Chhanda Mukhopadhyay

Heterogeneous ditopic ZnFe2O4 catalyzed synthesis of 4H-pyrans: further conversion to 1,4-DHPs and report of functional group interconversion from amide to ester

Highly stable, environmentally benign ZnFe2O4 nanopowder was prepared, characterized and applied in the one-pot, three-component synthesis of 4H-pyrans in water. The ZnFe2O4 catalyst provides both acidic (Fe3+) and basic functionalities (O2−) as the reaction requires. The advantages of this method lie in its simplicity, cost effectiveness, environmental friendliness and easier scaling up for large scale synthesis. Water was exploited both as a reaction medium as well as a medium for synthesis of the catalyst. Moreover, water was the only byproduct. The present report puts forward an application of 4H-pyrans for the synthesis of 1,4-DHPs. This is the first attempt towards the synthesis of 4H-pyran-3-carboxylate from 4H-pyran-3-carboxamide. The corresponding functional group interconversion from amide to ester is rare in organic synthesis.

An Expeditious and Efficient Synthesis of Highly Functionalized [1,6]-Naphthyridines under Catalyst-Free Conditions in Aqueous Medium

This is the first report of an innovative, one-pot, catalyst-free, pseudo-five-component synthesis of 1,2-dihydro[1,6]naphthyridines from methyl ketones, amines, and malononitrile in ecofriendly solvent water. The protocol avoids the use of expensive catalysts, toxic organic solvents and anhydrous condition. The approach to naphthyridines presented herein offers for the first time an unprecedented coupling which leads to the construction of both the nitrogen containing rings during the synthesis without starting from any nitrogen-containing heterocycle moiety.

Direct amide bond formation from carboxylic acids and amines using activated alumina balls as a new, convenient, clean, reusable and low cost heterogeneous catalyst

For the first time, we have used activated alumina balls (3–5 mm diameter) for amide synthesis from carboxylic acids (unactivated) and amines (unactivated) under neat reaction conditions that produce no toxic by-products and has the advantages of being low-cost, easily available, heterogeneous, reusable and environmentally benign with no troublesome/hazardous disposal of the catalyst.

Zinc titanate nanopowder: an advanced nanotechnology based recyclable heterogeneous catalyst for the one-pot selective synthesis of self-aggregated low-molecular mass acceptor–donor–acceptor–acceptor systems and acceptor–donor–acceptor triads

Highly stable, environmentally benign ZnTiO3 nanopowder has been prepared via a sustainable sol–gel method. The nanopowder (90 nm) has been thoroughly characterized by SEM, XRD, EDS, Laser Raman, photoluminescence, UV and IR. The activity of the catalyst was probed through one-pot four-component reaction of aldehydes, ketones and two equivalent propanedinitriles in water without requiring any additives or anhydrous conditions. The reaction requires two different catalytic functions, i.e., an acidic one which is given by Ti(IV) ions and a basic one, given by the oxide ion incorporated within the ZnTiO3 metal oxide framework. The advantages of this method lie in its simplicity, cost effectiveness, environmental friendliness, and easier scaling up for large scale synthesis without using high pressure, temperature and toxic chemicals. As water was used as a reaction medium and since we are particularly interested in the isolation of a non-aromatic intermediate, the elimination of poisonous HCN was prevented by the Lewis acid character of Ti4+ up to a sufficiently high temperature. Thus, this process can be considered as a “green” process. Elimination of HCN at higher temperatures still maintains “green” attributes as HCN can be trapped by the basic catalyst under such conditions. Spontaneous generation of low molecular mass self-aggregated organic materials, their one-dimensional packing, and interesting photophysical properties are reported.

