- Noninnocent Ligand in Rhodium(III)-Complex-Catalyzed C-H Bond Amination with Tosyl Azide
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Six-coordinate rhodium(III) complexes coordinated by a planar trianionic ligand (L3-) are synthesized. One of the axial positions is occupied by chloride (Cl-), bromide (Br-), or iodide (I-), and another axial position is coordinated by a solvent molecule such as acetonitrile (AN), water (H2O), tetrahydrofuran (THF), or pyridine (PY) to complete an octahedral rhodium(III) center; [RhIII(L3-)(X)(Y)]? (1X/Y X = Cl-, Br-, or I-, Y = AN, H2O, THF, or PY). Coordination of the AN, H2O, and THF ligands to the metal center is rather weak, so that these solvent molecules are easily replaced by PY to give [RhIII(L3-)(Cl)(PY)]?. In the electrochemical measurements, all complexes have two reversible redox couples based on the ligand-centered oxidation L3- to L·2- and to L-, as reflected by the very similar redox potentials regardless of the different axial ligands. The rhodium(III) complexes catalyze C-H bond amination of xanthene with tosyl azide (TsN3). Because the yields of the aminated product are nearly the same among the complexes, replacement of the axial solvent ligands with TsN3 readily occurs to give a nitrene-radical-bound rhodium(III) complex, [RhIII(L·2-)(N·Ts)(X)]?, as an active oxidant, which is generated by one-electron transfer from the trianionic L3- to the nitrene nitrogen atom. Generation of such a diradical intermediate was substantiated by the direct reaction of 1Cl/AN with TsN3 in the absence of the substrate (xanthene). In this case, a rhodium(III) iminosemiquinone complex, 2, was generated by the intramolecular reaction between the nitrene-radical moiety and the radical moiety of the ligand L·2-.
- Fujita, Daiki,Sugimoto, Hideki,Morimoto, Yuma,Itoh, Shinobu
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Read Online
- Micelle catalyzed oxidative degradation of norfloxacin by chloramine-T
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Present work reports influence of micellar media (CTAB) upon the oxidative degradation of fluoroquinolone family drug norfloxacin (NOR). The reaction has been studied at constant temperature (308 K). The stoichiometry of the reaction was found to be 1:4 a
- Shrivastava, Alpa,Singh, Ajaya Kumar,Sachdev, Neerja,Shrivastava, Dilip Raj,Katre, Yokraj,Singh, Surya P.,Singh, Man,Mejuto
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- Benzylic oxidation and functionalizations of xanthenes by ligand trasfer reactions of hypervalent iodine reagents
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The benzylic oxidation, amidation, and unprecedented heteroarylation proceed at room temperature using iodosobenzene, (sulfonylimido)iodobenzenes, and diaryliodonium(III) salts are described for the direct Csp3-H functionalizations of xanthene molecules. This study has demonstrated that hypervalent iodine reagents serve as unified synthetic tools for versatile xanthene Csp3-H transformations based on the radical and SET oxidation processes.
- Dohi, Toshifumi,Ito, Motoki,Kita, Yasuyuki,Komiyama, Keina,Ueda, Shohei,Yamaoka, Nobutaka
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- Uncatalyzed Oxidative C?H Amination of 9,10-Dihydro-9-Heteroanthracenes: A Mechanistic Study
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A new method for the one-step C?H amination of xanthene and thioxanthene with sulfonamides is reported, without the need for any metal catalyst. A benzoquinone was employed as a hydride (or two-electron and one-proton) acceptor. Moreover, a previously unknown and uncatalyzed reaction between iminoiodanes and xanthene, thioxanthene and dihydroacridines (9,10-dihydro-9-heteroanthracenes or dihydroheteroanthracenes) is disclosed. The reactions proceed through hydride transfer from the heteroarene substrate to the iminoiodane or benzoquinone, followed by conjugate addition of the sulfonamide to the oxidized heteroaromatic compounds. These findings may have important mechanistic implications for metal-catalyzed C?H amination processes involving nitrene transfer from iminoiodanes to dihydroheteroanthracenes. Due to the weak C?H bond, xanthene is an often-employed substrate in mechanistic studies of C?H amination reactions, which are generally proposed to proceed via metal-catalyzed nitrene insertion, especially for reactions involving nitrene or imido complexes that are less reactive (i.e., less strongly oxidizing). However, these substrates clearly undergo non-catalyzed (proton-coupled) redox coupling with amines, thus providing alternative pathways to the widely assumed metal-catalyzed pathways.
