- Benzoato and thiobenzoato ligands in the synthesis of dinuclear palladium(III) and -(II) compounds: Stability and catalytic applications
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New palladium(III) compounds of formula Pd2[(C6H4)PPh2]2[OXC(C6H5)]2Cl2 [3a (X = O); 3b (X = S)] were obtained by the oxidation of the analogous palladium(II) ones with PhICl2 and were characterized by 31P, 1H, and 13C NMR spectroscopy at 223 K. Compound 3a was also structurally characterized by single-crystal X-ray diffraction methods, which revealed a Pd-Pd distance of 2.5212(10) ?. DFT calculations were conducted to study the stability of all of these new palladium(III) and -(II) compounds with focus on the influence of the O虠S substitution of the donor atom in the ligand. The palladium(II) compounds Pd2[(C6H4)PPh2]2[OXC(C6H5)]2 [2a (X = O), 2b (X = S)] were also tested as precatalyst in two reactions: (1) the acetoxylation of 2-phenylpyridine and (2) the room-temperature 2-phenylation of indoles. Compound 2b is a better precatalyst than 2a in the first reaction (4 h; isolated yield, 67.5 vs. 50.4 %). In the second catalytic reaction, isolated yields of 97 (10 h, substrate: 1-methylindole) and 99 % (24 h, substrate: indole) were obtained with 2a as the precatalyst, whereas 2b gave low or no conversion. Dinuclear palladium(III) and -(II) compounds with benzoato and thiobenzoato ligands are synthesized. DFT calculations are performed to study the stability of these compounds and the influence of the O虠S substitution of the donor atom. The catalytic activity of the palladium(II) complexes is also tested in the acetoxylation of 2-phenylpyridine and the room-temperature 2-phenylation of indoles.
- Estevan, Francisco,Ibá?ez, Susana,Ofori, Albert,Hirva, Pipsa,Sanaú, Mercedes,úbeda, Ma Angeles
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- Palladium-Catalyzed C-H Bond Acetoxylation via Electrochemical Oxidation
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Here we describe the development of a method for the Pd-catalyzed electrochemical acetoxylation of C-H bonds. The oxidation step of the catalytic cycle is probed through cyclic voltammetry and bulk electrolysis studies of a preformed palladacycle of 8-methylquinoline. A catalytic system for C-H acetoxylation is then developed and optimized with respect to the cell configuration, rate of oxidation, and chemistry at the counter electrode. This transformation is then applied to substrates containing various directing groups and to the acetoxylation of both C(sp2)-H and C(sp3)-H bonds.
- Shrestha, Anuska,Lee, Melissa,Dunn, Anna L.,Sanford, Melanie S.
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Read Online
- Hypercrosslinked Polymer Platform-Anchored Single-Site Heterogeneous Pd-NHC Catalysts for Diverse C-H Functionalization
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We demonstrate a new class of hypercrosslinked polymer (HCP) platform-Anchored single-site heterogenized Pd-NHC catalysts for multipurpose C-H functionalization reactions. This new class is represented by a set of three catalysts, viz., HCP-B-MeNHC-Pd, HCP-B-BnNHC-Pd, and HCP-TPM-MeNHC-Pd, having a variation on the structural feature of the anchoring polymeric platform. All three catalysts were fully characterized via diverse solid-state characterization and analytical techniques such as X-ray photoelectron spectroscopy, 13C cross-polarization magic-Angle-spinning nuclear magnetic resonance, field-emission scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, and inductively coupled plasma-optical emission spectrometry. Three types of regularly practiced and very useful C-H functionalization reactions, viz., C-H halogenation, acetoxylation, and arylation, are tested with the new catalysts and found to be highly compatible and successful. With the HCP-TPM-MeNHC-Pd catalyst, up to 85, 75, and 70% yields of the functionalized products were achieved for the halogenation, acetoxylation, and arylation reactions, respectively. Demanding attributes such as enhanced activity, heterogeneity, and recyclability are offered by this new system, making it a promising candidate in the field of heterogeneous C-H functionalization, where only a few efficient catalysts are available.
