The X-ray structure of {C(NH2)3}[Tl(dota)]·H2O shows that the Tl(3+) ion is deeply buried in the macrocyclic cavity of the dota(4-) ligand (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) with average Tl-N and Tl-O distances of... more
The X-ray structure of {C(NH2)3}[Tl(dota)]·H2O shows that the Tl(3+) ion is deeply buried in the macrocyclic cavity of the dota(4-) ligand (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) with average Tl-N and Tl-O distances of 2.464 and 2.365 Å, respectively. The metal ion is directly coordinated to the eight donor atoms of the ligand, which results in a twisted square antiprismatic (TSAP') coordination around Tl(3+). A multinuclear (1)H, (13)C, and (205)Tl NMR study combined with DFT calculations confirmed the TSAP' structure of the complex in aqueous solution, which exists as the Λ(λλλλ)/Δ(δδδδ) enantiomeric pair. (205)Tl NMR spectroscopy allowed the protonation constant associated with the protonation of the complex according to [Tl(dota)](-) + H(+) ⇆ [Tl(Hdota)] to be determined, which turned out to be pK(H)Tl(dota) = 1.4 ± 0.1. [Tl(dota)](-) does not react with Br(-), even when using an excess of the anion, but it forms a weak mixed complex with cyanide, [Tl(dota)](-) + CN(-) ⇆ [Tl(dota)(CN)](2-), with an equilibrium constant of Kmix = 6.0 ± 0.8. The dissociation of the [Tl(dota)](-) complex was determined by UV-vis spectrophotometry under acidic conditions using a large excess of Br(-), and it was found to follow proton-assisted kinetics and to take place very slowly (∼10 days), even in 1 M HClO4, with the estimated half-life of the process being in the 10(9) h range at neutral pH. The solution dynamics of [Tl(dota)](-) were investigated using (13)C NMR spectroscopy and DFT calculations. The (13)C NMR spectra recorded at low temperature (272 K) point to C4 symmetry of the complex in solution, which averages to C4v as the temperature increases. This dynamic behavior was attributed to the Λ(λλλλ) ↔ Δ(δδδδ) enantiomerization process, which involves both the inversion of the macrocyclic unit and the rotation of the pendant arms. According to our calculations, the arm-rotation process limits the Λ(λλλλ) ↔ Δ(δδδδ) interconversion.
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... Submitted by FERENC JOO,* JOZSEF KOVACS,* AGNES KATHO,* ATTILA C. BENYE&* TARA DECUIR,' and DONALD J. DARENSBOURG' Checked by ALEX MIEDANER and DANIEL L. DUBOIS*' ... 3. AF Borowski, D. J.... more
... Submitted by FERENC JOO,* JOZSEF KOVACS,* AGNES KATHO,* ATTILA C. BENYE&* TARA DECUIR,' and DONALD J. DARENSBOURG' Checked by ALEX MIEDANER and DANIEL L. DUBOIS*' ... 3. AF Borowski, D. J. Cole-Hamilton, and G. Wilkinson, Noun J. Chem., 2 ...
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... 15 IS Kolomnikov, AI Gusev, GG Aleksandrov, TS Lobeeva, Yu. T. Struchkov and ME Vol'pin, J. Organometall. Chem., 59 (1973) 349. ... 20 RA Sanchez-Delgado, U. Thewalt, N. Valencia, A. Andriollo, KL. Marquez-Silva, J. Puga, H.... more
... 15 IS Kolomnikov, AI Gusev, GG Aleksandrov, TS Lobeeva, Yu. T. Struchkov and ME Vol'pin, J. Organometall. Chem., 59 (1973) 349. ... 20 RA Sanchez-Delgado, U. Thewalt, N. Valencia, A. Andriollo, KL. Marquez-Silva, J. Puga, H. Schollhorn, HP. Klein and B. Fontal, Inorg. ...
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New sulfonated tetrahydrosalen-type ligands and their water-soluble palladium(II) complexes have been synthesized. The palladium(II) complexes catalyze the Sonogashira coupling (23 examples) of various aryl halides (including... more
New sulfonated tetrahydrosalen-type ligands and their water-soluble palladium(II) complexes have been synthesized. The palladium(II) complexes catalyze the Sonogashira coupling (23 examples) of various aryl halides (including chloroarenes) with terminal alkynes, with good to excellent conversions under mild conditions (80°C, air, no Cu(I) cocatalyst) in aqueous-organic mixtures and turnover frequencies of up to 2790 h(-1) . Under optimized reaction conditions to minimize environmental contamination, diphenylacetylenes can be isolated in 76-98% yield. The aqueous catalyst solution can be recycled four times with decreasing activity; however, yields between 93 and 98% can still be achieved with extended reaction times. Several water-insoluble products can be isolated in excellent yield by simple filtration and purification by washing with water; this method is used, for the first time, for this type of C-C coupling procedure.
