Jayant Sindhu

Ultrasound promoted one pot synthesis of novel fluorescent triazolyl spirocyclic oxindoles using DBU based task specific ionic liquids and their antimicrobial activity.

Spirocyclic oxindoles and triazolyl derivatives posses remarkable biological activities. In present work, we have described an efficient one pot four-component domino reaction of 1-(prop-2-ynyl)indoline-2,3-dione, cyclic 1,3-diketones, malononitrile and various aryl azides in DBU based ionic liquids [DBU-H]OAc and [DBU-Bu]OH under ultrasonic irradiation for the construction of heterocycles, comprising spiro-oxindole, 2-amino-4H-pyran, and 1,2,3-triazoles substructures. The antimicrobial activity of all compounds has been investigated against six microbial strains. All compounds showed good antimicrobial activity. All newly synthesized compounds exhibit fluorescence in methanol with large stoke shift.

Synthesis of biologically as well as industrially important 1,4,5-trisubstituted-1,2,3-triazoles using a highly efficient, green and recyclable DBU–H2O catalytic system

Substituted 1,2,3-triazoles are important heterocyclic molecules with applications in diverse research areas. 1,3-Dipolar cycloaddition reaction of azides and enolizable compounds is an important method of generating substituted 1,2,3-triazoles. However, the reported methods in the literature for 1,3-cycloaddition of aryl azides involve long reaction time, use of hazardous/volatile reagents, and toxic organic solvents. In this paper we have reported the novel environment friendly protocols for the synthesis of 1,4,5-trisubstituted-1,2,3-triazoles by reaction of various aryl azides with active methylene compounds in a DBU–water system under conventional heating, ultrasonic and microwave irradiation. The methodologies defined herein showed synthetic advantages in terms of high atom economy, low environmental impact, mild reaction conditions and good yields in shorter reaction time and recyclability of the reaction medium.

Syntheses, biological evaluation and photophysical studies of novel 1,2,3-triazole linked azo dyes

We have reported synthesis of two novel series of 1,2,3-triazole linked azo dyes using 4-hydroxy-5-methyl-2H-pyran-2-one and sesamol as coupling components in view of the increasing resistance to existing antimicrobial drugs and the need for new antioxidant agents and fluorescent materials. All newly synthesized compounds were evaluated for antibacterial activity, antifungal activity, antioxidant activity and photophysical properties. Antimicrobial activity was evaluated against six microbial strains. Compound 6a was found to be the most potent antibacterial and antifungal agent, while other compounds showed good to moderate antimicrobial activity. Antioxidant activity was evaluated using DPPH free radical scavenging assay and nitric oxide radical scavenging assay. Compound 6b was found to be 5 fold more potent than standard antioxidant BHT. Other compounds showed good antioxidant activity. Photophysical properties of all compounds were also investigated in detail.

Efficient, green and regioselective synthesis of 1,4,5-trisubstituted-1,2,3-triazoles in ionic liquid [bmim]BF4 and in task-specific basic ionic liquid [bmim]OH

Convenient and environmentally benign procedures have been reported for the synthesis of 1,4,5-trisubstituted-1,2,3-triazoles by the reaction of aryl azides with active methylene compounds in ionic liquid [bmim]BF4 in the presence of l-proline as a catalyst and also in task-specific basic ionic liquid [bmim]OH. The methodologies defined herein avoid the severe conditions as posed by earlier existing methods and proved to be efficient in terms of good yields, operational simplicity, easy workup and short reaction time.

Multicomponent Synthesis of Novel 2-Aryl-5-((1-aryl-1H-1,2,3-triazol-4-yl)methylthio)-1,3,4-oxadiazoles using CuI as Catalyst and their Antimicrobial Evaluation

A series of novel 2-aryl-5-((1-aryl-1H-1,2,3-triazol-4-yl)methylthio)-1,3,4-oxadiazoles have been synthesised by C–S bond formation and azide–alkyne cyclocondensation between [5-(aryl)-[1,3,4]oxadiazol-2-yl]methanethiol, propargyl bromide, and substituted aryl azides in one pot with an aim to explore their effect on the in vitro growth of microorganisms causing microbial infection. In vitro antibacterial activity was determined against four strains, namely Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa and antifungal activity against two fungal strains, namely Aspergillus niger and Aspergillus flavus.

