Anupam Singha Roy

Synthesis of silver–graphene nanocomposite and its catalytic application for the one-pot three-component coupling reaction and one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles in water

A graphene based composite with silver nanoparticles has been synthesized via a simple chemical route and its catalytic activity has been tested for multi-component reactions and click reaction in a one-pot approach. This silver–graphene nanocomposite shows excellent catalytic activity at room temperature for three-component couplings between aldehydes, alkynes and amines (A3-coupling) and one-pot synthesis of 1,4-disubstituted 1,2,3-triazole via click reaction between in situ generated azides (derived from anilines or amines) and terminal acetylenes. This solid silver–graphene catalyst has been characterized by TEM, Raman, XRD and UV-Visible absorption spectra. The developed catalyst is air-stable, inexpensive, easy to prepare and can be facilely recovered and reused five times without significant decrease in activity and selectivity.

Enhanced catalytic performance by copper nanoparticle–graphene based composite

A graphene based composite with copper nanoparticles (Cu–G) has been synthesized and used as catalyst for N-arylation and O-arylation. The structure and composition of the nanocomposite have been characterized by TEM, AFM, Raman and XPS. The catalytic activity of the Cu–G has been tested for the N-arylation of N–H heterocycles using arylboronic acids and the O-arylation of phenols using aryl halides. The catalytic N-arylation produces N-aryl heterocyles and the catalytic O-arylation produces diaryl ethers, under mild reaction conditions with excellent yields and selectivities. The developed catalyst is air-stable, inexpensive, easy to prepare, easy to recover by simple filtration and can be reused without appreciable loss of activity.

Cu-grafted mesoporous organic polymer: a new recyclable nanocatalyst for multi-component, N-arylation and S-arylation reactions

A new mesoporous Cu-MPTA-1 nanocatalyst has been synthesized via a simple and facile in situ radical polymerization of triallylamine in the presence of an organic–organic self-assembly of anionic surfactant SDS, followed by grafting of Cu(II) at room temperature under an inert atmosphere. This nanomaterial has been characterized by elemental analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA), N2 adsorption–desorption studies, X-ray photoelectron spectroscopy (XPS) and EPR spectroscopy. Cu-MPTA-1 acts as an efficient heterogeneous nanocatalyst exhibiting a high catalytic activity for N-arylation and S-arylation reactions using water as a green solvent and also exhibits an excellent catalytic activity for the one-pot synthesis of propargylamines via a three component coupling of an alkyne, an amine and an aldehyde at room temperature. Moreover, the catalyst is easily recoverable and can be reused six times without an appreciable loss of catalytic activity in the three component coupling reaction. The highly dispersed Cu(II) sites in the Cu-grafted mesoporous polymer could be responsible for the observed high activities of the Cu-MPTA-1 catalyst in the coupling reactions. No evidence of leached Cu from the catalyst during the course of the reaction has been observed, suggesting true heterogeneity in the catalytic process.

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.

Chromium(VI) grafted mesoporous polyaniline as a reusable heterogeneous catalyst for oxidation reactions in aqueous medium

A new Cr(VI)-grafted mesoporous polyaniline material (Cr-MPANI) has been prepared via simple and facile in situ radical polymerization of aniline followed by reaction with potassium dichromate. This material has been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS) and Thermogravimetric analysis (TGA). Powder XRD and TEM studies suggested the presence of mesophase and disordered wormhole-like mesopores in this sample. Cr-MPANI acts as a very efficient catalyst for the liquid phase oxidation of alkenes, alkanes and aromatic alcohols using 30% H2O2 as oxidant in water. Oxidation reactions were carried out under very mild conditions, and the desired products were obtained with very high selectivity and relatively high yields. Cr-MPANI can be recycled more than five times without an appreciable loss in activity for its respective catalytic reactions.

