- Substrate-Selective Olefin Hydrogenation with a Cavitand-Based Bis(N-anisyl iminophosphorane)
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A distally-substituted resorcin[4]arene cavitand equipped with two remote N-anisyl-imino-phosphoranyl (AIP) units has been synthesised and assessed in the competitive hydrogenation of α-olefins (rhodium catalyst). A substrate-selectivity factor of 39.2 in
- Chavagnan, Thierry,Bauder, Claude,Sémeril, David,Matt, Dominique,Toupet, Lo?c
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- Electronic Structures and Reactivity Profiles of Aryl Nitrenoid-Bridged Dicopper Complexes
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Dicopper complexes templated by dinucleating, pacman dipyrrin ligand scaffolds (Mesdmx, tBudmx: Dimethylxanthine-bridged, cofacial bis-dipyrrin) were synthesized by deprotonation/metalation with mesitylcopper (CuMes; Mes: Mesityl) or by transmetalation with cuprous precursors from the corresponding deprotonated ligand. Neutral imide complexes (Rdmx)Cu2(μ2-NAr) (R: Mes, tBu; Ar: 4-MeOC6H4, 3,5-(F3C)2C6H3) were synthesized by treatment of the corresponding dicuprous complexes with aryl azides. While one-electron reduction of (Mesdmx)Cu2(μ2-N(C6H4OMe)) with potassium graphite initiates an intramolecular, benzylic C-H amination at room temperature, chemical reduction of (tBudmx)Cu2(μ2-NAr) leads to isolable [(tBudmx)Cu2(μ2-NAr)]-product salts. The electronic structures of the thermally robust [(tBudmx)Cu2(μ2-NAr)]0/-complexes were assessed by variable-temperature electron paramagnetic resonance spectroscopy, X-ray absorption spectroscopy (Cu L2,3/K-edge, N K-edge), optical spectroscopy, and DFT/CASSCF calculations. These data indicate that the formally Class IIIA mixed valence complexes of the type [(Rdmx)Cu2(μ2-NAr)]-feature significant NAr-localized spin following reduction from electronic population of the [Cu2(μ2-NAr)] ? manifold, contrasting previous methods for engendering iminyl character through chemical oxidation. The reactivity of the isolable imido and iminyl complexes are examined for prototypical radical-promoted reactivity (e.g., nitrene transfer and H-atom abstraction), where the divergent reactivity is rationalized by the relative degree of N-radical character afforded from different aryl substituents.
- Carsch, Kurtis M.,Lukens, James T.,Dimucci, Ida M.,Iovan, Diana A.,Zheng, Shao-Liang,Lancaster, Kyle M.,Betley, Theodore A.
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supporting information
p. 2264 - 2276
(2020/02/18)
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- Staudinger reaction using 2,6-dichlorophenyl azide derivatives for robust aza-ylide formation applicable to bioconjugation in living cells
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Efficient formation of water- and air-stable aza-ylides has been achieved using the Staudinger reaction between electron-deficient aromatic azides such as 2,6-dichlorophenyl azide and triarylphosphines. The reaction proceeds rapidly and has been successfully applied to chemical modification of proteins in living cells.
- Meguro, Tomohiro,Terashima, Norikazu,Ito, Harumi,Koike, Yuka,Kii, Isao,Yoshida, Suguru,Hosoya, Takamitsu
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supporting information
p. 7904 - 7907
(2018/07/25)
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- Synthesis of 4-fluoromethylsydnones and their participation in alkyne cycloaddition reactions
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We report the synthesis and some structural studies of 4-trifluoromethyl, 4-difluoromethyl-, and 4-monofluoromethylsydnones. All but the latter compounds are stable and represent effective precursors to a range of pyrazoles after cycloaddition reactions with alkynes. The cycloadditions are generally highly regioselective and provide 5-fluoromethylpyrazole products, although we have observed that Bn-substituted sydnones can provide an unexpected alkyne insertion mode that generates the 3-fluoromethyl isomer.
- Foster, Robert S.,Adams, Harry,Jakobi, Harald,Harrity, Joseph P. A.
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p. 4049 - 4064
(2013/06/05)
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- Kinetics and mechanism of the nitrosobenzene deoxygenation by trivalent phosphorous compounds
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The reaction of aryl nitroso compounds with organic phosphines and phosphites in aerated media is a convenient non-photolytic procedure to generate aromatic nitroso oxides. The reaction rate constants and activation parameters of the key (for the proposed method of nitroso oxide generation) reaction of nitrosobenzene with tripenyl phosphite or para-substituted phosphines (4-RC 6H4)3P (R = MeO, Me, H, F), as well as that of para-methoxynitrosobenzene with triphenylphosphine in acetonitrile were determined by kinetic spectrophotometry and chemiluminescence. A significant transfer of the electron density to the nitroso compound occurs in the transition state of the reaction as was revealed using the Hammett correlation analysis and DFT calculations in the M06L/6-311+G(d,p) approximation. The introduction of the electron-donor substituent MeO into the para-position of PhNO decreases the reactivity of the nitroso compound by two orders of magnitude. The reactivity of triphenyl phosphite in the oxygen atom transfer reaction is lower by two orders of magnitude compared to that of triphenylphosphine. In the case of the reactions of PhNO with phosphines, the apparent rate constant depends on the oxygen content in the reaction medium.
