(+/-)-7,7,9,9-Tetramethyl-2,3 : 4,5-dinaphthol,6,8-trioxa-7,9-disilacyclonona-2,4-diene

The title compound, C24H24O3Si2, is a twofold symmetric silicocrown ether with the two dimethylsilyl groups attached to the O atoms of 1,1'-bi-2-naphthol, and bridged by another O atom.

1-(2 '-pyridylazo)-2-naphtholate complexes of ruthenium: synthesis, characterization, and DNA binding properties

Reaction of 1-(2'-pyridylazo)-2 -naphthol (Hpan) with [Ru(dmso)(4)Cl-2] (dmso=dimethylsulfoxide), [Ru(trpy)Cl-3] (trpy=2,2',2 ''-terpyridine), [Ru(bpy)Cl-3] (bpy=2,2'-bipyridine) and [Ru(PPh3)(3)Cl-2] in refluxing ethanol in the presence of a base (NEt3) affords, respectively, the [Ru(pan)(2)], [Ru(trpy)(pan)](+) (isolated as perchlorate salt), [Ru(bpy)(pan)Cl] and [Ru(PPh3)(2)(pan)Cl] complexes. Structures of these four complexes have been determined by X-ray crystallography. in each of these complexes, the pan ligand is coordinated to the metal center as a monoanionic tridentate N,N,O-donor. Reaction of the [Ru(bpy)(pan)Cl] complex with pyridine (py) and 4-picoline (pic) in the presence of silver ion has yielded the [Ru(bpy)(pan)(py)](+) and [Ru(bpy)(pan)(pic)](+) complexes (isolated as perchlorate salts), respectively. All the complexes are diamagnetic (low-spin d(6), S = 0) and show characteristic H-1 NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on all the complexes shows a Ru(II)-Ru(III) oxidation on the positive side of SCE. Except in the [Ru(pan)(2)] complex, a second oxidative response has been observed in the other five complexes. Reductions of the coordinated ligands have also been observed on the negative side of SCE. The [Ru(trpy)(pan)]ClO4, [Ru(bpy)(pan)(py)]ClO4 and [Ru(bpy) (pan)(pic)]ClO4 complexes have been observed to bind to DNA, but they have not been able to cleave super-coiled DNA on UV irradiation. (c) 2008 Elsevier Ltd. All rights reserved.

Planar triazinium cations from VO2+-assisted ring cyclizations: a remarkably efficient thiazole species for nuclear staining, PDT and anaerobic photocleavage of DNA

Planar triazinium cationic species, from VO2+-assisted cyclization of 1-(2-thiazolylazo)-2-naphthol, shows efficient DNA intercalative binding, visible light-induced anaerobic plasmid DNA photocleavage activity and photocytotoxicity in HeLa and MCF-7 cancer cells by an apoptotic pathway with selective localization of the compound in the nucleus as evidenced from the nuclear staining and confocal imaging.

Synthesis, crystal structure and catalytic properties of (p-cymene)ruthenium(II) azophenol complexes: azophenyl to azophenol conversion by oxygen insertion to a ruthenium---carbon bond

Azophenol complexes of formulation [(η6-p-cymene)RuCl(Ln)] (1–6, n=1–6) were prepared by two synthetic methods involving either an oxygen insertion to the Ru---C bond in cycloruthenated precursors forming complexes 1 and 2 or from the reaction of [{(η6-p-cymene)RuCl}2(μ-Cl)2] with azophenol ligands (HL3–HL6) in the presence of sodium carbonate in CH2Cl2. The molecular structure of the 1-(phenylazo)-2-naphthol complex has been determined by X-ray crystallography. The complex has a η6-p-cymene group, a chloride and a bidentate N,O-donor azophenol ligand. The complexes have been characterized from NMR spectral data. The catalytic activity of the complexes has been studied for the conversion of acetophenone to the corresponding alcohol in the presence of KOH and isopropanol. Complexes 4 and 6 having a methoxy group attached to the ortho-position of the phenylazo moiety and 2 with a methyl group in the meta-position of the phenolic moiety show high percentage conversion (>84%).

