An efficient method for the synthesis of quinoxaline derivatives catalyzed by titanium silicate-1

Research on Chemical Intermediates - A series of quinoxaline derivatives were efficiently synthesized by convenient and simple procedure in excellent yields using 1 wt.% of titanium silicate (TS-1)...     

DNA-binding studies of mixed ligand cobalt(III) complexes

The DNA binding characteristics of mixed ligand complexes of the type [Co(en)₂(L)]Br₃ where en = N,N′-ethylenediamine and L = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 1,10-phenanthroline-5,6-dione (phendione), dipyrido[3,2-a:2′,3′-c]phenazine (dppz) have been investigated by absorption titration, competitive binding fluorescence spectroscopy and viscosity measurements. The order of intercalative ability of the coordinated ligands is dppz > phen > phendione > bpy in this series of complexes.     

Synthesis of 1,5-diphenylpent-3-en-1-yne derivatives utilizing an aqueous B-alkyl Suzuki cross coupling reaction

1,5-Diphenylpent-3-en-1-yne derivatives were isolated in minor quantities from terrestrial plants and exhibited strong anti-inflammatory activity. A cross coupling reaction between B-benzyl-9-BBN and chloroenynes under mild condition was developed resulting in the formation of different 1,5-diphenylpent-3-en-1-yne derivatives with a full control on the E/Z selectivity. Several substrates bearing electron-donating and electron-withdrawing substituents were tolerable under the reaction conditions affording the corresponding products in good yields. This is the first study to report the synthesis of a vast array of novel 1,5-diphenylpent-3-en-1-yne derivatives paving the way for the preparation of tailored derivatives on mass scale necessary for biological studies and drug development.     

Effect of preparation method on complexation of Cefdinir with β-cyclodextrin

The inclusion behaviour of β-cyclodextrin (βCD) was studied toward Cefdinir (CEF) in order to enhance the solubility and dissolution rate, following cyclodextrin complexation. Drug cyclodextrin solid systems were prepared by conventional methods of kneading (KN), co-evaporation (CE), spray drying (SD) and with a novel approach of microwave irradiation (MWI). The formation of inclusion complexes with βCD in the solid state, were confirmed by Differential scanning calorimetry (DSC), Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) studies, and comparative studies on the in vitro dissolution of CEF were carried out. Characterization of binary system by DSC, FTIR and SEM indicated that SD and MWI method resulted in formation of true complexes. Binary systems showed significant increase in dissolution rate as compared to plain drug. Amongst the binary systems MWI products were prepared in least time with better yield and highest dissolution rate.     

RF-PACVD of water repellent and protective HMDSO coatings on bell metal surfaces: Correlation between discharge parameters and film properties

Hexamethyldisiloxane (HMDSO) films have been deposited on bell metal using radiofrequency plasma assisted chemical vapor deposition (RF-PACVD) technique. The protective performances of the HMDSO films and their water repellency have been investigated as a function of DC self-bias voltage on the substrates during deposition. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. Optical emission spectroscopy (OES) analyses of the plasma during deposition reveal no significant change in the plasma composition within the DC self-bias voltage range of −40 V to −160 V that is used. Raman and X-ray photoelectron spectroscopy (XPS) studies are carried out for film chemistry analysis and indicate that the impinging ion energy on the substrates influences the physio-chemical properties of the HMDSO films. At critical ion energy of 113 qV (corresponding to DC self-bias voltage of −100 V), the deposited HMDSO film exhibits least defective Si-O-Si chemical structure and highest inorganic character and this contributes to its best corrosion resistance behavior. The hardness and elastic modulus of the films are found to be bias dependent and are 1.27 GPa and 5.36 GPa for films deposited at −100 V. The critical load for delamination is also bias dependent and is 11 mN for this film. The water repellency of the HMDSO films is observed to be dependent on the variation in surface roughness. The results of the investigations suggest that HMDSO films deposited by RF-PACVD can be used as protective coatings on bell metal surfaces.     

Effect of argon ion activity on the properties of Y2O3 thin films deposited by low pressure PACVD

Yttrium oxide thin films are deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition process using an indegeneously developed Y(thd)₃ {(2,2,6,6-tetramethyl-3,5-heptanedionate)yttrium} precursor. Depositions were carried out at two different argon gas flow rates keeping precursor and oxygen gas flow rate constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GIXRD) and infrared spectroscopy. Optical properties of the films are studied by spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. Stability of the film and its adhesion with the substrate is inferred from the nanoscratch test.It is shown here that, the change in the argon gas flow rates changes the ionization of the gas in the microwave ECR plasma and imposes a drastic change in the characteristics like composition, structure as well as mechanical properties of the deposited film.     

Synthesis and antimicrobial activity of novel spirocompounds with pyrazolone and pyrazolthione moiety

The paper focuses on the utility of 2‐pyrazoline‐5‐ones and 2‐pyrazoline‐5‐thiones as active Michael donors for the synthesis of novel spirocyclohexanone derivatives. The sulphur containing compounds when screened for antimicrobial activity showed promising inhibition of S. Typhi, S Aures and E Coli bacteria.     

Nano-graphitic clustering and break down of phonon selection rule in diamond-like carbon films

Diamond-like carbon films are deposited on silicon substrates at different substrate bias using ECR-CVD technique. Raman spectroscopic studies show the presence of broad G and D peaks. In contrast to the position of D peak, the G peak shows a systematic red-shift with increase in the bias voltage. From the analysis it is found that an increase in bias voltage decreases the sp² cluster diameter. Furthermore, two additional Raman peaks at around 690 and 880 cm^?1 are also observed. These peaks, forbidden in the first order Raman scattering, arise due to the breakdown of phonon selection rule in graphitic nanoclusters.     

Novel synthesis of 1,2,4‐triazolophanes and 1,3,4‐oxadiazolophanes: A dieckmann condensation approach

The Dieckmann condensation has been used for the first time for the syntheses of novel 1,2,4‐triazolophanes and 1,3,4‐oxadiazolophanes. The bis‐1,3,4‐oxadiazol‐2‐thiols 1a and 1b were reacted with ethyl bromoacetate to give the diesters 2a and 2b . Diesters 2a and 2b were treated under dry conditions with sodium methoxide in methanol to afford desired symmetrical 1,3,4‐oxadiazolophanes 3a and 3b . Similarly, diesters of macrocycle precursors containing 1,2,4‐triazole moiety, that is, 6a , 6b , 10 , 13a , 13b , and 13c were synthesized from 5a , 5b , 9 , 12a , 12b , and 12c , respectively. Dieckmann condensation of these diesters afforded symmetrical ketones 7a , 7b , 11 , 14a , 14b , and 14c . Extrusion of CO₂ was observed after in situ hydrolysis of the conventional Dieckmann product during neutralization by dilute mineral acids to afford highly symmetrical ketone in good yields. Further, the ketones 14a , 14b , and 14c were converted into their respective thiones by the reaction with Lawesson's reagent. All the products were synthesized with good yields, and structures were confirmed by various spectroscopic tools and elemental analyses. J. Heterocyclic Chem.,, (2012).