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Justin F Acheson, Lucas J Bailey, Thomas C Brunold, Brian G Fox
Electrophilic aromatic substitution is one of the most important and recognizable classes of organic chemical transformation. Enzymes create the strong electrophiles that are needed for these highly energetic reactions by using O2, electrons, and metals or other cofactors. Although the nature of the oxidants that carry out electrophilic aromatic substitution has been deduced from many approaches, it has been difficult to determine their structures. Here we show the structure of a diiron hydroxylase intermediate formed during a reaction with toluene...
March 27, 2017: Nature
Weiping Zhou, Chunjie Ni, Jiangfei Chen, Dong Wang, Xiaofeng Tong
The formal (3 + 3) annulations of δ-acetoxy allenoates and 1C,3O-bisnucleophiles are reported with the use of 6'-deoxy-6'-perfluorobenzamido-quinine (4g) as a catalyst, which provide rapid access to 4H-pyrans with excellent enantioselectivity. The reaction features a wide reaction scope and mild reaction conditions. The crucial roles of amide NH of 4g as a H-bond donor have also been elucidated, which not only activates allenoate to facilitate formation of cationic intermediate A but also enhances the electrophilicity of its δ-position for nucleophilic 1,6-addition...
March 27, 2017: Organic Letters
Saurabh S Chitnis, Rebecca A Musgrave, Hazel A Sparkes, Natalie E Pridmore, Vincent T Annibale, Ian Manners
Heterolytic cleavage of homoatomic bonds is a challenge, as it requires separation of opposite charges. Even highly strained homoatomic rings (e.g., cyclopropane and cyclobutane) are kinetically stable and do not react with nucleophiles or electrophiles. In contrast, cycloalkanes bearing electron-donating/withdrawing substituents on adjacent carbons have polarized C-C bonds and undergo numerous heterolytic ring-opening and expansion reactions. Here we show that upon electrophile activation phosphorus homocycles exhibit analogous reactivity, which is modulated by the amount of ring strain and extent of bond polarization...
March 27, 2017: Inorganic Chemistry
Puminan Punthasee, Adrian R Laciak, Andrea Hicks Cummings, Kasi Viswanatharaju Ruddraraju, Sarah M Lewis, Roman Hillebrand, Harkewal Singh, John J Tanner, Kent S Gates
Protein tyrosine phosphatase 1B (PTP1B) is a validated drug target but it has proven difficult to develop medicinally-useful, reversible inhibitors of this enzyme. Here we explored covalent strategies for the inactivation of PTP1B using a conjugate composed of an active site-directed 5-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxide inhibitor connected via a short linker to an electrophilic α-bromoacetamide moiety. The inhibitor-electrophile conjugate 5a caused time-dependent loss of PTP1B activity consistent with a covalent inactivation mechanism...
March 27, 2017: Biochemistry
Jun-Jie Wang, Hao-Sheng Lin, Chuang Niu, Guan-Wu Wang
The electrochemical cyclopropanation of [60]fullerobenzofurans with diethyl dibromomalonate has been investigated. Controlled by the steric effect, the sterically favored e bisadducts are obtained as the major products along with two trans-3 bisadducts as minor products. The addition sites and patterns of this reaction are very different from those of our previously reported reaction with benzyl bromide, providing insights into the controlling factors for the electrophilic reactions of dianionic fullerene derivatives...
March 27, 2017: Organic & Biomolecular Chemistry
Jin-Dong Yang, Ya Wang, Xiao-Song Xue, Jin-Pei Cheng
The recent uncovering of the radical reactivity of a few traditionally electrophilic N-F reagents has sparked a renaissance of radical fluorination. A knowledge of the N-F bond dissociation enthalpies (BDE) of electrophilic N-F reagents is essential for the understanding of their reactivities. However, a thorough literature survey revealed that such information is extremely sparse. This prompted us to carry out the first systematic computation on the N-F BDEs of electrophilic N-F reagents. The calculated N-F BDE scale of 88 electrophilic N-F reagents ranges from 49...
March 27, 2017: Journal of Organic Chemistry
Raquel de la Campa, Diego García, Sandra Rodríguez, Gabino A Carriedo, Alejandro Presa Soto
The direct chemical functionalization of poly(spirophosphazene) [NP(O2 C12 H8 )]n (1) can be performed by the lithiation of the aromatic rings at low temperature using Schlosser's base (Li(t) Bu/KO(t) Bu or "superbase"), and the subsequent reaction with various electrophiles such as ClSiMe3 , ClPPh2 , or MeOB(O2 C6 H12 ) (MeOBpin). The functionalized polymers, isolated in very high yields (>90%) and without degradation of the polymeric chains, have an average degree of substitution per repeat unit ranging from 0...