- van Leest, Nicolaas P.,Grooten, Lars,van der Vlugt, Jarl Ivar,de Bruin, Bas
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supporting information
p. 5987 - 5993
(2019/04/03)
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- Organocatalytic nitrenoid transfer: Metal-free selective intermolecular C(sp3)-H amination catalyzed by an iminium salt
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This report details the first organocatalytic method for nitrenoid transfer and its application to intermolecular, site-selective C(sp3)-H amination. The method utilizes a trifluoromethyl iminium salt as the catalyst, iminoiodinanes as the nitrogen source, and substrate as the limiting reagent. Activated, benzylic, and aliphatic substrates can all be selectively functionalized in yields up to 87%. A mechanistic proposal for the observed reactivity supported by experimental evidence invokes the intermediacy of a diaziridinium salt or related organic nitrenoid, species that have not been previously explored for the purpose of C-H amination. Finally, examples of late-stage functionalization of complex molecules highlight the selectivity and potential utility of this catalytic method in synthesis.
- Combee, Logan A.,Raya, Balaram,Wang, Daoyong,Hilinski, Michael K.
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p. 935 - 939
(2018/02/07)
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- Probe-dependent negative allosteric modulators of the long-chain free fatty acid receptor FFA4
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High-affinity and selective antagonists that are able to block the actions of both endogenous and synthetic agonists of G protein-coupled receptors are integral to analysis of receptor function and to support suggestions of therapeutic potential. Although there is great interest in the potential of free fatty acid receptor 4 (FFA4) as a novel therapeutic target for the treatment of type II diabetes, the broad distribution pattern of this receptor suggests it may play a range of roles beyond glucose homeostasis in different cells and tissues. To date, a single molecule, 4-methyl- N-9H-xanthen-9-yl-benzenesulfonamide (AH-7614), has been described as an FFA4 antagonist; however, its mechanism of antagonism remains unknown. We synthesized AH-7614 and a chemical derivative and demonstrated these to be negative allosteric modulators (NAMs) of FFA4. Although these NAMs did inhibit FFA4 signaling induced by a range of endogenous and synthetic agonists, clear agonist probe dependence in the nature of allosteric modulation was apparent. Although AH-7614 did not antagonize the second long-chain free fatty acid receptor, free fatty acid receptor 1, the simple chemical structure of AH-7614 containing features found in many anticancer drugs suggests that a novel close chemical analog of AH-7614 devoid of FFA4 activity, 4-methyl-N-(9H-xanthen-9-yl)benzamide (TUG-1387), will also provide a useful control compound for future studies assessing FFA4 function. Using TUG-1387 alongside AH-7614, we show that endogenous activation of FFA4 expressed by murine C3H10T1/2 mesenchymal stem cells is required for induced differentiation of these cells toward a more mature, adipocyte-like phenotype.
- Watterson, Kenneth R.,Hansen, Steffen V.F.,Hudson, Brian D.,Alvarez-Curto, Elisa,Raihan, Sheikh Zahir,Azevedo, Carlos M.G.,Martin, Gabriel,Dunlop, Julia,Yarwood, Stephen J.,Ulven, Trond,Milligan, Graeme
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p. 630 - 641
(2017/05/22)
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- A Mononuclear Nonheme Iron(V)-Imido Complex
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Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)FeV(NTs)]? (1). The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe - N bond length of 1.65(4) ?, and an Fe - N vibration at 817 cm-1. The reactivity of 1 was demonstrated in C - H bond functionalization and nitrene transfer reactions.
- Hong, Seungwoo,Sutherlin, Kyle D.,Vardhaman, Anil Kumar,Yan, James J.,Park, Sora,Lee, Yong-Min,Jang, Soojeong,Lu, Xiaoyan,Ohta, Takehiro,Ogura, Takashi,Solomon, Edward I.,Nam, Wonwoo
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supporting information
p. 8800 - 8803
(2017/07/12)
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- Catalytic C-H amination driven by intramolecular ligand-to-nitrene one-electron transfer through a rhodium(III) centre
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Werner type six-coordinate rhodium(iii) complexes coordinated by a planar trianionic ligand and two axial aniline ligands are synthesised. The trianionic ligand behaves as a redox-active ligand to form a ligand radical species upon one-electron oxidation of the complex. The rhodium(iii) complexes catalyse C-H amination of external substrates such as xanthene with tosylazide as the nitrene source. DFT-calculation and kinetic deuterium isotope effects indicate that a di-radical rhodium(iii) complex formed by one-electron transfer from the redox-active ligand to the nitrene group works as a reactive intermediate to induce aliphatic C-H activation.
