Classical and Advanced Chemical Sciences
Chemical transformation of 3-amino-5-hydroxy-4-phenylazo-1H-pyrazole (1) provided a series of new pyrazol derivatives such as N-(4-(2-phenyldiazenyl)-2,5-dihydro-3-hydroxy-1H-pyrazol-5-yl)-2 chloroacetamide (2) obtained in the reaction of 1 with chloroacetyl chloride. Reaction of 2 with malononitrile and ammonium isothiocyanate gave the corresponding 1-(4-(2-phenyldiazenyl)-5-hydroxy-1H-pyrazol-3-yl)-2-amino-4,5-dihydro-5-oxo-1H-pyrrol-3-carbonitrile (3) and 3-(2-phenyldiazenyl)-7-amino-2-hydroxypyrazolo[1,5-a]pyrimidin-5(1H)-one (4). Reaction of 1 with P2S5 gave the corresponding 3-amino-5-mercapto-4-phenylazo-1H-pyrazole 5. The reaction of compound 5 with chloroacetic acid, ethyl chloroacetate, tetrahydrofuran, 3-hydroxybenzaldehyde, phenacylbromide and ninhydrine gave the corresponding N-substituted derivatives (6, 7, 8, 9, 10, 11, 12, 13), respectively. The reaction of compound 7 with hydrazine hydrate and a consecutive cyclization in the presence of glacial acetic acid and sulfuric acid mixture afforded 12. 1-(4-(2-Phenyldiazenyl)-5-mercapto-1H-pyrazol-3-yl)-3- phenylthiourea 14 was obtained from reaction of 5 with phenyl isothiocyanate, which was transformed into pyrazolothiadiazole 15 and pyrazolotriazole 16 derivatives with bromine in different solvents. 3-Amino-5-hydrazino-4-phenylazo-1H-pyrazole 17 was obtained from reaction 5 with hydrazine hydrate. Cyclization of compound 17 by reacting it with ethyl acetoacetate, acetylacetone, phthalic anhydride and phenacyl bromide gave the corresponding N-pyrazolylpyrazoles (18 and 19), pyrazol-2,3-dihydrophthalazine-1,4-dione (20) and pyrazolotriazine (21), respectively. Reaction of 17 with sodium nitrite in the presence acetic acid, ethyl pyruvate and carbon disulfide gave the corresponding pyrazolotetrazole (22), imidazolopyrazole (23) and pyrazolotriazole derivatives (26).
Keywords: pyrazoles; pyrazolotriazines; pyrazolotriazoles; pyrazolopyrimidines; pyrazolothiadiazoles
Bidentate Schiff base, 4-[(p-dimethylaminobenzylidene)amino]-3-mercapto-6-methyl-1,2,4-triazin-5-one, and its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been prepared and characterized with the aid of various physicochemical techniques like IR, NMR, ESR, elemental, electronic and thermal analysis. The conductance data suggested the non-electrolytic behaviour of the metal complexes. Fluorescence emission study demonstrated that the metal complexes possess more fluorescent intensity as compared to the Schiff base. Stability of the metal complexes has been checked by using Horowitz-Metzger method. The redox property of Cu(II) complexes has been investigated by using cyclic voltammetry. All the newly synthesized compounds have been screened for their in vitro antimicrobial activity against six microbial strains and it has been found that some of the tested compounds show good antimicrobial activity as compared to standard drug.
Keywords: Chelate complex,1H-NMR spectra, antimicrobial activity, metal complexes, Schiff base
Reaction of 3-amino-5-hydroxy-4-phenylazo-1H-pyrazole (1) with phenacyl bromide, acetic acid anhydride, benzoyl chloride and aromatic aldehydes gave 3-N-alkylated/acylated derivatives (2, 4 and 5) and the corresponding Schiff bases (6), respectively. Ring closure for compound 2 in acetic anhydride afforded pyrazolopyrimidine 3. Reaction of 1 with acetylacetone, ethyl acetoacetate, ethyl cyanoacetate, diethyl malonate and ninhydrine resulted in pyrazolo[1,5-a]pyrimidine-5(H)-one (7, 8, 9), pyrazolo[1,5-a]pyrimidine-5,7(1H,6H))-dione (10) and pyrazol-3-ylimino-1H-indene-1,3-(2H)-dione (12) derivatives. Reaction of active methylene group of (phenyldiazenyl)pyrazolo[1,5-a]pyrimidin-5,7(1H,6H)-dione (10) with phenyldiazonium chloride gave 2-phenylhydrazono derivative (11). Moreover, reaction of 1 with POCl3 and P2S5 resulted in 5-chloro (13) and 5-mercapto (15) derivatives, while phthalic anhydride, chloroacetyl chloride, aroyl thiocyanates and ammonium thiocyanate gave the corresponding 3-N-substituted derivatives. Hydrazenolysis of 13 in presence of hydrazine hydrate afforded the 5-hydrazino derivative. The 2-mercapto -7-(phenyladiazenyl)-2,5-dihydropyrazolo[1,5-b]triazole-6-ol (20) and 2-amino -7-(phenyladiazenyl)-2,5-dihydropyrazolo[1,5-b][1,2,4]-thiadiazol-6-ol (21) were obtained by the reaction of 1-(5-hydroxy)-4-(phenyldiazenyl)-1H-pyrtazol-3-yl)thiourea with bromine in different solvents. The structures of newly synthesized compounds have been established by IR, 1H NMR and elemental analysis.
