Abstract

Background: Thiazolidine compounds are known to show interesting pharmacological activity. In particular, they are used as antiseizure, fungicidal, anti-bacterial, antitubercular, antiinflammatory, antiamoebic, anti-diabetic and local anesthetic agents. Some of these compounds have also shown antiparkinsonism, antioxidant, anticonvulsant, hypoglycemic and non-narcotic analgesic activities. On the other hand, pyrazoles have shown antibacterial, antitumor, antiviral, antifungal, anti-tubercular, antiparasitic, anesthetic, anti-diabetic, anti-inflammatory, analgesic and insecticidal activities. In order to improve the pharmacological effects of thiazolidine-4-ones, new pyrazole derivatives have been synthesized.

Material and Methods: A mixture of pyrazolcarbaldehydes, anilines, thioglycolic acid and DSDABCOC was stirred at room temperature for the required reaction times. The progress of the reaction was monitored by TLC (EtOAc: petroleum ether 1:3). After completion of the reaction as indicated by TLC, the ionic liquid was separated by extraction with 2×15 mL of water. The solid residue was separated by column chromatography. The product was recrystallized from EtOH. The pure products were collected in 82-92% yields.

Results: In continuation of our ongoing studies to synthesize heterocyclic and pharmaceutical compounds under mild and practical protocols, we wish to report herein our experimental results on the ultrasound promoted synthesis of 2-pyrazolo-3-phenyl-1,3-thiazolidine-4-ones using various synthesized pyrazolecarbaldehydes, anilines and thioglycolic acid at room temperature. The results illustrated that ionic liquid DSDABCOC certainly improved the yield of the products and reduced the reaction time.

Conclusion: In conclusion, we have developed an efficient and simple protocol for the synthesis of novel pyrazolo-1,3-thiazolidine-4-ones using DSDABCOC as an ionic liquid. The easy workup together with the use of inexpensive, reusable and eco-friendly ionic liquid is the notable feature of this novel procedure. To the best of our knowledge, this is the first report of the synthesis of a new library of 1,3-thiazolidine-4-ones bearing a pyrazolyl moiety that enhances the biological activity under solvent-free conditions.

Keywords: One-pot reaction, 1, 3-thiazolidine-4-one, thioglycolic acid, ionic liquid, effective media.