Showing papers in "Journal of Chemical Sciences in 2013"

Mannich reaction: A versatile and convenient approach to bioactive skeletons

Abstract: This review gives an insight into the recent applications of Mannich reaction and its variants in the construction of bioactive molecules. Emphasis is given to the Mannich reaction that provides bioactive molecules and/or modifies the property of an existing bioactive molecule. The role of Mannich reaction in the construction of antimalarial, antitumour, antimicrobial, antitubercular, antiinflammatory and anticonvulsant molecules and also the significance of aminoalkyl Mannich side chain on the biological property of molecules is discussed here.

Microwave-assisted silica-promoted solvent-free synthesis of triazoloquinazolinone and benzimidazoquinazolinones

Abstract: The derivative of triazolo/benzimidazoquinazolinones is prepared via silica-promoted solvent-free method using microwave irradiation with an excellent yield. The newly synthesized compounds were characterized by various techniques like IR, NMR and Mass spectroscopy. The compound with 1a was crystallized and analysed by single crystal X-ray diffraction studies.

Synthesis of 2-amino-4H-chromene derivatives under microwave irradiation and their antimicrobial activity

Abstract: Libraries of 2-amino-4H-chromenes, were efficiently synthesized via one-pot, three-component reactions of 5-chloro-3-methyl-1-aryl-4,5-dihydro-1H-pyrazole-4-carbaldehyde (1a–c), 2-naphthols (2a–f) and malononitrile in the presence of catalytic amount of ammonium acetate under microwave irradiation. The protocol offers rapid synthesis of structurally diverse 2-amino-4H-chromenes for biological screening. All the synthesized compounds were evaluated for their antimicrobial activity, and several compounds exhibited moderate to potent antimicrobial activity.

Application of chalcones in heterocycles synthesis: Synthesis of 2-(isoxazolo, pyrazolo and pyrimido) substituted analogues of 1,4-benzodiazepin-5-carboxamides linked through an oxyphenyl bridge

Abstract: Versatility of chalcone derivative of 2-(4′-acetyl)-phenoxyl-5-carboxamido-1,4-benzodiazepin-5-(4′-methylpiperazinyl)-carboxamide (6) was explored to provide an easy one-pot access to its 2-(isoxazolo, pyrazolo and pyrimido) substituted analogues 9, 10, 11, 12, 13, 14, 15, and 16.

Catalytic non-thermal plasma reactor for the decomposition of a mixture of volatile organic compounds

Abstract: The decomposition of mixture of selected volatile organic compounds (VOCs) has been studied in a catalytic non-thermal plasma dielectric barrier discharge reactor. The VOCs mixture consisting n-hexane, cyclo-hexane and p-xylene was chosen for the present study. The decomposition characteristics of mixture of VOCs by the DBD reactor with inner electrode modified with metal oxides of Mn and Co was studied. The results indicated that the order of the removal efficiency of VOCs followed as p-xylene > cyclo-hexane > n-hexane. Among the catalytic study, MnOx/SMF (manganese oxide on sintered metal fibres electrode) shows better performance, probably due to the formation of active oxygen species by in situ decomposition of ozone on the catalyst surface. Water vapour further enhanced the performance due to the in situ formation of OH radicals.

PbO as an efficient and reusable catalyst for one-pot synthesis of tetrahydro benzo pyrans and benzylidene malonitriles

Abstract: PbO nanoparticles have been employed as an efficient catalyst for the solvent-free synthesis of tetrahydrobenzo pyrans (yields 81–91%) and benzylidene malonitriles (yields 90–96%) at room temperature using green chemistry approach. PbO nanoparticles were found to be highly efficient, eco-friendly and recyclable heterogeneous catalyst. PbO nanoparticles were prepared by hydrothermal method and characterized by IR, XRD, BET Surface area, SEM, EDAX and TEM with SAED techniques.

Nano n-propylsulphonated γ-Fe2O3: A novel magnetically recyclable heterogeneous catalyst for the efficient synthesis of bis(pyrazolyl)methanes in water

Abstract: Nano n-propylsulphonated γ-Fe2O3 (NPS-γ-Fe2O3) was applied as a new magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of bis(pyrazolyl)methanes in water. The catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least five times without significant degradation in activity.