Planar triazinium cations from vanadyl-mediated ring cyclizations: the thiazole species for efficient nuclear staining and photocytotoxicity

Planar triazinium cationic species from vanadyl-assisted cyclization of 1-(2-thiazolylazo)-2-naphthol (H-TAN, 1), 1-(2-pyridylazo)-2-naphthol (H-PAN, 2), 2-(2'-thiazolylazo)-p-cresol (H-TAC, 3) and 6-(2'-thiazolylazo)- resorcinol (H-TAR, 5) were prepared and characterized. A dioxovanadium(V) species VO2(TAR)] (4) was also isolated. Compounds 1, 2 and 4 were structurally characterized. Both 1 and 2 have planar structures. Complex 4 has (VO3N2)-O-V coordination geometry. The cyclised triazinium compound forms a radical species within -0.06 to -0.29 V vs. SCE in DMF-0.1 M tetrabutylammonium perchlorate with a second response due to formation of an anionic species. A confocal microscopic study showed higher nuclear uptake for 1 having a fused thiazole moiety than 2 with a fused pyridine ring. The compounds showed a partial intercalative mode of binding to calf thymus DNA. Compound 1 showed plasmid DNA photo-cleavage activity under argon and photocytotoxicity in HeLa and MCF-7 cells with IC50 values of 15.1 and 3.4 mu M respectively in visible light of 400-700 nm, while being essentially non-toxic in the dark with IC50 values of 90.4 and 21.9 mu M. ATDDFT study was done to rationalize the experimental data.

Ternary ion-pair complexation: a protocol for chiral discrimination and the assignment of absolute configuration of chiral hydroxy acids

The study demonstrates the utility of ternary ion-pair complex formed among BINOL (1,1'-Bi-2-naphthol), a carboxylic acid and an organic base, such as, dimethylpyridine (DMAP), 1,4-diazabicyclo2.2.2]octane (DABCO), as a versatile chiral solvating agent (CSA) for the enantiodiscrimination of carboxylic acids, measurement of enantiomeric excess (ee) and the assignment of absolute configuration of hydroxy acids. The proposed mechanism of ternary complex has wider application for testing the enantiopurity owing to the fact that the binary mixture using BINOL alone does not serve as a solvating agent for their discrimination. In addition, the developed protocol has an excellent utility for the assignment of the absolute configurations of hydroxy acids.

Synthesis, characterization and catalytic properties of chiral BINOL functionalized mesoporous silicas for enantioselective Morita-Baylis-Hillman reaction

Several Chiral BINOL functionalized mesoporous silicas were prepared by post grafting of organosilane derivatives of (S)-BINOL (1,1'-bi-2-naphthol) on SBA-15 and characterized by C-13 CP/MAS NMR, FT-IR, UV-visible absorption spectra, elemental analysis, powder XRD, nitrogen adsorption-desorption isotherms and TEM techniques. Their catalytic properties were demonstrated in enantioselective Morita-Baylis-Hillman reaction of 3-phenylpropanal and cyclohexenone.

Asymmetric Michael addition of aldehydes to nitroolefins catalyzed by L-prolinamide derivatives using phenols as co-catalysts

The asymmetric Michael addition of aldehydes to nitroolefins was investigated using L-prolinamide derivatives of 2-(2'-piperidinyl)pyridine as catalyst and a variety of phenols as co-catalyst. Extensive screening toward the effect of prolinamides, phenols, and solvents on this transformation revealed that a combination of (S)-2-(2'-piperidinyl)pyridine-derived trans-4-hydroxy-L-prolinamide 2c, (S)-1,1'-bi-2-naphthol, and dichloromethane was a promising system. This system was shown to be amenable to a rich variety of aldehydes and nitroolefins and afforded the nitroaldehyde products with excellent yield, enantiomeric excess (up to 99%) and diastereoselectivity ratio (up to 99/1), even in the case of 1 mol % catalyst loading and 1.5 equiv of aldehydes.

