbinols
#14
Susovan Jana, Animesh Roy, Salvatore D Lepore
The unique reactivity of γ-silyl allenyl esters is described. Taking advantage of the silyl group as a fluoride acceptor, these allenoates readily underwent addition to a variety of electrophiles to selectively yield products with all-carbon quaternary centers or allenoate dicarbinols. These dicarbinols were subsequently converted to novel highly substituted 6-hydro-2-pyrones.
April 24, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28435866/layered-microporous-polymers-by-solvent-knitting-method
#15
Shaolei Wang, Chengxin Zhang, Yu Shu, Shulan Jiang, Qi Xia, Linjiang Chen, Shangbin Jin, Irshad Hussain, Andrew I Cooper, Bien Tan
Two-dimensional (2D) nanomaterials, especially 2D organic nanomaterials with unprecedentedly diverse and controlled structure, have attracted decent scientific interest. Among the preparation strategies, the top-down approach is one of the considered low-cost and scalable strategies to obtain 2D organic nanomaterials. However, some factors of their layered counterparts limited the development and potential applications of 2D organic nanomaterials, such as type, stability, and strict synthetic conditions of layered counterparts...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28431352/degradation-of-sulfamethoxazole-by-uv-uv-h2o2-and-uv-persulfate-pds-formation-of-oxidation-products-and-effect-of-bicarbonate
#16
Yi Yang, Xinglin Lu, Jin Jiang, Jun Ma, Guanqi Liu, Ying Cao, Weili Liu, Juan Li, Suyan Pang, Xiujuan Kong, Congwei Luo
The frequent detection of sulfamethoxazole (SMX) in wastewater and surface waters gives rise of concerns about their ecotoxicological effects and potential risks to induce antibacterial resistant genes. UV/hydrogen peroxide (UV/H2O2) and UV/persulfate (UV/PDS) advanced oxidation processes have been demonstrated to be effective for the elimination of SMX, but there is still a need for a deeper understanding of product formations. In this study, we identified and compared the transformation products of SMX in UV, UV/H2O2 and UV/PDS processes...
March 28, 2017: Water Research
https://www.readbyqxmd.com/read/28429870/induction-of-axial-chirality-in-8-arylquinolines-via-halogenation-reactions-using-bifunctional-organocatalysts
#17
Ryota Miyaji, Keisuke Asano, Seijiro Matsubara
The enantioselective syntheses of axially chiral heterobiaryls were accomplished via the aromatic electrophilic halogenation of 3-(quinolin-8-yl)phenols using bifunctional organocatalysts, which control the molecular conformations during successive halogenations. Axially chiral quinoline derivatives, which have rarely been synthesized in an enantioselective catalytic manner, were afforded in moderate-to-good enantioselectivities via bromination, and an analogous protocol also enabled enantioselective iodination...
April 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28429494/a-modular-approach-to-inorganic-phosphazane-macrocycles
#18
Alex J Plajer, Raúl García-Rodríguez, Callum G M Benson, Peter D Matthews, Andrew D Bond, Sanjay Singh, Lutz H Gade, Dominic S Wright
Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host-guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ-NR)]2 . The method involves the in situ generation of the key intermediate [E....._ (S...
April 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28429392/metal-free-formal-oxidative-c-c-coupling-by-in%C3%A2-situ-generation-of-an-enolonium-species
#19
Daniel Kaiser, Aurélien de la Torre, Saad Shaaban, Nuno Maulide
Much contemporary organic synthesis relies on transformations that are driven by the intrinsic, so-called "natural", polarity of chemical bonds and reactive centers. The design of unconventionally polarized synthons is a highly desirable strategy, as it generally enables unprecedented retrosynthetic disconnections for the synthesis of complex substances. Whereas the umpolung of carbonyl centers is a well-known strategy, polarity reversal at the α-position of a carbonyl group is much rarer. Herein, we report the design of a novel electrophilic enolonium species and its application in efficient and chemoselective, metal-free oxidative C-C coupling...
April 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28426208/global-and-local-partitioning-of-the-charge-transferred-in-the-parr-pearson-model
#20
Angel Ulises Orozco-Valencia, José Luis Gázquez, Alberto Vela
Through a simple proposal, the charge transfer obtained from the cornerstone theory of Parr and Pearson is partitioned, for each reactant, in two channels: an electrophilic, through which the species accepts electrons, and the other, a nucleophilic, where the species donates electrons. It is shown that this global model allows us to determine unambiguously the charge transfer mechanism prevailing in a given reaction. The partitioning is extended to include local effects through the Fukui functions of the reactants...
April 20, 2017: Journal of Physical Chemistry. A
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