- Khursan,Shamukaev,Chainikova,Khursan,Safiullin
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p. 2477 - 2486
(2014/11/08)
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- Copper(II) acetate/oxygen-mediated nucleophilic addition and intramolecular C-H activation/C-N or C-C bond formation: One-pot synthesis of benzimidazoles or quinazolines
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Diarylcarbodiimides or benzylphenylcarbodiimides are converted to 1,2-disubstituted benzimidazoles or 1,2-disustituted quinazolines via addition/intramolecular C-H bond activation/C-N or C-C bond forming reaction using copper(II) acetate/oxygen [Cu(OAc)2/O2] as the oxidant at 100°C in one-pot cascade procedure. Copyright
- He, Hua-Feng,Wang, Zhi-Jing,Bao, Weiliang
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supporting information; experimental part
p. 2905 - 2912
(2010/12/29)
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- Selective synthesis of 4-alkylidene-β-lactams and N,N′- diarylamidines from azides and aryloxyacetyl chlorides via a ketenimine-participating one-pot cascade process
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(Chemical Equation Presented) A one-pot cascade approach to 4-alkylidene-β-lactams and N,N-diarylamidines from aryl azides and aryloxyacetyl chlorides has been developed. The chemical outcome of the reaction can be controlled selectively by an appropriate choice of the stoichiometric ratio of different substrates and reagents. The products should find use in pharmaceutical discovery, especially in the development of new antimicrobial agents against multidrug-resistant pathogens.
- Yang, Yun-Yun,Shou, Wang-Ge,Hong, Deng,Wang, Yan-Guang
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p. 3574 - 3577
(2008/09/20)
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- Asymmetric transfer hydrogenation of β,γ-alkynyl α-lmino esters by a bronsted acid
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Asymmetric synthesis of trans-alkenyl α-amino esters was realized by chiral phosphoric acid catalyzed transfer hydrogenatlon of β,γ- alkynyl α-imino esters. Utilizing Hantzsch esters as the hydrogen donor, both the alkyne and Imine moieties of β,γ-alkynyl
- Kang, Qiang,Zhao, Zhuo-An,You, Shu-Li
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supporting information; experimental part
p. 2031 - 2034
(2009/04/10)
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- Acyclic amides as estrogen receptor ligands: Synthesis, binding, activity and receptor interaction
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We have prepared a series of bisphenolic amides that mimic bibenzyl and homobibenzyl motifs commonly found as substructures in ligands for the estrogen receptor (ER). Representative members were prepared from three classes: N-phenyl benzamides, N-phenyl acetamides, and N-benzyl benzamides; in some cases the corresponding thiocarboxamides and sulfonamides were also prepared. Of these three classes, the N-phenyl benzamides had the highest affinity for ER, the N-phenyl acetamides had lower, and the N-benzyl benzamides were prone to fragmentation via a quinone methide intermediate. In the N-phenyl benzamide series, the highest affinity analogues had bulky N-substituents; a CF3 group, in particular, conferred high affinity. The thiocarboxamides bound better than the corresponding carboxamides and these bound better than the corresponding sulfonamides. Binding affinity comparisons suggest that the p-hydroxy group on the benzoate ring, which contributes most to the binding, is playing the role of the phenolic hydroxyl of estradiol. Computational studies and NMR and X-ray crystallographic analysis indicate that the two anilide systems studied have a strong preference for the s-cis or exo amide conformation, which places the two aromatic rings in a syn orientation. We used this structural template, together with the X-ray structure of the ER ligand binding domain, to elaborate an additional hydrogen bonding site on a benzamide system that elevated receptor binding further. When assayed on the individual ER subtypes, ERα and ERβ, these compounds show modest binding affinity preference for ERα. In a reporter gene transfection assay of transcriptional activity, the amides generally have full to nearly full agonist character on ERα, but have moderate to full antagonist character on ERβ. One high affinity carboxamide is 500-fold more potent as an agonist on ERα than on ERβ. This work illustrates that ER ligands having simple amide core structures can be readily prepared, but that high affinity binding requires an appropriate distribution of bulk, polarity, and functionality. The strong conformational preference of the core anilide function in all of these ligands defines a rather rigid geometry for further structural and functional expansion of these series. Copyright (C) 2000 Elsevier Science Ltd.
- Stauffer, Shaun R.,Sun, Jun,Katzenellenbogen, Benita S.,Katzenellenbogen, John A.
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p. 1293 - 1316
(2007/10/03)
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- A one-pot aza-Wittig based solution and polymer supported route to amines
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This paper presents a high yielding one-pot solution phase and polymer supported synthesis of a range of primary and secondary amines starting from azides and aldehydes. The synthesis utilises a tandem process which begins with an aza-Wittig reaction between the aldehyde and an iminophosphorane, followed by reduction, or organometallic 1,2-addition reaction, of the resultant imine. The requisite iminophosphoranes were accessed using the highly efficient Staudinger reaction between the azide starting material and a phosphine. The process was applicable to the solid phase by the use of polymer supported iminophosphoranes and polymer supported cyanoborohydride.
- Hemming,Bevan,Loukou,Patel,Renaudeau
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p. 1565 - 1568
(2007/10/03)
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