A Simple, Efficient and Green Procedure for the Knoevenagel Condensation of Aldehydes with N-Methylpiperazine at Room Temperature under Solvent-Free Conditions

Abstract Knoevenagel condensation of aromatic, aliphatic, and heteroaromatic aldehydes with active methylene compounds such as ethylcyanoacetate, malononitrile, and cyanoacetamide proceed very smoothly at room temperature by simply mixing the ingredients together under solvent-free conditions in the presence of N-methylpiperazine in excellent yields of the E-configured products.

A new MCM-41 supported HPF6 catalyst for the library synthesis of highly substituted 1,4-dihydropyridines and oxidation to pyridines: report of one-dimensional packing towards LMSOMs and studies on their photophysical properties

A new heterogeneous MCM-41 silica supported HPF6 catalyst has been synthesized and characterized using an array of sophisticated analytical techniques like BET, XRD, HRTEM, EDX, 29Si MAS NMR, TGA, FTIR, and pH measurement. The broad applicability of silica-HPF6 was probed through a library synthesis of highly substituted 1,4-dihydropyridines (1,4-DHPs). The 1,4-DHPs are further oxidized to pyridines with aqueous H2O2 as stoichiometric oxidant which is considered as an abundant and green oxidant. The pyridines spontaneously generate low molecular mass self-aggregated organic materials (LMSOMs). Their one-dimensional packing and interesting photophysical properties are reported. Synthesis using water as a solvent is of paramount importance for its sustainable green impact. Further, carbon dioxide and water were the only by-products, which added to its attractiveness. This silica-HPF6 catalyst retained its activity even after being exposed to ambient atmosphere for 10 days.

Exploitation of dual character of CN moiety in the synthesis of uniquely decorated 3H-pyrroles: a rare observation.

This is the first report of an innovative, one-pot, organocatalyzed, multicomponent synthesis of 3H-pyrroles from ketones, thiols, and malononitrile in ecofriendly solvent water. The approach to 3H-pyrroles presented herein offers, for the first time, an unprecedented coupling which leads to the construction of the nitrogen containing ring without starting from any amine moiety. In this context, cyanide-based multicomponent reactions involving the dual nature of the CN moiety has blossomed in an unprecedented way.

Multicomponent, one-pot and expeditious synthesis of highly substituted new spiro[indolo-3,10′-indeno[1,2-b]quinolin]-2,4,11′-triones under micellar catalytic effect of CTAB in water

A convenient multicomponent reaction strategy for the synthesis of highly substituted new spiro[indolo-3,10′-indeno[1,2-b]quinolin]-2,4,11′-triones has been developed under CTAB/H2O system (easily recovered and recycled) to provide spiro products with excellent yields. The most exciting feature of this methodology is its mechanism involving the unusual ring opening of an isatin moiety followed by recyclisation.

Synthesis of 2-alkyl substituted benzimidazoles under microwave irradiation: Anti-proliferative effect of some representative compounds on human histiocytic lymphoma cell U937

The objective of this research was the synthesis of 2-alkyl substituted benzimidazoles under microwave irradiation using 62% aqueous hexafluorophosphoric acid (10 mol%) as catalyst. Some of the newly synthesised compounds were tested for their potential to inhibit proliferation of cancer cells (histiocytic lymphoma cell U937) by cell viability assay.

First use of p-tert-butylcalix[4]arene-tetra-O-acetate as a nanoreactor having tunable selectivity towards cross azo-compounds by trapping silver ions

p-tert-Butylcalix[4]arene-tetra-O-acetate was established for the first time as a member of the nanoreactor series, even without having any –OH group. The nano range distribution of this nanoreactor was ascertained by DLS, SEM and TEM studies. The capability of this cavitand towards hosting amines in a competitive manner generates a new green pathway for cross coupling of aromatic amines to give the corresponding azo-compounds. In this context, using p-tert-butylcalix[4]arene-tetra-O-acetate as a nanoreactor and silver nitrate as a catalyst, we got the cross azo-compound in good to excellent yields in the eco-friendly solvent water. This green methodology is also applicable for the synthesis of respective homo-compounds.