Deepa K. Dumbre

Calcium oxide supported gold nanoparticles as catalysts for the selective epoxidation of styrene by t-butyl hydroperoxide.

Gold nanoparticles are deposited on basic CaO supports as catalysts for the selective conversion of styrene into styrene oxide. Synthetic methods, gold loading and calcination temperatures are varied to permit an understanding of their influence on gold nanoparticle size, the presence of cationic gold species and the nature of interaction between the gold nanoparticles and the CaO support. Based on these studies, optimal conditions are designed to make the Au/CaO catalyst efficient for the selective epoxidation of styrene.

FeCl3/Montmorillonite K10 as an efficient catalyst for solvent-free aza-Michael reaction between amine and α,β-unsaturated compounds

A highly efficient, inexpensive and greener protocol for aza-Michael addition reaction of different aromatic and aliphatic/cyclic amines to α,β-unsaturated compounds using a FeCl3/MontK10 catalyst under solvent-free conditions has been developed. The Michael addition products are obtained in good to excellent yields. The catalyst was insensitive to moisture and it also showed excellent reusability in the reaction. Its high activity is attributed mostly to redox properties of FeCl3.

Thermally decomposed mesoporous Nickel Iron hydrotalcite: An active solid-base catalyst for solvent-free Knoevenagel condensation

Thermal decomposition of co-precipitated Ni-Fe-HT materials led to the formation a mesoporous Ni-Fe-HT catalyst and we have demonstrated here its active role as solid and active catalyst for the Knoevenagel condensation reaction of various aldehydes with active methylene compounds (R-CH2-CN, where R=CN or CO2Et). High product yields are obtained at moderate temperature under solvent-free conditions and the catalyst can be easily separated from the reaction mixture, simply by filtration and reused several times without a significant loss of its activity. Since these mesoporous metal oxides derived from the NiFe hydrotalcites, their basicity mediated abstraction of the acidic protons from the active methylene compounds was responsible for their catalytic activity under solvent-free conditions.

Synthesis of magnetic carbon nanocomposites by hydrothermal carbonization and pyrolysis

The fabrication of magnetic carbon nanostructures is emerging to develop composites with unique properties. Consolidating magnetic nanoparticles with carbon materials can be used in nanoelectronics, catalysis, optical application, biosensors, environmental remediation, energy, hydrogen storage, drug transport, magnetic resonance imaging and cancer diagnosis. In addition, thermochemical methods such as hydrothermal carbonization and pyrolysis are low energy processes that offer an efficient synthesis of the controlled morphology of magnetic carbon nanocomposite. These methods provide chemical and morphological improvements of the structure, such as high surface area, ordered nanosizes, crystal matrix, material stability, electrical conductivity, magnetic saturation and coercivity. This paper reviews the fabrication and properties of magnetic carbon nanocomposites.

Greener Ullmann-Type Coupling of Aryl Halides for Preparing Biaryls Using Reusable Pd/ZrO2 Catalyst

Biaryls with excellent yields can be prepared by the Ullmann-type coupling of aryl halides in the presence of potassium carbonate (as a base) and dimethylformamide (as a solvent), at 140 °C, using a reusable Pd (2.5 wt%)/ZrO2 catalyst. The product yield of 4-iodoanisole coupling is strongly influenced by the catalyst preparation method, solvent, and base.

Solvent-Free One-Pot Synthesis of Sulfonephthaleins from Saccharin and Phenols

Abstract Sulfonephthaleins can be synthesized in a single pot from saccharin and phenol via the in situ formation of 2-sulfobenzoic anhydride, followed by its reaction with phenol using H2SO4 as the condensing agent, in the absence of any solvent. This solvent-free synthesis is more economical and environmentally benign. GRAPHICAL ABSTRACT

Synthesis of substituted styrenes and stilbenes mediated by palladium on zirconia

Palladium on zirconia has been found to be an effective catalyst for the synthesis of various substituted styrenes and stilbenes, including biologically active natural products, by reaction of aryl halides with olefins.

Nanocrystalline FeOClx grafted MCM-41 as active mesoporous catalyst for the solvent-free multi-condensation reaction

Thermal condensation reaction between the surface silanol groups of MCM-41 and FeCl3 led to the formation of nanocrystalline iron oxychloride (FeOCl) grafted MCM-41 and its role as an active Lewis acid site for the solvent-free multi-condensation reaction has been demonstrated. TGA/TGA-FTIR-GC-MS analysis of the FeCl3/MCM-41 material showed the release of HCl molecules as a result of the condensation reaction and the formation of FeOClx species on the surface of MCM-41. Solid state Si29 NMR and HT-XRD analysis of these materials clearly showed the grafting of FeOClx species on the surface of MCM-41 and nanocrystalline FeOClx formation during the thermal condensation reaction. HRTEM mapping and EDX mapping further confirm the nanocrystalline iron oxychloride species formation and its uniform distribution on the surface of MCM-41. It was further demonstrated that these materials were found to be highly active towards solvent-free one pot multi condensation reaction between napthols, amides and aldehydes to produce pharmaceutically active alkylnapthols. The role of calcination temperature was demonstrated to be a key factor in the formation and distribution of FeOClx species, therefore the catalytic activity of these materials vary as a function of calcination temperature. XPS analysis of these materials confirmed the presence of FeOClx species and its role as an active acid site for the multi-condensation reaction was proposed.