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1.
Int J Biol Macromol ; 106: 840-850, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28830777

RESUMO

To find potential inhibitors of human carbonic anhydrase IX (CAIX), we have successfully deigned, synthesized and characterized three p-toluene sulphonylhydrazone derivatives (1-3). Molecular docking studies provided the structural basis of CAIX inhibition and a deeper insight into the protein-ligand interactions. p-Toluene sulphonylhydrazone derivatives show a well organized conformational compatibility with the active site of CAIX. The protein-ligand complex was stabilized by several non-covalent interactions offered by residues present in the active site cavity. The actual binding affinity of synthesized compounds with CAIX was experimentally measured by fluorescence and isothermal titration calorimetry (ITC). Results of both fluorescence binding and ITC measurements show the binding affinity of p-Toluene sulphonylhydrazone derivatives to the CAIX in the µM range. CAIX enzyme inhibition assay showed the IC50 values in nM range. Though all the three compounds (1-3) showed a good binding with CAIX, compound 2 showed the best inhibition of CAIX activity. These compounds were non-toxic on normal cell lines (HEK-293) and significantly inhibit the proliferation of hypoxic cancer cells. All compounds induce apoptosis in the hypoxic cancer cells. These compounds may be further exploited as promising therapeutic agents to control the hypoxia-induced tumors.


Assuntos
Anidrase Carbônica IX/antagonistas & inibidores , Inibidores da Anidrase Carbônica/farmacologia , Hidrazonas/química , Neoplasias/tratamento farmacológico , Anidrase Carbônica IX/química , Inibidores da Anidrase Carbônica/síntese química , Inibidores da Anidrase Carbônica/química , Hipóxia Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Células HEK293 , Humanos , Hidrazonas/síntese química , Hidrazonas/farmacologia , Simulação de Acoplamento Molecular , Neoplasias/enzimologia , Tolueno/síntese química , Tolueno/química , Tolueno/farmacologia , Hipóxia Tumoral/efeitos dos fármacos
2.
Nature ; 532(7600): 484-8, 2016 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-27088605

RESUMO

In the classic Diels-Alder [4 + 2] cycloaddition reaction, the overall degree of unsaturation (or oxidation state) of the 4π (diene) and 2π (dienophile) pairs of reactants dictates the oxidation state of the newly formed six-membered carbocycle. For example, in the classic Diels-Alder reaction, butadiene and ethylene combine to produce cyclohexene. More recent developments include variants in which the number of hydrogen atoms in the reactant pair and in the resulting product is reduced by, for example, four in the tetradehydro-Diels-Alder (TDDA) and by six in the hexadehydro-Diels-Alder (HDDA) reactions. Any oxidation state higher than tetradehydro (that is, lacking more than four hydrogens) leads to the production of a reactive intermediate that is more highly oxidized than benzene. This increases the power of the overall process substantially, because trapping of the reactive intermediate can be used to increase the structural complexity of the final product in a controllable and versatile manner. Here we report an unprecedented overall 4π + 2π cycloaddition reaction that generates a different, highly reactive intermediate known as an α,3-dehydrotoluene. This species is in the same oxidation state as a benzyne. Like benzynes, α,3-dehydrotoluenes can be captured by various trapping agents to produce structurally diverse products that are complementary to those arising from the HDDA process. We call this new cycloisomerization process a pentadehydro-Diels-Alder (PDDA) reaction-a nomenclature chosen for chemical taxonomic reasons rather than mechanistic ones. In addition to alkynes, nitriles (RC≡N), although non-participants in aza-HDDA reactions, readily function as the 2π component in PDDA cyclizations to produce, via trapping of the α,3-(5-aza)dehydrotoluene intermediates, pyridine-containing products.


Assuntos
Reação de Cicloadição , Hidrogênio/química , Tolueno/análogos & derivados , Benzeno/química , Ciclização , Di-Inos/química , Hidrogenação , Isomerismo , Nitrilos/química , Oxirredução , Piridinas/química , Terminologia como Assunto , Tolueno/síntese química , Tolueno/química
3.
J Antibiot (Tokyo) ; 69(4): 273-9, 2016 04.
Artigo em Inglês | MEDLINE | ID: mdl-26860468

RESUMO

The practical synthesis of the C-ring precursor of paclitaxel starting from 3-methoxytoluene is described. Lipase-catalyzed kinetic resolution of a substituted cyclohexane-1,2-diol, derived from 3-methoxytoluene in three steps, successfully afforded a desired enantiomer with >99% ee, which was transformed to a cyclohexenone. 1,4-Addition of a vinyl metal species, followed by Mukaiyama aldol reaction with formalin in the presence of a Lewis acid provided the known C-ring precursor of paclitaxel in a 10 g scale.


