A new and efficient approach to isoxazolines. First synthesis of 3-aryl-5-dichloromethyl-2-isoxazolines

An efficient synthetic method for 3-aryl-5-dichloromethyl-2-isoxazolines has been established. Reactions between anhydrous chloral and acetophenones in hot acetic acid lead to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones (chloralacetophenones), which provided 1-aryl-4,4-dichlorobut-3-en-1-ones (2,2-dichlorovinylacetophenones) by dehydration and subsequent electrochemical reduction. These β,γ-unsaturated enones reacted with hydroxylamine yielding oxime intermediates whose treatment with aqueous sodium hydroxide gave novel 3-aryl-5-dichloromethyl-2-isoxazolines in fair to high yields. The molecular structure of a member of this family of compounds, 5-dichoromethy1-3-(4-methoxyphenyl)-2-isoxazoline, was determined by X-ray crystallography.     

First synthesis of 1-aryl-4,4-dichlorobut-3-en-1-ones. The electrochemical reduction of 1-aryl-4,4,4-trichlorobut-2-en-1-ones as a key step

The first method for the synthesis of 1-aryl-4,4-dichlorobut-3-en-1-ones is reported. Treatment of acetophenones with anhydrous chloral leads to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones in near quantitative yields. These compounds were efficiently dehydrated with either sulfuric or p-toluenesulfonic acid to give 1-aryl-4,4,4-trichlorobut-2-en-1-ones, which were selectively converted to the title compounds in fair to quantitative yields by electrochemical reduction. The X-ray crystallographic structure of 4,4-dichloro-1-(4-methoxyphenyl)but-3-en-1-one has been determined. The preferential formation of β,γ-unsaturated ketones with total exclusion of the corresponding α,β-unsaturated isomers has been discussed with the aid of HF and B3LYP density functional theory methods.     

呋喃甲酸醋与三氯乙醛缩合反应研究

系统地研究了呋喃甲酸酯与三氯乙醛的缩合反应规律，提出了路易斯酸催化该反应的机制。当呋喃甲酸酯：无水三氯乙醛：三氯化铝（摩尔比）为２：１：１时，在６０～７０℃下反应６ｈ，双分子缩合产物的收率为５３～７５％。     

Haloaldehyde polymers,XLIX: Analysis of linear bornyl oxide initiated,acetate endcapped chloral oligomers by potassium ionization of desorbed species mass spectrometry

Linear chloral oligomers initiated with lithium bornyl oxide and acetate endcapped were analyzed by potassium ionization of desorbed species (K⁺ IDS) mass spectrometry. Using this technique we observed ions resulting from the [unimer]K⁺ with a mass of 381 daltons, to the [hexamer]K⁺ with a mass of 1 119 daltons. Furthermore, analysis of the isotope pattern supported our structural assignment. The individual lower oligomers were also investigated by GC and NMR spectroscopy.Previous paper in this series: Haloaldehyde Polymers XL VIII. W. J. Simonsick Jr., K. Hatada, Fu Xi, and O. Vogl [27]     

Application of the Iodide Ion-Selective Electrode in the Potentiometric Determination of Chloral Hydrate

Abstract

A simple and sensitive micro method for chloral hydrate determination based on oxidation with iodine in chloroform solution is described. The produced iodide ion in the extract is determined using the iodide ion-selective electrode by either a direct measurement, standard addition technique or potentiometric titration with standard silver nitrate solution. Samples containing 0.1 - 4.0 mg chloral hydrate are analyzed with an average recovery of 99-9% and standard deviation of 0.1%.     

First synthesis of 3-aryl-5-dichloromethyl-2-pyrazolines. The electrochemical generation of 2,2-dichlorovinylacetophenones as a key step

An efficient synthetic route to the title compounds has been established. Chloralacetophenones 2 were prepared by treatment of acetophenones 1 with anhydrous chloral. Dehydration of intermediates 2 under acidic conditions yielded 2,2,2-trichloroethylideneacetophenones 3, which were transformed to 2,2-dichlorovinylacetophenones 5 in nearly quantitative yields by selective electrochemical monodechlorination at either mercury or graphite electrodes. Finally, 3-aryl-5-dichloromethyl-2-pyrazolines 7 were efficiently obtained on treatment of compounds 5 with either hydrazine or methylhydrazine.     

Liquid chromatographic methods for chloral hydrate determination

Liquid chromatographic methods, based on reversed-phase (RP) and anion-exchange mechanisms, have been developed for chloral hydrate determination. Both methods are preceeded by derivatization of chloral hydrate. For RP separations, different reagents [namely dansylhydrazine and o-(4-nitrobenzyl)hydroxylamine] have been studied, but the best results have been achieved using 1,2-benzenedithiol with UV detection at 220 nm. The anion-exchange method is based on derivatization with NaOH to form sodium formate that is then analyzed by anion-exchange, with suppressed conductivity detection. Derivatization conditions were optimized in order to reach the best yield of reaction. The optimization of the procedure allowed to determine chloral hydrate with detection limits as low as 0.2 μg/l with good linearity and reproducibility. The anion-exchange method was also applied for chloral hydrate determination in a drinking water sample. A preconcentration procedure has also been studied.     

Bestimmung der einzelnen Komponenten bei der Kondensationsreaktion von Chloral und Benzol

Ohne Zusammenfassung

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Determination of the single components in the condensation reaction of chloral and benzene

     

Spectrophotometric Determination of Barbituric Acid

Abstract

Barbituric acid reacts with chloral hydrate in alkaline media, after heating for 1 min. at 100°C to give an orangish yellow colour having maximum absorbance at 450 nm. The reaction is selective for barbituric acid with 0.01 mg/ml as the visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's Law from 0.001 to 0.6 mg/ml and the relative standard deviation is 1.1%. The quantitative assessment of tolerable amounts of other drugs is also studied.     

A new and efficient approach to pyrazolines. First synthesis of 3-aryl-5-dichloromethyl-2-pyrazolines

An efficient synthetic method for dichloromethylated pyrazolines has been established. 1-Aryl-4,4-dichlorobut-3-en-1-ones 4 were efficiently prepared by treatment of acetophenones with anhydrous chloral, followed by dehydration and reductive dechlorination. Compounds 4 reacted with hydrazine hydrate and methylhydrazine to give the respective 5-dichloromethyl-2-pyrazolines in high to quantitative yields. The molecular structure of 5-dichoromethyl-1-methyl-3-(2-naphthyl)-2-pyrazoline has been determined by X-ray crystallography.