CONDENSATION REACTION OF 1-OXO-4-CHLOROCARBONYL-1-PHOSPHA-2,6,7-TRIOXABICYCLO[2.2.2]OCTANE WITH N-t-BUTYL-N-BENZOYLHYDRAZINE

Abstract

1-Oxo-4-chlorocarbony1-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane (5) was obtained from phosphorus oxychloride. Benzyl chloroformate was synthesized by the reaction of benzyl alcohol and triphosgene in good yield for the first time. N-r-Butyl-N-benzoylhydrazine(II) was prepared in a new and convenivent procedure with good yield. The reaction of 5 and II proceeded smoothly in the presence of sodium carbonate and afforded the desired compound 13 in good yield, while in the presence of triethylamine, the elimination of butyl was observed and afforded the compound 12.     

Studies on Poly(Dialkoxyphosphazenes) for the Medical Applications

Abstract

The presence of trace of chlorine in poly(diorganophosphazenes) [-N=P(OR)2-]., where R = C₂H₅, CH₂CF₃, C₂F₅, C₄H₅, C₆H₁₃, C₈H₁₇, C₁₂H₂₅, CH₂C₆H₅ in many cases leads to the substantial changes of their physicochemical properties and limits application possibilities of this class of polymers especial for the medical materials. Despite the optimization of reaction conditions for each nucleophilic alkoxy substituent, the obtained poly(dia1koxyphosphaenes) exhibited some physicochemical anomalies.     

Efficient synthesis of unsymmetrical diaryl thioethers via TBAF-mediated denitrative substitution of nitroarenes with PhSTMS under mild and neutral conditions

Tetrabutylammonium fluoride(TBAF) effectively facilitated a denitrative substitution reaction of electron-deficient nitroarenes with phenylthiotrimethylsilane(PhSTMS) under mild and base-free neutral conditions at room temperature,providing a practical and efficient synthesis of useful unsymmetrical diaryl thioethers.Nitroarenes bearing ortho-and para-positioned electron-withdrawing groups are the most reactive substrates,indicating that this reaction most possibly proceeded via the nucleophilic aromatic substitution(S_NAr) mechanism.     

Preparation of Bromoiodopropenoic Acids by Stereospecific Nucleophilic Substitution at Vinylic Carbon

The bromoiodopropenoic acids (E)‐2‐bromo‐3‐iodopropenoic acid 5 and (Z)‐2‐bromo‐3‐iodopropenoic acid 6 were prepared by stereospecific nucleophilic substitution of the corresponding vinylic bromides. The structure of the (Z)‐isomer was confirmed by X‐ray crystallography.     

Polyethylene Glycol–Enhanced Chemoselective Synthesis of Organic Carbamates from Amines,CO2, and Alkyl Halides

An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO₂, and alkyl halides underwent a three-component reaction with the aid of K₂CO₃ and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.

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Reduced odd–even effects in liquid crystalline carbonate dimers: molecular field analysis

Four liquid crystalline carbonate dimers DCn containing the dimethylbenzalazine mesogen, bis(oxycarbonyloxy)alkane flexible spacers with three to six methylene units and acetate terminal groups were synthesised and their mesogenic behaviour investigated. As compared with the corresponding ester dimers a strong reduction of odd–even fluctuations of nematic–isotropic (N–I) transition entropy is observed. A theoretical analysis of the dimers within the rotational isomeric states (RIS) mean-field approach is also reported. A satisfying agreement between calculated and observed thermodynamic properties is obtained. In fact, the theoretical analysis correctly predicts a significant reduction of the odd–even fluctuations for the core order parameter S as well as for the nematic to isotropic transition entropy △S_NI . The calculated distributions of conformers also show reduced differences between even and odd members. In particular, for even dimers the calculated fraction of linear extended conformers in the nematic phase at the N–I transition is around 27%, which is far below that of the corresponding ester dimers (46%).     

Synthesis of Different 3,5‐Diazidofuranoses: A New and General Synthesis Pathway

Diamino‐ and diazidofuranoses represent useful precursors, for example, for the synthesis of substituted nucleosides and metal complexes, respectively. Known procedures for their synthesis lack the availability of cheap starting materials, adequate yields, and the access to all possible diastereomeres. Therefore, 3,5‐diazido‐3,5‐dideoxy‐ and ‐2,3,5‐trideoxyfuranoses both with ribo‐ and xylo‐configuration were prepared using different approaches.     

Synthetic strategies to 2′-hydroxy-4′-methylsulfonylacetophenone,a key compound for the preparation of flavonoid derivatives

Different strategies for the synthesis of 2′-hydroxy-4′-methylsulfonylacetophenone are reported in the present paper. This compound is considered as a key synthon for the synthesis of new flavonoid derivatives designed as potential cyclooxygenase-2 inhibitors. The retrosynthetic approach via 3′-methylsulfonylacetophenone, which included three synthetic pathways, did not allow us to obtain the expected compound. However, a synthesis from 3-mercaptophenol led to the desired acetophenone in three steps: thiophenol methylation, Friedel–Crafts acetylation and oxidation of the sulphide to the corresponding sulfone. The desired compound, 2′-hydroxy-4′-methylsulfonylacetophenone, will be used as a synthon for the preparation of novel flavonoid derivatives, such as 2′-hydroxychalcones, flavanones, flavones, and flavonols.     

FeO(OH)@C-Catalyzed Selective Hydrazine Substitution of p-Nitro-Aryl Fluorides and their Application for the Synthesis of Phthalazinones

An efficient hydrazine substitution of p-nitro-aryl fluorides with hydrazine hydrates catalyzed by FeO(OH)@C nanoparticles is described. This hydrazine substitutions of p-nitro-aryl fluorides bearing electron-withdrawing groups proceeded efficiently with high yield and selectivity. Similarly, hydrogenations of p-nitro-aryl fluorides containing electron-donating groups also smoothly proceeded under mild conditions. Furthermore, with these prepared aryl hydrazines, some phthalazinones, interesting as potential structures for pharmaceuticals, have successfully been synthesized in high yields.