- Fujita, Daiki,Sugimoto, Hideki,Shiota, Yoshihito,Morimoto, Yuma,Yoshizawa, Kazunari,Itoh, Shinobu
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supporting information
p. 4849 - 4852
(2017/07/06)
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- Suppressing cyclic polymerization for isoselective synthesis of high-molecular-weight linear polylactide catalyzed by sodium/potassium sulfonamidate complexes
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A new sodium/potassium crown ether complex system with a series of bichelating sulfonamides as ligands was developed for the ring-opening polymerization (ROP) of rac-lactide. In this system, the side reaction of cyclic polymerization can be suppressed very well because of very different ROP rates initiated by BnOH and sulfonamide anion. The synthesis of high molecular weight linear polylactide with molecular weight high up to 107 kg/mol was successful. The best isoselectivity also can reach to a high value of Pm = 0.84. The NMR analysis of the reaction mixture of rac-lactide and complex 3 together with kinetic studies suggests the mechanism of ROP in the absence of alcohol is a coordination-insertion mechanism. After addition of BnOH, the ROP rate can increase remarkably due to the cooperation interaction of alcohol and complex 3.
- Chen, Changjuan,Cui, Yaqin,Mao, Xiaoyang,Pan, Xiaobo,Wu, Jincai
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- Mechanistic aspects for the oxidation of brilliant green dye by chloramine-T in the presence of perchloric acid: A spectrophotometric kinetic approach
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The kinetics of a triarylmethane dye, brilliant green (BG), by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) was studied spectrophotometrically in HClO4 media at 303 K. Under identical experimental conditions, the rate law was -d [BG]/dt = k [BG] [H+]. Variations in ionic strength (μ) of the medium had no effect on the oxidation velocity. Addition of p-toluenesulfonamide, the reduction product of CAT and Cl-, had no significant effect on the rate of reaction. The values of rate constants observed at five different temperatures (298, 303, 308, 313, and 318 K) were utilized to calculate the activation parameters. The observed results have been explained by a general mechanism and the related rate law has been obtained. The process demonstrated in this study is cost effective, which holds great promise in potential application for pollutant control.
- Singh, Ajaya Kumar,Bano, Shakila
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p. 605 - 617
(2014/02/14)
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- Identification of diarylsulfonamides as agonists of the free fatty acid receptor 4 (FFA4/GPR120)
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The exploration of a diarylsulfonamide series of free fatty acid receptor 4 (FFA4/GPR120) agonists is described. This work led to the identification of selective FFA4 agonist 8 (GSK137647A) and selective FFA4 antagonist 39. The in vitro profile of compounds 8 and 39 is presented herein.
- Sparks, Steven M.,Chen, Grace,Collins, Jon L.,Danger, Dana,Dock, Steven T.,Jayawickreme, Channa,Jenkinson, Stephen,Laudeman, Christopher,Leesnitzer, M. Anthony,Liang, Xi,Maloney, Patrick,McCoy, David C.,Moncol, David,Rash, Vincent,Rimele, Thomas,Vulimiri, Padmaja,Way, James M.,Ross, Sean
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p. 3100 - 3103
(2014/06/24)
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- Nonheme iron-mediated amination of C(sp3)-H bonds. Quinquepyridine-supported iron-imide/nitrene intermediates by experimental studies and DFT calculations
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The 7-coordinate complex [Fe(qpy)(MeCN)2](ClO4) 2 (1, qpy = 2,2′:6′,2″:6″, 2′′′:6′′′,2′′′′- quinquepyridine) is a highly active nonheme iron catalyst for intra- and intermolecular amination of C(sp3)-H bonds. This complex effectively catalyzes the amination of limiting amounts of not only benzylic and allylic C(sp3)-H bonds of hydrocarbons but also the C(sp3)-H bonds of cyclic alkanes and cycloalkane/linear alkane moieties in sulfamate esters, such as those derived from menthane and steroids cholane and androstane, using PhI=NR or "PhI(OAc)2 + H2NR" [R = Ts (p-toluenesulfonyl), Ns (p-nitrobenzenesulfonyl)] as nitrogen source, with the amination products isolated in up to 93% yield. Iron imide/nitrene intermediates [Fe(qpy)(NR)(X)]n+ (CX, X = NR, solvent, or anion) are proposed in these amination reactions on the basis of experimental studies including ESI-MS analysis, crossover experiments, Hammett plots, and correlation with C-H bond dissociation energies and with support by DFT calculations. Species consistent with the formulations of [Fe(qpy)(NTs)2] 2+ (CNTs) and [Fe(qpy)(NTs)]2+ (C) were detected by high-resolution ESI-MS analysis of the reaction mixture of 1 with PhI=NTs (4 equiv). DFT calculations revealed that the reaction barriers for H-atom abstraction of cyclohexane by the ground state of 7-coordinate C NTs and ground state of C are 15.3 and 14.2 kcal/mol, respectively, in line with the observed high activity of 1 in catalyzing the C-H amination of alkanes under mild conditions.