Theoretical study of intramolecular hydrogen bonding in the halo derivatives of 1-amino-3-imino-prop-1-ene

Abstract: Intramolecular hydrogen bonding (IHB) of 1-amino-3-imino-prop-1-ene (AIP), as the simplest resonance-assisted hydrogen bond system in symmetric N-H ··· N class, and its halo derivatives (F, Cl, and Br) have been studied at the DFT-B3LYP/6-311++G ∗∗ level of theory. For better understanding of the nature of substituent effects, nitro and methoxy derivatives of AIP were also added to our consideration. Good linear correlations between IHB energies based on Espinosa's equation and −G(r )/V (r ) values, total electronic den- sity, Laplacian of total electronic density in critical points, π -electron delocalization parameter (Q), hyper con- jugative interaction energy of lp(N) → σ ∗ (N-H), (Fi, j /Si, j ) 2 parameter, natural charges of bridged hydrogen, frequency shift of the N-H stretching vibration, and chemical shift of bridged hydrogen were obtained.

Sulphamic acid-functionalized magnetic Fe3O4 nanoparticles as recyclable catalyst for synthesis of imidazoles under microwave irradiation

Abstract: Trisubstituted imidazoles have been synthesized in high yield in the presence of sulphamic acid- functionalized magnetic Fe3O4 nanoparticles (SA-MNPs) as a novel solid acid catalyst under solvent-free classical heating conditions or using microwave irradiation. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of catalytic activity.

Multi-component reaction on free nano-SiO2 catalyst: Excellent reactivity combined with facile catalyst recovery and recyclability

Abstract: Nano-SiO2 catalyst was readily prepared from inexpensive starting materials in aqueous media which catalysed the synthesis a-aminophosphonates from aldehydes, amines and diethylphosphate under ultrasonication in water. High catalytic activity and ease of recovery from the reaction mixture using filtration, and reuse without significant losses in performance are additional eco-friendly attributes of this catalytic system.

Density functional theory, natural bond orbital and quantum theory of atoms in molecule analyses on the hydrogen bonding interactions in tryptophan-water complexes

Abstract: The tryptophan-water (Trp-H2O) complexes formed by hydrogen bonding interactions were investigated at the ωB97XD/6–311+ +G(d,p) level. Five Trp-H2O complexes possessing various types of hydrogen bonds (H-bonds) were characterized by geometries, energies, vibrational frequencies. The nature of the H-bonds were characterized by the natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analyses as well. The intramolecular H-bond formed between the amino and carboxyl oxygen atom of tryptophan was retained in most of the complexes, and the cooperativity between the intra and intermolecular H-bonds exist in some complexes. The intramolecular H-bond and some intermolecular H-bonds are strong and have partial covalent character. The H-bonds formed between carboxyl and oxygen/nitrogen atoms are stronger than other H-bonds. The H-bonds involving methylene of tryptophan as H-donor are weak H-bonds. For all complexes, ΔE ele and ΔE ex makes major contributions to the total interaction energy (ΔE MP2), while ΔE disp is the smallest component of the interaction energy. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Regardless of strong H-bonds, the stabilities of some complexes are weakened by the serious structural deformations.

Synthesis of new series of 3-hydroxy/acetoxy-2-phenyl-4H-chromen-4-ones and their biological importance

Abstract: 3-Hydroxy-2-aryl/heteroaryl-4H-chromones 4(a–n) were synthesized from appropriate chalcones 3(a–n) and acetylated to afford the corresponding acetoxy derivatives 5(a–n). All compounds were evaluated for antimicrobial activity against Staphylococus aureus, Bacillus subtillis, Escherichia coli and Pseudomonas aeruginosa as well as fungi e.g., Candida albicans and Aspergius niger. Inhibition caused by hydroxy flavones was relatively low, whereas that of their acetoxy ester analogues was substantially high. Structure of 6-chloro-2-(furan-2-yl)-4-oxo-4H-chromen-3-yl acetate (5j) was also supported by means of single crystal X-ray diffraction.

Synthesis, structural characterization and biological activity of a trinuclear zinc(II) complex: DNA interaction study and antimicrobial activity

Abstract: A trinuclear zinc(II) complex [Zn3 L 2(μ-O2CCH3)2(H2O)2]·H2O·2CH3OH (1) was synthesized from an in situ reaction between zinc acetate and a Schiff base ligand (H2 L = 2-((2-hydroxyphenylimino)methyl)-6-methoxyphenol). The ligand was prepared by (1:1) condensation of ortho-vanillin and ortho-aminophenol. The ligand and zinc(II) complex were characterized by elemental analysis, Fourier Transform Infrared (FTIR), 1H-Nuclear Magnetic Resonance (NMR), UV-Vis spectroscopy, Powder X-ray Diffraction (PXRD) and thermogravimetric analysis. 1 crystallizes in P-1 space group with a = 11.9241(3) A, b = 12.19746 A, c = 20.47784 A with unit cell volume is 2674.440 (A)3. Binding property of the complex with calf thymus DNA (CT-DNA) has been investigated using absorption and emission studies. Thermal melting and viscosity experiments were further performed to determine the mode of binding of 1 with CT-DNA. Spectroscopic and viscosity investigations revealed an intercalative binding mode of 1 with CT-DNA. The ligand and its zinc complex were screened for their biological activity against bacterial species and fungi. Activity data show that the metal complex has more antibacterial and antifungal activity than the parent Schiff base ligand and against those bacterial or fungi species.