- Mandal, Tanmoy,Mondal, Moumita,Choudhury, Joyanta
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supporting information
p. 2443 - 2449
(2021/08/03)
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- Rhodium(III)-Catalyzed Selective C-H Acetoxylation and Hydroxylation Reactions
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An efficient Cp?Rh(III)-catalyzed, chelation-assisted C(sp2)-H acetoxylation and hydroxylation reaction has been developed for the first time. The reaction proceeds under mild conditions and allows for selective preparation of C-H acetoxylation
- Wu, Yunxiang,Zhou, Bing
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supporting information
p. 3532 - 3535
(2017/07/17)
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- Directed Aromatic C-H Activation/Acetoxylation Catalyzed by Pd Nanoparticles Supported on Graphene Oxide
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The first solid-supported directed aromatic C-H activation/acetoxylation has been successfully developed by using palladium nanoparticles supported on graphene oxide (PdNPs/GO) as a catalyst. The practicability of this method is demonstrated by simple preparation of catalyst, high catalytic efficiency, wide functional group tolerance, and easy scale up of the reaction. A hot filtration test and Hg(0) poisoning test indicate the heterogeneous nature of the catalytic active species.
- Zhang, Yi,Zhao, Yu,Luo, Yu,Xiao, Liuqing,Huang, Yuxing,Li, Xingrong,Peng, Qitao,Liu, Yizhen,Yang, Bo,Zhu, Caizhen,Zhou, Xuechang,Zhang, Junmin
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supporting information
p. 6470 - 6473
(2017/12/26)
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- Ligand Control in Selective C–H Oxidative Functionalization Using Pd-PEPPSI-Type Complexes
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To achieve high selectivity in directed C–H activation, an NHC ligand was introduced to a palladium catalyst. A range of Pd-PEPPSI complexes were applied in the direct acetoxylation of 2-phenylpyridine. The best catalyst was found to be the one based on a
- Bolbat, Ekaterina,Wendt, Ola F.
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p. 3395 - 3400
(2016/07/26)
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- Selective N -Chelation-directed C-H activation reactions catalyzed by pd(II) nanoparticles supported on multiwalled carbon nanotubes
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N-Chelation-directed C-H activation reactions that utilize the Pd(II)/Pd(IV) catalytic cycle have been previously reported. To date, these reactions employ only homogeneous palladium catalysts. The first use of a solid-supported Pd(II) catalyst [Pd(II) nanoparticles on multiwalled carbon nanotubes, Pd(II)/MWCNT] to carry out N-chelation-directed C-H to C-O, C-Cl, and C-Br transformations is reported. The results presented demonstrate that the solid-supported Pd(II)/MWCNT catalyst can effectively catalyze C-H activation reactions using the Pd(II)/Pd(IV) catalytic cycle.
- Korwar, Sudha,Brinkley, Kendra,Siamaki, Ali R.,Gupton, B. Frank,Ellis, Keith C.
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p. A1782 - A1785
(2015/04/14)
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- COMPLEXES AND CATALYTIC PROCESSES
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The present application is directed towards complexes of formula (I), to methods for preparing such complexes, and to use of such complexes in catalysis. The complexes show utility in a range of catalytic cycles, including Pd(ll)/Pd(IV) cycles. (Formula (I))
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Page/Page column 49
(2015/06/25)
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- Chelating Bis-N-heterocyclic Carbene-Palladium(II) Complexes for Oxidative Arene C-H Functionalization
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Bis-N-heterocyclic carbene (NHC)-chelated palladium(II) complexes have been synthesized, characterized fully including single-crystal X-ray structural analyses, and utilized for the first time toward catalytic oxidative C-H functionalization of arenes with PhI(OAc)2 and N-bromosuccinimide. (Figure Presented).
