Rajashree Chakravarti

Nanocrystalline magnesium oxide stabilized gold nanoparticles: an advanced nanotechnology based recyclable heterogeneous catalyst platform for the one-pot synthesis of propargylamines

A simple and elegant synthesis of gold nanoparticlesvia counter ion stabilization of AuCl4− on nanocrystalline magnesium oxide support followed by sodium borohydride reduction is described here. A thorough characterization of the resulting heterogeneous material revealed the presence of uniformly distributed gold nanoparticles (10–12 nm) deposited on to (111) plane of quasi-crystalline icosahedral lattice of nanocrystalline magnesium oxide which exhibits excellent catalytic activity for the one pot synthesis of structurally divergent propargylamines via a three component coupling of an alkyne, an amine and an aldehyde without requiring any additives or inert atmosphere. The catalyst contains ultra low loading of gold (0.236 mol%), and turnover numbers as high as 400 are obtained. The catalyst can be isolated by simple centrifugation and reused for four cycles.

A facile synthesis of alkylated nitrogen heterocycles catalysed by 3D mesoporous aluminosilicates with cage type pores in aqueous medium

Friedel–Crafts alkylation of nitrogen heterocycles such as indoles and pyrroles with epoxides has been efficiently carried out using cage-type mesoporous aluminosilicates as recyclable catalysts in water under environmentally benign and mild conditions.

Functionalization of Mesoporous Carbon with Superbasic MgO Nanoparticles for the Efficient Synthesis of Sulfinamides

Highly basic MgO nanoparticles with different sizes have been successfully immobilized over mesoporous carbon with different pore diameters by a simple wet-impregnation method. The prepared catalysts have been characterized by various sophisticated techniques, such as XRD, nitrogen adsorption, electron energy loss spectroscopy, high-resolution TEM, X-ray photoelectron spectroscopy, and the temperature-programmed desorption of CO(2). XRD results reveal that the mesostructure of the support is retained even after the huge loading of MgO nanoparticles inside the mesochannels of the support. It is also demonstrated that the particle size and dispersion of the MgO nanoparticles on the support can be finely controlled by the simple adjustment of the textural parameters of the supports. Among the support materials studied, mesoporous carbon with the largest pore diameter and large pore volume offered highly crystalline small-size cubic-phase MgO nanoparticles with a high dispersion. The basicity of the MgO-supported mesoporous carbons can also be controlled by simply changing the loading of the MgO and the pore diameter of the support. These materials have been employed as heterogeneous catalysts for the first time in the selective synthesis of sulfinamides. Among the catalysts investigated, the support with the large pore diameter and high loading of MgO showed the highest activity with an excellent yield of sulfinamides. The catalyst also showed much higher activity than the pristine MgO nanoparticles. The effects of the reaction parameters, including the solvents and reaction temperature, and textural parameters of the supports in the activity of the catalyst have also been demonstrated. Most importantly, the catalyst was found to be highly stable, showing excellent activity even after the third cycle of reaction.

High temperature microwave-assisted synthesis and the physico-chemical characterisation of mesoporous crystalline titania

Mesoporous TiO2 with nanocrystalline architecture has been synthesised by using microwave-assisted high temperature method using polymeric surfactant. The polymeric template was removed by stepwise carbonisation process. The structural order, band structure and the textural parameters of the calcined mesoporous titania were investigated by using numerous sophisticated techniques such as XRD, nitrogen adsorption, HRSEM, UV-Vis DRS and HRTEM. The obtained mesoporous TiO2 material have mesoscopic order, high surface area, crystalline walls and narrow pore size distribution as evident from the XRD and nitrogen adsorption results. Wide-angle X-ray diffraction pattern obtained for calcined mesoporous TiO2 shows that the pore wall of the sample is composed of highly crystalline Ti-O-Ti framework with an anatase phase. The photoluminescence properties of the mesoporous TiO2 was also analysed and the results were discussed in detail.

Mesoporous Carbons Functionalized with Aromatic, Aliphatic, and Cyclic Amines, and their Superior Catalytic Activity

A highly ordered mesoporous carbon has been successfully functionalized with various amino compounds including aliphatic, aromatic, and cyclic diamines via a simple C‐N coupling process. The bonding between the carbon wall structure and the amino groups was confirmed by FT‐IR, Raman, and X‐ray photoelectron spectroscopy. The basicity of the materials can be tuned by simply changing the nature of the diamines on the carbon walls. The catalytic activity of the material as a solid base in the aza‐Michael reaction of amines to activated alkenes was investigated. The functionalized materials were found to be highly active at room temperature and without any solvents, selective and can be recycled several times with consistent activity. The nature of the amine groups on the carbons significantly affects the formation of the β‐amino carbonyl compounds. Among functionalized carbons, carbon with aliphatic diamines showed the highest performance with a high yield of β‐amino carbonyl compounds.

Efficient Synthesis of 2,3,4-TrisubstitutedQuinolines via Friedländer Annulation with NanoporousCage-Type Aluminosilicate AlKIT-5 Catalyst

2-Aminoaryl ketones undergo smooth Friedlander condensation/annulation with α-methyleneketones on the surface of nanoporous aluminosilicate catalyst to afford the corresponding quinoline derivatives in good yields with high selectivity due to its high surface area, large pore volume, and high acidity. The use of highly acidic and reusable AlKIT-5 catalyst makes the Friedlander annulation simple, convenient, and practical.