Kajari Ghosh

Mesoporous poly-melamine-formaldehyde stabilized palladium nanoparticle (Pd@mPMF) catalyzed mono and double carbonylation of aryl halides with amines

A new mesoporous poly-melamine-formaldehyde material supported Pd nano catalyst (mPMF–Pd0) has been synthesized and characterized by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectroscopy (DRS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and a N2 adsorption study. The mPMF–Pd0 material showed very good catalytic activity in the field of mono and double amino carbonylation of aryl bromides/iodides. Moreover, the catalyst is easily recoverable and can be reused six times without appreciable loss of catalytic activity in the above reactions. So, the highly dispersed and strongly bound palladium(0) sites in the mPMF–Pd0 could be responsible for the observed high activities. Due to strong binding with the functional groups of the polymer, no evidence of leached Pd from the catalyst during the course of reaction occurred, suggesting true heterogeneity in the catalytic process.

A highly active recyclable gold–graphene nanocomposite material for oxidative esterification and Suzuki cross-coupling reactions in green pathway

A graphene based composite with gold nanoparticles has been synthesized via a simple chemical route and the structure and compositions of nanocomposite has been characterized. The catalyst was found to be remarkably stable and active for the oxidative esterification of alcohols under present reaction conditions using molecular oxygen as green oxidant and Suzuki cross-coupling reactions between aryl halides and phenylboronic acids using environmentally friendly water as solvent. The versatility of both the protocols was demonstrated by taking a number of substrates. This protocol offers several advantages like high yields, clean reactions, recyclability of the catalyst, reaction in water and use of green oxidant. This study suggests graphene, as an economical substitute for carbon nanotubes, could act as a prominent support in heterogeneous catalysis.

An aerobic oxidative synthesis of aryl nitriles and primary aryl amides from benzylic alcohols catalyzed by a polymer supported Cu(II) complex

A new polymer supported Cu(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the direct conversion of benzylic alcohols to aryl nitriles. In this reaction ammonium formate was used as the nitrogen source and O2 as the oxidant. Furthermore, the copper-catalyzed one-pot synthesis of primary aryl amides from alcohols was also achieved. The effects of solvents, reaction time and catalyst amount for the aryl nitriles and aryl amides synthesis were reported. This catalyst showed excellent catalytic activity and recyclability. The polymer supported Cu(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.

Silver nanoparticles embedded over porous metal organic frameworks for carbon dioxide fixation via carboxylation of terminal alkynes at ambient pressure.

Ag nanoparticles (NPs) has been supported over a porous Co(II)-salicylate metal-organic framework to yield a new nanocatalyst AgNPs/Co-MOF and it has been thoroughly characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectrometry (EDX), high-resolution transmission electron microscopy (HR-TEM), UV-vis diffuse reflection spectroscopy (DRS) and N2 adsorption/desorption analysis. The AgNPs/Co-MOF material showed high catalytic activity in the carboxylation of terminal alkynes via CO2 fixation reaction to yield alkynyl carboxylic acids under very mild conditions. Due to the presence of highly reactive AgNPs bound at the porous MOF framework the reaction proceeded smoothly at 1atm CO2 pressure. Moreover, the catalyst is very convenient to handle and it can be reused for several reaction cycles without appreciable loss of catalytic activity in this CO2 fixation reaction, which suggested a promising future of AgNPs/Co-MOF nanocatalyst.

Pd Nanoparticles Decorated on Hypercrosslinked Microporous Polymer: A Highly Efficient Catalyst for the Formylation of Amines through Carbon Dioxide Fixation

CO2 fixation reaction is one of the most challenging chemical transformations not only in the context of environmental remediation but also for effective utilization of abundant carbon sources in nature. Here, we have stabilized palladium nanoparticles (NPs) at the surfaces of a hypercrosslinked porous polymer bearing carbazole and α,α′‐dibromo‐p‐xylene monomeric units to obtain a Pd@HMP‐1 nanocatalyst. The material has been thoroughly characterized by powder XRD, high‐resolution (HR)‐TEM, field‐emission (FE)‐SEM, Brunauer–Emmett–Teller (BET), thermogravimetric (TGA), and FTIR analysis. Pd@HMP‐1 showed excellent catalytic activity towards formylation of amines by carbon dioxide fixation under mild reaction conditions. The high surface area and nitrogen‐rich porous surface make the polymer a suitable support for the palladium nanoparticles and endow it with high recycling efficiency in this CO2 fixation reaction.

