Synthesis of Some Novel 2,4-Disubstituted Thiazoles as Possible Antimicrobial Agents

Abstract

A series of 4-aryl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3-thiazoles ( 6a–l ) and 4-substituted alkyl-2-(3-methyl-7-substituted quinoxaline-2-one-1-yl)-1,3-thiazoles ( 8a–i ) were synthesized in good yield by condensing 2-(3-methyl-7-substituted l,2-oxoquinoxalin-1(2H)-yl)ethanethioamides ( 5a–c ) with substituted phenacyl bromide and dichloroacetone followed by treatment with secondary amines, respectively. The intermediates, 5a–c were conveniently obtained by reacting phosphorus pentasulphide with 2-(3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetamides ( 4a–c ) which in turn were synthesized from ethyl (3-methyl-7-substituted-2-oxoquinoxalin-1(2H)-yl) acetates ( 3a–c ) by aqueous ammonia treatment. The newly synthesized compounds were characterized by IR, ¹ H NMR, ¹³ C NMR, and Mass spectral and elemental analyses. These compounds were screened for in vitro antibacterial activity against five pathogenic strains and antifungal activity against four fungi. Preliminary results revealed that some of the synthesized compounds showed promising antimicrobial activity.

Keywords:

• 2,4-Disubstituted thiazoles
• 3,7-Dimethyl quinoxalines
• antibacterial
• antifungal activity
• phenacyl bromide

Acknowledgments

The authors are grateful to the Head, SAIF, CDRI, Lucknow and the Head, NMR Research Centre IISc, Bangalore for providing NMR and mass spectral data. They are also thankful to the Heads of Department of Chemistry, NITK, Department of Biochemistry, KSHMA, Strides Research and Specialty Chemicals Ltd, Mangalore for providing necessary laboratory facilities.