Rare-Earth Metal Triflates in Organic Synthesis

Kobayashi, Shū; Sugiura, Masaharu; Kitagawa, Hajime; Lam, Wai Kwan

doi:10.1021/cr010289i

Cited by 1,043 publications

(606 citation statements)

References 611 publications

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“…17 Finally, we hybridized the substrate strand with its cDNA forming a duplex, where all the bases are paired and 2 | J. Name., 2012, 00, [1][2][3] This journal is © The Royal Society of Chemistry 2012 lanthanide binding takes place only via the backbone phosphate ( Figure 1D). This is intended to serve as a negative control.…”

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The group trend of lanthanides binding to DNA and DNAzymes with a complex but symmetric pattern

et al. 2014

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Using sensitized Tb 3+ luminescence spectroscopy as a tool, binding of 14 lanthanides to a lanthanide-dependent DNAzyme is studied, where the binding affinity is symmetric cross the series and the tightest binding occurs with Nd 3+ and Ho 3+ . This trend does not correlate with DNAzyme activity, suggesting that metal binding may not be the rate-limiting step of the DNAzyme catalysis.Lanthanides refer to the elements in the periodic table from La to Lu. Beyond their critical roles in modern technologies, lanthanides also emerge as important probes for biology and medicine. 1,2 In particular, they have been extensively used to study the structure and function of nucleic acids. These applications take advantage of a few of their unique properties. First, lanthanides and their complexes can efficiently cleave nucleic acids, 3 and thus are used as RNA structural probes 4 and DNA cleaving agents. 5 In addition, a number of in vitro selection experiments were carried out using lanthanides as metal cofactors to obtain DNA-based catalysts (so called DNAzymes 6-12 ) for RNA or DNA cleavage. 13,14 Second, a few lanthanides (especially Tb 3+ ) are luminescent and DNA can act as an antenna to increase their light absorption and thus emission intensity. This is useful for probing metal binding sites, 15 and for developing biosensors. 16 Third, lanthanides are hard Lewis acids and some have a similar size as Ca 2+ . Lanthanides can compete with other metal ions in enzymes and act as enzyme inhibitors. For example, both the 17E DNAzyme and the hammerhead ribozyme are inhibited by lanthanides. 15,17 On the other hand, the Leadzyme and a DNA-based ligase are accelerated by lanthanides. [18][19][20] All these examples suggest strong interactions between lanthanides and nucleic acids. Finally, nucleotides and lanthanides can form coordination complexes with useful luminescence and DNA binding properties. [21][22][23][24] Given these progresses, few studies explored the binding of the whole lanthanide series with DNA or correlated metal binding with enzyme activity. Such studies are important for revealing the coordination chemistry of lanthanides, and for DNA bioinorganic chemistry in general. 25,26 We recently performed an in vitro selection experiment using Ce 4+ as the intended metal cofactor. The selected DNAzyme (named Ce13d) was found to have similar activity with all trivalent lanthanides. 14 Therefore, Ce13d must bind all the lanthanides and this DNAzyme might provide a good scaffold for studying lanthanide binding. Herein, we employed Tb 3+ luminescence as a tool to study lanthanide binding to DNAzymes and its relation to catalytic activity. The secondary structure of the Ce13d DNAzyme complex is shown in Figure 1A. It consists of a substrate strand named Sub-rA with a single RNA linkage (rA, ribo-adenosine), and an enzyme strand named Ce13d. In the presence of a trivalent lanthanide, the substrate is cleaved into two fragments at the position pointed by the arrowhead. Lanthanides alone can catalyze the reaction and no div...

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The group trend of lanthanides binding to DNA and DNAzymes with a complex but symmetric pattern

et al. 2014

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“…Due to these advantages, they are widely used in organic synthesis. 19 Recently, we have successfully applied metal triflates into several reactions. 20 In continuation of our interest in green chemistry and Lewis acid-catalyzed organic reactions, 21 we herein develop a green, simple and practical method for the synthesis of pyrazoles from 1,3-diketones with hydrazines, acylhydrazines and sulfonyl hydrazines catalyzed by Sc(OTf) 3 under solvent-free conditions.…”

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A general and efficient synthesis of pyrazoles catalyzed by Sc(OTf)3 under solvent-free conditions

