6326-06-3Relevant articles and documents
Noninnocent Ligand in Rhodium(III)-Complex-Catalyzed C-H Bond Amination with Tosyl Azide
Fujita, Daiki,Sugimoto, Hideki,Morimoto, Yuma,Itoh, Shinobu
, p. 9738 - 9747 (2018)
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-.
Micelle catalyzed oxidative degradation of norfloxacin by chloramine-T
Shrivastava, Alpa,Singh, Ajaya Kumar,Sachdev, Neerja,Shrivastava, Dilip Raj,Katre, Yokraj,Singh, Surya P.,Singh, Man,Mejuto
, p. 1 - 11 (2012)
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
Benzylic oxidation and functionalizations of xanthenes by ligand trasfer reactions of hypervalent iodine reagents
Dohi, Toshifumi,Ito, Motoki,Kita, Yasuyuki,Komiyama, Keina,Ueda, Shohei,Yamaoka, Nobutaka
, p. 85 - 103 (2020/01/28)
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.
Uncatalyzed Oxidative C?H Amination of 9,10-Dihydro-9-Heteroanthracenes: A Mechanistic Study
van Leest, Nicolaas P.,Grooten, Lars,van der Vlugt, Jarl Ivar,de Bruin, Bas
, p. 5987 - 5993 (2019/04/03)
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.
Organocatalytic nitrenoid transfer: Metal-free selective intermolecular C(sp3)-H amination catalyzed by an iminium salt
Combee, Logan A.,Raya, Balaram,Wang, Daoyong,Hilinski, Michael K.
, p. 935 - 939 (2018/02/07)
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.
Probe-dependent negative allosteric modulators of the long-chain free fatty acid receptor FFA4
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
, p. 630 - 641 (2017/05/22)
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.
A Mononuclear Nonheme Iron(V)-Imido Complex
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
supporting information, p. 8800 - 8803 (2017/07/12)
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.
Suppressing cyclic polymerization for isoselective synthesis of high-molecular-weight linear polylactide catalyzed by sodium/potassium sulfonamidate complexes
Chen, Changjuan,Cui, Yaqin,Mao, Xiaoyang,Pan, Xiaobo,Wu, Jincai
, p. 83 - 96 (2017/04/03)
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.
Catalytic C-H amination driven by intramolecular ligand-to-nitrene one-electron transfer through a rhodium(III) centre
Fujita, Daiki,Sugimoto, Hideki,Shiota, Yoshihito,Morimoto, Yuma,Yoshizawa, Kazunari,Itoh, Shinobu
supporting information, p. 4849 - 4852 (2017/07/06)
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.
Mechanistic aspects for the oxidation of brilliant green dye by chloramine-T in the presence of perchloric acid: A spectrophotometric kinetic approach
Singh, Ajaya Kumar,Bano, Shakila
, p. 605 - 617 (2014/02/14)
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.