- Liu, Yungen,Guan, Xiangguo,Wong, Ella Lai-Ming,Liu, Peng,Huang, Jie-Sheng,Che, Chi-Ming
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supporting information
p. 7194 - 7204
(2013/06/27)
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- Efficient synthesis of N -(9-Xanthyl)-4-toluenesulfonamides enabled by an addition-cyclization cascade of arynes
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An efficient synthesis of N-(9-xanthyl)-4-toluenesulfonamides is described in which salicyl N-tosylimines react with silylaryl triflates in the presence of CsF. This mild process involves an addition-cyclization cascade in which arynes are generated and t
- Lu, Shan-Shan,Lu, Chong-Dao
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supporting information
p. 640 - 644
(2013/04/10)
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- Highly efficient synthesis of 9-aminoxanthenes via the tandem reaction of arynes with salicyl N-tosylimines
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A cascade insertion-nucleophilic annulation reaction of salicyl N-tosylimines with aryne generated in situ from 2-(trimethylsilyl) aryl triflate and KF-18-crown-6 has been developed, providing 9-aminoxanthenes efficiently in one step.
- He, Lin,Pian, Ji Xin,Zhang, Jing,Li, Yuan Zhen
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p. 1359 - 1362
(2013/02/23)
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- Catalytic asymmetric α-alkylation of ketones and aldehydes with N-benzylic sulfonamides through carbon-nitrogen bond cleavage
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A range of ketones and aldehydes smoothly undergo asymmetric SN1 α-alkylation with N-benzylic sulfonamides in the presence of 10 mol % of a chiral imidazolidinone and trifluoroacetic acid to give the corresponding products in good to excellent
- Weng, Zhen-Tao,Li, Yuan,Tian, Shi-Kai
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experimental part
p. 8095 - 8099
(2011/11/07)
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- Imido transfer from bis(imido)ruthenium(VI) porphyrins to hydrocarbons: Effect of imido substituents, C-H bond dissociation energies, and Ru VI/V reduction potentials
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[RuVI(TMP)(NSO2R)2] (SO2R = Ms, Ts, Bs, Cs, Ns; R = p-C6H4OMe, p-C6H 4Me, C6H5, p-C6H4-Cl, p-C6H4NO2, respectively) and [Ru VI(Por)(NTs)2] (Por = 2,6-Cl2TPP, F 20-TPP) were prepared by the reactions of [RuII(Por)(CO)] with Phl=NSO2R in CH2Cl2. These complexes exhibit reversible RuVI/V couple with E1/2 = -0.41 to -0.12 V vs Cp2Fe+/10 and undergo imido transfer reactions with styrenes, norbornene, cis-cyclooctene, indene, ethylbenzenes, cumene, 9,10-dihydroanthracene, xanthene, cyclohexene, toluene, and tetrahydrofuran to afford aziridines or amides in up to 85% yields. The second-order rate constants (k2) of the aziridination/amidation reactions at 298 K were determined to be (2.6 ± 0.1) × 10-5 to 14.4 ± 0.6 dm3 mol-1 s-1, which generally increase with increasing RuVI/V reduction potential of the imido complexes and decreasing C-H bond dissociation energy (BDE) of the hydrocarbons. A linear correlation was observed between log K (K is the k2 value divided by the number of reactive hydrogens) and BDE and between log k2 and E1/2(RuVI/V); the linearity in the former case supports a H-atom abstraction mechanism. The amidation by [RuVI(TMP)(NNs) 2] reverses the thermodynamic reactivity order cumene > ethylbenzene/toluene, with K(3° C-H)/K(2° C-H) = 0.2 and K(3° C-H)/K(1° C-H) = 0.8.
- Leung, Sarana Ka-Yan,Tsui, Wai-Man,Huang, Jie-Sheng,Che, Chi-Ming,Liang, Jiang-Lin,Zhu, Nianyong
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p. 16629 - 16640
(2007/10/03)
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- HETEROCYCLOALKYLATION OF BASES WITH XANTHYLIUM AND THIOXANTHYLIUM SALTS
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Xanthylium and thioxanthylium perchlorates convert tertiary amines into quaternary salts having xanthene and thioxanthene residues at the nitrogen atom.When these reagents are used, the heterocycloalkylation of amines, amides, sulfonamides, imides, and alcohols is not accompanied by disproportionation.
- Ivanov, G. E.,Pavlyuk, G. V.,Turov, A. V.,Ryzhakov, M. K.
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p. 752 - 755
(2007/10/02)
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