Davinder Prasad

DBSA catalyzed, one-pot three-component “on water” green protocol for the synthesis of 2,3-disubstituted 4-thiazolidinones

A simple and environmentally benign one-pot three-component tandem synthesis of a series of novel 4-thiazolidinones has been accomplished “on water” by reacting aliphatic or aromatic primary amines with thioglycolic acid and a wide range of aromatic aldehydes at ambient temperature using p-dodecylbenzenesulfonic acid (DBSA) as a Bronsted acid-surfactant combined catalyst. The unique ability of the catalyst has been utilised to form emulsion droplets with organic substrates in aqueous medium whose interior core is hydrophobic enough to exclude the water molecules generated during the rate limiting dehydration step of the reaction. This protocol worked well with a variety of substrates and the desired products were obtained in fairly good yields.

PEG–SO3H catalyzed, environmentally benign synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions

A highly efficient, eco-friendly and high yielding procedure for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes has been developed through one-pot condensation reaction of β-naphthol with various aromatic aldehydes in the presence of a catalytic amount of sulfonated polyethylene glycol 6000 (PEG–SO3H) as a stable, recyclable and bio-degradable polymeric catalyst under solvent-free conditions. This protocol was found to be applicable to obtain a diverse range of dibenzoxanthene derivatives in 82–98% isolated yields and the catalyst was recycled for four cycles.

Design, synthesis and antimicrobial evaluation of novel 2-aryl-thiazolidin-4-one derivatives

Novel 2-arylthiazolidin-4-one derivatives (8a-q and 11) have been synthesized in good-to-excellent yields (70-96%) by one-pot three-component condensation-cyclization reaction of aromatic or aliphatic primary amines, aromatic aldehydes, and thioglycolic acid in polypropylene glycol at 110°C temperature. The in vitro antimicrobial activity of the synthesized 2-arylthiazolidin-4-ones was investigated against a panel of six pathogenic fungal strains, a Gram-positive and three Gram-negative bacteria. Results revealed that the compounds (8a-d) bearing 3-(4-(1H-imidazolylmethyl)phenyl)-substituent displayed significant antibacterial efficacy specifically against Klebsiella pneumoniae (minimum inhibitory concentration 12.5 μg/mL). In addition, some of the synthesized compounds have also shown antimicotic activity against Sporothrix schenckii, Trichophyton mentagrophytes, and Aspergillus fumigatus at the concentration of 50 μg/mL. Graphical abstract A series of novel 2-arylthiazolidin-4-one analogues was prepared and assessed for their in vitro antimicrobial efficacy. Some of the synthesized compounds displayed significant antibacterial efficacy against Klebsiella pneumoniae and selective antimycotic activity against Trichophyton mentagrophytes.