In situ external reflection FTIR spectroelectrochemical investigation of poly(o-phenylenediamine) film coated on a platinum electrode

The electrochemically deposited poly(o-phenylenediamine) film on a Pt electrode has been investigated utilizing in situ external reflection FTIR spectroelectrochemistry technique. The prepared ladder polymer film is found to be partially ring-opened. The dopant ClO4- is evidenced to orient in such a way that more than one oxygen atom attach to the charge sites of the polymer. This suggests that positive charges of oxidized polymer are partially delocalized over the whole chains. The proton movement observed during the oxidation reaction is associated with the solvated MeCN molecule. It is proposed that the proton diffusion, dissolvation and protonation of the film may be essential to the electrochemical reduction reaction of the film. Copyright (C) 1996 Elsevier Science Ltd.

Iron organic speciation determination in rainwater using cathodic stripping voltammetry

A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17 ± 0.05 nM (n = 14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10–70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52–6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of β′Fe3+3(NN)β′Fe3+(NN)3 increased linearly with increasing pH according to log β′Fe3+3(NN)=2.4±0.6×pH+11.9±3.5log β′Fe3+(NN)3=2.4±0.6×pH+11.9±3.5 (salinity = 2.9, T = 20 °C). The validation of the method was carried out using desferrioxamine mesylate B (DFOB) as a natural model ligand for Fe. Adequate detection windows were defined to detect this class of ligands in rainwater with 40 μM of NN from pH 5.52 to 6.20. The concentration of Fe-complexing natural ligands was determined for the first time in three unfiltered and one filtered rainwater samples. Organic Fe-complexing ligand concentrations varied from 104.2 ± 4.1 nM equivalent of Fe(III) to 336.2 ± 19.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe3+, varied from 21.1 ± 0.2 to 22.8 ± 0.3. This method will provide important data for improving our understanding of the role of wet deposition in the biogeochemical cycling of iron.

Sensor technologies based on a cellulose supported platform

A simple approach to sensor development based on encapsulating a probe molecule in a cellulose support followed by regeneration from an ionic liquid solution is demonstrated here by the codissolution of cellulose and 1-(2-pyridylazo)-2-naphthol in 1-butyl-3-methylimidazolium chloride followed by regeneration with water to form strips which exhibit a proportionate (1 : 1) response to Hg(II) in aqueous solution.

Total synthesis of (S)-4-hydroxy-[a]-Lapachone

(S)-4-Hydroxy-a-lapachone has been prepared for the first time. The commercially available compound 2-acetyl-1-naphthol was used as the starting material. The synthesis involved methylation, followed by Baeyer-Villiger oxidation, and hydrolysis of the acetate to give 1-methoxy-2-naphthol. After protecting of the hydroxyl group, t-BuLi was used to form 3-(3',3'-dimethyl-acryloyl)-1- meth oxy-2- (meth oxymethoxy)-naphthalen e. eycl izationand oxidation then gave 4-keto-a-lapachone. Finally enzymic biotransformation by Mortierella isabellina ATCC 42613 was used to yield the target compound. The enantiomeric excess of the product was determined to be ~98% by using 1H NMR chiral shift analysis. The overall yield is 80/0. The biological activity of (S)-4-hydroxy-alapachone and its acetate are under investigation.

