44 research outputs found

    Mechanistic Study on the Formation of Compounds from Thioureas

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    Formation of 2-(N-arylamino)benzothiazole takes place, when N,N′-diphenylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst under solvent free conditions. However, when N-substituted-N′-benzoylthioureas are treated with polymer-supported tribromide or with iodine-alumina as catalyst either under various conditions or under solvent free conditions, decomposition takes place to give the respective benzamides and thiobenzamides. Mechanistic study of the formation of these compounds is studied using DFT calculations. It is found that electron donating group at the para-position of the aryl group of benzoylthiourea favors the formation of benzamide whereas the presence of electron withdrawing group at para-position of the aryl group of benzoylthiourea, formation of thiobenzamide takes place. When the catalyst is changed to diacetoxyiodobenzene (DIB) under similar reaction conditions, benzoxazole amides are formed; expected benzothiazoles or the decomposition products are not obtained. Mechanistic study of the reaction using DFT calculation again shows that the reaction followed through carbodiimide intermediate undergoes the formation of C-O bond in benzoxazole moiety, instead of the expected C-S bond formation of benzothiazole moiety via a sequential acylation and deacylation process

    One-Pot Multicomponent Synthesis of Novel 2-Thioxo-Benzo[6,7]Chromeno[2,3d]Pyrimidin-4-one Derivatives using Cetylpyridinium Chloride

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    The novel 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives were prepared by one pot multicomponent condensation reaction involving thiobarbituric acids, aromatic aldehydes and β-napthol in acetonitrile-water as solvent using surfactant, cetylpyridinium chloride (CPC) at water bath temperature in good yields. The structures of the compounds were confirmed by elemental analyses and spectral data

    Green synthesis of Ag nanoparticles using aqueous extract of Kaempferia galanga Linn. (Zingiberaceae) rhizomes

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    Green synthesis of noble metal nanoparticles (NPs) is a vast developing area of research. In the present study, silver nanoparticles (Ag-NPs) were rapidly synthesized by treating silver ions through a simple and green synthetic route using water extract of the rhizomes of Kaempferia galanga Linn.(KG), which acted simultaneously as a reductant and stabilizer. The reaction process was monitored using ultraviolet–visible (UV-Vis) spectroscopy. The  EPR spectra of AgKG NPs was found to be confined in a single line which showed  the presence of an unpaired electron indicating of  Ag in neutral state at room temperature. The size and morphology of AgNPs recorded by Scanning electron  microscopy (SEM) were further confirmed by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The formation of AgNPs is evidenced by the appearance of signatory brown colour of the solution. FT-IR spectrum indicates the presence of different functional groups in capping the nanoparticles with K. galanga. Average size range estimated from our studies is  2 to 4 nm. It consists of a spherical like particles

    Synthesis and screening for antioxidant and cytotoxic activities of novel 2-thioxo-benzo[f]chromeno[2,3-d]pyrimidin-4-ones derived by cetylpyridinium chloride catalyzed multicomponent reactions in aqueous micellar media 

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    The cetylpyridinium chloride (CPC) has been used as micellar catalyst in three-component one-pot reaction involving thiobarbituric acids, aromatic aldehydes and β-napthol for synthesizing the novel 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives in aqueous media. These 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives have been screened for antioxidant and cytotoxic activities. It has been found that 2-thioxo-5-(4-nitrophenyl)-benzo[f]chromeno[2,3-d]pyrimidin-4-one (4a) has shown highest scavenging activity value to reduce DPPH free radicals, which may be due to the presence of nitro group at para-position. Three compounds, 4a, 4b and 4o show significant in vitro antitumor activity. The study of the antioxidant and cytotoxic activities reveal that all the compounds show moderate to good activity indicating that the presence of thiouriedo linkage in the pyrimidine nucleus and the chromeno group attached to pyrimidene moiety are responsible for these activities.