Assuntos
Antineoplásicos Fitogênicos/síntese química , Paclitaxel/síntese química , Tolueno/análogos & derivados , Tolueno/síntese química , Cicloexanos/química , Formaldeído/química , Lipase/química
4.
J Chem Neuroanat ; 72: 8-15, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26708322

RESUMO

Drug therapy of seizures involves producing high levels of antiepileptic drugs in the blood. Drug must enter the brain by crossing from the blood into the brain tissue, called a transvascular route (TVR). Even before the drug can reach the brain tissue, factors such as systemic toxicity, macrophage phagocytises and reduction in oxygen content limit the success of this TVR. Encapsulating the drug within a nano scale delivering system, synthesising drugs with low molecular weight are the best mechanisms to deliver the drug to the brain. But through this article, we have explored a possibility of attaching a molecule 4-(trifluoromethyl) benzoic acid (TFMBA), that possess more number of fluorine atom, to benzodiazepine (BDZ) resulting in an ionic salt (S)-(+)-2,3-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine5,11(10H,11aH)-dione with 4-(trifluoromethyl)benzoic acid. By this way, reducing the toxicity of BDZ than the conventional anti-epileptic drugs (AEDs), increasing the solubility, reducing the melting point, enriching the TVR with excess oxygen content with the support of fluorine. With all these important prerequisites fulfilled, the drug along with the attached molecule is expected to travel more comfortably through the TVR without any external support than any other conventional AEDs. FTIR, (1)H NMR, (13)C NMR, HRMS spectroscopy, HRTEM and In vitro cytotoxicity analysis supports this study.


Assuntos
Anticonvulsivantes/química , Benzodiazepinonas/química , Pirróis/química , Tolueno/análogos & derivados , Anticonvulsivantes/síntese química , Anticonvulsivantes/metabolismo , Anticonvulsivantes/toxicidade , Benzodiazepinonas/síntese química , Benzodiazepinonas/toxicidade , Carbamazepina/toxicidade , Frutose/análogos & derivados , Frutose/toxicidade , Halogenação , Humanos , Células MCF-7 , Peso Molecular , Pirróis/síntese química , Pirróis/toxicidade , Solubilidade , Estereoisomerismo , Tolueno/síntese química , Tolueno/química , Tolueno/toxicidade , Topiramato , Temperatura de Transição
5.
Pak J Biol Sci ; 18(4): 166-72, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26506646

RESUMO

Reaction of p-toluenesulfonyl chloride with amino acids gave sulfonamides p-T1a-k which upon amidation afforded p-T2a-k. Similarly, treatment involving α-toluenesulfonyl chloride and amino acids afforded the sulfonamides α-T1a-k. These two classes of sulfonamides were synthetically modified at their COOH end position to achieve N,N-diethylamido substituted p-toluenesulfonamides p-T2a-k and α-toluenesulfonamides α-T2a-k, respectively. The chemical structures of the compounds were validated with IR, Mass spectra, NMR as well as elemental analytical data. Both classes of compounds were screened against Escherichia coli and Staphylococcus aureus and their activity werecompared. It was remarkable to note that the α-toluene sulfonamides α-T2a-k were more active than their p-toluenesulfonamide counterparts p-T2a-k. Compound 1-(benzylsulfonyl)-N,N-diethylpyrrolidine-2-carboxamide α-T2a was the most potent antibacterial compound on S. aureus with MIC value of 3.12 µg mL(-1) while N,N-Diethyl-3-phenyl-2-(phenylmethylsulfonamide) propanamide α-T2j emerged as the best antibacterial motif against E. coli with MIC value of 12.5 µg mL(-1). Hence, these compounds especially the α-toluenesulfonamide core structural templates are good candidates for further study for future drug discovery.