Polymer supported Pd catalyzed thioester synthesis via carbonylation of aryl halides under phosphine free conditions

A new polymer supported phosphine free Pd(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the carbonylation of aryl halides into aryl thioesters under mild reaction conditions. Thioesters were obtained in excellent yields from various aryl iodides and thiols in the presence of carbon monoxide and polymer supported palladium catalyst. The effects of solvent, base, reaction time and catalyst amount for the thioester synthesis were reported. This catalyst showed excellent catalytic activity and recyclability. The polymer supported Pd(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.

Polymer supported Pd catalyzed carbonylation of aryl bromides for the synthesis of aryl esters and amides

A polymer-anchored palladium(II) catalyst was synthesized and characterized using various spectroscopic techniques. Its catalytic activity was evaluated for the alkoxycarbonylation and aminocarbonylation reactions. These carbonylation reactions were carried out for various substituted aryl bromides using alcohols and amines. Both the reactions were optimized by varying the bases, temperature and solvents. These experiments were carried out under high CO pressure. The catalyst was very stable and can be facilely recovered and reused six times without a significant decrease in its activity and selectivity.

A route for direct transformation of aryl halides to benzyl alcohols via carbon dioxide fixation reaction catalyzed by a (Pd@N-GMC) palladium nanoparticle encapsulated nitrogen doped mesoporous carbon material

A nitrogen doped mesoporous carbon material was synthesized from glucose and melamine under hydrothermal treatment. A soft template, Brij-35 was used as a template. A nitrogen containing high surface area and porous channels makes this material an important support for palladium nanoparticles as well as a carbon dioxide capturing agent. Ethylene glycol was used as a reducing agent for the palladium nanoparticle synthesis. The palladium nanoparticle embedded porous nitrogen doped carbon material (Pd@N-GMC) was used for the synthesis of benzyl alcohols from aryl iodides via carbon dioxide fixation reaction. The catalyst was highly stable and reusable without any significance loss of its activity.

Direct oxidative esterification of alcohols and hydration of nitriles catalyzed by a reusable silver nanoparticle grafted onto mesoporous polymelamine formaldehyde (AgNPs@mPMF)

A nitrogen-rich mesoporous organic polymer was synthesized as a novel support. A silver nanoparticle was synthesized and grafted onto it. The prepared catalyst (AgNPs@mPMF) was characterized by powder X-ray diffraction (XRD), scanning electron microscopy(SEM) and energy dispersive X-ray spectrometry (EDS), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS), N2 adsorption, Raman spectroscopy and EPR study. The catalytic activity was evaluated for the oxidative esterification reaction of alcohols and hydration of nitriles. The oxidative esterification reaction was carried out for various activated alcohols giving excellent yields of the corresponding ester products. The catalyst was also efficient in the hydration of nitriles. Both reactions were optimized by varying the bases, temperatures and solvents. The catalyst can be facilely recovered and reused six times without a significant decrease in its activity and selectivity.

A mesoporous organosilica grafted Pd catalyst (MOG-Pd) for efficient base free and phosphine free synthesis of tertiary butyl esters via tertiary-butoxycarbonylation of boronic acid derivatives without using carbon monoxide

A mesoporous organosilica grafted palladium(II) catalyst was synthesized and characterized using various spectroscopic techniques. Its catalytic activity was evaluated for the synthesis of tertiary butyl esters via tert-butoxycarbonylation of boronic acid derivatives. The tertiary butyl esters were obtained directly from boronic acid pinacol esters and di-tert-butyl dicarbonate. The reaction was optimized by varying the bases, temperatures and solvents. The catalyst was very stable and could be facilely recovered and reused six times with no significant decrease in its activity and selectivity.