Double cyclisation of phenylglycine-o-carboxylic acids—I: New stable mesoionic oxazolones

Remarkably stable mesoionic oxazolones possessing an oxazolo[3,2-a]quinolinium structure (5a–b),8,16, 17) were obtained by the double cyclisation of phenylglycine-o-carboxylic acids (3a–c) in refluxing acetic anhydride or in benzoic anhydride at 140°, The 0-Ac group was eliminated to give the corresponding lactones (6a–b) or replaced by O-Ts (7). IR stretching vibrations of the endo-carbonyl were in the range 1710–1768 cm^?1, while v_1-CH exhibited unusually high values (3159–3194 cm^-1). 1-Acyl derivatives could be obtained only with TFAA (23–24), although easy deuteration of the same position took place in the presence of traces of trifluoroacetic acid. Hydrolysis of 5b led to the α-quinolone-N-acetic acid 27a. In the case of 5a, hydrolysis was accompanied by self-acylation of the nucleophilic site at C-4 with formation of a dimeric acid 28a. The presence of an additional Me group in phenylalanine-o-carboxylic acid (36) activates the corresponding mesoionic oxazolone 37 so that 1-acylation becomes possible with formation of the fused oxazole 38 by the Dakin-West reaction. Temperature dependent magnetic non-equivalence of methylene protons has been observed in acids 3b-d and f and also in the 7-membered anhydride 48b.     

Kinetics of solid-state synthesis and properties of lead-containing niobate pyrochlores

The main features of the synthesis of (Pb_1-x Sr_x)₂Nb₂O₇ and (Pb_1-x Ba_x)₂Nb₂O₇ pyrochlore solid solutions were determined using isothermal thermogravimetry in tandem with formal-kinetic analysis. The stability and electron-transport properties of the triple niobates were studied, which allowed us to test them as electrode-active materials for membranes in ion-selective electrodes (ISEs).     

The crystal structure of the inorganic surface films formed on Mg and Li intercalation compounds and the electrode performance

A crystallographic approach was applied to elucidate the influence of the nature of the surface films on the electrochemical behavior of Li and Mg intercalation compounds. This paper presents two examples: (1) protection of graphite electrodes by Li₂CO₃ surface films, and (2) the unique electrochemical behavior of Mg-containing Chevrel phases (MgCP) obtained by different synthetic routes. In the former case, the elucidation of the protection mechanism and the explanation of the high performance of such protected electrodes are based on the analysis of possible Li-ion motion in the carbonate crystal structure. In the latter case, a combination of synthesis, electrochemistry and XRD analysis was used to explain an unusual phenomenon: the difference between the excellent electrochemical behavior of the Chevrel phase (CP) based on Cu-leached Cu₂Mo₆S₈ (CuCP), and the poor electrochemical activity of the high-temperature synthesized MgCP, with the same phase composition. It is shown that this phenomenon is caused by MgO formation on the surface of the latter material. The different surface chemistry of the MgCPs obtained by the two different synthetic routes was substantiated by revealing the correlation between the electrochemical activity and the chemical stability of these materials under ambient atmosphere conditions. Dedicated to Prof. Mikhail A. Vorotyntsev on the occasion of his 60th birthday.     

Structure and Electrochemical Properties of Cation-Exchange Membranes Based on Partially Imidized Polyamidoacid

The transport of water molecules and the distribution of functional groups in polyamidoacid carboxyl-containing cation-exchange membranes based on pyromellitic acid are studied by NMR and ESR techniques. It is shown that the self-diffusion coefficients of water differ in the gel and intergel regions. Structural parameters of conducting channels in the gel regions are determined. In electrodialysis of one-component and binary solutions, polyamidoacid membranes possess higher transport numbers and separation coefficients of counterions that are less hydrated in solution.     

Synthesis and spatial structure of the geometrical isomers of 4-substituted 1-tert-butyl-3-methyl-piperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines

In order to study the interrelationship between the structure, reactivity, and spectroscopic characteristics of the stereoisomeric piperidines, starting from 1-tert-butyl-3-methylpiperidin-4-one the synthesis has been performed of the geometric isomers of some 4-substituted 1-tert-butyl-3-methylpiperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines. The spatial structures of the compounds obtained have been determined by IR and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1056–1061, August, 1973.     

Weighted bounds for the carleson maximal operator inR n

The Carleson maximal operator is shown to be bounded inL ^p (w) for certain values ofp and certain radial weightsw when acting on products of radial functions and homogeneous harmonic polynomials. Partially supported by DGICYT (MEC Spain). PB 92/187.     

Synthesis and three-dimensional structures of geometrical isomers of some 4-substitute d 1,2,5-trimethyl-4-acetoxy- and 1,2,5-trimethyl-4-benzoxypiperidines

Stereoisomers of the corresponding 4-substituted 1,2,5-trimethyl-4-acetoxy- and 1,2,5-trimethyl-4-benzoxypiperidines were obtained by acylation of the geometrical isomers of 1,2, 5-trimethyl-4-piperidol and its 4-ethynyl, 4-ethyl, and 4-phenyl-substituted derivatives. The preferred conformations of the investigated esters were elucidated by means of the PMR and IR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.1, pp. 50–55, January, 1973.     

A study of certain complex compounds of iron with the aid of magnetic measurements and the method of nuclearγ-resonance

Russian Chemical Bulletin -