Sanjay Paul

Design and synthesis of benzylpyrazolyl coumarin derivatives via a four-component reaction in water: investigation of the weak interactions accumulating in the crystal structure of a signified compound

A combinatorial library of benzylpyrazolyl coumarin derivatives have been synthesized by a green one-pot four-component reaction between aryl hydrazine/hydrazine hydrate (1), ethyl acetoacetate (2), aromatic aldehydes (3) and 4-hydroxycoumarin (4). Molecular scaffolds which assimilate bio-active 3-benzylsubstituted 4-hydroxycoumarins as well as a pyrazolone ring in a single nucleus may be worthwhile molecules from a biological point of view. The reactions were performed in water and employed glacial acetic acid as the right choice of catalyst, and was demonstrated to be the key for rendering the reaction possible and obtained good to excellent yields under reflux conditions within a short period of time. The crystal structures of (R/S)-benzylpyrazolyl coumarin, easily produced by a chromatography-free highly product-selective reaction, were explored by means of single crystal X-ray diffraction analysis and the main intra- and intermolecular interactions perceivable through crystal structure analysis. The presence of a strong intramolecular hydrogen bond was confirmed. In addition, the whole crystal structure consists of other intermolecular hydrogen bonds, such as CH⋯O and aromatic CH⋯π interactions between R- and S-molecules and CH⋯O, NH⋯O and aromatic CH⋯π interactions among only R-molecules and S-molecules in the asymmetric unit.

Magnetically retrievable nano crystalline CuFe2O4 catalyzed multi-component reaction: a facile and efficient synthesis of functionalized dihydropyrano[2,3-c]pyrazole, pyrano[3,2-c]coumarin and 4H-chromene derivatives in aqueous media

CuFe2O4 magnetic nanoparticles were synthesized and recognized as an efficient catalyst for the one-pot synthesis of dihydropyrano[2,3-c]pyrazole, pyrano[3,2-c]coumarin and 4H-chromene derivatives at mild conditions and in excellent yields. The four component reaction (4CRs) of a wide variety of substituted hydrazine derivatives, ethyl acetoacetate, dialkyl acetylenedicarboxylates and alkyl nitrile derivatives (malononitrile and ethyl cyanoacetate) gave the targeted dihydropyrano[2,3-c]pyrazoles. When two equivalents of dialkyl acetylenedicarboxylates were introduced replacing ethyl acetoacetate, a new four-component reaction took place providing another type of dihydropyrano[2,3-c]pyrazole derivatives. An efficient and practical route to pyrano[3,2-c]coumarin and 4H-chromene framework has also been developed by one-pot, three-component reaction (3CRs) of 4-hydroxycoumarin/dimedone/cyclohexane-1,3-dione, dialkyl acetylenedicarboxylates and alkyl nitriles. CuFe2O4 magnetic nanoparticles were prepared by a simple and effective citric acid complex method and characterized by using XRD, FT-IR, EDX and TEM image. The catalyst was recycled for six cycles with almost unaltered catalytic activity. All reactions were easily performed and proceeded with high efficiency under very simple and mild conditions and gave excellent yields avoiding time-consuming, costly syntheses, and tedious workup and purification of products.

Three-component synthesis of a polysubstituted pyrrole core containing heterocyclic scaffolds over magnetically separable nanocrystalline copper ferrite

A highly convergent, efficient and practical heteroannulation protocol for the synthesis of a library of coumarin and uracil fused pyrrole derivatives has been developed. Reactions involving the CuFe2O4 catalyzed one-pot three-component domino coupling of 6-aminouracil/4-aminocoumarin, aldehydes and nitromethane resulted in highly substituted coumarin and uracil fused pyrrole derivatives, making this strategy very useful in diversity-oriented synthesis (DOS). CuFe2O4 magnetic nanoparticles were prepared by a simple and effective citric acid complex method and characterized by using XRD, FT-IR, and TEM images. The easy recovery of the catalyst and high yield of the products makes the protocol attractive, sustainable and economic. The catalyst was recycled for six cycles with almost unaltered catalytic activity.

A new application of polymer supported, homogeneous and reusable catalyst PEG–SO3H in the synthesis of coumarin and uracil fused pyrrole derivatives

A highly efficient, simple and convenient synthetic protocol for the synthesis of coumarin and uracil fused pyrrole derivatives has been demonstrated. A biodegradable, polymer supported catalyst, PEG–SO3H, was applied for the two component coupling of 4-aminocoumarin or 6-aminouracil and α,β-unsaturated nitroalkene. The catalyst has efficiently catalyzed the Michael addition and intramolecular cyclisation with the concomitant removal of the nitro group. The catalyst was recycled for five cycles with almost unaltered catalytic activity.

PhIO promoted synthesis of nitrile imines and nitrile oxides within a micellar core in aqueous media: a regiocontrolled approach to synthesizing densely functionalized pyrazole and isoxazoline derivatives

A highly efficient and general protocol has been developed for the facile synthesis of highly diversified 1,3,5-trisubstituted pyrazoles and 3,5-disubstituted 2-isoxazolines through one-pot tandem intermolecular, as well as intramolecular, dipolar [3 + 2] cycloaddition reactions. Chemoselective oxidation of aldohydrazone to nitrile imine and aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media was performed. The scope of the reactions in regiocontrolled dipolar cycloaddition with olefins in the presence of PhIO toward highly substituted pyrazole and isoxazoline derivatives has been demonstrated. SDS converted the initially floating reaction mass and the organo-oxidant PhIO into a homogeneous mixture, which on stirring became a turbid emulsion. The micellar arrangement was confirmed by dynamic light scattering and optical microscopy. The new, green and metal free synthetic method enabled the execution of regiocontrolled tandem cycloaddition oxidation sequences leading to a library of pyrazole and isoxazoline derivatives.

