Substituent and structural effects on the kinetics of the reaction of N-(substituted phenylmethylene)-m- and -p-aminobenzoic acids with diazodiphenylmethane

The rate constants for the reaction of twenty-two N-(substituted phenyl methylene)-m- and -p-aminobenzoic acids with diazodiphenylmethane were determined in absolute ethanol at 30 °C. The effects of substituents on the reactivity of the investigated compounds were interpreted by correlation of the rate constants with LFER equations. The results of quantum mechanical calculations of the mole cular structure together with experimental results gave a better insight into the effects of structure on the transmission of electronic effects of the substituents. New σ constants for substituted benzylideneamino group were calculated

Infrared study of some 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. Correlation with MO-calculations

The IR spectra of a series of 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids (substituent = OH, SH, CH3, CH3S and NH2) were studied from the aspect of the influence of the subsitutent on the polarizability of some bonds, keto-enol tautomerism and hydrogen bond formation. The spectra were taken using solids due to the low solubility of the acids. Theoretical calculations were done using the MNDO-AM1 semiempirical molecular-orbital method. The stabilities of various tautomers were calculated simulating the dielectric continuum using the COSMO facility of the MOPAC program package. Theoretical calculations were made for all the possible tautomers of the 2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. For the most stable isomers, the vibrational spectra were calculated. For the majority of the compounds the most stable isomer was identified having the structure 2-Y-6-oxo-4-carboxy-3H-pyrimidine. Besides this structure, for the 2-amino-, and 2-methyl- derivatives the zwitterionic forms have very similar stability. The 2-hydroxy compound is most stable as the 2,6-dioxo-1H, 3H isomer. The calculated vibrations for the compounds with a single stable structure correlate very well with the experimental frequencies. For the 2-methyl- and 2-amino- compounds the correlation is considerably less satisfactory. The most probable reason for this deviation is the existence of two or more tautomets in equilibrium. The correlation of the measured frequencies and the pKa values of the acids, indicate that the same tautomers exist in the solid state and in the solution

Docking studies and Anti-inflammatory Activity of β-hydroxy-β-arylpropanoic Acids

Abstract: The article describes a two-step synthesis of diastereomeric 3-hydroxy-2methyl-3-(4-biphenylyl)butanoic acids. In the first step an intermediate α-bromo propanoic acid 1-ethoxyethyl ester was synthesized. The second step is a new modified Reformatsky reaction in presence of Zn in tetrahydrofuran (THF) at –5 to 10 °C between the previously synthesized intermediate and 4-acetylbiphenyl. Synthesis of the other studied β-hydroxy-βarylpropanoic acids has already been reported. These β-hydroxy-β-arylpropanoic acids belong to the arylpropanoic acid class of compounds, structurally similar to the NSAIDs such as ibuprofen. The anti-inflammatory activity and gastric tolerability of the synthesized compounds were evaluated. Molecular docking experiments were carried out to identify potential COX-2 inhibitors among the β-hydroxy-β-aryl-alkanoic acids class. The results indicate that all compounds possess significant anti-inflammatory activity after oral administration and that the compounds 2-(9-(9-hydroxy-fluorenyl))-2methylpropanoic acid (5) and 3-hydroxy-3,3-diphenyl-propanoic acid (3) possess the strongest anti-inflammatory activity, comparable to that of ibuprofen, a standard NSAID, and that none of tested substances or ibuprofen produced any significant gastric lesions

Effect of substituents on the 13C-NMR chemical shifts of 3-methylene-4-substituted-1,4-pentadienes. Part I.

The principles of linear free energy relationships were applied to the 13C substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the substituent parameters of Swain and Lupton provide a mutually consistent picture of the electronic effects in these compounds. The pattern of the electronic effects can be fully rationalized by a model based on the direct transmission of substituent effects through-space (direct through-space field effects), and via conjugative interactions (resonance effects), or by substituent-induced polarization of the p-system in the unsaturated chain (p-polarization effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis conformation of 3-methylene-4-substituted-1,4- -pentadienes as the one with minimal heat of formation

Synthesis, structure and magnetic properties of the first copper(II) complex with an (E)-4-aryl-4-oxo-2-butenoato ligand

A new binuclear Cu(II) complex with an (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato ligand (L) was successfully synthesized and characterized by elemental analysis and IR-spectroscopy. The structures of (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoic acid (HL), and the corresponding (tetrakis)-mu-[(E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato]-bis(ethanol)-copper(II) complex, [Cu2L4(C2H5OH)(2)], were determined by single crystal X-ray analyses and are preliminarily discussed. This is the first complex of a transition metal with ligand L. as well as the first determined crystal structure of a metal complex with this type of ligand. Analysis of the magnetic susceptibility measurements of the isolated [Cu2L4(C2H5OH)(2)]center dot H2O complex shows the existence of a strong anti-ferromagnetic intra-dimer coupling, with an exchange integral value 2J of -260 cm(-1). (C) 2006 Elsevier B.V. All rights reserved