An efficient and reusable vanadium based catalytic system for room temperature oxidation of alcohols to aldehydes and ketones

A simple and efficient vanadium based catalyst system for the oxidation of primary and secondary alcohols to aldehydes or ketones is reported using tert-butyl hydroperoxide as oxidizing agent and vanadyl sulfate as catalyst at room temperature. The versatility of the catalytic protocol is studied with wide variety of substrates.     

Optically definable reaction-diffusion-driven pattern generation of Ag-Au nanoparticles on templated surfaces

We introduce a new lithographic method for the generation of 2D patterns of composite nanoparticles (NPs) of Ag and Au by taking recourse to combine top-down and bottom-up approaches. Micrometer-scale and submicrometer-scale patterned Ag foils of commercially available compact disks (CDs) and digital versatile disks (DVDs), respectively, were used as templates. The galvanic replacement reaction of Ag by HAuCl(4) in the presence of the dye coatings on the foils led to the formation of patterned NP composites of Ag and Au, in addition to the formation of AgCl. The resultant structures appeared in the form of cross patterns of particles with micrometer and submicrometer dimensions. The AgCl crystals thus formed could be removed by using either a saturated NaCl solution or aqueous ammonia. In addition, AgCl could be converted to Ag by electrochemical reduction, thus generating Ag-coated Au NPs. Interestingly, the digital writing on CDs led to the formation of tertiary imprints on the patterns, based on the original writing patterns. This provided an additional handle in generating hierarchical patterns using light in combination with a chemical reaction diffusion process and the nearly parallel line patterns originally present in commercial CDs. The reactions could be carried out in aqueous solution, and the method does not require any additional curing. Also, the density of patterned particles is scalable on the basis of the choice of the original line patterns as present in CDs and DVDs.     

Synthesis of potassium 2,3,4-trihydroxy-2-methylbutanoate: a leaf-closing substance of Leucaena leucocephalam

Starting from citraconic anhydride (2), a six step synthesis of leaf closing substance (±)-erythro potassium 2,3,4-trihydroxy-2-methyl-butanoate (1) has been described with 29% overall yield via diesterification, OsO₄-dihydroxylation, acetonide protection, regioselective mono hydrolysis of unhindered ester moiety, borane-dimethylsulfide induced chemoselective reduction of carboxylic group and hydrolysis pathway. Surprisingly, the sodium borohydride reduction of monoester 5 and lithium borohydride reduction of 11 furnished the undesired regioisomer 7.     

Enantioselective Synthesis of C−O Axially Chiral Diaryl Ethers by NHC-Catalyzed Atroposelective Desymmetrization**

Axially chiral diaryl ethers, a distinguished class of atropisomers possessing unique dual C−O axis, hold immense potential for diverse research domains. In contrast to the catalytic enantioselective synthesis of conventional single axis bearing atropisomers, the atroposelective synthesis of axially chiral ethers containing flexible C−O axis remains a significant challenge. Herein, we demonstrate the first N-heterocyclic carbene (NHC)-catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde-containing diaryl ethers. Mechanistically, the reaction proceeds via NHC-catalyzed desymmetrization strategy to afford the corresponding axially chiral diaryl ether atropisomers in good yields and high enantioselectivities under mild conditions. The derivatization of the synthesized product expands the utility of present strategy via access to a library of C−O axially chiral compounds. The temperature dependency and preliminary investigations on the racemization barrier of C−O bonds are also presented.     

Microwave-assisted Pd-catalyzed synthesis of fused steroidal and non-steroidal pyrimidines from β-halo-α,β-unsaturated aldehydes

A Pd-catalyzed protocol has been developed for the synthesis of fused steroidal and non-steroidal pyrimidines from β-halo-α,β-unsaturated aldehydes under microwave irradiation. The β-halo-α,β-unsaturated aldehydes are synthesized from corresponding ketones using Vilsmeier formylation reaction. This synthetic protocol is utilized to synthesize some more novel steroidal pyrimidine derivatives and are currently being evaluated for their biological activities.     

Transport and stability studies on high band gap a-Si:H films prepared by argon dilution

Device quality hydrogenated amorphous silicon films (a-Si:H) are deposited at a high deposition rate (4–5 Å/s) using a mixture of argon and hydrogen-diluted silane. The films exhibit good opto-electronic properties and show less degradation upon light soaking. Light-induced changes in conductivity could be annealed at much lower temperature. The presence of Ar^* and atomic hydrogen in plasma replaces the weak Si-Si bonds, which are responsible for light-induced degradation by strong Si-Si bonds. This results in the improved stability of the films.     

A highly efficient heterogeneous montmorillonite K‐10‐supported palladium catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

A heterogeneous montmorillonite K‐10‐supported palladium triphenylphosphine catalyst is reported for the Suzuki–Miyaura cross‐coupling reaction at room temperature. A library of electronically diverse aryl bromides and arylboronic acids underwent the cross‐coupling reaction at very good rates in aqueous solvent. The reusability of the catalyst was also examined and it was found to be effective up to three catalytic cycles. Copyright © 2014 John Wiley & Sons, Ltd.     

Studies on adsorptive removal of radioactive cobalt from alkaline waste generated in sodium cooled fast breeder reactors

The removal of radioactive cobalt from alkaline waste containing sodium has been studied in batch process using two different inorganic compounds (a) hydrous manganese oxide (HMO), and (b) copper hexa-ferrocyanide (CFC) and compared with a strongly acidic cation exchange resin (Dowex50W×8). The percentage removal of cobalt was examined by varying experimental conditions, viz. pH of the solution, contact time and interfering ions. The studies showed that HMO can be used as an efficient adsorbent for the removal of cobalt from sodium containing wastes.     

Rings, chains and cages in metal phosphate chemistry: The interdependence and possible interconversion between various structural forms

Our endeavour to build soluble model compounds of basic building blocks in zeolite structures have resulted in a plethora of main group and transition metal phosphate complexes. Many of these complexes show highly intriguing and novel structural features. Careful examination of the core structures allowed us to rationalize the interdependence between the different structural types and visualize their plausible pathway of formation. Due to the high reactivity and short life span of the intermediates it has not been possible to characterize many intermediates. However, the common structural features present in the isolated products drive us to arrive at a plausible mechanism. Further investigation and isolation of other structural types will definitely provide more credential to these hypotheses and help us to solve the zeolite jigsaw.     

Structural and stability studies of CdS and SnS nanostructures synthesized by various routes

CdS nanorods and SnS nano-flakes have been synthesized by solvothermal process and CdS nanoparticles have been synthesized by aqueous media process. Structural properties of these nanocomposites are performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Chemical purity of these nanocomposites has been confirmed by energy dispersive analysis of X-ray (EDAX). Thermal stability of these nanocomposites is investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Different parameters such as activation energy (E) for the degradation, Arrhenius parameter (A) and the entropy change (ΔS) have been calculated by Coats-Redfern and Satava model. It is observed that the activation energy of the CdS nanorods is much higher compared to that of CdS nanoparticles and SnS nano-flakes.