Search results for "Chemical Synthesis"
showing 10 items of 285 documents
Synthesis and stereochemical properties of "extended" biphenols bridged by ortho-, meta-, and para-phenylene spacers
2009
A series of isomeric biphenols based on para- (1), meta- (2), and ortho- (3) terphenyl backbones was synthesized. Suzuki cross-coupling methodology was employed for the construction of the terphenyl backbone of their methyl-protected precursors (respectively 8, 13, and 16). Using K2CO3 as the base, the best reaction conditions involved DMF at 100 °C as solvent. Anhydrous conditions greatly improved the yields of the sterically crowded systems (particularly 16). ortho-Terphenyls 3 and 16 exist as mixtures of syn/anti atropisomers in solution. Compound 16 crystallizes in the anti-in form. DFT calculations at the B3LYP/6-311+G(d,p) level indicate that for both compounds the anti-in form is mor…
3-(Pyridin-2-yl)[1,2,3]triazolo[1,5-a]quinoline: A Theoretical and Experimental Analysis of Ring-Chain Isomerisation
2009
In the course of the synthesis of new fluorophores for molecular recognition an experimental (1H NMR) and theoretical (DFT) study of the ring-chain isomerism of 3-(pyridin-2-yl)[1,2,3]triazolo[1,5-a]quinoline derivatives (A) into 2-([1,2,3]triazolo[1,5-a]pyridin-3-yl)quinoline derivatives (B) has been carried out. The rearrangement is influenced by steric and electronic effects of the substituents present on the quinoline ring. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
nBuLi-Mediated hydrophosphination: a simple route to valuable organophosphorus compounds
2010
A straightforward synthesis of homoallyl- and allylphosphanes has been developed using nBuLi-mediated hydrophosphination of conjugated dienes. In all the cases the phosphorus atom of the reacting phosphane attacked the sterically less demanding side of the diene exclusively. In addition, high regioselectivities towards 1,2- or 1,4-addition products were observed depending on the nature of the dienes. This hydrophosphination reaction was extended to a variety of substrates such as styrene derivatives, alkynes and 1,3,5-cycloheptatriene. The structures of three hydrophosphination products were confirmed by X-ray diffraction studies.
Fine–grained spinel ferrites: From the reactivity to magnetic properties
1998
The oxidation at low temperature of fine-grained ferrites containing oxidizable cations such as Cu + , Fe 2+ , Mn 2+ , Mo 3+ , V 3+ , has led to new mixed-valent cation deficient ferrites with a large number of vacancies. It has been demonstrated by DTG analysis that each cation oxidizes at a specific temperature in close relation with the cation-oxygen distance. The kinetics oxidation of each oxidizable cation has been explained on the basis of a diffusion-induced stress effect when these stresses are generated by the chemical gradient induced during the oxidation process. When fine-grained ferrites contain some Co-cations, it has been revealed that the stresses have a significant influenc…
Synthesis, structure and reaction chemistry of a nucleophilic aluminyl anion.
2018
The reactivity of aluminium compounds is dominated by their electron deficiency and consequent electrophilicity; these compounds are archetypal Lewis acids (electron-pair acceptors). The main industrial roles of aluminium, and classical methods of synthesizing aluminium–element bonds (for example, hydroalumination and metathesis), draw on the electron deficiency of species of the type AlR3 and AlCl31,2. Whereas aluminates, [AlR4]−, are well known, the idea of reversing polarity and using an aluminium reagent as the nucleophilic partner in bond-forming substitution reactions is unprecedented, owing to the fact that low-valent aluminium anions analogous to nitrogen-, carbon- and boron-centred…
An Easy Stereoselective Access to β,γ-Aziridino α-Amino Ester Derivatives via Mannich Reaction of Benzophenone Imines of Glycine Esters with N-Sulfon…
2007
Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the ste…
Synthesis of new fluorinated Tebufenpyrad analogs with acaricidal activity through regioselective pyrazole formation.
2008
In previous studies, our group has shown that the use of fluorinated alcohols such as trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) as solvents dramatically increases the regioselectivity in the pyrazole formation from 1,3-diketone with methylhydrazine. We have now applied this synthetic method to the preparation of new fluorinated pyrazoles, which have then been used as synthetic intermediates in the preparation of fluorinated analogs of Tebufenpyrad, a commercial acaricide. These compounds display a strong acaricidal activity that is either comparable to or better than that of the commercial compound.
New propylamine oligopyrrole carboxamides linked to a heterocyclic or anthraquinone system: synthesis, DNA binding, topoisomerase I inhibition and cy…
2003
Continuing our studies on combilexines, compounds consisting of a DNA intercalator linked to a minor groove ligand, new results are presented. The synthesis of a series of new propylamine oligopyrrole carboxamides closely related to netropsin and distamycin A, linked to a heterocyclic or anthraquinone system is reported. The cytotoxic activity in vitro, the DNA binding characteristics and the inhibition of the topoisomerase I of the compounds were studied in order to explain the biological mechanism of action of these new potential combilexines. Some of the synthesised compounds showed cytotoxic activity against human tumour cell lines, as well as DNA binding and topoisomerase I inhibiting …
Resorcinarene Podand with Amine-Functionalized Side Arms â Synthesis, Structure, and Binding Properties of a Neutral Anion Receptor
2009
The synthesis and structure of a neutral resorcinarene host bearing four amine-functionalized side arms is described. The anion binding properties were investigated in solution by 1H NMR spectroscopic titration and diffusion experiments and in the gas phase by mass spectrometric studies. It was observed that in solution 1:2 (host/guest) complexes were formed between the resorcinarene host and the basic fluoride and acetate anions, whereas in the gas phase 1:1 complexes with other anions (Cl–, HCOO–, NO3–, and BF4–) were detected additionally. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Synthesis and Characterisation of Chiral Triazole-Based Halogen-Bond Donors: Halogen Bonds in the Solid State and in Solution
2017
A general platform for the synthesis of various chiral halogen-bond (XB) donors based on the triazole core and the characterisation of factors that influence the strength of the halogen bond in the solid state and in solution are reported. The characterisation of XB donors in the solid state by X-ray crystallography and in solution by 1H NMR titration can be used to aid the design of new XB donors. We describe the first example of a XB between iodotriazoles and thioureas in solution. In addition, the enantiodiscrimination of acceptors in solution through halogen-bond participation is described.