Développement de nouveaux sels Binol-imidazoliums : de la catalyse asymétrique aux applications biologiques

Le 1,1'-bi-2-naphtol ou Binol, présentant une chiralité axiale, est un ligand très utilisé en catalyse asymétrique. Au cours des vingt dernières années, le Binol a servi de synthon à l’élaboration de très nombreux ligands permettant la catalyse asymétrique de tous types de réactions, allant de l’hydrogénation, à l’alkylation, en passant par diverses réactions péricycliques. Le grand intérêt pour ce ligand vient de sa versatilité et des nombreuses possibilités de fonctionnalisation qu’il offre, permettant d’altérer ses propriétés catalytiques à volonté, aussi bien en modifiant son caractère électronique, qu’en introduisant des facteurs stériques autour du site catalytique. Parallèlement aux développements de la catalyse par des dérivés de Binol, le domaine des liquides ioniques a connu un intérêt croissant ces dernières années. Les liquides ioniques, sels dont le point de fusion est inférieur à 100°C, cumulent de nombreuses qualités convoitées : faible pression de vapeur, stabilité thermique et chimique et fort pouvoir de solvatation. Dû à ces propriétés, les liquides ioniques ont principalement été étudiés dans l’optique de développer une gamme de solvants recyclables. Alors que les propriétés des liquides ioniques sont facilement modulables en fonction de l’anion et du cation choisi, le concept de liquide ionique à tâche spécifique va plus loin et propose d’introduire directement, sur le cation ou l’anion, un groupement conférant une propriété particulière. En suivant cette approche, plusieurs ligands ioniques ont été rapportés, par simple couplage d’un cation organique à un ligand déjà connu. Étonnamment, le Binol a fait l’objet de très peu de travaux pour l’élaboration de ligands ioniques. Dans cette thèse, nous proposons l’étude d’une famille de composés de type Binol-imidazolium dont les unités Binol et imidazolium sont séparées par un espaceur méthylène. Différents homologues ont été synthétisés en variant le nombre d’unités imidazolium et leur position sur le noyau Binol, la longueur de la chaîne alkyle portée par les unités imidazolium et la nature du contre-anion. Après une étude des propriétés thermiques de ces composés, l’utilisation des Binol-imidazoliums en tant que ligands dans une réaction asymétrique d’éthylation d’aldéhydes aromatique a été étudiée en milieu liquide ionique. La réaction a été conduite en solvant liquide ionique dans le but de recycler aussi bien le ligand Binol-imidazolium que le solvant, en fin de réaction. Cette étude nous a permis de démontrer que la sélectivité de ces ligands ioniques dépend grandement de leur structure. En effet, seuls les Binols fonctionnalisés en positions 6 et 6’ permettent une sélectivité de la réaction d’éthylation. Alors que les dérivés de Binol fonctionnalisés en positions 3 et 3’ ne permettent pas une catalyse énantiosélective, il a déjà été rapporté que ces composés avaient la capacité de complexer des anions. D’autre part, il a déjà été rapporté par notre groupe, que les composés comportant des unités imidazolium pouvaient permettre le transport d’anions à travers des bicouches lipidiques en fonction de leur amphiphilie. Ceci nous a amenés à la deuxième partie de cette thèse qui porte sur les propriétés ionophores des Binols fonctionnalisés en positions 3 et 3’ par des unités imidazoliums. Dans un premier temps, nous nous sommes intéressés à l’étude de la relation structure-activité et au mécanisme de transport de ces composés. Le transport d’anions étant un processus clé dans la biologie cellulaire, l’activité biologique des composés présentant une activité ionophore dans des systèmes modèles (liposomes) a été étudiée par la suite. L’activité antibactérienne des nos composés a été testée sur quatre souches de bactéries. Il s’est avéré que les composés Binol-imidazolium sont actifs uniquement sur les bactéries Gram positives. Finalement, la cytotoxicité des composés présentant une activité antibactérienne a été étudiée sur des cellules humaines.

Two pentacoordinate copper(II) complexes that display accessible Cu(III/II) couples

Two copper(II) complexes of the type CuL2.imidazole (1) and Cu2L4(4.4'-bpy).2H(2)O.C6H14 (2), where LH = 1-nitroso-2-naphthol and 4.4'-bpy = 4,4'-bipyridine, are characterised by X-ray crystallography. In 2, the two copper atoms are linked by 4,4'-bpy. In both the complexes, copper is found to have a distorted square pyramidal N3O2 coordination sphere. The axial position in I is occupied by an oxygen atom while those in 2 by the nitrogen atoms of 4.4'-bpy. The two complexes display quasireversible Cu(III/II) couples around 0.68 V vs. saturated calomel electrode in cyclic voltammetry in dichloromethane.

