• Volume 124, Issue 5

September 2012,   pages  969-1135

• Electrochemical sensing and photocatalysis using Ag-TiO2 microwires

Anatase Ag-TiO2 microwires with high sensitivity and photocatalytic activity were synthesized via polyol synthesis route followed by a simple surface modification and chemical reduction approach for attachment of silver. The superior performance of the Ag-TiO2 composite microwires is attributed to improved surface reactivity, mass transport and catalytic property as a result of wiring the TiO2 surface with Ag nanoparticles. Compared to the TiO2 microwires, Ag-TiO2 microwires exhibited three times higher sensitivity in the detection of cationic dye such as methylene blue. Photocatalytic degradation efficiency was also found to be significantly enhanced at constant illumination protocols and observation times. The improved performance is attributed to the formation of a Schottky barrier between TiO2 and Ag nanoparticles leading to a fast transport of photogenerated electrons to the Ag nanoparticles.

• Supported lipid bilayers as templates to design manganese oxide nanoparticles

This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) have been used as templates to synthesize these nanoparticles in a waterbased medium at room temperature. The Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) show manganese oxide nanostructures that are composed of crystals or small clusters in the size range of 20-50 nm in diameter. Small angle XRD showed that template removal through calcining process results in nanostructures of the manganese oxide in sizes from 30 to 50 nm. Using these organized assemblies it is possible to control the nano and mesoscopic morphologies of particles and both rod-like and spherical particles can be synthesized.

• Comparative study of spectroscopic properties of the low-lying electronic states of 2,4-pentadien-1-iminium cation and its N-substituted analogues

Semiempirical and ab initio-based CI methods have been employed to study the low-lying electronic states of 2,4-pentadien-1-iminium cation and its N-substituted analogues with electron-donating (methyl, isopropyl) and electron-withdrawing (fluoromethyl) groups on nitrogen. Variations of the dihedral angles ($\Gamma_3$, $\Gamma_4$) of the ground state have given the global minima and global maxima at (180°, 180°) and (90°, 0°) conformations, respectively, with some exceptions in the case of fluoromethyl compound. Increase in the +I effect on nitrogen shifts the TICT conical intersection point away from the 90° ($\Gamma_3$ dihedral angle) value, when the $\Gamma_4$ value is kept fixed at 180°. Transition moment values of the allowed S0(1A$_g$ -like) → S1 (2B$_u$-like) transitions are expectedly higher than the forbidden S0(1A$_g$ -like) → S2(2A$_g$ -like) transitions by almost 5.6 D. Radiative lifetime values of the first excited states are calculated to be around 215 ps for all the four compounds. At (180°, 180°) conformation the vertical excitation energy (VEE) between the S0 and S1 states of the 2,4-pentadieniminium cation is found to be 3.3 eV, which corresponds to the absorption wavelength value of roughly 375 nm. The VEE value increases with substituents having +I effect on nitrogen, while for the fluoromethyl compound it is calculated to be around 2.85 eV. The energy gap between the first two excited singlet states is found to have the least value in the isopropyl-substituted compound, where the S2 state contains a huge contribution from the HOMO2→LUMO2 configuration.

• Theoretical studies on a series of 1,2,4-triazoles derivatives as potential high energy density compounds

Density functional theory calculations at B3LYP/6-31G∗∗ and B3P86/6-31G∗∗ levels were performed to predict the densities (𝜌), detonation velocities (D), pressures (P) and the thermal stabilities for a series of 1,2,4-triazole derivatives for looking high energy density compounds (HEDCs). The heats of formation (HOFs) are also calculated via designed isodesmic reactions. The calculations on the bond dissociation energies (BDEs) indicate that the position of the subsitutent group has great effect on the BDE and the BDEs of the initial scission step are between 31 and 65 kcal/mol. In addition, the condensed phase heats of formation are also calculated for the title compounds. These results would provide basic information for further studies of HEDCs.

• A facile and expedient one-pot three-component reaction leading to multifunctionalized stabilized phosphorus ylides

A three-component reaction between triphenylphosphine, a dialkyl acetylenedicarboxylate and phthalazin-1(2H)-ones that affords novel organic phosphorane derivatives in good to excellent yields is reported. FTIR, 1H, 13C and 31P NMR and elemental analyses have been utilized to characterize the synthesized compounds.

