Microwave Assisted Heterocyclization : A Rapid and Efficient Synthesis and Antibacterial Activity of Novel Thiazolidinones

As a target to synthesize various Thiazolidinone derivatives, 2-Amino-4(coumarin-3-yl)-thiazole has been prepared by the reactions of 3-Bromo acetyl coumarin with thiourea. 3-Bromo acetyl coumarin was prepared from 3-Acetyl coumarin. The resulting compound 2-amino-4-(coumarin-3-yl)thiazole was treated with different Aldehydes to give the intermediate Schiff base, which on further reaction with Thioglycolic acid and Thiolactic acid to give titled compound Thiazolidinone. The structures of the compounds have been confirmed by elemental analysis and spectral analysis. The antibacterial activity of the compounds has also been screened against Staphylococcus aureus and Escherichia coli.


I Introduction ntroduction
A survey of literature reveals that Thiazolo Coumarins posses a broad spectrum of biological importance.Thiazolo Coumarin derivatives are well known biologically active compounds.Schiff bases from 2-Amino-4-(coumarin-3-yl)-thiazole and various Aldehydes are reported to have significant antibacterial activity.These derivatives have been reported as bacteriostatic 1 and fungisidic 2 .Schiff Base gives good antimicrobial activity and pharmacological applications 3 and it can be prepared by the acid catalyzed reaction of amines & Ketones or Aldehydes.It gives a good fungicidal activity 4 .4-Thiazolidinones gives good pharmacological properties 5 .4-Thiazolidinones are known to exhibit antitubercular 6 , antibacterial 7 , anticonvulsant 8 , antifungal 9 , and antithyroid activities.
The application of microwave irradiation (MWI) to organic synthesis has been the focus of considerable attention in recent years and is becoming an increasingly popular technology 10 .The salient features of the microwave approach are rapid reaction rates, cleaner reaction conditions and enhancements in chemical yields [11][12] .
Under the framework of "Green Chemistry" we have developed an environmentally benign synthesis of Thiazolidinones.Further attractions of this method are that it allows reactions in open vessels (thus avoiding the risk of high pressure development) and synthesis on preparative scale 13 .Herein we wish to report a facile microwave synthesis of Thiazolidinone from 2-Amino-4-(coumarin-3yl)-thiazole and various aldehydes using DMF as a reaction mediator.
Different Aldehydes were condensed with 2-Amino-4-(coumarin-3-yl)-thiazole to yield Schiff base.The Schiff bases were further reacted with Thioglycolic acid and Thiolactic acid to yield Thiazolidinone derivatives

Experimental Experimental
All the melting points were determined on a PMP-DM scientific melting point apparatus and are uncorrected.IR spectra were recorded with KBr on Shimatzu FT-IR 8300 spectrophotometer.Reactions were carried out in a "QPro "QPro--M Modified Microwave System" M Modified Microwave System" made in CANADA.

ANTIBACTERIAL ACTIVITY:
This part deals with the in-vitro screening of newly synthesized compounds for their antimicrobial activity for filter paper disc method at a concentration of 50 ìg; the species, Staphylococcus aureus and Escherichia coli have been taken for the antibacterial activity.The compounds possess moderate to good activity against all stains in comparison with ampicillin, penicillin and tetracycline against Escherichia coli and Staphylococcus aureus.(Table Table --2 2.
Structures of compounds synthesized have been elucidated by elemental analysis & IR measurements.