Assuntos
Antibacterianos/farmacologia , Escherichia coli/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Sulfonamidas/farmacologia , Tolueno/análogos & derivados , Antibacterianos/síntese química , Descoberta de Drogas , Escherichia coli/crescimento & desenvolvimento , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Testes de Sensibilidade Microbiana , Estrutura Molecular , Espectrofotometria Infravermelho , Staphylococcus aureus/crescimento & desenvolvimento , Relação Estrutura-Atividade , Sulfonamidas/síntese química , Tolueno/síntese química , Tolueno/farmacologia
6.
Chem Commun (Camb) ; 51(90): 16255-8, 2015 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-26399606

RESUMO

We report the first example of the highly enantioselective synthesis of structurally diverse chiral dithioketals via asymmetric sulfenylation of various types of S-based nucleophiles, catalyzed by a cheap cinchona alkaloid derivative, dihydroquinine.


Assuntos
Quinidina/análogos & derivados , Ácidos Sulfínicos/química , Tolueno/análogos & derivados , Catálise , Estrutura Molecular , Quinidina/química , Tolueno/síntese química , Tolueno/química
7.
Molecules ; 20(8): 14595-610, 2015 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-26274947

RESUMO

The current pharmacological Chagas disease treatments, using Nifurtimox or Benznidazole, show limited therapeutic results and are associated with potential side effects, like mutagenicity. Using random screening we have identified new chemotypes that were able to inhibit relevant targets of the Trypanosoma cruzi. We found 3H-[1,2]dithioles with the ability to inhibit Trypanosoma cruzi triosephosphate isomerase (TcTIM). Herein, we studied the structural modifications of this chemotype to analyze the influence of volume, lipophilicity and electronic properties in the anti-T. cruzi activity. Their selectivity to parasites vs. mammalian cells was also examined. To get insights into a possible mechanism of action, the inhibition of the enzymatic activity of TcTIM and cruzipain, using the isolated enzymes, and the inhibition of membrane sterol biosynthesis and excreted metabolites, using the whole parasite, were achieved. We found that this structural framework is interesting for the generation of innovative drugs for the treatment of Chagas disease.


Assuntos
Tolueno/análogos & derivados , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Animais , Linhagem Celular , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Macrófagos/efeitos dos fármacos , Camundongos , Esteróis/antagonistas & inibidores , Esteróis/biossíntese , Tolueno/síntese química , Tolueno/química , Tolueno/farmacologia , Tripanossomicidas/síntese química , Trypanosoma cruzi/metabolismo
8.
Chem Commun (Camb) ; 50(70): 10102-4, 2014 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-25050417

RESUMO

The deprotection of a common precursor moiety in dithiolene chemistry was discovered to be fully reversible, which, besides being relevant for researchers working in very different fields with these non-innocent ligand systems, may even have an impact on CO2 housekeeping, as the deprotected ligand acts as an efficient trap.


Assuntos
Tolueno/análogos & derivados , Espectroscopia de Ressonância Magnética/métodos , Tolueno/síntese química , Tolueno/metabolismo
9.
Artigo em Inglês | MEDLINE | ID: mdl-22940048

RESUMO

Replacement reactions of toluene-3,4-dithiolatoarsenic(III) chloride with oxygen and sulphur donor ligands like benzoic acid, thiobenzoic acid, anhydrous sodium acetate, thioacetic acid, phenol, thiophenol, sodium salicylate and thio glycolic acid in 1:1 molar ratio as well as disodium oxalate in 2:1 molar ratio in refluxing anhydrous benzene yielded toluene-3,4-dithiolatoarsenic(III) mono oxo or thio carboxylic or phenolic derivatives of the general formula SC(6)H(3)(CH(3))SAsR {where R=OOCC(6)H(5), SOCC(6)H(5), OOCCH(3), SOCCH(3), OC(6)H(5), SC(6)H(5), OOCC(6)H(4)(OH), SCH(2)COOH} and SC(6)H(3)(CH(3))SAsOOC-COOAsS(CH(3))C(6)H(3)S. These synthesized derivatives are yellow, yellow-brown solids/ liquids and are soluble in common organic solvents like benzene, chloroform, dichloromethane, dimethyl formamide, dimethyl sulphoxide etc. These derivatives have been characterized by melting point determination, molecular weight determination, elemental analysis (C, H, S and As), spectral {UV, IR, NMR ((1)H and (13)C), ESI-Mass, SEM and powder X-ray diffraction} and thermal (TGA, DTA and DSC) studies. Some of these compounds have been screened for their antimicrobial activities using the disc diffusion method. These derivatives have shown good activity as antibacterial and antifungal agents on some selected bacterial and fungal strains, which increased on increasing the concentration. Chloroamphenicol and terbinafin were used as standards for the comparison.