Xiong¹,

Chen²,

Liu³

et al. 2009

J. Braz. Chem. Soc.

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Pirazóis foram preparados em excelentes rendimentos via reação de condensação entre várias 1,3-dicetonas (R 1 COCHXCOCH 3 , R 1 = Me, Ph; X = H, Me, Cl) e hidrazinas, acilhidrazinas ou sulfonil hidrazinas, na presença de quantidades catalíticas de Sc(OTf) 3 , a temperatura ambiente, na ausência de solventes. Adicionalmente, o catalisador foi facilmente recuperado após as reações e reutilizado sem perda evidente na atividade.Pyrazoles were prepared in excellent yields via solventless condensation of various 1,3-diketones (R 1 COCHXCOCH 3 , R 1 = Me, Ph; X = H, Me, Cl) and hydrazines, acylhydrazines or sulfonyl hydrazines in the presence of a catalytic amount of Sc(OTf) 3 at room temperature. Additionally, the catalyst could be recovered easily after the reactions and reused without evident loss in activity.Keywords: scandium(III) triflate, pyrazoles, 1,3-diketones, hydrazines, hydrazides, solvent-free IntroductionPyrazole and its derivatives constitute an important class of compounds, which exhibit various biological and pharmaceutical activities 1 ranging from antitumor 2 to antiinflammatory, 3 antipsychotic, 4 antimicrobial, 5 antiviral 6 and antifungal 7 activities. They are also useful intermediates for many industrial products. 8 It is therefore not surprising that many synthetic methods have been developed for the preparation of the heterocycles. The heterocycles can be synthesized via 1,3-dipolar cycloadditions of diazo compounds, 9 reaction of acetylenic ketones 10 or chalcones 11 and hydrazines, a four-component coupling of terminal alkynes, hydrazine, carbon monoxide, and aryl iodides. 12 Recently, a few efficient methods have been reported, too. 13 Moreover, pyrazoles can also be successfully obtained from the direct condensation of 1,3-diketones and hydrazines. 14 This is the most simple and straightforward procedure for their synthesis, a variety of catalysts such as H 2 SO 4 , 15 17 have been employed to effect this transformation. Although these methods are suitable for certain synthetic conditions, sometimes, however, many of these procedures are associated with one or more disadvantages such as long reaction time, low yield, use of volatile organic solvents, requirement of excess of reagents or catalysts, special apparatus and harsh reaction conditions. And some of them need stoichiometric amount of acids which can be trapped by hydrazines in this condensation. Due to the importance of these compounds, the development of convenient, environmentally benign, high-yielding and clean approaches is highly desirable. To our knowledge, less attention has been paid to the synthesis of pyrazoles from 1,3-diketones and acylhydrazines/ sulfonyl hydrazines in the presence of Lewis acid.Metal triflates are unique Lewis acids that are currently of great research interest. 18 Firstly, metal triflates are air-and water-stable, thermal stable, less toxic, easily recovered and reused. In addition, metal triflates are still active in the coexistence of many substrates containing nitrogen, oxygen, phosphorous, and s...

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Lanthanide(III) Nitrobenzenesulfonates as New Nitration Catalysts: The Role of the Metal and of the Counterion in the Catalytic Efficiency

Parac‐Vogt¹,

Pachini²,

Nockemann³

et al. 2004

Eur J Org Chem

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Lanthanide(III) complexes of p-nitrobenzenesulfonic acid, Ln(p-NBSA) 3 , m-nitrobenzenesulfonic acid, Ln(m-NBSA) 3 , and 2,4-nitrobenzenesulfonic acid, Ln(2,4-NBSA) 3 , were prepared, characterized and examined as catalyst for the nitration of benzene, toluene, xylenes, naphthalene, bromobenzene and chlorobenzene. The initial screening of the catalysts showed that lanthanum(III) complexes were more effective than the corresponding ytterbium(III) complexes, and that catalysts containing the bulky 2,4-NBSA ligand were less effective than the catalyst containing p-NBSA (nosylate) or m-NBSA ligands. Examination of a series of Ln(p-NBSA) 3 and Ln(m-NBSA) 3 catalysts revealed that there is a clear correlation between the ionic radii of the lanthanide(III) ions and the yields of nitration, with the lighter lanthanides being more effective. The X-ray single crystal structure of Yb(m-

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Rare-Earth Metal Triflates in Organic Synthesis

Cited by 1,043 publications

References 611 publications

The group trend of lanthanides binding to DNA and DNAzymes with a complex but symmetric pattern

The group trend of lanthanides binding to DNA and DNAzymes with a complex but symmetric pattern

A general and efficient synthesis of pyrazoles catalyzed by Sc(OTf)3 under solvent-free conditions

Lanthanide(III) Nitrobenzenesulfonates as New Nitration Catalysts: The Role of the Metal and of the Counterion in the Catalytic Efficiency

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