Synthesis, characterization and photo-epoxidation performance of Au-loaded photocatalysts

Abstract: Titanium silicalite-1 (TS-1) was synthesized by hydrothermal crystallization. Au-loaded TS-1 (Au/TS-1) was prepared by the photo-deposition method. The prepared photocatalysts have been fully characterized by Raman, Brunauer–Emmett–Teller (BET), transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet visible light spectroscopy to reveal their structure, surface morphology and chemical composition. Photocatalytic activity of these photocatalysts was ascertained by gas phase photo-epoxidation of propylene-to-propylene oxide in the presence of molecular oxygen only under light irradiation. No sacrificial reductant such as hydrogen was used during the photoreaction. Au/TS-1 photocatalyst remained highly stable under reaction conditions. It is found that the increased Ti3+ sites due to the incorporation of Au will not only enhance the selectivity of the photocatalyst to form epoxide but also its stability during C3H6 conversion.

Synthesis, characterization and biological activity of new cyclization products of 3-(4-substituted benzylidene)-2H-pyrido(1,2-a)pyrimidine 2,4-(3H)-diones

Abstract: A method is presented for the synthesis of 4-(substituted phenyl)-3-(3-substituted phenyl)4H-spiro[isoxazole-5,3′-pyrido[1,2-a]pyrimidine]-2′,4′-dione (3), 3-(4-substituted phenyl)-3H-isoxazole[3, 4-d]pyrido[1,2-a]pyrimidin-4-(3aH)-one (4) and 3-(4-substituted phenyl) 3,3a-dihydropyrazolo[3,4-d]pyrido[1,2-a]pyrimidin-4-(2H)-one (5) which consists of the conversion of 2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione (1) to chalcones (2) and their 1,3-dipolar cycloaddition with appropriate aldoximes to give spiro compounds and heterocyclization using amines to yield isoxazolines and pyrazolines. All the compounds were screened for their antimicrobial and antitubercular activity.

Polymer supported sulphanilic acid: A highly efficient and recyclable green heterogeneous catalyst for the construction of 4,5-dihydropyrano[3,2-c]chromenes under solvent-free conditions

Abstract: Polystyrene divinylbenzene supported sulphanilic acid was prepared, characterized and tested as an acidic catalyst in multicomponent organic synthesis. This is the first report focusing on the development of one-pot solvent-free synthesis of 4,5- dihydropyrano [3,2-c]chromenes under acidic conditions. It proved to be a versatile catalyst for microwave-assisted synthesis of 4,5-dihydropyrano[3,2-c]chromenes. This methodology is mild, high yielding, green and the catalyst could be easily recycled for several times.

Calcined eggshell (CES): An efficient natural catalyst for Knoevenagel condensation under aqueous condition

Abstract: A convenient, eco-friendly and economic method for Knoevenagel condensation of aromatic aldehydes with active methylene compounds using calcined eggshell (CES) as an efficient natural catalyst in aqueous medium has been reported. CES is a new, ecologically safe and inexpensive green catalyst obtained from renewable resources.

Green and solvent-free procedure for microwave-assisted synthesis of 2,4,6-triarylpyridines catalysed using MgAl2O4 nanocrystals

Abstract: Design and development of a heterogeneous nanocatalyst for condensation reaction of acetophenone derivatives, aromatic aldehydes, and ammonium acetate to yield 2,4,6-triarylpyridines followed by microwave irradiation is described. Nanocrystalline MgAl2O4 as a novel heterogeneous recyclable catalyst shows high activity for the above reaction. In addition, the easily recoverable nanosized catalysts showed good reusability.

One-pot multi-component synthesis of 1,4-dihydropyridine derivatives in biocompatible deep eutectic solvents

Abstract: An efficient protocol for the synthesis of differently substituted 1, 4-dihydropyridines in deep eutectic solvents under solvent-free conditions is reported here. Excellent yields of the resultant products have been obtained. Recyclability studies have also been performed for deep eutectic solvents with very little loss in activity up to five recycles.