Keywords: Pyrazoles, Triazoles, pyrazolopyrimidines
The structural diversity of steroids as well as their surpassed biological potential qualify them as challenging targets for chemical synthesis and as lead structures for pharmacological research. A total number of thirty-three structures of pregnane derivatives were obtained from the CSD for a comparative analysis of their crystallographic structures, computation of their possible biological activities and molecular packing interaction analysis. Intra and intermolecular interactions of the type X-H…A [X=C,O, N; A=O, N, S, Cl, F] have been analysed for a better understanding of molecular packing in pregnane class of steroids and discussed on the basis of distance-angle scatter plots. Molecular conformations of all the structures have been computed on the basis of the magnitude of torsion angles present in these structures. Results presented in this paper is a part of our ongoing work on the crystallographic aspects of steroidal derivatives of different classes.
Keywords: pregnane, hydrogen bonding, bifurcated hydrogen bond, biological activity, intramolecular interactions, intermolecular interactions, steroids
An efficient and green synthesis of 2,3-dihydroquinazolin-4(1H)-ones by microwave-assisted reaction of isatoic anhydride, ammonium acetate and an aldehyde or a ketone under catalyst- and solvent-free conditions is described.
Keywords: 2,3-Dihydroquinazolin-4(1H)-ones, microwave irradiation, catalyst- and solvent-free synthesis, isatoic anhydride, aldehydes, ketones.
Oxidation of thioglycolic, thiolactic and thiomalic acids by morpholinium fluorochromate (MFC) in dimethylsulphoxide (DMSO) leads to the formation of disulphide dimers. The reaction is first order in MFC. Michaelis-Menten type of kinetics is observed with respect to the thioacids. Reaction failed to induce the polymerisation of acrylonitrile. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence has the form kobs = a + b [H+]. The oxidation of thiolactic acid has been studied in nineteen different organic solvents. The solvent effect has been analysed by using Kamlet’s and Swain’s multiparametric equations. A mechanism involving the formation of a thioester and its decomposition in slow step has been proposed.
Keywords: Halochromates, kinetics, mechanism, oxidation, thioacids, morpholinium fluorochromate
Materials and Environmental Chemistry
Corrosion resistance of mild steel in simulated concrete pore solution (SCPS) in presence of simulated urine (SU), tartaric acid and lactic acid has been evaluated by electrochemical studies such as polarization study and AC impedance spectra. These studies lead to the conclusion that, the corrosion resistance of mild steel in various test solutions is as follows. Lactic acid+ SCPS+ urine > tartaric acid+ SCPS+ urine > SCPS > SCPS+ urine > urine. This leads to the conclusion that urination on the concrete structures such as bridges and building should be discouraged. Otherwise, the structure may collapse one day without prior information. However, the inclusion of tartaric acid or better lactic acid during the preparation of concrete admixtures strengthens the structures and should be encouraged.
Keywords: Concrete corrosion, mild steel, urine corrosion, lactic acid, tartaric acid
Chemical and Biological Aspects of Life
This study is designed to investigate the effects of carbon nanomaterials (multi-walled carbon nanotubes, MWCNTs) under controlled conditions on three different plant species. The study covers the effects of MWCNT dosage, treatment duration, and the plant-developmental stage, including imbibition, germination and seedling development. Germination experiments are conducted under standardized laboratory conditions based on the protocols of the International Seed Testing Association with aqueous MWCNT suspensions at a dosage of 0, 100 and 1000 mg L-1 applied as seed treatments during 36 h after sowing prior to radicle emergence, using soybean (Glycine max (L.) Merr. cv. BR-16 Conquista), common bean (Phaseolus vulgaris L. cv. Bohnen maxi) and maize (Zea mays L. cv. Surprise) as test plants. The seed treatment with MWCNTs reduced the speed of water uptake particularly by soybean seeds. This is associated with an increased germination percentage and reduced development of abnormal seedlings, while mean germination time is unchanged. However, during later seedling development, negative effects on root growth, particularly affecting fine root development are recorded for all investigated plant species. In soybean, this effect is first detected at 8 days after sowing and requires a minimum MWCNT seed exposure of 36 h. Inhibition of root growth is associated with reduced metabolic activity of the root tissue as indicated by tetrazolium vitality staining. The nitrate uptake was lower in MWCNT-treated plants, which is mainly attributed to the smaller root system. The results demonstrate that even under standardized experimental conditions, excluding environmental factors and effects induced by carbon nanomaterials, plant responses to MWCNT exposure exhibit differences, depending on plant species but also on the physiological status and the developmental stage of individual plants.
Keywords: germination, seedling growth, carbon nanotubes, soybean, common bean, maize