Search results for "Pyridine"
showing 10 items of 2516 documents
Thioetherification of Chloroheteroarenes: A Binuclear Catalyst Promotes Wide Scope and High Functional-Group Tolerance
2014
A constrained binuclear palladium catalyst system affords selective thioetherification of a wide range of functionalized arenethiols with chloroheteroaromatic partners with the highest turnover numbers (TONs) reported to date and tolerates a large variety of reactive functions. The scope of this system includes the coupling of thiophenols with six- and five-membered 2-chloroheteroarenes (i.e., functionalized pyridine, pyrazine, quinoline, pyrimidine, furane, and thiazole) and 3-bromoheteroarenes (i.e., pyridine and furane). Electron-rich congested thiophenols and fluorinated thiophenols are also suitable partners. The coupling of unprotected amino-2-chloropyridines with thiophenol and the s…
Optimization of Triazine Nitriles as Rhodesain Inhibitors: Structure-Activity Relationships, Bioisosteric Imidazopyridine Nitriles, and X-ray Crystal…
2013
The cysteine protease rhodesain of Trypanosoma brucei parasites causing African sleeping sickness has emerged as a target for the development of new drug candidates. Based on a triazine nitrile moiety as electrophilic headgroup, optimization studies on the substituents for the S1, S2, and S3 pockets of the enzyme were performed using structure-based design and resulted in inhibitors with inhibition constants in the single-digit nanomolar range. Comprehensive structure-activity relationships clarified the binding preferences of the individual pockets of the active site. The S1 pocket tolerates various substituents with a preference for flexible and basic side chains. Variation of the S2 subs…
Three-Component Entanglements Consisting of Three Crescent-Shaped Bidentate Ligands Coordinated to an Octahedral Metal Centre
2007
3,3'-biisoquinoline ligands (biiq) L, bearing aromatic substituents on their 8 and 8' positions, have been used to generate interwoven systems consisting of three crescent-shaped ligands disposed around an octahedral metal centre. Mono-ligand complexes of the type [ReL(CO)3py]+ (py: pyridine) have also been prepared, leading to sterically non-hindering complexes in spite of the endotopic nature of the chelate used. The three-component entanglements have been prepared by using either FeII or RuII as gathering metal centre. The synthetic procedure is simple and efficient, affording fully characterised complexes as their PF6 or SbCl6 salts. X-ray crystallography clearly shows that the crescent…
Imidazolate bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes of a terpyridinophane azamacrocycle: a solution and solid state study.
2007
The dinuclear Cu2+ and Zn2+ as well as the mixed Cu2+-Zn2+ complexes of a 5,5''-pentaazaterpyridinophane ligand (L) are able to incorporate imidazolate (Im-) as a bridging ligand. The crystal structure of [Cu(2)L(Im)(Br)(H2O)](CF(3)SO(3))(2).3H2O (1) shows one copper coordinated by the three pyridine nitrogens of the terpyridine unit, one nitrogen of the imidazolate bridge (Im-) and one bromide anion occupying the axial position of a distorted square pyramid. The second copper atom is coordinated by the remaining imidazolate nitrogen, the three secondary nitrogens at the centre of the polyamine bridge and one water molecule that occupies the axial position. Magnetic measurements have been p…
The synthesis, structure and properties of N-acetylated derivatives of ethyl 3-amino-1H-pyrazole-4-carboxylate.
2007
Ethyl 3-amino-1H-pyrazole-4-carboxylate (1) was yielded through total synthesis and reacted with acetic anhydride to give the acetylated products 2-6. Compounds 1-6 were studied with HPLC, X-ray, FT-IR, (1)H-NMR, (13)C-NMR and MS. Acetylation was carried out in solvents of various polarity, namely; chloroform; dioxane; DMF; acetic anhydride, at room temperature and at boiling points; and in the presence and absence of DMAP. The acetylated products are mainly nitrogen atoms in the ring. The position of the ring proton in the solution was based on NOESY; multinuclear HMBC, HSQC spectra and calculations. For equivalent amounts (1-1.5 mol) of acetic anhydride at room temperature two products of…
A synthetic molecular pentafoil knot
2011
Knots are being discovered with increasing frequency in both biological and synthetic macromolecules and have been fundamental topological targets for chemical synthesis for the past two decades. Here, we report on the synthesis of the most complex non-DNA molecular knot prepared to date: the self-assembly of five bis-aldehyde and five bis-amine building blocks about five metal cations and one chloride anion to form a 160-atom-loop molecular pentafoil knot (five crossing points). The structure and topology of the knot is established by NMR spectroscopy, mass spectrometry and X-ray crystallography, revealing a symmetrical closed-loop double helicate with the chloride anion held at the centre…
Orientational preferences of aromatic guests in dimeric capsules of tetraurea calix[4]arenes—MD and NMR studies
2006
Molecular dynamics (MD) simulations have been performed for complexes of a dimeric capsule of a tetraurea calixarene with a series of twelve aromatic guests. A distinct orientational preference and a restriction of the internal mobility was found which depend on the size and electronic properties of the guests. The results are in agreement with the CIS values obtained from (1)H NMR spectroscopic measurements and with complexation selectivities obtained by competition experiments.
3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]pyridines. An experimental and theoretical (DFT) study of the ring-chain isomerization
2005
An experimental (1H NMR) and theoretical (DFT) study of the ring-chain-ring isomerization of 3-(2-pyridyl)-[1,2,3]triazolo[1,5-a]pyrid-7-yl derivatives (A) into 6-{[1,2,3]triazolo[1,5-a]pyrid-3-yl}-2-pyridyl derivatives (B) has been carried out. Based on the calculations, a mechanism of several steps will be proposed. The experimental results as well as the calculations lead to the conclusion that the A-B ratio depends on the electronic properties of the substituents. © The Royal Society of Chemistry 2005.
Synthesis, Optical Properties, and DNA Interaction of New Diquats Based on Triazolopyridines and Triazoloquinolines
2017
New diquat derivatives based on [1,2,3]triazolo[1,5-a]pyridine and [1,2,3]triazolo[1,5-a]quinoline have been synthesized in excellent yields. To evaluate the effect of the alkyl bridge length, ethane and propane dibromo alkane substrates were used for their synthesis. Theoretical calculations predicted a very small energetic barrier between the two possible enantiomers P (Ra ) and M (Sa ), which makes them very difficult to resolve. Thermal denaturation studies, UV/Visible spectroscopy, and fluorescence titrations with ct-DNA evidenced the intercalation of the quinoline derivatives in DNA.
Structural studies of five novel bile acid-4-aminopyridine conjugates
2012
Abstract Synthesis and solid-state structural characterization of five bile acid amides of 4-aminopyridine (4-AP) are reported. Systematic crystallization experiments revealed a number of structural modifications and/or solvate/hydrate systems for these conjugates. Particularly, cholic acid conjugate exhibited five distinct structure modifications, including one anhydrous form, mono- and dihydrates, as well as ethanol and 2-butanol solvates. The obtained crystal forms were examined extensively with various analytical methods, including solid-state NMR, Raman, and IR spectroscopies, powder and single crystal X-ray diffraction methods, thermogravimetry, and differential scanning calorimetry. …