Yogesh B. Wagh

β-Cyclodextrin-mediated highly efficient [2+3] cycloaddition reactions for the synthesis of 5-substituted 1H-tetrazoles

A β-cyclodextrin-promoted [2+3] cycloaddition reaction between nitriles and sodium azide in the presence of ammonium chloride in DMF at 120 °C is reported, affording various 5-substituted 1H-tetrazoles in good to excellent yields in short reaction times. The presence of β-CD renders the formation of a precipitate-like gel in the reaction media when heated. No precipitation occurs in the absence of NaN3 and NH4Cl. The precipitation responses with other salts such as LiCl and NiCl2 were weaker than with NH4Cl. In the present paper the application of supramolecular aggregates is reported for the [2+3] cycloaddition reaction. β-Cyclodextrin can be recovered and reused without any significant loss of activity.

An efficient synthesis of 3-indolyl-3-hydroxy oxindoles and 3,3-di(indolyl)indolin-2-ones catalyzed by sulfonated β-CD as a supramolecular catalyst in water

Abstract Sulfonated-β-cyclodextrin (β-CD-SO3H) promoted efficient and fast electrophilic substitution reaction of indoles with various isatins reflux in water is reported affording various 3-indolyl-3-hydroxy oxindoles and 3,3-di(indolyl)indolin-2-ones in good to excellent yields in short reaction time.

Highly selective fluorimetric sensor for Cu2+ and Hg2+ using a benzothiazole-based receptor in semi-aqueous media and molecular docking studies

A new chemosensor (Z)-ethyl 2-((Z)-2-(benzo[d]thiazol-2-ylimino)-4-oxo-3-phenylthiazolidin-5-ylidene)acetate (receptor 1) was designed and synthesized under catalyst-free conditions. Receptor 1 was characterized by various spectroscopic techniques and its structure was solved by single-crystal X-ray diffraction. Receptor 1 was shown to be based on an internal charge transfer mechanism with the benzothiazole unit. These results were complemented by density functional theory calculations. The fluorescent emission of receptor 1 in CH3OH/H2O (50:50 v/v) was significantly quenched in the presence of Cu2+ and Hg2+, but not in the presence of other tested metal ions. Receptor 1 formed complexes in a 1:1 stoichiometry with Cu2+ and Hg2+ and the detection limits were 0.36 and 2.49 μM, respectively. In addition to the sensing study, the nature of the interactions of 1 with aldose reductase inhibitor was investigated using molecular docking studies.

Bovine serum albumin catalyzed one-pot, three-component synthesis of dihydropyrano[2,3-c]pyrazole derivatives in aqueous ethanol

Bovine serum albumin (BSA) catalyzed synthesis of dihydropyrano[2,3-c]pyrazole derivatives via a one pot, three component reaction of an aldehyde/ketone/isatin, malononitrile and 3-methyl-1H-pyrazol-5-(4H)-one in H2O–EtOH (7 : 3) at ambient temperature was developed in this work. The catalyst was found to work efficiently for aldehydes, ketones and isatins to give the corresponding dihydropyrano[2,3-c]pyrazole and spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives in high yields. BSA showed a broad range of catalytic promiscuity towards various aldehydes, aromatic/aliphatic ketones and substituted isatins. The use of an environmentally benign protocol, reusability of the catalyst, avoidance of hazardous solvents, excellent yields, easy work up and no byproduct formation make BSA an attractive candidate for further applications as a biocatalyst.

Green Process Development for the Synthesis of Aliphatic Symmetrical N,N′-Disubstituted Thiourea Derivatives in Aqueous Medium

Abstract A highly efficient green process for the synthesis of N,N′-disubstituted aliphatic thiourea derivatives using primary aliphatic amines and carbon disulfide in aqueous medium at room temperature via a nonisothiocyanate route is described. This protocol illustrates the rapid preparation of N,N′-disubstituted aliphatic thiourea derivatives in excellent yields with some advantages such as no catalyst and simple workup without any side product formation. Moreover the new route is concise, chromatography-free, and adaptable to pilot-scale preparation. GRAPHICAL ABSTRACT

Simple and Efficient Synthesis of 5-Substituted-3-phenyl-2-thioxoimidazolidin-4-one Derivatives from S-Amino Acids and Phenylisothiocyanate in Et3N/DMF-H2O

Abstract A concise approach for the transformation of various S-amino acids into the 5-alkyl-3-phenyl-2-thioxoimidazolidin-4-one heterocycles using phenylisothiocyanate is described. Phenylthiohydantoins of amino acid were synthesized at room temperature in Et3N/DMF-H2O with easy workup and excellent yields. GRAPHICAL ABSTRACT

Hen Egg White Lysozyme Catalyzed Efficient Synthesis of 3-Indolyl-3-hydroxy Oxindole in Aqueous Ethanol

A green synthesis of 3-indolyl-3-hydroxy oxindoles was reported using hen egg white lysozyme (HEWL) in an aqueous ethanol. The HEWL promotes this reaction efficiently from various isatins and indoles under mild reaction conditions with yields up to 98% bearing good adaptability to varied substrates in the reaction. This conversion has provided a new strategy to synthesize 3-indolyl-3-hydroxy oxindole derivatives employing biocatalytic promiscuity of less explored lysozyme. Based on the experimental studies, the plausible reaction mechanism is proposed.Graphical Abstract