March 27, 2017: Macromolecular Rapid Communications
Daniel Meyer, Toni Smeilus, Dimanthi Pliatsika, Farnoush Mousavizadeh, Athanassios Giannis
Several artemisinin derivatives carrying several groups (alkyl, hydroxyalkyl, allyl or azide) at position 9 have been synthesized starting from artemisinin via enolate formation and subsequent reaction with appropriate electrophiles.
March 14, 2017: Bioorganic & Medicinal Chemistry
Donald C McAteer, Erman Javed, Lily Huo, Shouquan Huo
A unique, platinum-catalyzed, direct C-H acylation of 2-(aryloxy)pyridines with acyl chlorides is discovered. The reaction requires neither an oxidant nor other additives. When both ortho positions of the aryl group are accessible, the double acylation occurs readily to produce the diacylated products. Aliphatic, aromatic, and α,β-unsaturated acyl groups can all be introduced. The acylation reaction may proceed through an analogous aromatic electrophilic substitution triggered by the nucleophilic attack of the platinum at the acyl chloride...
March 24, 2017: Organic Letters
Meirong Jia, Reuben J Peters
Isoprenoid precursors readily undergo (poly)cyclization in electrophilic reaction cascades, presumably as internal addition of the carbon-carbon double-bonds from neighboring isoprenyl repeats readily forms relatively stable cyclohexyl tertiary carbocation intermediates. This hypothesis is agnostic regarding alkene configuration (i.e., Z or E). Consistent with this, here it is shown that certain class II diterpene cyclases, which normally convert (E,E,E)-geranylgeranyl diphosphate to 13E-trans-decalin bicycles, will also act upon (Z,Z,Z)-nerylneryl diphosphate, producing novel 13Z-cis-decalin bicycles instead...
March 24, 2017: Organic & Biomolecular Chemistry
Ying-Chun Chen, Gu Zhan, Ming-Lin Shi, Wei-Jia Lin, Yang Ouyang, Wei Du
Nitrones commonly act as 1,3-dipoles and electrophiles to furnish valuable isoxazolidine and N-hydroxyl products, respectively. They also can be converted to nitrone ylide species, and undergo [3+2] formal cycloadditions to access N-hydroxyl pyrrolidines. Here we first present asymmetric direct aza-vinylogous-type additions of nitrones from isatins to nitroalkenes catalyzed by a bifunctional thiourea-tertiary amine, producing highly functionalized nitrones with extended carbon skeletons in excellent stereoselectivity...
March 23, 2017: Chemistry: a European Journal
Sarah Mas Y Mas, Gilles Curien, Cécile Giustini, Norbert Rolland, Jean-Luc Ferrer, David Cobessi
Enzymatic and non-enzymatic peroxidation of polyunsaturated fatty acids give rise to accumulation of aldehydes, ketones, and α,β-unsaturated carbonyls of various lengths, known as oxylipins. Oxylipins with α,β-unsaturated carbonyls are reactive electrophile species and are toxic. Cells have evolved several mechanisms to scavenge reactive electrophile oxylipins and decrease their reactivity such as by coupling with glutathione, or by reduction using NAD(P)H-dependent reductases and dehydrogenases of various substrate specificities...
2017: Frontiers in Plant Science
Ehsan Faghih-Mirzaee, Maryam Dehestani, Leila Zeidabadinejad
In this study, the transfer of L-ascorbic acid by UlaA through Escherichia coli (E. coli) membrane was evaluated using density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulation methods. DFT calculations at the B3lyp/6[Formula: see text]311[Formula: see text]G(p,d) level were performed to investigate the interaction properties and molecular descriptors. The physical properties, such as chemical potential, chemical hardness, and chemical electrophilicity of all studied molecules, were investigated...
February 24, 2017: Journal of Bioinformatics and Computational Biology
Gerui Ren, Qinheng Zheng, Hua Wang
A chemoselective Staudinger reduction/sulfur(VI) fluoride exchange cascade has been developed to join two chemical segments through an aryl sulfamate ester (RNH-SO2-OAr) linkage. Aryl fluorosulfate is exploited in this work as the first tetrahedral electrophilic trap for the in situ generated iminophosphorane. Ten examples using azide-containing compounds are presented.
