Synthesis of 6-Heterocyclically Appended Tri-<Emphasis Type="Italic">O</Emphasis>-methyl Protected 6-Desmethyl Emodin Derivatives

Summary. A convenient synthesis of several 6-heterocyclically appended tri-O-methyl 6-desmethyl emodin derivatives including the tetrazolyl, oxazolyl, oxazolinyl, benzimidazolyl, benzoxazolyl, and benzothiazolyl derivatives of potential biological and medicinal interest was achieved starting from the tri-O-methyl protected emodin aldehyde or nitrile. In addition, these derivatives could serve as synthons for heterocyclic hypericin derivatives.     

New methods of preparation of nitrile oxides and the corresponding disubstituted furoxans by interaction of N2O4 with salts of substituted dinitromethanes

A new method of generation of nitrile oxides through interaction of N₂O₄ with salts of substituted dinitromethanes (1) has been worked out. It has been shown by¹H,¹³C,¹⁴N NMR spectroscopy that this reaction proceeds via dinitronitrosomethyl intermediates (one of these has been isolated), and that the reaction is feasible only for substituents capable of conjugation with the nitrile oxide fragment. On the basis of cyclodimerization of the obtained nitrile oxides, preparative methods of synthesis of symmetrically substituted furoxans have been developed.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 147–151, January, 1993.     

Über Reaktionen mit Betain, 24. Mitt.: Über Umsetzungen von Trimethylammoniumessigsäurebetain mit reaktiven Halogenverbindungen

Summary Diethyl bromomalonate and bromoacetonitrile, respectively, react with trimethylammonium acetic acid betaine in ethanol to give diethyl tartronate and glycolic acid nitrile, respectively. By analogy, ethyl -chloroacetonate and ethyl bromopyruvate yield the respective hydroxy derivatives which were identified by their osazones2 and3. Under the same experimental conditions, mesoxalic acid and its dimethyl ester, respectively, are formed from dibromo malonic acid and its dimethyl ester and were characterized by their known hydrazones8 and9.

Herrn o. Prof. Mag. pharm. Dr. H. Junek, Karl-Franzens-Universität Graz, zur Vollendung des 60. Lebensjahres mit besten Wünschen gewidmet     

Addition of Nitrile Oxides to N-Allylsaccharin

The addition of nitrile oxides to N-allylsaccharin has been studied and it has been shown that the reaction occurs regiospecifically to form a 5-substituted isomer. The molecular structure of 2-{ 5-[(3-methyl)isoxazolin-2-yl]methyl}-3-oxo-2,3-dihydrobenz[d]isothiazole 1,1-dioxide has been determined by X-ray analysis. A feature of the crystal of this compound is the presence of a supersymmetrical crystalline structure with two independent molecules associated by a center of pseudoinversion.Dedicated to Professor V. I. Minkin on the occasion of his anniversary__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 450–456, March, 2005.     

Efficient Approach for the Synthesis of Novel Functionalized Isoxazolines from Limonene

New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl₃‐NaIO₄ oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data.     

A VERSATILE METHOD FOR THE CONVERSION OF ALDOXIMES TO NITRILES USING SILICA GEL/THIONYL CHLORIDE

A simple convenient procedure for dehydration of aldoximes has been developed using silica gel/thionyl chloride in heterogeneous conditions. The method has been found to be effective for a wide range of aromatic oximes.     

One-step synthesis of diazadihydroacenaphthylene derivatives with an isoxazoline ring, starting from 1-benzylamino-1-methylsulfanyl-2-nitroethenes

At low temperature in trifluoromethanesulfonic acid, 1-benzylamino-1-methylthio-2-nitroethene derivatives form hydroxynitrilium ions (or O-protonated nitrile oxides) observed by NMR. Quenching with water leads to the formation of a reactive nitrile oxide, dipole which undergoes an unexpected INOC reaction leading to new 3-methylsulfanyl-8a,8b-dihydro-5H-1-oxa-2,4-diazaacenaphthylenes.     

Di(propargyl)nitramine: synthesis and reactivity

An improved synthesis of (propargyl)nitramine and its pioneering conversion to di(propargyl)nitramine involve the alkylation of NH nitramines with propargyl halides or tosylate as the key steps. The standard (p° = 0.1 MPa) molar enthalpy of formation at 298.15 K for di(propargyl)nitramine was determined from the experimental standard molar energy of combustion in oxygen, measured by static bomb combustion calorimetry. Propargyl nitramines are suitable substrates for 1,3-dipolar cycloaddition reactions with azides, nitrile oxides and diazo compounds.     

An MEDT study of the mechanism and selectivities of the [3+2] cycloaddition reaction of tomentosin with benzonitrile oxide

The [3+2] cycloaddition (32CA) reaction of tomentosin with benzonitrile oxide yielding a spiro-isoxazoline has been studied within the Molecular Electron Density Theory at the B3LYP/6-31(d,p) computational level. Given the multifunctionality of tomentosin, this 32CA reaction can take place along 16 competitive reaction paths. The chemo-, regio-, and stereoisomeric reaction paths involving the two C C double bonds of tomentosin have been studied. Density functional theory (DFT) calculations account for the total chemo- and regioselectivity, in complete agreement with the experimental outcomes, being suggestive of low diastereofacial selectivity. Analysis of the conceptual DFT indices accounts for the nonpolar character of this 32CA reaction. On the other hand, the topological analysis of the electron localization function of the selected points of the intrinsic reaction coordinate associated with the formation of the C C and C O single bonds emphasizes the zw-type reactivity of the phenyl nitrile oxide; the reaction taking place through a non-concerted two-stage one-step mechanism initialized with the formation of the C C single bond involving the β-conjugated carbon of tomentosin.