- Desai, Sai Puneet,Mondal, Moumita,Choudhury, Joyanta
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p. 2731 - 2736
(2015/06/30)
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- Palladium catalyzed ortho-C-H-benzoxylation of 2-arylpyridines using iodobenzene dibenzoates
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A palladium-catalyzed ortho-C-H-benzoxylation of 2-arylpyridines using iodobenzene dibenzoates has been developed. The reaction employed the stable and easily accessible hypervalent iodine reagents as both benzoxylate source and oxidant which made the protocol simple and facile. It showed high regioselectivity and good functional group tolerance, and gave the mono-benzoxylation products in moderate to excellent yields.
- Zhang, Qian,Wang, Ying,Yang, Tingting,Li, Li,Li, Dong
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p. 6136 - 6141
(2015/10/28)
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- Bis-cyclometalated complexes of Pd(II) and Pd(IV) from iminophosphoranes: Synthesis, structure and reactivity This contribution is dedicated to Prof. Maria Pilar García Clemente, who passed away on May 27, 2013.
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The mononuclear bis-orthopalladated complexes [Pd(?N){C 6H4(PPh2NPh)-2}] [?N = (2-(pyridin-2-yl)phenyl) 3a, (2-((dimethylamino)methyl)phenyl) 3b, (S)-(2-(1-(dimethylamino)ethyl)phenyl) 3c, (quinolin-8-ylmethyl) 3d, (4-methoxy-2-((triphenyl-λ5-phosphanylidene)carbamoyl)phenyl) 3e] have been synthesized as single isomers by reaction of the corresponding chloride dimers [Pd(μ-Cl)(?N)]2 (1a-1e) with the lithium derivative [Li{C6H4(PPh2NPh)-2}] (2) in Et 2O. Spectroscopic data show that the two palladated C atoms are in cis disposition, which is confirmed by the X-ray structure of 3a. Oxidation of 3a with PhI(OAc)2 affords the corresponding Pd(IV) derivative (OC-6-32)[Pd(OAc)2{C6H4(PPh2NPh)-2} {C6H4-(2′-NC5H4)-2}] 4a also as a single isomer. 4a undergoes reductive elimination through C-O coupling to give the dimer [Pd(μ-OAc){C6H4(PPh2NPh)-2}] 25 and the ortho-acetoxylated phenylpyridine 6. The reactivity of 3b-3e towards oxidants is also discussed.
- Aguilar, David,González, Greco,Villuendas, Pedro,Urriolabeitia, Esteban P.
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- Electrochemical ortho functionalization of 2-phenylpyridine with perfluorocarboxylic acids catalyzed by palladium in higher oxidation states
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The electochemical oxidation of palladium acetate or palladium perfluoroacetate in the presence of 2-phenylpyridine promotes catalytic ortho C-H substitution reactions. As possible intermediates, Pd(II) metallacycles with Pd-bound acetate, perfluoroacetat
- Dudkina, Yulia B.,Mikhaylov, Dmitry Y.,Gryaznova, Tatyana V.,Tufatullin, Artem I.,Kataeva, Olga N.,Vicic, David A.,Budnikova, Yulia H.
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p. 4785 - 4792
(2013/09/24)
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- Sequential chelation-assisted aromatic C-H functionalisation via catalytic meta sulfonation
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The sequential functionalisation of 2-phenylpyridine is presented using selective ortho- and meta-directing processes. It was found that performing a reaction sequence with meta functionalisation first followed by ortho functionalisation provided novel reaction products in good yields and with complete regioselectivity. Georg Thieme Verlag Stuttgart New York.
- Reynolds, William R.,Liu, Po Man,Kociok-K?hn, Gabriele,Frost, Christopher G.