• Highly efficient solvent-free synthesis of pyranopyrazoles by a Brønsted-acidic ionic liquid as a green and reusable catalyst

A simple, green and efficient protocol for synthesis of dihydropyrano[2,3-c]pyrazole derivatives is developed by a four component reaction of various benzaldehydes, ethyl acetoacetate, hydrazine hydrate and malononitrile in the presence of 3-methyl-1-(4-sulphonic acid)butylimidazolium hydrogen sulphate [(CH2)4SO3HMIM][HSO4], an acidic ionic liquid and as a catalyst, under solvent-free conditions. The key advantages of this process are high yields, shorter reaction times, easy work-up, purification of products by non-chromatographic method and the reusability of the catalyst.

• Synthesis of novel 2-(4-(2-morpholinoethoxy)phenyl)-N-phenylacetamide analogues and their antimicrobial study

A new class of potential biologically active 2-(4-(2-morpholinoethoxy)phenyl)-N-phenylacetamides has been synthesized from hydroxyphenylacetic acid. The products were characterized through IR, 1H NMR, mass spectral studies and elemental analysis. The compounds were screened for antimicrobial activity by disc agar diffusion technique. The potency of compounds is tested against variety of fungal and bacterial strains in comparison to clotrimazole and streptomycin, respectively. Some of the synthesized compounds exhibit superior in vitro activity compared to the standard drugs.

• Preparation of different amides via Ritter reaction from alcohols and nitriles in the presence of silica-bonded N- propyl sulphamic acid (SBNPSA) under solvent-free conditions

A number of methods have been proposed for the modification of the Ritter reaction. However, many of these methods involve the use of strongly acidic conditions, stoichiometric amounts of reagents, harsh reaction conditions and extended reaction times. Therefore, the development of mild, efficient, convenient and benign reagents for the Ritter reaction is desirable. In this research, we have developed a clean and environmentally friendly protocol for the synthesis of amides by using different benzylic or tertiary alcohols and different nitriles in the presence of silica-bonded N- propyl sulphamic acid (SBNPSA) as catalyst under solvent-free conditions in high yields.

• Substituted quinolinones. Part 17: Some nucleophilic reactions with 4-hydroxy-1-methyl-3-[(2-oxo-2𝐻-chromen-3-yl)carbonyl]quinolin-2(1𝐻)-one

The reactivity of 4-hydroxy-1-methyl-3-[(2-oxo-2𝐻-chromen-3-yl)carbonyl]-quinolin-2(1𝐻)-one (2), as a new asymmetric diheterocyclic ketone, towards different nucleophilic reagents, was examined. The reaction of the ketone 2 with hydrazine led to pyrazolinone 5, and excess of hydrazine pyrazolinopyrazole 7 was obtained. Treatment of the ketone 2 with 2,2-dimethoxyethanamine gave pyrrolocoumarin 12, while cyanoguanidine afforded pyrimidinone 15. Under PTC conditions, the ketone 2 was reacted with chloroacetonitrile, diethyl malonate, ethyl cyanoacetate, malononitrile, and cyanoacetamide to give coumarinyl furoquinoline 18, pyranoquinolines 20a, 20b, 21, and benzonaphthyridine 22, respectively.

• Synthesis and antimicrobial activities of new oxime carbamates of 3-aryl-2-thioquinazolin-4(3H)-one

S-alkylation of 3-aryl-2-thioquinazolin-4(3H)-one (1) with chloroacetone gave 2-(propanonyl thio)-3-arylquinazol-4(3H)ones (2). Further, the treatment of compound (2) with hydroxylamine hydrochloride gave the corresponding oximes (3) which on reaction with phenyl isocyanate in THF yielded corresponding oxime carbamates 4. The synthesized compounds have been confirmed using IR and 1H NMR, mass spectral data together with elemental analysis. All newly synthesized compounds have been tested for their antibacterial and antifungal activities.

