Diastereoselective 1,3-dipolar cycloaddition of C,N-diaryl- and C-amido-N-arylnitrones to arylpropenones

C,N-diarylnitrones and C-amido-N-arylnitrones add diastereoselectively to the substituted arylpropenones to give the substituted isoxazolidine possessing 3RS,4SR,5SR configuration. Replacement of the aryl groups either in the position 3 of chalcone or at the nitrogen atom of nitrone by the methyl group decreased the rate of cycloaddition.     

Regioselective cycloaddition of C-aryl- and C-carbamoylnitrones to methyl 2-benzylidenecyclopropanecarboxylate

C-Aryl- and C-carbamoylnitrones reacted with methyl 2-benzylidenecyclopropanecarboxylate in highly regioselective fashion to give the corresponding 1,3-dipolar cycloaddition products, substituted methyl 5-oxa-6-azaspiro[2.4]heptane-1-carboxylates as mixtures of two diastereoisomers.     

Synthesis of dispiro[2.1.3.1]nonane and trispiro[2.1.1.37.15.13]-dodecane

Russian Journal of Organic Chemistry -     

Reduction and hydrolysis of substituted 5-oxa-6-azaspiro[2.4]heptane-1,2-dicarboxylic acid esters

Substituted 5-oxa-6-azaspiro[2.4]heptane-1,2-dicarboxylic acid esters synthesized by reaction of nitrones with dimethyl 3-methylidenecyclopropane-1,2-dicarboxylate were reduced with lithium tetrahydridoaluminate to the corresponding bis(hydroxymethyl)cyclopropanes. Alkaline hydrolysis of the title compounds gave substituted cyclopropane-1,2-dicarboxylic acids. In both cases, the 5-oxa-6-azaspiro[2.4]heptane fragment remained intact.     

Enthalpies of solvation for dopamine hydrochloride in water-ethanol solutions

The enthalpies of dissolution of dopamine hydrochloride (H₂Dop · HCl) in water-ethanol solvents containing from 0 to 0.8 mole fraction of ethanol are measured by calorimetry at 298.15 K. Standard enthalpies of transfer (??_tr H ^°) for the molecular (H₂Dop) and cationic (H₃Dop⁺) forms of dopamine from water into binary solvents are calculated from the obtained data. The enthalpies of transfer of H₃Dop⁺ cation are determined from the enthalpies of dissolution of H₂Dop · HCl using the familiar method of separating the molar quantities into ionic contributions (Ph₄P⁺ = BPh ₄ ^? ), and by an original alternative procedure. The effect of the composition of the binary solvent on the solvation of dopamine is considered.     

1H NMR, 13C NMR, and computational DFT studies of the structure of 2-acylcyclohexane-1,3-diones and their alkali metal salts in solution

1H and 13C NMR spectra of 2-acyl-substituted cyclohexane-1,3-diones (acyl = formyl, 1; 2-nitrobenzoyl, 2; 2-nitro-4-trifluoromethylbenzoyl, 3) and lithium sodium and potassium salts of 1 have been measured. The compound 3, known as NTBC, is a life-saving medicine applied in tyrosinemia type I. The optimum molecular structures of the investigated objects in solutions have been found using the DFT method with B3LYP functional and 6-31G** and/or 6-311G(2d,p) basis set. The theoretical values of the NMR parameters of the investigated compounds have been calculated using GIAO DFT B3LYP/6-311G(2d,p) method. The theoretical data obtained for compounds 1-3 have been exploited to interpret their experimental NMR spectra in terms of the equilibrium between different tautomers. It has been found that for these triketones an endo-tautomer prevails. The differences in NMR spectra of the salts of 1 can be rationalized taking into account the size of the cation and the degree of salt dissociation. It seems that in DMSO solution the lithium salt exists mainly as an ion pair stabilized by the chelation of a lithium cation with two oxygen atoms. The activation free energy the of formyl group rotation for this salt has been estimated to be 51.5 kJ/mol. The obtained results suggest that in all the investigated objects, including the free enolate ions, all atoms directly bonded to the carbonyl carbons lie near the same plane. Some observations concerning the chemical shift changes could indicate strong solvation of the anion of 1 by water molecules. Implications of the results obtained in this work for the inhibition mechanism of (4-hydroxyphenyl) pyruvate dioxygenase by NTBC are commented upon.     

Mechanism of epitaxial ferrite-spinel layer formation on magnesium oxide substrate

The initial stage of small gap heteroepitaxial growth of magnesium-manganese ferrite films during chemical gas transportation reactions on orientation (100) magnesium oxide substrate was studied. Film growth would begin with origination of parallely oriented three-dimensional nuclei, their shapes at lower (1170 K) and at appear (1420 K) film synthesis temperature limits being different. After little islands had grown together and continuous layer formed the secondary nuclei would appear, their shapes resembling cut-up pyramids. Continuous layer minimum thickness was 0.15 μm. The growing together of little islands results in film block structure. Block sizes could be as big as 300–400 μm if films grow at the speed of 2 μm/min, the density of islands being 10⁶ cm⁻². Linear density of unconformity dislocations at film-substrate boundary would be (3.7 ÷ 7.4) 10³ cm⁻¹. It would depend on magnesium content for a film. Elastic stresses in films would come to 7 · 10⁸ ÷ 3 · 10⁹ dyne/cm². X-ray topography pictures of block structures and of accumulations of admixtures at block boundaries are presented.