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supporting information
p. 2687 - 2690
(2014/01/06)
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- Study of the transient reactive Pd(IV) intermediate in the Pd(OAc) 2-catalyzed oxidative coupling reaction system by electrospray ionization tandem mass spectrometry
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Pd-catalyzed oxidative coupling reaction was of great importance in the aromatic C - H activation and the formation of new C - O and C - C bonds. Sanford has pioneered practical, directed C - H activation reactions employing Pd(OAc)2 as catalys
- Zhu, Wei,Wang, Haoyang,Peng, Haihui,Liu, Guosheng,Guo, Yinlong
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p. 371 - 376
(2013/08/22)
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- 'Ligand-free' palladium-catalyzed direct C-H bond oxidative acyloxylation of 2-arylpyridines with aromatic carboxylic acids
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A palladium-catalyzed direct C-H bond oxidative acyloxylation of 2-arylpyridines with aromatic carboxylic acids is described. Several 2-arylpyridines derivatives and aromatic carboxylic acids participate in the reaction, providing a series of mono-acyloxy
- Hu, Chao-Jun,Zhang, Xiao-Hong,Ding, Qiu-Ping,Lv, Ting,Ge, Shao-Peng,Zhong, Ping
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scheme or table
p. 2465 - 2468
(2012/06/01)
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- On the mechanism of palladium-catalyzed aromatic C-H oxidation
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The mechanism of Pd-catalyzed aromatic C-H oxidation chemistry continues to be vigorously discussed. Historically, Pd(II)/Pd(IV) catalysis cycles have been proposed. Herein, we present a detailed study of Pd(OAc)2-catalyzed aromatic C-H chlorination and propose dinuclear Pd(III) complexes as intermediates. We have identified a succinate-bridged dinuclear Pd(II) complex, which self-assembles during catalysis, as the catalyst resting state. In situ monitoring of catalysis has revealed that chlorination proceeds with turnover-limiting oxidation of a dinuclear resting state, and that acetate ions, liberated during the formation of the catalyst resting state, catalyze the bimetallic oxidation. Informed by reaction kinetics analysis, relevant dinuclear Pd(III) complexes have been prepared and observed to undergo selective C-Cl reductive elimination. Based on the combination of kinetic data obtained during catalysis and explicit structural information of relevant intermediates, we propose a Pd(II)2/Pd(III)2 catalysis cycle for Pd(OAc)2-catalyzed aromatic C-H chlorination.
- Powers, David C.,Xiao, Daphne Y.,Geibel, Matthias A. L.,Ritter, Tobias
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supporting information; experimental part
p. 14530 - 14536
(2010/12/18)
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- Copper(II)-catalyzed ortho-acyloxylation of the 2-arylpyridines sp 2 C-H bonds with anhydrides, using O2 as terminal oxidant
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(Figure Presented) A chelation-assisted copper(II)-catalyzed ortho-acyloxylation of the 2-arylpyridine sp2 C-H bond with anhydride is described. The procedure tolerates various functional groups, such as carbomethoxyl, methoxyl, fluoro, bromo, chloro, and cyano groups, affording the mono- or diacyloxylated products in moderate to good yields. Importantly, this procedure uses O2 as a clean terminal oxidant.
- Wang, Wenhui,Luo, Fang,Zhang, Shouhui,Cheng, Jiang
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supporting information; experimental part
p. 2415 - 2418
(2010/06/16)
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- Bimetallic palladium catalysis: Direct observation of Pd(III)-Pd(III) intermediates
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(Chemical Equation Presented) PhI(OAc)2 is a common oxidant for Pd-catalyzed C-H bond functionalizations. Mechanistic hypotheses since the 1960s have suggested a Pd(II)/Pd(IV) mechanism. Here we present evidence for the relevance of bimetallic Pd(III) complexes to catalysis. A bimetallic Pd(III) acetate was isolated and can afford product by bimetallic reductive elimination.