• Synthesis, docking and anticancer activity studies of D-proline-incorporated wainunuamide

D-proline-incorporated wainunuamide — a cyclic octapeptide was synthesized and characterized by FTIR, 1H and 13C NMR and Mass spectral analysis. Molecular docking studies were carried out for the designed cyclic octapeptide and the results showed greater affinity for HPV18-2IOI receptor (HeLa cancer cell line). The synthesized cyclic octapeptide exhibited potent anticancer activity against HeLa cancer cells.

• Tandem base-free synthesis of 𝛽-hydroxy sulphides under ultrasound irradiation

Rongalite® promotes cleavage of diaryl disulphides generating the corresponding thiolate species in situ which then undergo facile ring-opening of epoxides in a regioselective manner under ultrasound irradiation, affording 𝛽-hydroxy sulphides in good to excellent yields. The important features of this methodology are base-free, odourless, high yield, reasonably rapid reaction rate, simple workup, high regioselectivity, costeffective and no requirement of transition metal catalysts. It is noteworthy that ring-opening reaction of 1,2-diphenyldiselane with 2-(phenoxymethyl)oxirane are also conducted smoothly to afford 𝛽-hydroxy selenide in excellent yield under the standard conditions.

• Heterocyclyl linked anilines and benzaldehydes as precursors for biologically significant new chemical entities

Benzylidene and benzyl thiazolidinediones, oxazolidinediones, isoxazolidinediones and their acyclic analogs like alpha alkylthio/alkoxy phenylpropanoic acids, beta-keto esters and tyrosine-based compounds possess broad therapeutic potential in general and as Peroxisome Proliferator Activated Receptors (PPARs) agonists in particular in the management of hyperglycemia and hyperlipidaemia for the treatment of Type 2 Diabetes (T2D). We have synthesised and characterized some novel and suitably substituted heterocyclyl linked benzaldehydes and anilines, which can be easily and very readily derivatized to all the above mentioned classes to generate new chemical entities of broader biological significance. Synthesis of their benzylidene thiazolidinedione and diethyl malonate and also benzyl diethyl malonate and alpha-bromoesters derivatives is reported in some of the cases in the present work.

• Cannizzaro reaction of 2-chloro-3-formylquinolines and its synthetic utility for 2-acetylfuro[2,3-𝑏]quinolines: The alkaloid analogues

Cannizzaro reaction of 2-chloro-3-formylquinolines was investigated under two different conditions. Under both conditions, redox and methoxylation proceeded simultaneously and gave 2-methoxy- 3-formylquinolines, 2-methoxyquinolin-3-yl-methanols and 2-methoxyquinoline-3-carboxylic acids. The synthesized 2-methoxy-3-formylquinolines were then condensed with acetone in the presence of sulphuric acid to give 4-(2-methoxy-quinolin-3-yl)-but-3-en-2-ones which in turn were bromocyclized and dehydrobrominated to get 2-acetylfuro[2,3-𝑏]quinolines.

• An alternative approach to synthesis of 2-𝑛-butyl-5-nitrobenzofuran derivative: A key starting material for dronedarone hydrochloride

A practical synthesis of (2-butyl-5-nitrobenzofuran-3-yl)(4-hydroxyphenyl)methanone, a key intermediate in the preparation of anti arrhythmic drug, is described. The commercially available 4-nitrophenol (3) is converted in five steps to 2-butyl-5-nitrobenzofuran (9) which upon Friedel-Crafts acylation with 4-methoxybenzoyl chloride followed by deprotection of methyl group gives (2).

• Selective synthesis of thiodiglycol dicarboxylic acid esters via 𝑝-TsOH/C-catalysed direct esterification

The esterification of thiodiglycol and long alkyl-chain carboxylic acids is reported. Reaction of thiodiglycol with carboxylic acid via 𝑝-TsOH/C-catalysed direct esterification afforded thiodiglycol dicarboxylic acid esters in good yields and chemoselectivity. The use of immobilized 𝑝-TsOH on activated carbon as catalyst is crucial for the transformation.