A new class of multi-substituted oxazole derivatives: Synthesis and antimicrobial activity

Abstract: A new and efficient method for the synthesis of multi-substituted oxazole derivatives from various aldehydes has been described. Twenty novel multi-substituted oxazoles containing a heterocyclic moiety were synthesized and evaluated for their antimicrobial activity. The prepared compounds are all reported for the first time and their structures were established by elemental analysis, IR, 1H-NMR, and 13C-NMR and Mass spectra. All the synthesized compounds exhibited in vitro antimicrobial activity.

Activity, stability and kinetic parameters for α -chymotrypsin catalysed reactions in AOT/isooctane reverse micelles with nonionic and zwitterionic mixed surfactants

Abstract: Reverse micelles (RMs) of sodium 1,4-bis(2-ethylhexyl)sulphosuccinate (AOT) in nonpolar organic solvents are widely known to have very high solubilization power for water. The method is applied to the hydrolysis of p-nitrophenyl acetate (PNPA) catalysed by α-chymotrypsin (α-CT) in AOT/isooctane/buffer RMs. The increase in α-CT activity and stability was an optimum at w o ([H2O]/[AOT]) = 10, z [Isooctane]/[AOT]) = 5. Three typical surfactants were selected based on their head group charges: a non-ionic surfactant Triton-X 100 and two zwitterionic sulphobetaine surfactants of the type C n H2n + 1N + Me2 (CH $_{2})_{3\thinspace }$ SO $_{3}^{-}$ (n = 10; SB3–10, n = 16; SB3–16). The kinetic parameters (such as k cat and K M) of the α-CT at 27°C were determined and compared in the absence and presence of three surfactants. The effect of chain length of zwitterionic surfactant (SB3–10 and SB3–16) on the enzymatic efficacy of α-CT as a function of mixed surfactant addition has been investigated in AOT/isooctane RMs at pH 7.75.

Antileishmanial polyphenols from Corymbia maculata

Abstract: An activity–guided fractionation was used to identify the antileishmanial compounds of Corymbia maculata. The hexane, ethyl acetate and methanol extracts were active in in vitro antileishmanial assay. Twelve polyphenols including 8-demethyl eucalyptin (1), eucalyptin (2), myrciaphenone A (3), myrciaphenone B (4), quercetin-3-O-β-d-xylopyranoside (5), myricetin-3-O-α-l-rhamnopyranoside (6), quercetin-3-O-β-d-galactopyranoside (7), quercetin-3-O-β-d-glucopyranoside (8), quercetin-3-O-α-l-rhamnopyranoside (9), syringic acid (10), gallic acid-3-methyl ether (11), gallic acid-4-methyl ether (12) and gallic acid (13) were isolated from the active extracts. All the tested compounds except 8-demethyleucalyptin and myrciaphenone B showed strong to moderate (6.9–24.5 $\upmu$ M) antileishmanial activity against Leishmania donovani promastigotes. An HPLC-PDA method has been developed to detect/quantify 29 compounds in the extracts of C. maculata leaves. This validated method allows simultaneous quantitation of seven flavonoids, fourteen phloroglucinols and eight other polyphenols and can be applied for qualitative as well as quantitative determination of phytoconstituents in Eucalyptus matrices.

Silver iodide nanoparticle as an efficient and reusable catalyst for the one-pot synthesis of benzofurans under aqueous conditions

Abstract: Recyclable heterogeneous AgI nanoparticles were efficiently catalysed one-pot three-component reaction of aldehydes, secondary amines and alkyne in aqueous media. This method provides a novel and improved approach for the synthesis of 2,3-disubstituted benzo[b]furan derivatives to obtain excellent yields, short reaction times and low catalyst loading.

Modified calcium oxide as stable solid base catalyst for Aldol condensation reaction

Abstract: A highly efficient and stable solid-base catalyst for Aldol condensation was prepared by modifying commercial CaO with benzyl bromide in a simple way. It was found that modified CaO can effectively catalyse the Aldol condensation of cyclohexanone and benzaldehyde, as well as various benzaldehydes, to produce 2-benzylidenecyclohexanone with a good selectivity and high yield. Higher yield of 95.8% was obtained over modified CaO after 3 h, which is short compared with the yield of 92.1% after 12 h over commercial CaO. The influence of several reaction parameters, such as temperature, catalyst loading, was investigated. The humidity test over modified CaO reveals that the basic centres of modified CaO are stable for CO2 and moisture. From the results of Fourier transform-infrared (FT-IR) and Thermogravity analysis (TG) characterization, the modifier was bonded on surface of CaO chemically and almost no Ca(OH)2 formed during the modification process. The type of aldehyde has great influence on the yield of aldol condensation.

