Sudarshan Singha

Amine functionalized layered double hydroxide: a reusable catalyst for aldol condensation

Zn : Al layered double hydroxide-supported 3-aminopropyltriethoxysilane (APTES) and N-methyl 3-aminopropyltriethoxy silane (MAPTES) are found to be efficient, environmentally attractive and selective solid base catalysts for liquid phase aldol condensation reactions at room temperature. The organic functionalized solid catalysts were characterized by XRD, FT-IR, Raman, EDX, SEM, TG-DTA, 13C and 29Si CP MAS NMR techniques. The XRD pattern indicated the anti-parallel monolayer arrangements of organic moieties in the interlayer space of LDH. 29Si NMR confirmed that the linking silicon atom is fully condensed in the framework. The reusability study shows consistent activity of the heterogeneous catalyst after several cycles.

A reusable Mn(II)-dampy-MCM-41 system for single step amination of benzene to aniline using hydroxylamine

Reaction methodology for C–H bond amination of benzene catalyzed by Mn(II)-dien (ampy) immobilized organo modified MCM-41 in the presence of hydroxylamine in acetic acid–water medium is described. The organic–inorganic hybrid heterogeneous catalyst achieves high catalytic activity and selectivity for one step amination of benzene. Characterization of the immobilized catalyst by powder X-ray diffraction (XRD), N2 adsorption–desorption, CP MAS NMR spectroscopy (13C and 29Si), Fourier transform infrared spectroscopy (FT-IR) and diffuse reflectance UV–Vis spectroscopy demonstrates the successful grafting of the complex into functionalized mesoporous silica and that the mesostructure has not been destroyed in the multistep synthetic procedure. The variation of reaction conditions such as solvent, temperature, time, catalyst concentration etc. is well demonstrated to achieve high catalytic activity. Moreover, the anchored catalyst can be recovered and reused for multiple cycles without appreciable loss in catalytic activity, which is an alternative to the conventional industrial process.