March 23, 2017: Organic Letters
Matthew Neurock, Zhiyuan Tao, Ashwin Chemburkar, David D Hibbitts, Enrique Iglesia
Condensation and esterification are important catalytic routes in the conversion of polyols and oxygenates derived from biomass to fuels and chemical intermediates. Previous experimental studies show that alkanal, alkanol and hydrogen mixtures equilibrate over Cu/SiO2 and form surface alkoxides and alkanals that subsequently promote condensation and esterification reactions. First-principle density functional theory (DFT) calculations were carried out herein to elucidate the elementary paths and the corresponding energetics for the interconversion of propanal + H2 to propanol and the subsequent C-C and C-O bond formation paths involved in aldol condensation and esterification of these mixtures over model Cu surfaces...
March 23, 2017: Faraday Discussions
Jin-Shun Lin, Fu-Li Wang, Xiao-Yang Dong, Wei-Wei He, Yue Yuan, Su Chen, Xin-Yuan Liu
Although great success has been achieved in asymmetric fluoroalkylation reactions via nucleophilic or electrophilic processes, the development of asymmetric radical versions of this type of reactions remains a formidable challenge because of the involvement of highly reactive radical species. Here we report a catalytic asymmetric radical aminoperfluoroalkylation and aminodifluoromethylation of alkenes with commercially available fluoroalkylsulfonyl chlorides as the radical sources, providing a versatile platform to access four types of enantioenriched α-tertiary pyrrolidines bearing β-perfluorobutanyl, trifluoromethyl, difluoroacetyl and even difluoromethyl groups in excellent yields and with excellent enantioselectivity...
March 23, 2017: Nature Communications
Thomas Roach, Theresa Baur, Wolfgang Stöggl, Anja Krieger-Liszkay
High light causes photosystem II to generate singlet oxygen ((1) O2 ), a reactive oxygen species (ROS) that can react with membrane lipids, releasing reactive electrophile species (RES), such as acrolein. To investigate how RES may contribute to light stress responses, Chlamydomonas reinhardtii was high light-treated in photoautotrophic and mixotrophic conditions and also in an oxygen-enriched atmosphere to elevate ROS production. The responses were compared to exogenous acrolein. Non-photochemical quenching (NPQ) was higher in photoautotrophic cells, as a consequence of a more de-epoxidized state of the xanthophyll cycle pool and more LHCSR3 protein, showing that photosynthesis was under more pressure than in mixotrophic cells...
March 21, 2017: Physiologia Plantarum
Ruby Srivastava
We study the binding of the neutral Agn (n = 8, 10, 12) to the DNA base- adenine (A), guanine (G) and Watson-Crick -adenine-thymine (AT), guanine-cytosine (GC) pairs. Geometries of complexes were optimized at the DFT level using the hybrid B3LYP functional. LANL2DZ effective core potential (ECP) was used for silver and 6-31+G(**) was used for all other atoms. NBO charges were analyzed using the Natural population analysis. The absorption properties of Agn-A,G/WC complexes were also studied using time-dependent density functional theory (TDDFT)...
March 21, 2017: Journal of Biomolecular Structure & Dynamics
Gonzalo Abellán, Milan Schirowski, Konstantin F Edelthalhammer, Michael Fickert, Katharina Werbach, Herwig Peterlik, Frank Hauke, Andreas Hirsch
Covalently functionalized graphene derivatives were synthesized via benchmark reductive routes using graphite intercalation compounds (GICs), in particular KC8. We have compared the graphene arylation and -alkylation of the GIC using 4-tert-butylphenyldiazonium- and bis-(4-(tert-butyl)phenyl)-iodonium salts as well as phenyl iodide, n-hexyl- and n-dodecyl iodide as electrophiles in model reactions. We have put a particular focus on the evaluation of the degree of addition and the bulk functional-ization homogeneity Hbulk...
March 21, 2017: Journal of the American Chemical Society
Alexander Sapegin, Angelina Osipyan, Mikhail Krasavin
Imidazoline-fused [1,4]oxazepines (prepared in two simple steps from methyl 2-hydroxyaroates, ethylene diamine and bis-electrophilic aromatics) undergo a facile, good-yielding hydrolytic imidazoline ring expansion (HIRE) upon N-alkylation and treatment with aqueous K2CO3. The resulting arene-fused ten-membered lactams significantly add to the contemporary arsenal of small-molecule scaffolds where medium-sized ring systems are severely underrepresented.
March 21, 2017: Organic & Biomolecular Chemistry
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