Ionic liquid-mediated three-component synthesis of fluorinated spiro-thiazine derivatives and their antimycobacterial and DNA cleavage activities

Abstract: A simple, green and catalyst-free novel protocol is developed for the synthesis of medicinally important spiro[indole-3,2′[1,3]-thiazine]-2,4′-dione and spiro[acenaphthylene-1,2′-[1,3]thiazine]dione libraries by the tandem reaction of readily available reagents in 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6]. The ionic liquid has been used as a solvent as well as catalyst for this reaction. This reaction proceeded smoothly in good to excellent yields and offered several other advantages including short reaction time, simple experimental workup procedure and no by-products. The synthesized compounds were subjected to antimycobacterial efficacy against Mycobacterium tuberculosis H37Rv strain and DNA cleavage activity.

L-proline-catalysed synthesis of functionalized unsymmetrical dihydro-1H-indeno[1,2-b]pyridines

Abstract: Aromatic aldehydes have been employed in a one-pot four-component reaction with ethyl acetoacetate, 1,3-indandione and ammonium acetate in the presence of L-proline in water and under reflux condition to afford the corresponding dihydro-1H-indeno[1,2-b]pyridines in very good yields.

Tandem synthesis of N,N′-alkylidenebisamides promoted by nano-SnCl4.SiO2

Abstract: A highly efficient procedure for the preparation of N,N ′-alkylidenebisamides in the presence of nano-SnCl4.SiO2 as a catalysis described. N,N ′-alkylidenebisamides have been prepared via condensation reaction of various aldehydes and amides. All of the reactions proceeded in high yields and in moderately short reaction times.

Assembling of H5PW10V2O40/MCM-48 and studying its superior catalytic performance in the synthesis of 14-aryl-14-H-dibenzo[a, j]xanthenes

Abstract: A highly efficient, green, and reusable heterogeneous catalytic system is introduced for the preparation of aryl-14-H-dibenzo[a,j]xanthenes via one-pot condensation of β-naphthol with aryl-aldehydes by the mediation of a heterogeneous material composed of Keggin-type tungsto-divanado-phosphoric acid, H5PW10V2O40, supported on MCM-48 under solvent-free condition. Excellent yields (85–100%), short reaction time (<60 min.), mild condition, simple work-up, and using a cheap and environmentally friendly catalyst bearing remarkable reusability are advantages of the present methodology. The catalytic efficacy of H5PW10V2O40/MCM-48 over some reported protocols are also overviewed.

Super acid catalysed sequential hydrolysis/cycloisomerization of o-(acetylenic)benzamides under microwave condition: Synthesis, antinociceptive and antiinflammatory activity of substituted isocoumarins

Abstract: Synthesis of isocoumarins and related compounds via triflic acid promoted hydrolysis/cyclization sequence of 2-(alkynyl)benzamides under microwave condition was achieved. The substrate scope of the reaction was broad to include not only aromatic but also polyaromatic and heteroaromatic motifs, thus highlighting the significance of this methodology. One-pot operation, short reaction time, good chemical yields and excellent regioselectivity are the advantages of this protocol. All the synthesized compounds were evaluated for their antinociceptive and antiinflammatory activities using in vivo rodent models.

Computational and experimental studies on oxalic acid imprinted polymer

Abstract: Computational approach plays an important role to pre-evaluate the interactions between template and functional monomer, so that to choose functional monomer having stronger interactions with template during synthesis of molecularly imprinted polymers (MIPs). Hence template-monomer interactions in pre-polymerization were mainly focused. In this paper, computational chemistry was applied to screen the number of mol of functional monomer that interacts with one mol of template. Intermolecular interactions between oxalic acid and acrylamide have been investigated. The binding energies ΔEbind were calculated by DFT (B3LYP) level of theory with the 6−31+G(d,p) basis set. It was found that four mol of acrylamide were sufficient to interact with one mol of oxalic acid in the pre-polymerization mixture. Four possible conformations and frequency calculations were performed to locate minima. Oxalic acid specific bulk polymer was obtained by the thermal initiated free radical co-polymerization of acrylamide and ethylene glycol dimethacrylate with oxalic acid as template and acetonitrile as porogen. The synthesized MIP efficiently adsorbed oxalic acid from aqueous solutions. The binding parameters of MIP and non-imprinted polymer (NIP) were compared by Freundlich and Langmuir adsorption isotherms.