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ABSTRACT Two new pyridine-containing limonoids, xylogranatopyridines A and B (I and 2) and their formal precursor, prexylogranatopyridine (3) were isolated from the twigs and leaves of the Chinese mangrove, Xylocarpus granatum.... more
ABSTRACT Two new pyridine-containing limonoids, xylogranatopyridines A and B (I and 2) and their formal precursor, prexylogranatopyridine (3) were isolated from the twigs and leaves of the Chinese mangrove, Xylocarpus granatum. Xylogranatopyridine B (2) possesses an unprecedented rearranged B-ring together with a seco-ring A, supporting the biogenetic connection of 1-2 with 3. The chemical structures were elucidated by means of detailed spectroscopic analysis and X-ray single-crystal diffraction. The absolute configurations were assigned using electronic solid-state circular dichroism (ECD) supported by time-dependent density functional theory (TDDFT) ECD calculations and X-ray analysis. Xylogranatopyridine A (1) exhibited a significant inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with an IC50 value of 22.9 mu M. This is the first report of PTP1B inhibitory activity of limonoids.
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ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ABSTRACT The interactions between [(η6-p-cymene)Ru(H2O)3]2+ and L-malic acid (H2mal), L-tartaric acid (H2tart), and their sulfur-containing analogues dl-thiomalic acid (H3thiomal) and meso-2,3-dimercaptosuccinic acid (H4dmsa) were studied... more
ABSTRACT The interactions between [(η6-p-cymene)Ru(H2O)3]2+ and L-malic acid (H2mal), L-tartaric acid (H2tart), and their sulfur-containing analogues dl-thiomalic acid (H3thiomal) and meso-2,3-dimercaptosuccinic acid (H4dmsa) were studied by pH potentiometry, NMR spectroscopy, and ESI-MS. The hydroxycarboxylates are potent metal ion binders and prevent hydrolysis at pH 7.4 in aqueous solution. Although H2mal forms mononuclear complexes with different degrees of protonation by the involvement of the alcohol/alkoxide group in addition to the carboxylate groups, the presence of binding isomers is detected for the H2tart system. The replacement of the alcohol group by a thiolate group results in the formation of dinuclear [Ru2A2] complexes as the single species over a wide pH range. Complexes with identical binding modes with H3thiomal or polymeric species with H4dmsa are identified, and the X-ray structure of [{(η6-p-cym)Ru}2(Hthiomal)2] is reported. The stereochemistry of the chiral-at-metal complexes was explored by NMR spectroscopy and is also discussed.
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ABSTRACT Novel water soluble half-sandwich complexes of the general formulae [M(η6-p-cym)(ha)]2(CF3SO3)2, [M(η6-p-cym)(ha)Cl] or [M(η6-p-cym)(ha)(py)]X (M = Os, Ru; ha = hydroxamate; py = pyridine; X = Cl− or CF3SO3−), incorporating... more
ABSTRACT Novel water soluble half-sandwich complexes of the general formulae [M(η6-p-cym)(ha)]2(CF3SO3)2, [M(η6-p-cym)(ha)Cl] or [M(η6-p-cym)(ha)(py)]X (M = Os, Ru; ha = hydroxamate; py = pyridine; X = Cl− or CF3SO3−), incorporating metal-containing entities and hydroxamates both with potential anti-proliferative features, were prepared and characterized by elemental analysis, spectroscopy (NMR, IR) and ESI mass spectrometry. The X-ray crystal structure of [Ru(η6-p-cym)(μ-meaha)]2(CF3SO3)2 (5), [Os(η6-p-cym)(meaha)Cl] (6), [Ru(η6-p-cym)(phebha)Cl], (9), [Ru(η6-p-cym)(bha)(py)](CF3SO3) (12) and [Ru(η6-p-cym)(phebha)(py)](CF3SO3) (14), 6 is the first published structure of an organometallic Os(II)-hydroxamate reported. The effect of size differences of the metal ions, the steric demand of the RC and RN substituents at the hydroxamategroup and the type of the monodentate ligand co-present in the stoichiometry, along with the binding architecture of the half-sandwich metal(II) hydroxamate complexes are discussed. A novel dinuclear, dihydroxo bridged complex [Os(η6-p-cym)(py)(μ-OH)]2(CF3SO3)2 (16) is prepared and characterized by X-ray crystallography. Unexpected formation of a dinuclear oxo bridged OsII/OsVI complex [{Os(η6-p-cym)(meaha)}(μ-O){Os(O)(meaha)2}]Cl (17) occurs, and the crystal and molecular structure has been determined by X-ray method. Complexes 1, 5–8, 10 and 14 were tested for their in vitro cytotoxicity, using human-derived ovarian cancer cell lines (A2780 and A2780 cisR), and showed no anti-proliferative effect in the concentration range (0–200 μM) studied.
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Octahydroquinolizine-1, 2, 3, 8-tetraols 12, 16 and 23, analogs of castanospermine, were synthesized from D-glucose, L-arabinose and D-mannose, respectively, using hetero-Diels-Alder reactions of sugar-derived azomethines as the key step.