Assuntos
Antibacterianos/síntese química , Antibacterianos/farmacologia , Arsenicais/química , Oxigênio/química , Enxofre/química , Temperatura , Tolueno/síntese química , Tolueno/farmacologia , Antibacterianos/química , Bactérias/efeitos dos fármacos , Varredura Diferencial de Calorimetria , Elétrons , Fungos/efeitos dos fármacos , Ligantes , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura , Pós , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , Termogravimetria , Tolueno/química , Difração de Raios X
10.
Angew Chem Int Ed Engl ; 51(34): 8577-80, 2012 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-22807209

RESUMO

Doubly radical: A novel entry to α,n-didehydrotoluene (DHT) diradicals is disclosed and proceeds through the photochemical activation of (chlorobenzyl)trimethylsilanes with chloride loss and elimination of the SiMe(3) (+) group. The products formed in solution are indicative of the intermediacy of the three isomers of the α,n-DHT.


Assuntos
Silanos/química , Tolueno/análogos & derivados , Tolueno/síntese química , Alcadienos/química , Alquinos/química , Ciclização , Processos Fotoquímicos , Fotoquímica/métodos , Tolueno/química
11.
Artigo em Inglês | MEDLINE | ID: mdl-22446785

RESUMO

In this study, the molecular structure and spectroscopic properties of title compound were characterized by X-ray diffraction, FT-IR and UV-vis spectroscopies. These properties of title compound were also investigated from calculative point of view. The X-ray diffraction and FT-IR analyses reveal the existence of keto form in the solid state. UV-vis spectra were recorded in different organic solvents. The results show that title compound exists in both keto and enol forms in DMSO, EtOH but it exists in enol form in benzene. In addition, the title compound in DMSO showed new absorption band at 436 nm due to the high ionizing effect of this solvent. The geometry optimization of title compound in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set. TD-DFT calculations starting from optimized geometry were carried out in gas phase to calculate excitation energies of title compound. The non-linear optical properties were computed with the same level of theory and title compound showed a good second order nonlinear optical property. In addition, thermodynamic properties were obtained in the range of 100-500 K.


Assuntos
Compostos Azo/química , Corantes/química , Cicloexenos/química , Cicloexenos/síntese química , Tolueno/análogos & derivados , Compostos Azo/síntese química , Corantes/síntese química , Cristalografia por Raios X , Isomerismo , Modelos Moleculares , Teoria Quântica , Análise Espectral , Tolueno/síntese química , Tolueno/química
12.
Org Lett ; 13(20): 5608-11, 2011 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-21916460

RESUMO

BF(3)·OEt(2)-catalyzed direct cyanation of indoles and pyrroles using a less toxic, bench-stable, and easily handled electrophilic cyanating agent N-cyano-N-phenyl-para-toluenesulfonamide (NCTS) affords 3-cyanoindoles and 2-cyanopyrroles in good yields with excellent regioselectivity. The substrate scope is broad with respect to indoles and pyrroles.


Assuntos
Indóis/síntese química , Ácidos de Lewis/química , Nitrilos/química , Nitrilos/síntese química , Pirróis/síntese química , Sulfonamidas/química , Sulfonamidas/síntese química , Tolueno/análogos & derivados , Catálise , Indóis/química , Estrutura Molecular , Pirróis/química , Estereoisomerismo , Tolueno/síntese química , Tolueno/química
13.
J Am Chem Soc ; 133(35): 13864-7, 2011 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-21834576

RESUMO

Pd-catalyzed highly para-selective C-H arylation of monosubstituted arenes (including toluene) is developed for the first time using an F(+) reagent as a bystanding oxidant. This finding provides a new retrosynthetic disconnection for para-substituted biaryl synthesis via C-H/C-H cross-coupling.


Assuntos
Hidrocarbonetos Aromáticos/síntese química , Paládio/química , Catálise , Técnicas de Química Sintética/métodos , Hidrocarbonetos Aromáticos/química , Oxidantes/química , Tolueno/síntese química , Tolueno/química
14.
Bioorg Med Chem Lett ; 21(12): 3743-8, 2011 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-21561767

RESUMO

Ponatinib (AP24534) was previously identified as a pan-BCR-ABL inhibitor that potently inhibits the T315I gatekeeper mutant, and has advanced into clinical development for the treatment of refractory or resistant CML. In this study, we explored a novel series of five and six membered monocycles as alternate hinge-binding templates to replace the 6,5-fused imidazopyridazine core of ponatinib. Like ponatinib, these monocycles are tethered to pendant toluanilides via an ethynyl linker. Several compounds in this series displayed excellent in vitro potency against both native BCR-ABL and the T315I mutant. Notably, a subset of inhibitors exhibited desirable PK and were orally active in a mouse model of T315I-driven CML.