Bidentates versus monodentates in asymmetric hydrogenation catalysis: synergic effects on rate and allosteric effects on enantioselectivity

C-1-Symmetric phosphino/phosphonite ligands are prepared by the reactions of Ph2P(CH2)(2)P(NMe2)(2) with (S)-1,11'-bi-2-naphthol (to give L-A) or (S)-10,10'-bi-9-phenanthrol (to give L-B). Racemic 10,10'-bi-9-phenanthrol is synthesized in three steps from phenanthrene in 44% overall yield. The complexes [PdCl2(L-A,L-B)] (1a,b), [PtCl2(L-A,L-B)] (2a,b), [Rh(cod)(L-A,L-B)]BF4 (3a,b) and [Rh(L-A,L-B)(2)]BF4 (4a,b) are reported and the crystal structure of la has been determined. A P-31 NMR study shows that M, a 1:1 mixture of the monodentates, PMePh2 and methyl monophosphonite L-1a (based on (S)-1,11'-bi-2-naphthol), reacts with 1 equiv of [Rh(cod)(2)]BF4 to give the heteroligand complex [Rh(cod)(PMePh2)(L-1a)]BF4 (5) and homoligand complexes [Rh(cod)(PMePh2)(2)]BF4 (6) and [Rh(cod)(L-1a)(2)]BF4 (7) in the ratio 2:1:1. The same mixture of 5-7 is obtained upon mixing the isolated homoligand complexes 6 and 7 although the equilibrium is only established rapidly in the presence of an excess of PMePh2. The predominant species 5 is a monodentate ligand complex analogue of the chelate 3a. When the mixture of 5-7 is exposed to 5 atm H-2 for 1 h (the conditions used for catalyst preactivation in the asymmetric hydrogenation studies), the products are identified as the solvento species [Rh(PMePh2)(L-1a)(S)(2)]BF4 (5'), [Rh(S)(2)(PMePh2)(2)]BF4 (6') and [Rh(S)(2)(L-1a)(2)]BF4 (7') and are formed in the same 2:1:1 ratio. The reaction of M with 0.5 equiv of [Rh(cod)(2)]BF4 gives exclusively the heteroligand complex cis-[Rh(PMePh2)(2)(L-1a)(2)]BF4 (8), an analogue of 4a. The asymmetric hydrogenation of dehydroamino acid derivatives catalyzed by 3a,b is reported, and the enantioselectivities are compared with those obtained with (a) chelate catalysts derived from analogous diphosphonite ligands L-2a and L-2b, (b) catalysts based on methyl monophosphonites L-1a and L-1b, and (c) catalysts derived from mixture M. For the cinnamate and acrylate substrates studied, the catalysts derived from the phosphino/phosphonite bidentates L-A,L-B generally give superior enantioselectivities to the analogous diphosphonites L-2a and L-2b; these results are rationalized in terms of delta/lambda-chelate conformations and allosteric effects of the substrates. The rate of hydrogenation of acrylate substrate A with heterochelate 3a is significantly faster than with the homochelate analogues [Rh(L-2a)(cod)]BF4 and [Rh(dppe)(cod)]BF4. A synergic effect on the rate is also observed with the monodentate analogues: the rate of hydrogenation with the mixture containing predominantly heteroligand complex 5 is faster than with the monophosphine complex 6 or monophosphonite complex 7. Thus the hydrogenation catalysis carried out with M and [Rh(cod)(2)]BF4 is controlled by the dominant and most efficient heteroligand complex 5. In this study, the heterodiphos chelate 3a is shown to be more efficient and gives the opposite sense of optical induction t the heteromonophos analogue