Facile synthesis of pyridopyrimidine and coumarin fused pyridine libraries over a Lewis base-surfactant-combined catalyst TEOA in aqueous medium

A highly convergent and efficient protocol, for the facile synthesis of a library of coumarin fused pyridine and pyridopyrimidine derivatives, has been developed by applying a Lewis base-surfactant-combined catalyst (LBSC) triethanolamine (TEOA). The method described has the benefits of operational simplicity and excellent yields of the targeted molecule. The LBSCs were found to form stable colloidal dispersions rapidly in the presence of reaction substrates in water, even when the substrates are solid. In light of the increased demand for reduction of organic solvents in industry, the surfactant aided Lewis base catalysis described here may have immense practical consequences in organic synthesis. This work may not only lead to environmentally benign systems but also will provide a newer aspect of organic chemistry in water.

A facile and efficient synthesis of functionalized 4-oxo-2-(phenylimino)thiazolidin-5-ylideneacetate derivatives via a CuFe2O4 magnetic nanoparticles catalyzed regioselective pathway

Nano-CuFe2O4 spinel has been found to exhibit strong catalytic activity in the cascade reaction involving 1,4-addition and intramolecular electrophilic cyclization in a perfectly regiocontrolled manner and a series of functionalized 4-oxo-2-(phenylimino)thiazolidin-5-ylideneacetate derivatives were generated successfully. The reaction is mild and selective with good to high yields and displays significant functional group tolerance. The dual role of the thiocarbonyl moiety as an electrophile and as a nucleophile has been observed in this three component coupling reaction. CuFe2O4 magnetic nanoparticles were prepared by a simple and effective citric acid complex method and characterized by using XRD, FT-IR, and TEM analysis. The catalyst was recycled for six cycles without any loss of catalytic activity. All reactions were easily performed and proceeded with high efficiency under very simple and mild conditions and gave excellent yields avoiding time-consuming, costly syntheses, tedious workup and purification hazards.

Synthesis of a SO3H-bearing carbonaceous solid catalyst, PEG–SAC: application for the easy access to a diversified library of pyran derivatives

A SO3H-bearing carbonaceous solid catalyst (PEG–SAC) has been synthesized through sulfonation followed by a hydrothermal carbonization method from renewable resources like polyethylene glycol. The biodegradable catalyst was characterized by XRD, TEM, FT-IR and EDX. The surface area and pore diameter of the catalyst were determined from a nitrogen adsorption–desorption isotherm experiment. A highly convergent, efficient and practical PEG–SAC catalyzed heteroannulation protocol for the synthesis of a library of diversified pyran fused heterocyclic scaffolds has been demonstrated. This synthesis was established to follow the group-assistant-purification (GAP) chemistry process, which can avoid traditional chromatography. A recrystallization purification appeared to be a very good alternative to the traditional classical methods, demonstrating that a carbon-based catalyst is very effective in producing pyran fused heterocyclic molecules. The aqueous reaction medium, easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economic.

Synthesis of indeno and acenaphtho cores containing dihydroxy indolone, pyrrole, coumarin and uracil fused heterocyclic motifs under sustainable conditions exploring the catalytic role of the SnO2 quantum dot

A tin oxide (SnO2) quantum dot (QD) catalyzed approach for the synthesis of indeno and acenaphtho cores containing dihydroxy indolone, pyrrole, coumarin and uracil fused derivatives was achieved via a multicomponent one-pot approach in aqueous medium. A variety of functional groups were compatible with the reaction conditions. This synthesis was established to follow the group-assistant-purification chemistry process, thus avoiding the use of traditional chromatography. An SnO2 QD was prepared using a simple solvothermal method and characterized using X-ray diffraction and transmission electron spectroscopy images. The easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economic. The catalyst was reused for seven cycles with almost unaltered catalytic activity. The low cost, ease of handling and the simplicity of this catalytic system make the method competitive with other strong mineral acid-catalysed multicomponent protocols.

Expeditious synthesis of functionalized tricyclic 4-spiro pyrano[2,3-c]pyrazoles in aqueous medium using dodecylbenzenesulphonic acid as a Brønsted acid–surfactant-combined catalyst

An efficient, three-component, one-pot synthesis of highly functionalized tricyclic 4-spiro pyrano[2,3-c]pyrazoles incorporating medicinally privileged heterocyclic moieties has been developed, which also involves the tandem Knoevenagel/Michael addition reaction followed by dehydrative cyclization of pyrazolone derivatives, cyclic 1,3-diketones and cyclic ketones, catalyzed by dodecylbenzenesulphonic acid (DBSA) as a Bronsted acid–surfactant-combined catalyst in aqueous medium. The catalyst is found to be highly competent in accelerating this reaction that results in a considerable short reaction time, alleviating the need for high thermal energy. Wide substrate scope, high to excellent product yield, operational simplicity, absence of any hazardous organic solvent, mild reaction conditions, a simple work up procedure and easily available starting materials are the salient features of this protocol.