Assuntos
Alquinos/síntese química , Alquinos/farmacologia , Compostos de Anilina/síntese química , Proteínas de Fusão bcr-abl/antagonistas & inibidores , Tolueno/síntese química , Administração Oral , Alquinos/química , Compostos de Anilina/química , Compostos de Anilina/farmacologia , Animais , Ciclização , Modelos Animais de Doenças , Proteínas de Fusão bcr-abl/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Camundongos , Modelos Moleculares , Estrutura Molecular , Mutação , Ratos , Relação Estrutura-Atividade , Tolueno/química , Tolueno/farmacologia
15.
Bioorg Med Chem ; 19(5): 1649-57, 2011 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-21324703

RESUMO

Since activation of p53 in response to cytotoxic stress may have proapoptotic or protective effects depending on the nature of the injury, inhibitors of p53 may have therapeutic interest as modulators of chemotherapy toxicity or efficacy. In an attempt to identify novel p53 inhibitors, a quality collection of compounds structurally related to pifithrin-ß were designed and synthesized as potential inhibitors of p53. The biochemical and biological evaluations supported that compounds of the tetrahydrobenzothiazole series were inhibitors of the p53 transcriptional activity and were effective in enhancing paclitaxel-induced apoptosis. In contrast, in spite of the increased cytotoxic potency, selected compounds of the benzothiazole series were not able to modulate the transcriptional activity of p53, as indicated by lack of change of p21 expression. The therapeutic interest of the compounds of the former series in combination with taxanes was confirmed in a human tumor xenograft model.


Assuntos
Antineoplásicos , Benzotiazóis/síntese química , Benzotiazóis/farmacologia , Neoplasias Ovarianas/tratamento farmacológico , Tolueno/análogos & derivados , Proteína Supressora de Tumor p53/antagonistas & inibidores , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Benzotiazóis/química , Linhagem Celular Tumoral , Modelos Animais de Doenças , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , Tolueno/síntese química , Tolueno/química , Tolueno/farmacologia , Transplante Heterólogo
16.
Org Lett ; 12(22): 5146-9, 2010 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-20945851

RESUMO

A scalable synthesis of a potent renin inhibitor (1) is described. The absolute stereochemistry is set via an unprecedented diastereoselective Dieckmann cyclization directed by a remote chiral protecting group. This transformation enables preparation of chiral 1,3-[3.3.1]-diazabicyclononenes by desymmetrization of alkyl-esters, with selectivities ranging from 4 to 17:1.


Assuntos
Compostos Azo/síntese química , Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Inibidores de Proteases/síntese química , Inibidores de Proteases/farmacologia , Renina/antagonistas & inibidores , Tolueno/análogos & derivados , Compostos Azo/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Cristalografia por Raios X , Ciclização , Conformação Molecular , Estrutura Molecular , Inibidores de Proteases/química , Estereoisomerismo , Tolueno/síntese química , Tolueno/química , Tolueno/farmacologia
17.
Photochem Photobiol ; 86(4): 821-6, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20456654

RESUMO

A total of eight CF(3)-substituted phenylacetic and mandelic acids are shown to undergo efficient photodecarboxylation (PDC; Phi = 0.37-0.74) in basic aqueous solution to give the corresponding trifluoromethyltoluenes or trifluoromethylbenzyl alcohols. The products are consistent with the almost exclusive formation of benzylic carbanions that subsequently react with water, with minor amounts (< or = 5%) of radical-derived products detected. Quenching studies indicate that the reaction likely proceeds from the singlet excited state. This work demonstrates that the CF(3) group greatly facilitates the excited state ionic PDC of phenylacetic acids.


Assuntos
Hidrocarbonetos Fluorados/química , Ácidos Mandélicos/química , Fenilacetatos/química , Álcoois Benzílicos/síntese química , Álcoois Benzílicos/química , Descarboxilação , Estrutura Molecular , Fotoquímica , Teoria Quântica , Estereoisomerismo , Tolueno/análogos & derivados , Tolueno/síntese química , Tolueno/química , Raios Ultravioleta
18.
Molecules ; 14(11): 4634-43, 2009 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-19924091

RESUMO

A new process is described for preparing very pure linear alkanethiols and linear alpha,omega-alkanedithiols using a sequential alkylation of the title compound, followed by a ring closure to quantitatively give the corresponding 3-methyl[1,3]thiazolo[3,2-a]-[3,1]benzimidazol-9-ium salt and the alkanethiol derivative under mild conditions. The alkanethiol and the heteroaromatic salt are easily separated by a simple extraction process. The intermediate thiazolium quaternary salts resulting from the first reaction step can be isolated in quantitative yields, affording an odourless protected form of the thiols.