    Construction of Biologically Active Five- and Six-Membered Fused Ring Pyrimidine Derivatives from 1,3-Diarylthiobarbituric Acids (DTBA)

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    Several derivatives of fused pyrimidines were synthesized in maximum yields by using the respective condensation products, namely, 5-ethoxymethylene-1,3-diaryl-2-thiobarbituric acids and 5-phenyl-methylene-1,3-diaryl-2-thiobarbituric acids, which can be obtained from 1,3-diarylthiobarbituric acids (DTBA). These condensation products possessing three electrophilic centres could undergo cyclocondensation with various binucleophiles to give various fused heterocycles of pyrimidine derivatives, such as pyrazolo[3,4-d]pyrimidine-6-thiones, 5,7-diaryl-4-oxo-isoxazolo[5,4-d]pyrimidine-6-thiones, 5-oxo-pyrimido[4,5-d]pyrimidine-7-thiones, 2-thioxo-pyrano[2,3-d]pyrimidine-4-ones, pyrido[2,3-d]pyrimidines, quinazoline-4-oxo-2-thiones

    Green Synthesis of Silver Nanoparticles using Strobilanthes flaccidifolius Nees. Leaf Extract and its Antibacterial Activity

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    The leaf extract of Strobilanthes flaccidifolius Nees. was used for the synthesis of silver nanoparticles through a green technique of synthesis. The nanoparticles was characterized by UV-VIS spectroscopy which proves the formation silver nanoparticles. FTIR (Fourier Transmission infra red spectroscopy) study was carried out to assess the biomolecule as indigo precursors, Energy dispersion X-ray analysis(EDX) data further proves it. EPR (Electron paramagnetic resonance technique) shows the free radical in silver neutral state and XRD(X-ray diffraction technique) also repots silver neutral formation.The morphology and the shape of the silver nanoparticles were determined by Scanning electron microscopy(SEM) and Tunneling electron microscopy (TEM).The nanoparticles adopted spherical morphology and the size ranging from 6nm to 54.11nm and average size was determined as 12.15± 5.3nm.The nanoparticles had antimicrobial activit

    Synthesis of biologically active 2-thio-5-arylbenzo[4,5]thiazolopyrimido [5,4-d]pyrimidin-4-one derivatives catalyzed by metal proline in water  

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    A facile and highly efficient one pot multi-component reaction for the synthesis of 2-thio-5-arylbenzo [4,5]thiazolopyrimido[5,4-d]pyrimidin-4-one derivatives 4 under aqueous medium has been developed. The reaction takes place by condensation of thiobarbituric acids 1, 2-aminobenzothiazole 2 and aldehydes 3 using metal-proline catalyzed domino Knoevenagel, Michael and intramolecular cyclization approach

    Synthesis of biologically active 2-thio-5-arylbenzo[4,5]thiazolopyrimido [5,4-d]pyrimidin-4-one derivatives catalyzed by metal proline in water

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    1230-1242A facile and highly efficient one pot multi-component reaction for the synthesis of 2-thio-5-arylbenzo [4,5]thiazolopyrimido[5,4-d]pyrimidin-4-one derivatives 4 under aqueous medium has been developed. The reaction takes place by condensation of thiobarbituric acids 1, 2-aminobenzothiazole 2 and aldehydes 3 using metal-proline catalyzed domino Knoevenagel, Michael and intramolecular cyclization approach

    Synthesis and screening for antioxidant and cytotoxic activities of novel 2-thioxo-benzo[f]chromeno[2,3-d]pyrimidin-4-ones derived by cetylpyridinium chloride catalyzed multicomponent reactions in aqueous micellar media

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    1243-1257The cetylpyridinium chloride (CPC) has been used as micellar catalyst in three-component one-pot reaction involving thiobarbituric acids, aromatic aldehydes and β-napthol for synthesizing the novel 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives in aqueous media. These 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivativeshave been screened for antioxidant and cytotoxic activities. It has been found that 2-thioxo-5-(4-nitrophenyl)-benzo[f]chromeno[2,3-d]pyrimidin-4-one (4a) has shown highest scavenging activity value to reduce DPPH free radicals,which may be due to the presence of nitro group at para-position. Three compounds, 4a, 4b and 4o show significant in vitroantitumor activity. The study of the antioxidant and cytotoxic activities reveal that all the compounds show moderate togood activity indicating that the presence of thiouriedo linkage in the pyrimidine nucleus and the chromeno group attachedto pyrimidene moiety are responsible for these activities

    Henry reaction catalyzed by recyclable [C<sub>4</sub>dabco]OH ionic liquid

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    110-113DABCO-based ionic liquid, 1-butyl-4-aza-1-azaniabicyclo[2.2.2]octane hydroxide, has been used as an efficient catalyst for Henry reaction of various carbonyl compounds with nitroalkanes affording very high yields within a short duration. This method is very simple, clean and avoids hazardous organic solvents. The catalyst can be easily recovered and recycled several times
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