New spiro (thio) barbiturates based on cyclohexanone and bicyclo [3.1.1]heptan-6-one by nonconcerted [1+5] cycloaddition reaction and their conformational structures

Crossed-aldol condensation reaction of aromatic aldehydes with ketones such as; acetone and cyclohexanone leads to the efficient formation of cross conjugated α,β-unsaturated ketones in excellent yield. The intermolecular and then intramolecular Michael addition reaction of α,β-unsaturated ketones derived from acetone and cyclohexanone with (thio)barbituric acids lead to synthesis new type of 7,11-diaryl-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone and 2,4-diaryl-1'H-spiro[bicyclo[3.3.1]nonane-3,5'-pyrimidine]-2',4',6',9(3'H)-tetraone, respectively in good yield. Structure elucidation is carried out by 1H NMR, 13C NMR, FT-IR, UV-Visible, mass spectroscopy and X-ray crystallography techniques. A possible mechanism of the formation is discussed. The structural conformation also demonstrated by coupling constants derived from dihedral angles between vicinal and geminal protons. The 1H NMR spectra of NH protons of spiro compounds derived from barbituric acid show a broad singlet peak instead, these protons in the spiro compounds derived from thiobarbituric acid show two distinct peaks. KEY WORDS: Crossed-aldol condensation, Michael addition, [1+5] Cycloaddition, Barbituric acid, Conformation, Spiro barbiturate Bull. Chem. Soc. Ethiop. 2014, 28(3), 423-440.DOI: http://dx.doi.org/10.4314/bcse.v28i3.1

GC/MS analysis of the essential oils of Cupressus arizonica Greene, Juniperus communis L. and Mentha longifolia L.

ABSTRACT. The chemical composition of the essential oils obtained by hydrodistillation from Cupressus arizonica Greene, Juniperus communis L. and Mentha longifolia L. were determined by gas chromatography-mass spectrometry (GC/MS) analysis. The chemical composition of the essential oils were identified by GC/MS. Eicosane (27.4%), umbellulone (13%) and α-pinene (10.51%) were the major components of C. arizonica oil; sabinene (32%), limonene (26%) and bornyl acetate (7.4%) were the major components of J. communis oil and pulegone (26%), L-menthone (13.4%) and cis-para-menthan-3,8-diol (10.2%) were the major components of M. longifolia oil. The percentage of monoterpenes in the three essential oils was compared. The percentage of monoterpenes in C.arizonica is about 5.2%, J. communis 46%, and M. longifolia is 50.1%. The percentage of terpenes in C. Arizonica (16.3%), J. communis (5.2%) and M. longifolia (9.3%) were reported. But the percentage of cyclic monoterpenes in C. arizonica is about 6%, J. communis 26.1%, and M. longifolia is 3%. Monoterpenes are the most components that make up essential oils.               KEY WORDS: Cupressus arizonica, Juniperus communis, Mentha longifolia, Essential oil, Chemical composition Bull. Chem. Soc. Ethiop. 2019, 33(3), 389-400.DOI: https://dx.doi.org/10.4314/bcse.v33i3.

Alumina and Silica Oxides as Catalysts for the Oxidation of Benzoins to Benzils under Solvent-free Conditions

Alumina or silica gel are used as catalysts for a solvent-free oxidation of benzoins to the corresponding benzils. These catalysts are easily recovered after completion of the reactions, which are carried out either by heating in a sand bath or using microwave irradiation. Comparison of the results obtained with both catalysts indicates that all the reactants examined were oxidized faster on alumina than on silica under these conditions

Alumina and Silica Oxides as Catalysts for the Oxidation of Benzoins to Benzils under Solvent-free Conditions

Abstract: Alumina or silica gel are used as catalysts for a solvent-free oxidation of benzoins to the corresponding benzils. These catalysts are easily recovered after completion of the reactions, which are carried out either by heating in a sand bath or using microwave irradiation. Comparison of the results obtained with both catalysts indicates that all the reactants examined were oxidized faster on alumina than on silica under these conditions

Synthesis, spectroscopic and photophysical studies of xanthene derivatives

We report on the experimental, crystal structure and computational investigation of a new class of xanthenes obtained by the reaction of salicylaldehyde and its derivatives with, 5,5-Dimethylcyclohexane-1,3-dione (Dimedone). The synthesized xanthenes were characterized by state-of-the-art techniques, such as IR, Raman, 1H and 13C NMR, Single Crystal X-ray crystallography, UV–Vis and photophysical measurements. The structure, ground- and excited-state properties of one xanthene derivative was investigated using Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations with and without solvent (ethanol). The optimized geometries and predicted IR frequencies were in good agreement with experimental data. Hirshfeld surface analyses were carried out to gain insight on the close-contact interactions of the crystal, where hydrogen showed the highest contribution (66.1%). The synthetic route proposed in this work does not use any catalysts and leads to high yields (75–85%), therefore being an interesting alternative to synthesize xanthene derivatives. © 2017 Elsevier B.V

Investigation of interactional behavior and relative photo-physical properties in a group of bioactive compounds

In recent years, numerous researchers have faced the challenge of synthesizing bioactive compounds. Hence, chalcones with bioactive anti�cancer characteristics have attracted interests in many pharmaceutical studies. In this work, we focused on photo�physical behavior of three chalcones, with similar structures, in various solvent media, in order to study and compare their similarities and differences. Theoretical techniques were used to validate the experimental results. The experimental and theoretical results help to expand and better the realization of the photo�physical characteristics of these compounds and reveal essential information about the activity of this group of compounds in biological systems. The results show that photo�physical behavior of the chalcones is related to the solvent�solute interactions. Linear solvation energy relationship (LSER)model of Kamlet�Abboud�Taft and Catalán were used to analyze the interactions of chalcones in various media. The ground and excited state dipole moments of these bioactive compounds were obtained using Lippert's, Bakshiev's and Ghamma�Viallet's solvatochromic shift methods and their molecular resonance forms were presented. Finally, these results were compared and discussed by time�dependent density functional theory and configuration interaction calculations. © 2019 Elsevier B.V