Search results for "Toni"

Treatment of scalar-relativistic effects on nuclear magnetic shieldings using a spin-free exact-two-component approach.

2013

A cost-effective treatment of scalar-relativistic effects on nuclear magnetic shieldings based on the spin-free exact-two-component theory in its one-electron variant (SFX2C-1e) is presented. The SFX2C-1e scheme gains its computational efficiency, in comparison to the four-component approach, from a focus on spin-free contributions and from the elimination of the small component. For the calculation of nuclear magnetic shieldings, the separation of spin-free and spin-dependent terms in the parent four-component theory is carried out here for the matrix representation of the Dirac equation in terms of a restricted-magnetically balanced gauge-including atomic orbital basis. The resulting spin…

MECHANISM OF INHIBITION OF GASTRIC ACID SECRETION BY HYPERTONIC SOLUTIONS

1978

Efficient synthesis of 2-bromo-1-[18F]fluoroethane and its application in the automated preparation of 18F-fluoroethylated radiopharmaceuticals

2001

An efficient synthesis of 2-bromo-1-[18F]fluoroethane from commercially available 1,2-dibromoethane and its integration into an automated preparation device was developed for the routine synthesis of 18F-fluoroethylated radiopharmaceuticals. The precursor 1,2-dibromoethane was reacted with the [18F]fluoride/Kryptofix®2.2.2./carbonate-complex in acetonitrile at 70°C for 3 minutes. The crude reaction mixture was diluted with water, loaded on a LiChrolute ®EN-cartridge, eluated with acetonitrile and passed through an Alumina ®B-cartridge. The method can provide 2-bromo-1-[18F]fluoroethane with 98% radiochemical purity completely free of 1, 2-dibromoethan within 10 min, thus avoiding a purifyin…

Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)am…

2006

Abstract Bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX4·0.5 CH3CN (X=Br or Cl) in monoclinic space group P21/n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl) crystallized without solvent molecules. The formed…

Iodolactonization of 3-Alkynylthiophene-2-Carboxylic and 3-Alkynylpicolinic Acids for the Synthesis of Fused Heterocycles

2020

The iodolactonization of 3-alkynylthiophene-2-carboxylic acids and 3-alkynylpicolinic acids has been investigated. Using I2 as the iodine source and NaHCO3 as the base in MeCN, the process took place smoothly to afford thienopyranones and pyranopyridinones, respectively, from 6-endo-dig cyclization. The method also worked nicely for the transformation of 2-(phenylethynyl)thiophene-3-carboxylic acid and 3-(phenylethynyl) isonicotinic acid into 7-iodo-6-phenyl-4H-thieno[3,2-c]- pyran-4-one and 4-iodo-3-phenyl-1H-pyrano[4,3-c]pyridin-1- one, respectively. Although with some 3-alkynylpicolinic acids the process led to a mixture of the 6-endo-dig and 5-exo-dig products, it could be still made se…

Syntheses, Structure, and Reactivity of Chiral Titanium Compounds: Procatalysts for Olefin Polymerization

2001

Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(η2-maltolato)2] (1, 89 %), and cis-[TiCl2(η2-guaiacolato)2] (2, 80 %) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82 %). The titanium compound cis-[Ti(OEt)2(η2-maltolato)2] (4, 74 %) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(μ-OEt)2(OEt)4(η2-maltolato)2] (5, 45 %)…

Fluorinated heterocyclic compounds. A photochemical synthesis of 3-amino-5-perfluoroaryl-1,2,4-oxadiazoles

2001

Abstract A photochemical methodology for the synthesis of 3-amino- (or 3- N -substituted amino) 5-pentafluorophenyl-1,2,4-oxadiazoles is reported. Irradiation of 3-pentafluorobenzoylamino-4-methyl-1,2,5-oxadiazole (Furazan) at 254 nm in methanol and in the presence of ammonia, primary or secondary aliphatic amines produces 3-amino-, 3-( N -alkylamino)-, 3-( N , N -dialkylamino)-5-pentafluorophenyl-1,2,4-oxadiazoles. The photoreaction follows the fragmentation pattern of the furazan ring with the extrusion of acetonitrile and the formation of a counterpart fragment which the nitrogen nucleophile will capture. Depending on the nature of the reagent, displacement of a fluoride anion at the C(5…

Preparation and characterization of organofunctionalized bentonite clay bearing aminophosphonic groups in heavy metal uptake

2019

Abstract Bentonite (Bnt) with covalently immobilized N-propylaminodi(methylenephosphonic) groups (Bnt-ADPA) was obtained through a two-step synthesis including aminosilanization and phosphorylation of resulting aminobentonite through Moedritzer-Irani reaction. The grafting of an aminosilane layer in the interplanar space of the bentonite was investigated by XRD, and the presence of N and P-containing groups was confirmed by FTIR, 31P and 29Si MAS NMR. The immobilization of the organic functional groups increased the interplanar distance in bentonite matrix at 52% that essentially improved filtration properties compared to raw bentonite. The number of surface acid groups was evaluated to 0.8…

Reaction of melatonin with hemoglobin-derived oxoferryl radicals and inhibition of the hydroperoxide-induced hemoglobin denaturation in red blood cel…

2001

Melatonin has been shown to act as a radical scavenger in various chemical and biological model systems in vitro. Kinetic evidence is now provided showing that melatonin inhibits the irreversible degradation of hemoglobin (Hb), when incubated with red blood cells exposed to the oxidant activity of cumene hydroperoxide (cumOOH). A decrease of heme loss and accumulation of soluble methemoglobin (met-Hb) are explained in terms of the interaction of the indoleamine with perferryl Hb ( . Hb[Fe IV = O]), a highly reactive Hb-derived radical species responsible for the irreversible Hb degradation. A kinetic study, in pure chemical solution, showed that melatonin can effectively reduce the oxoferry…

Elastohydrodynamic Collision of Two Spheres Allowing Slip on Their Surfaces.

2000

Our goal is to study theoretically the effect of deformation on the collision of two solid spheres allowing slip on their surfaces. The deformed shape of the solid surface is determined via an asymptotic technique assuming that deformation is small compared with the separation between the surfaces. It has previously been shown that the slippage makes collision possible even without any surface attractive force. Here we demonstrate that even a small amount of deformation can preclude spheres from coagulation. Copyright 2000 Academic Press.