- Powers, David C.,Geibel, Matthias A. L.,Klein, Johannes E. M. N.,Ritter, Tobias
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supporting information; experimental part
p. 17050 - 17051
(2010/03/25)
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- COPPER-MEDIATED FUNCTIONALIZATION OF ARYL C-H BONDS, AND COMPOUNDS RELATED THERETO
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One aspect of the present invention relates to methods for direct functionalization of pyridyl-substituted aromatic compounds. In certain embodiments, 2-arylpyridine substrates react with anionic nucleophiies in the presence of copper(II) to furnish substituted arylpyridines. In other embodiments, the present invention allows for both mono- and di- functionalizations from manipulation of the reaction conditions. The transition metal- mediated carbon-heteroatom bond-forming methods are applicable to a variety of synthetic transformations of aryl C-H bonds.
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Page/Page column 28; 41-42
(2008/06/13)
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- Intermolecular amidation of unactivated sp2 and sp3 C-H bonds via palladium-catalyzed cascade C-H activation/nitrene insertion
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This communication describes the Pd(OAc)2-catalyzed intermolecular amidation reactions of unactivated sp2 and sp3 C-H bonds using primary amides and potassium persulfate. The substrates containing a pendent oxime or pyridine group were amidated with excellent chemo- and regioselectivities. It is noteworthy that reactive C-X bonds were well-tolerated and a variety of primary amides can be effective nucleophiles for the Pd-catalyzed C-H amidation reactions. For the reaction of unactivated sp3 C-H bonds, β-amidation of 1° sp3 C-H bonds versus 2° C-H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C-H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated complex. Copyright
- Thu, Hung-Yat,Yu, Wing-Yiu,Che, Chi-Ming
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p. 9048 - 9049
(2007/10/03)
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- Cu(II)-catalyzed functionalizations of aryl C-H bonds using O2 as an oxidant
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Cu(II)-catalyzed acetoxylation and halogenation of aryl C-H bonds are developed. ortho-Selectivity was observed with a wide range of 2-arylpyridine substrates. Both mono- and difunctionalizations are achieved by tuning the reaction conditions. Excellent functional group tolerance and use of O2 as a stoichiometric oxidant are significant advantages over our recently developed Pd-catalyzed C-H functionalization reactions. These newly discovered reaction conditions are also applicable for cyanation, amination, etherification, and thioetherification of aryl C-H bonds. Mechanistic investigations are carried out to gain insights into the Cu(II)-catalyzed C-H functionalization reactions. Copyright
- Chen, Xiao,Hao, Xue-Shi,Goodhue, Charles E.,Yu, Jin-Quan
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p. 6790 - 6791
(2007/10/03)
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- A Highly Selective Catalytic Method for the Oxidative Functionalization of C-H Bonds
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This communication describes a new and highly practical Pd(II)-catalyzed method for the regio- and chemoselective oxidative functionalization of arenes and alkanes. Carbon?hydrogen bonds of substrates that contain a variety of directing groups (e.g., pyridine, azobenzene, pyrazole, and imine derivatives) are selectively transformed into esters, ethers, and aryl-halides under mild conditions. The scope of this reaction in terms of substrate, directing group, and oxidant is described, and a preliminary catalytic cycle is proposed. Copyright
- Dick, Allison R.,Hull, Kami L.,Sanford, Melanie S.
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p. 2300 - 2301
(2007/10/03)
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- Hydroxyphenyl-1-methylpyridinium-iodide as Potential Reactivators of Acetylcholinesterase Poisoned with Organophosphorus Compounds
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It was our aim to reactivate acetylcholinesterase poisoned with sarin.We synthesized 2-(o-hydroxyphenyl)-1-methylpyridinium-iodide (9), 2-(p-hydroxyphenyl)-1-methylpyridinium-iodide (19) and 4-(o-hydroxyphenyl)-1-methylpyridinium-iodide (14) as potential reactivators.All substances showed moderate toxicity against mice; their reactivity potency in vitro and in vivo was negligible.
- Riggio, Gaetano,Hopff, Wolfgang Herbert,Hofmann, Alfred Andre,Waser, Peter Gaudenz
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p. 1039 - 1045
(2007/10/02)
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