A Facile Eco-Friendly One-Pot Five-Component Synthesis of Novel 1,2,3-Triazole-Linked Pentasubstituted 1,4-Dihydropyridines and their Biological and Photophysical Studies

An eco-friendly one-pot five-component synthesis of novel 1,2,3-triazole-linked pentasubstituted 1,4-dihydropyridines under ultrasonic and microwave irradiation in polyethylene glycol (PEG) 400 is described. All newly synthesised compounds were evaluated for antibacterial activity, antifungal activity, antioxidant activity, and photophysical properties. Antimicrobial activity was evaluated against six microbial strains. All compounds exhibited antifungal activity against Aspergillus niger and Aspergillus flavus and moderate antibacterial activity against Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis). Antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. All compounds showed good to moderate antioxidant activity. Furthermore all new compounds showed strong fluorescence in solution.

An efficient, green synthesis of novel regioselective and stereoselective indan-1,3-dione grafted spirooxindolopyrrolizidine linked 1,2,3-triazoles via a one-pot five-component condensation using PEG-400

An efficient synthesis of highly diversified novel functionalized indan-1,3-dione grafted spirooxindolopyrrolizidine linked 1,2,3-triazole conjugates via a one-pot, five-component condensation of indan-1,3-diones, aldehydes, sarcosine, N-propargylated isatin and azides using Cu(I) as a catalyst in PEG-400 as the reaction medium is reported. The reaction proceeds in a highly regio- and stereoselective manner involving a catalyst free Knoevenagel condensation followed by two successive 1,3-dipolar cycloaddition reactions. This protocol is suitable for aromatic, heteroaromatic and aliphatic aldehydes. In situ generation of azomethine ylides and their selectivity towards exocyclic double bonds result in highly functionalized molecular hybrids. All the compounds are obtained in high yield (6a–6s) and were characterized by spectroscopic methods.

A green, multicomponent, regio- and stereo-selective 1,3-dipolar cycloaddition of azides and azomethine ylides generated in situ with bifunctional dipolarophiles using PEG-400.

A series of novel dispiropyrrolidine-linked 1,2,3-triazole derivatives have been prepared by one-pot, four-component protocol that employed 5-arylidene-3-(prop-2-ynyl)thiazolidine-2,4-dione, isatin, sarcosine and substituted azides using Cu(I) generated in situ as catalyst in PEG-400 as a highly efficient and green media. This is the first report of a four-component reaction involving a classical Huisgen reaction, in which the two dipolar moieties (substituted azides and in situ generated azomethine ylides) react with acetylenic and olefinic dipolarophiles, respectively. The 1,3-dipolar cycloaddition proceeds in a highly regio- and stereo-selective manner. This methodology can be an ideal tool for the preparation of biologically important five-membered heterocyclic compounds in one pot.

Synthesis and biological evaluation of some functionalized 1H-1,2,3-triazole tethered pyrazolo[3,4-b]pyridin-6(7H)-ones as antimicrobial and apoptosis inducing agents

A series of novel molecular hybrids containing pyrazole, pyridinone and 1,2,3-triazoles have been synthesized by one-pot four-component reaction of Meldrum’s acid, substituted aryl azides, 4-(prop-2-yn-1-yloxy)aryl aldehyde and 3-methyl-1-phenyl-1H-pyrazol-5-amine using L-proline as a basic organocatalyst besides CuSO4.5H2O and sodium ascorbate as catalysts for click chemistry in PEG-400 as a highly efficient and green media. Apoptosis studies have been carried out on ovarian follicles of goat (Capra hircus) and in vitro antibacterial activity has been done against six strains namely Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa and antifungal activity against two yeast strains namely, Candida albicans and Saccharomyces cerevisiae.

Efficient Synthesis of Spiro[diindenopyridine-indoline]triones Catalyzed by PEG-OSO3H-H2O and [NMP]H2PO4

Abstract One-pot, three-component synthesis of spiro[diindenopyridine-indoline]triones has been reported via the reaction of 1,3-indandione, aromatic amines, and isatins with (PEG-OSO3H) as an efficient, polymeric acid surfactant–based catalyst in water and also in presence of acidic ionic liquid [NMP]H2PO4, which acts both as a medium and catalyst under conventional heating and ultrasonic irradiation. The reactions were complete in short reaction times with excellent yield of products. Surfactant-based PEG-OSO3H could be recycled and reused several times without any significant loss of activity. The compounds exhibit fluorescence in methanol with large Stokes shift. GRAPHICAL ABSTRACT