Highly efficient base catalysis and sulfide oxidation reactions over new functionalized mesoporous polymers

Base catalyzed aldol condensation reactions and selective partial oxidation of sulfides are very important classes of reactions in synthetic organic chemistry. We have prepared a new alkali exchanged form of mesoporous polytriallylamine, OH-MPTA-1 and a Cr-grafted material Cr-MPTA-1 via the simple and facile in situ radical polymerization of a triallylamine template by organic–organic self-assembly of anionic surfactant systems. The materials have been characterized by elemental analysis, powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Powder XRD and TEM image analyses suggests the presence of mesophase and disordered wormhole-like mesopores in these samples. Our experimental results reveal that the alkali exchanged material OH-MPTA-1 acts as a very efficient base catalyst for the direct aldol reaction of different aromatic aldehydes with acetone. On the other hand, the Cr-grafted material Cr-MPTA-1, obtained through the reaction of potassium chromate with MPTA-1, acts as a very efficient catalyst for the liquid phase partial oxidation of sulfides to sulfoxides. Both OH-MPTA-1 and Cr-MPTA-1 can be recycled more than five times without an appreciable loss in activity for their respective catalytic reactions.

Efficient Allylic Oxidation of Olefins Catalyzed by Polymer Supported Metal Schiff Base Complexes with Peroxides

Three homogeneous Cu(II), Co(II) and Ni(II) complexes of a Schiff base ligand and their heterogeneous complexes supported on poly(4-aminostyrene) were prepared and characterized by using elemental analysis, fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, thermogravimetric analysis and scanning electron microscopy. The catalytic performance of both homogeneous and heterogeneous complexes was evaluated in the liquid phase oxidation of cyclohexene, styrene and trans-stilbene in acetonitrile with tert-butylhydroperoxide or hydrogen peroxide as the oxidant. All types of catalyst were active in oxidation; and, the complexes produce allylic oxidation products in all cases. Immobilized complexes are slightly more active than their homogeneous complexes. The polymer-supported Cu(II) complex shows a higher catalytic activity than the other metal species. The activities of the immobilized catalysts remained nearly the same after five cycles, suggesting the true heterogeneous nature of the catalyst.

In situ prepared mesoporous silica nanosphere supported palladium(II) 2-aminopyridine complex catalyst for Suzuki–Miyaura cross-coupling reaction in water

We report the synthesis and catalytic activities of a mesoporous silica nanosphere supported palladiumII 2-aminopyridine complex (Pd-AMP-MSN). First, chloroalkyl functionalized mesoporous silica nanospheres (Cl-MSN) is prepared by an in situ co-condensation reaction of tetraethyl orthosilicate (TEOS) with ((chloromethyl)phenylethyl)trimethoxysilane (CMPE-TMS) using cetyltrimethylammonium bromide (CTAB) as the structure directing agent. The reaction of Cl-MSN with 2-aminopyridine followed by complexation with palladium acetate produces the catalyst Pd-AMP-MSN. FTIR spectroscopic analysis confirms the presence of 2-aminopyridine functionality inside the mesopores of the Pd-AMP-MSN. Nitrogen adsorption–desorption and X-ray diffraction analyses reveal mesoporous structures of the Pd-AMP-MSN catalyst with a specific surface area of 372 m2 g−1, a pore volume of 0.172 cm3 g−1 and a narrow pore size distribution (D ∼ 1.92 nm). FESEM and HRTEM results indeed show the formation of nanospheres with mesoporous structures. This catalytic system exhibits excellent activity in Suzuki–Miyaura cross-coupling reactions of aryl iodides, aryl bromides and also aryl chlorides with phenylboronic acids in water medium with high yields. This Pd-AMP-MSN catalyst could be quantitatively recovered by simple filtration and is found to be highly active without any significant loss of its catalytic activity in eight consecutive runs.

Functionalized Polystyrene Supported Copper(I) Complex as an Effective and Reusable Catalyst for Propargylamines Synthesis in Aqueous Medium

An efficient procedure for the one-pot synthesis of propargylamines is A3 coupling in which an alkyne, an aldehyde, and an amine are coupled together. Here, we report that polystyrene supported Cu(I) catalyst is excellent for A3 coupling in water without using any additives or hazardous organic solvents. The polystyrene supported Cu(I) catalyst was synthesized and its catalytic activity was also evaluated in the synthesis of propargylamines in oxidative A3-coupling reaction with benzyl alcohols instead of their aldehydes in water. This protocol offers several advantages such as high yields of the desired product, reaction in aqueous medium and recyclability of the catalyst. It gives well to excellent yields for a variety of substrates. As it acts as heterogeneous catalyst, it can be easily separated from the reaction mixture and reused without appreciable loss of activity.Graphical AbstractPolymer supported copper catalyst, Cu-PS-ala, acts as a heterogeneous catalyst for the one pot synthesis of propargylamines via A3 coupling reaction in water using aldehydes or alcohols, amines and alkynes.

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.