One-carbon homologation of carboxylic acids via BtCH(2)TMS: a safe alternative to the Arndt--Eistert reaction

Carboxylic acids are converted into the corresponding homologated acids or esters, using easily available 1-(trimethylsilylmethyl)benzotriazole (1) as a one-carbon synthon. The effectiveness of the reaction has been investigated on six aryl and seven alkyl carboxylic acids.     

Spectrophotometric determination of ciprofloxacin in pure form and in tablets through charge-transfer complexation reactions

Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as -acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 g ml^–1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 g ml^–1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 11 DDQ and CL complexes were 1.086 × 10⁴ and 2.581 × 10⁴ lmol^–1, respectively, whereas for the 12 TCNQ complex it was 3.62 × 10⁸1. mol^–1.     

Reaction of Cα,O-dilithiooximes with functionalized carbonyl compounds. Part 2 . Reaction with α-chloroketones and α,β-unsaturated aldehydes and ketones

The reaction of Cα,O-Dilithiooximes 2 and α-chloroketones afforded 5-(hydroxymethyl)-Δ²-soxazolines 4 . α,β-Unsaturated aldehydes and ketones reacted with 2 to give the corresponding acyclic 1,2-addition products 5 . The latter were cyclized with phosphorus pentoxide to 5-vinyl-Δ²-isoxazolines 6 .     

Comparison of Py*+/dU*- charge transfer state dynamics in 5-(1-pyrenyl)-2'-deoxyuridine nucleoside conjugates with amido-, ethylenyl-, and ethynyl linkers

Femtosecond, picosecond, and nanosecond transient absorbance (TA) and picosecond emission kinetics results are presented for three 5-(1-pyrenyl)-2'-deoxyuridine nucleosides each with a different two-atom linker joining pyrenyl C-1 to uracil C-5. The linkers are respectively -NHCO-, -(CH(2))(2)-, and -C[triple bond]C- for PAdU, PEdU, and PYdU. For all three nucleoside conjugates, most conformers undergo intramolecular charge transfer (CT) from their pyrenyl (1)(pi,pi) excited states to form Py(*+)/dU(*-) CT products in ultrashort times: 相似文献   

XY-ZH compounds as potential 1,3-dipoles. Part 63: Silver catalysed azomethine ylide cycloaddition—the synthesis of spiro homoserine lactone analogues

A range of room temperature 1,3-dipolar cycloaddition reactions of imines of 2-amino-γ-lactone and thiolactone, catalysed by a combination of AgOAc or Ag₂O with NEt₃ or DBU, are described. The spiro lactones/thiolactones are formed regio- and stereoselectively as single cycloadducts in good yield via the syn dipoles and an endo-transition states.     

Pyrazoles and Pyrazolo[4,3- e]pyrrolo[1,2- a]pyrazines, I. Synthesis and Antimicrobial Activity

The synthesis of the title compounds was achieved using 1-phenyl-5-(pyrrol-1-yl)-1H-pyrazole-3-carboxylic acid azide as starting material. The latter compound was allowed to react with alcohols and amines to afford the corresponding carbamates and urea derivatives. Alkaline hydrolysis of the carbamates gave the corresponding amine, which was acylated and/or aroylated to give amide derivatives. These and the urea derivatives were subjected to cyclodehydration to give the title compounds. Antibacterial and antifungal activities were observed for several derivatives.     

Parametric study of catalytic reforming process?

Summary A parametric study of catalytic reforming process in a pilot plant was carried out by varying the pressure, H₂/HC ratio, and space velocity. The results show that lower aromatics and higher hydrogen yields can be accomplished by increasing the space velocity in existing reformers, which will also result in better C₅⁺yield.     

Asphaltene self-association and water-in-hydrocarbon emulsions

The configuration of asphaltenes on the water-oil interface was evaluated from a combination of molar mass, interfacial tension, drop size distribution, and gravimetric measurements of model emulsions consisting of asphaltenes, toluene, heptane, and water. Molar mass measurements were required because asphaltenes self-associate and the level of self-association varies with asphaltene concentration, the resin content, solvent type, and temperature. Plots of interfacial tension versus the log of asphaltene molar concentration were employed to determine the average interfacial area of asphaltene molecules on the interface. The moles of asphaltenes per area of emulsion interface were determined from the molar mass data as well as drop size distributions and gravimetric measurements of the model emulsions. The results indicate that asphaltenes form monolayers on the interface even at concentrations as high as 40 kg/m(3). As well, large aggregates with molar masses exceeding approximately 10,000 g/mol did not appear to adsorb at the interface. The area occupied by the asphaltenes on the interface was constant indicating that self-associated asphaltenes simply extend further into the continuous phase than nonassociated asphaltenes. The thickness of the monolayer ranged from 2 to 9 nm.     

Synthesis of the southern furan segment of furanocembranoids

Abstract

A convergent synthesis of the southern furan segment of novel furanocembranoids from Croton oblongifolius has been accomplished involving silver-catalyzed cyclization of alkynyl diol as the key step towards 2, 5-disubstituted furan ring formation.     

Production of carrier-free scandium radioisotopes from a neutron-irradiated potassium titanium oxalate target

Summary Extraction of scandium and calcium radioactivities with 1% HDEHP in benzene from nitric acid solution was investigated. The effect of potassium titanium oxalate concentration on the extraction from 1.5M nitric acid was studied. From the data obtained, two procedures based on batch solvent extraction and extraction chromatography were developed for separation and production of radioscandium from a neutron-irradiated potassium titanium oxalate target. The radiochemical purity of the separated scandium radioactivities was more than 98%.

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Zusammenfassung Die Extraktion der Aktivitäten des Scandiums und Calciums aus salpetersaurer Lösung mit 1% Diäthylhexylphosphorsäure in Benzol wurde untersucht. Der Einfluß der Kalium-Titanoxalat-Konzentration auf die Extraktion aus 1,5-m Salpetersäure wurde geprüft. Auf Grund der Ergebnisse wurden zwei Verfahren zur Trennung und Gewinnung von Radio-Scandium aus einem neutronenbestrahlten Kalium-Titanoxalat-Target ausgearbeitet, die auf einmaliger Extraktion mit dem Lösungsmittel bzw. auf Extraktionschromatographie beruhen. Die radiochemische Reinheit der Sc-Aktivitäten war besser als 98%.