• 1-Methylimidazolium trifluoroacetate [Hmim]Tfa: Mild and efficient Brønsted acidic ionic liquid for Hantzsch reaction under microwave irradiation

One pot synthesis of 1,4-dihydropyridine derivatives was achieved via condensation of various 𝛽-ketoesters with aromatic/aliphatic aldehydes and ammonium acetate. The reaction was catalysed by a stable and reusable Brønsted acidic ionic liquid (IL), 1-methyl-imidazolium trifluoroacetate ([Hmim]Tfa), under microwave (MW) irradiation. The synergistic combination ofMWwith IL can potentially go a long way tomeet the increasing demand for chemical processes. This homogeneous catalytic procedure is simple and efficient. The catalyst can be reused at least four times with almost complete retention in its activity.

• A practical one pot synthesis of novel 2-hydroxy-4-chromanone derivatives from 3-formylchromone

A one pot synthesis of 4-chromanone derivatives (5a-j) is described using Zn[(L)(proline)]2 as catalyst in aqueous media. The compounds have been characterized on the basis of elemental and spectral data (IR, 1H NMR and mass). The advantages of this protocol include high yields, mild reaction conditions, environmentally benign and simple operational procedure. The use of water as solvent and Zn[(L)proline]2 as recyclable, non-toxic catalyst make such synthesis a truly green process.

• Selective oxidation of benzyl alcohol with tert-butylhydroperoxide catalysed via Mn (II) 2, 2-bipyridine complexes immobilized over the mesoporous hexagonal molecular sieves (HMS)

A series ofMn(II)bipy complexes with different loading of Mn2+ supported on HMS was prepared. These samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Thermogravimetric and Differential Scanning Calorimetry (TG-DSC), Ultraviolet and Visible spectra (UV-Vis) and Fourier transforms Infrared (FT-IR). The catalytic activity of the supportedMn(II)bipy complexes, [Mn(bipy)2]2+/HMS was evaluated in the oxidation of benzyl alcohol in the liquid phase using tert-butylhydroperoxide (TBHP) as an oxidant. The effects of Mn2+ loading and various solvents on the conversion and selectivity were studied. A second order function for the variation in catalytic activity with respect to the loading of Mn2+ ions in different catalyst samples was observed. The activity of the [Mn(bipy)2]2+/HMS catalyst differs with the type of the solvent and in this case, acetonitrile gives the best conversion results. The kinetic of benzyl alcohol oxidation was investigated at temperatures of 27, 46, 60, 75 and 90°C using [Mn(bipy)2]2+/HMS and excess TBHP. The order of reaction with respect to benzyl alcohol was determined to be pseudo-first order. The value of the apparent activation energy was also determined.

• Characterization of novel Cs and K substituted phosphotungstic acid modified MCM-41 catalyst and its catalytic activity towards acetylation of aromatic alcohols

TheMCM-41 supported Cs2.5H0.5PW12O40 and K2.5H0.5PW12O40 salts were synthesized by incipient wetness impregnation method. The solids were characterized by N2 adsorption-desorption isotherms, FTIR, XRD, and temperature programmed desorption, etc. This catalyst has been found to exhibit excellent activity for acetylation of phenolic compounds. The catalyst is stable and reusable giving 96% conversion with 100% selectivity towards acetate products.

• Functionalization of oxidized single-walled carbon nanotubes with 4-benzo-9-crown-3 ether

Functionalization of oxidized single-walled carbon nanotubes (SWCNTs) by a zwitterionic interaction (COO−NH$^+_3$) between protonated amine on crown ether and an oxyanion from a carboxylic acid group on SWCNT has been described. This ionic interaction has led to a considerable increase in the solubility of SWCNTs in both organic and aqueous solvents such as ethanol, dimethyl sulphoxide, dimethylformamide, and H2O. The highest solubility was attained in DMF and DMSO. The ionic bonded 4-benzo-9-crown-3 ether allowed the hosting of Li+. The ionic bond of crown ether (4-(benzo-9-crown-3)) to SWCNT was identified and confirmed by infrared spectroscopy, transmission electron-microscopy, atomic force microscopy and thermogravimetric analysis methods.

• Journal of Chemical Sciences

Volume 132, 2019
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• Editorial Note on Continuous Article Publication

Posted on July 25, 2019