Assuntos
Compostos de Sulfidrila/química , Enxofre/química , Estrutura Molecular , Compostos de Sulfidrila/síntese química , Tiazolidinas/síntese química , Tiazolidinas/química , Tolueno/análogos & derivados , Tolueno/síntese química , Tolueno/química
19.
Inorg Chem ; 48(20): 9754-66, 2009 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-19769378

RESUMO

The reaction of [Ru(III)(cyclam)Cl(2)]Cl with 2 equiv of sodium N,N-diethyldithiocarbamate in methanol afforded [Ru(II)(cyclam)(Et(2)dtc)](BPh(4)) (1(BPh(4))). The same reaction with only 1 equiv of toluene-3,4-dithiol and a base yielded [Ru(cyclam)(tdt)](PF(6)) (2(PF(6))) which was oxidized by 1 equiv of ferrocenium hexafluorophosphate generating [Ru(cyclam)(tdt)](PF(6))(2) (2(ox)(PF(6))(2)). The crystal structures of 1 and 2 have been determined by X-ray crystallography at 100 K. The electronic structures of diamagnetic 1(BPh(4)), paramagnetic 2(PF(6)) (S = (1)/(2)), and diamagnetic 2(ox)(PF(6))(2) have been studied by magnetochemistry, spectroelectrochemistry, electron paramagnetic resonance spectroscopy, and (1)H NMR spectroscopy. X-ray absorption spectroscopy on Ru K- and L-edges as well as S K-edges has been employed. Finally, the molecular and electronic structures of all three species have been calculated by using density functional theory (B3LYP). It is shown that 2(ox) comprises an electronic structure which is best described by three resonance structures {[Ru(II)(cyclam)(tdt(0))](2+) <--> [Ru(III)(cyclam)(tdt(*))](2+) <--> [Ru(IV)(cyclam)(tdt(2-))](2+)} with a closed-shell singlet ground state. This is in stark contrast to the isoelectronic iron species, namely, [Fe(III)(cyclam)(tdt(*))](2+) which is a singlet diradical with a low-spin ferric ion coupled intramolecularly antiferromagnetically to a ligand pi radical monoanion (tdt(*))(-).


Assuntos
Cristalografia por Raios X , Elétrons , Compostos Heterocíclicos/química , Compostos de Rutênio/química , Tiocarbamatos/química , Etanol/síntese química , Etanol/química , Compostos Heterocíclicos/síntese química , Modelos Moleculares , Estrutura Molecular , Teoria Quântica , Compostos de Rutênio/síntese química , Tiocarbamatos/síntese química , Tolueno/análogos & derivados , Tolueno/síntese química , Tolueno/química
20.
J Org Chem ; 74(19): 7238-44, 2009 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-19725551

RESUMO

Septet 2,4,6-trinitrenotoluene is the major paramagnetic product formed during the photolysis of 2,4,6-triazidotoluene in cryogenic matrices. This trinitrene displays different electron paramagnetic resonance (EPR) spectra in solid argon and in 2-methyltetrahydrofuran (2MTHF) glass, corresponding to septet spin states with the zero-field splitting (ZFS) parameters D(S) = -0.0938 cm(-1), E(S) = -0.0040 cm(-1) and D(S) = -0.0934 cm(-1), E(S) = -0.0015 cm(-1), respectively. Analysis of these parameters shows that the molecular and electronic structure of the septet trinitrene derived from the EPR spectrum in argon is in good agreement with the expectations from DFT calculations. The very small parameter E(S) in 2MTHF glass is explained by significant changes of the spin densities on the three nitrene units due to interactions of the nitrogen atom with surrounding 2MTHF molecules.


Assuntos
Magnetismo , Nitrocompostos/química , Tolueno/análogos & derivados , Espectroscopia de Ressonância de Spin Eletrônica , Estrutura Molecular , Nitrocompostos/síntese química , Fotólise , Tolueno/síntese química , Tolueno/química
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