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Novel fused azecine ring systems were synthesized via the microwave-assisted thermal isomerization of terphenyl or biphenyl-pyridazine compounds possessing a vinyl and a tert-amino group, through application of a new extension of the... more
Novel fused azecine ring systems were synthesized via the microwave-assisted thermal isomerization of terphenyl or biphenyl-pyridazine compounds possessing a vinyl and a tert-amino group, through application of a new extension of the tert-amino effect. Substrates for the ring closure were prepared from ortho-dihalobenzene or pyridazinone by consecutive Suzuki couplings with ortho-sec-amino- and formylphenylboronic acids, followed by Knoevenagel condensation of the
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A new analogue of the antitumor pericosines possessing a bicyclo [2.2. 2] octene skeleton has been synthesized from methyl gallate using oxidative dearomatization and regio-and diastereoselective Diels–Alder reaction as the key steps.
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The synthesis, separation and stereochemistry of 1-epimeric (k)-1-thioflavanone 1-oxide isomers with equatorial phenyl group are described. The higher melting isomer (2a) has a 12-cis-, the lower melting one (2b) a 1,2-trans... more
The synthesis, separation and stereochemistry of 1-epimeric (k)-1-thioflavanone 1-oxide isomers with equatorial phenyl group are described. The higher melting isomer (2a) has a 12-cis-, the lower melting one (2b) a 1,2-trans configuration. H NMR and mass spectral data for both isomers and X-ray diffraction analysis of 2a are also presented.
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ABSTRACT For applications in aqueous media, sulfonated tetrahydrosalen (sulfosalan, HSS) was synthesized by sulfonation of tetrahydrosalen in fuming sulfuric acid. The Pd(II) complex of this ligand, [Pd(HSS)], showed outstanding activity... more
ABSTRACT For applications in aqueous media, sulfonated tetrahydrosalen (sulfosalan, HSS) was synthesized by sulfonation of tetrahydrosalen in fuming sulfuric acid. The Pd(II) complex of this ligand, [Pd(HSS)], showed outstanding activity in hydrogenation and redox isomerization of allylic alcohols in homogeneous aqueous solutions or in aqueous–organic biphasic systems (for oct-1-en-3-ol TOF(hydrogenation) = 1580 h–1, TOF(redox isomerization) = 400 h–1). DFT calculations revealed that H2 is activated heterolytically, resulting in a Pd(II)–hydride complex, [Pd(H)(HSS-Hphen)], in which one of the phenolate oxygens is protonated. Both hydrogenation and redox isomerization take place via concerted transfer of a proton and a hydride from the hydrogenated catalyst to the allylic alcohol.
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ABSTRACT New air-stable, water-soluble Ru(II)–phosphane complexes were synthesized in high purity by the reaction of cis-[RuCl2(dmso)4] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its N-methyl and N-benzyl derivatives... more
ABSTRACT New air-stable, water-soluble Ru(II)–phosphane complexes were synthesized in high purity by the reaction of cis-[RuCl2(dmso)4] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its N-methyl and N-benzyl derivatives (pta-Me and pta-Bn, respectively). All new complexes were characterized by elementary analysis and spectroscopic methods (NMR, ESI-MS) and the molecular structures of cis-cis-trans-[RuCl2(dmso)2(pta)2], cis-cis-trans-[RuCl2(dmso)2(pta-H)2]Cl2 (obtained in acidic solutions) and that of cis-cis-trans-[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 were determined by single crystal X-ray diffraction.Under mild conditions, cis-[RuCl2(dmso)4] actively catalyzed the transformation of allylic alcohols into the corresponding ketones with 100% selectivity while in the same reaction the new Ru(II)–pta complexes showed moderate activity and selectivity.
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... Strikingly, fumaric acid is hydrogenated approximately five times faster than maleic acid, contrary to the behavior of Wilkinson's catalyst, which, in organic solvents, is con ... The help given by TaraJ. Decuir (Texas AM... more
... Strikingly, fumaric acid is hydrogenated approximately five times faster than maleic acid, contrary to the behavior of Wilkinson's catalyst, which, in organic solvents, is con ... The help given by TaraJ. Decuir (Texas AM University) in writing the manuscript is grate fully acknowledged ...
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A series of N-heterocyclic carbene precursors, containing an imidazoline or tetrahydropyrimidine framework, were prepared from omega-chloroalkanoyl chlorides. The sequential attachment of nitrogen nucleophiles and subsequent ring closure... more
A series of N-heterocyclic carbene precursors, containing an imidazoline or tetrahydropyrimidine framework, were prepared from omega-chloroalkanoyl chlorides. The sequential attachment of nitrogen nucleophiles and subsequent ring closure gave, depending on the reagents used, either the desired dihydroimidazolium and tetrahydropyrimidinium salts or their parent heterocycles. In this latter case, the second substituent was introduced in an alkylation step. The preparation of carbene precursors bearing chiral or bulky substituents was acieved with comparable efficiency.