Recyclization of Products Formed by Addition of 5-Hydrazino-2-phenyl-1,3-oxazoles Functionally Substituted in 4-Position to Aryl Isothiocyanates

Russian Journal of General Chemistry -     

Cyclocondensation of [1-Cyano-2-(methylsulfanyl)vinyl]triphenylphosphonium Iodide with Amidine Nucleophiles

The substituted vinylphosphonium salt (E)-MeSCH=C(CN)P⁺Ph₃I⁻ readily cyclizes under the action of benzamidine and 3-amino-s-triazole, but it does not enter cyclocondensation with 2-aminopyridine. The structure of the cyclization product with 3-amino-s-triazole was confirmed by its transformation to 7-imino-6-(triphenylphosphoranylidene)-6,7-dihydro-s-triazolo[1,5]pyrimidine which was identified by X-ray diffraction. This stabilized ylide and its analogs proved useful starting materials for regioselective syntheses of 2-R-4-alkyl-4,7-dihydro-s-triazolo[1,5-a]pyrimidin-7-ones.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 565–570.Original Russian Text Copyright © 2005 by Smolii, Muzychka, Chernega, Drach.     

Isoperimetric inequality for curves with curvature bounded below

For embedded closed curves with curvature bounded below, we prove an isoperimetric inequality estimating the minimal area bounded by such curves for a fixed perimeter.     

Mesomeeuc Phosphonium Ylides and Betaines Containing Imidazole Cycle

Abstract

Three types of high-polar phosphonlum compounde (1-111) containing imidazole cycle were obtained from the readily available acylaminomethylphosphonlum ralts (1).

In spite of meeorneric character, these compounde react with electrophilic reagentr in a regfoeelective manner. Depending on the nature of endo- and exocyclic nucleophi-lic centere they can rhow properties either of typical ylidee or betainee. Many of them are valuable precuraore In aynthesis of new types of substituted imidazoles (IV, V)     

An Improved Large Scale Synthesis of 2-Amino-4-chloropyridine and Its Use for the Convenient Preparation of Various Polychlorinated 2-Aminopyridines

An efficient large scale synthesis of 2-amino-4-chloropyridine (3) has been achieved through a modification of existing literature procedures. Compound 3 was used to prepare the previously unreported 2-amino-4,5-dichloropyridine (4). The known 2-amino-3,4-dichloropyridine (5) and 2-amino-3,4,5-trichloropyridine (6) were prepared from 3 by new routes and in higher yields than previously reported.     

New transformations of the reaction product of 4-(dichloromethylene)-2-phenyl-1,3-oxazol-5(4<Emphasis Type="Italic">H</Emphasis>)-one with triphenylphosphine

Consecutive treatment of the available 4-(dichloromethylene)-4-phenyl-1,3-oxazol-5(4H)-one with triphenylphosphine, water, and triethylamine gives a stabilized ylide Ph₃P=CHCONHCOPh. Its structure was proved by X-ray diffraction. The ylide reacts with hydrogen chloride and phosphorus pentachloride to give a many-center phosphonium reagent with a 1,3-dichloro-2-aza-1,3-diene group, which enters cyclocondensations with hydrazine hydrate, phenylhydrazine, and benzamidine. These reactions allowed synthesis of phosphonium salts of the general formula Ph₃ CH₂HtAn^– derived from 1,2,4-triazole or 1,3,5-triazine. The structure of the cyclization products was established by spectral methods, as well as by alkaline dephosphorylation.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1434–1440.Original Russian Text Copyright © 2004 by Brovarets, Golovenko, Sviripa, Zyuz, Chernega, Drach.This revised version was published online in April 2005 with a corrected cover date.     

Co-adsorption of surfactants and propyl gallate on the hydrophilic oxide surfaces

Propyl gallate (PG) adsolubilisation in the cationic, anionic and nonionic surfactant micelles formed in the bulk solution and at the silica/solution interface has been investigated. It was found that in the absence of surfactant, propyl gallate does not adsorb on the silica surface from aqueous solution. However, in the presence of hexyltrimethylammonium bromide (CTAB), its uptake by silica significantly increases. Alumina is quite an effective adsorbent for SDS and propyl gallate and does not adsorb nonionic TX-100. The addition of PG promotes adsorption of SDS and TX-100.     

Recyclization of Acylation Products of 2-Aryl-5-hydrazino-4-(dialkoxyphosphoryl)oxazoles

Russian Journal of General Chemistry -     

Recyclization of 2-Aryl-4-cyano-5-hydrazinooxazoles

The available 2-benzoylamino-3,3-dichloroacrylonitrile and its analogs when treated with excess hydrazine hydrate convert to 2-aryl-4-cyano-5-hydrazinooxazoles. The products are fairly stable in usual conditions but undergo recyclization on heating in acetic acid to give previously unknown derivatives of 2-methyl-1,3,4-oxadiazole with a 5-acylamino(carbamoyl)methyl substituent, whose structure was established by spectroscopy and X-ray diffraction. An important role in this complex transformation is probably played by prototropic forms of 4-cyano-5-hydrazinooxazoles, viz. hydrazones of substituted 2-oxazolin-5-ones which are not aromatic and thus can be cleaved with acetic acid and then recyclize.