Tahshina Begum

Palladium-Schiff-base-silica framework as a robust and recyclable catalyst for Suzuki–Miyaura cross-coupling in aqueous media

A silica supported palladium catalyst, Pd@imine–SiO2 was prepared by immobilizing Pd(OAc)2 onto silica gel through coordination of imine, generated via Schiff-base condensation between 3-aminopropyltriethoxysilane (APTES) functionalized silica gel and salicylaldehyde. The prepared catalyst was characterized by FT-IR, BET surface area measurements, XRD, SEM-EDX, EDS-mapping and ICP-AES analysis. The imine-based catalyst exhibited excellent activity in the Suzuki–Miyaura cross-coupling reactions of aryl bromides with arylboronic acids in iPrOH/H2O (1 : 1) at room temperature. The reaction proceeds under mild reaction conditions and the catalyst is recyclable, thus offering an environmentally benign alternative to the existing protocols.

Rice husk derived nanosilica supported Cu(II) complex: an efficient heterogeneous catalyst for oxidation of alcohols using TBHP

We have developed a heterogenized catalyst of Cu(II) complex immobilized onto nanosilica obtained from rice husk (RH), through coordination of imine, generated via Schiff-base condensation between 3-aminopropyltriethoxysilane (APTES) functionalized nanosilica and acetamide. The synthesized catalysts were characterized by FT-IR, XRD, BET surface area measurements, ESR, SEM-EDX and ICP-AES. The synthesized catalyst showed excellent activity towards controlled oxidation of different primary and secondary alcohols in the presence of tert-butyl hydrogen peroxide (TBHP). Furthermore, the catalysts could be recovered by simple filtrations and can be reused upto many consecutive cycles without loss in activity.

Chemoselective acyl C–O bond activation in esters for Suzuki–Miyaura coupling

Exploitation of the low binding affinity of NHC–palladium complex for the carbonyl oxygen of ester to form three-centered transition state led to the discovery of Suzuki–Miyaura coupling via unprecedented C(acyl)–O bond cleavage. The use of bulky NHC ligand resulted in direct coupling as it prevented decarbonylation of ester. This access to alternative chemoselectivity by careful selection has extended the synthetic portfolio of esters for the diversification of interesting molecular scaffolds.