Microwave Assisted Synthesis of Some Novel Thiopyrano[2,3-b]quinolines as a New Class of Antimicrobial Agent

A series of novel substituted thiopyrano[2,3-b]quinolines 4a–e , 5a–e , and 6a–e were prepared from substituted 3-formyl-2-mercapto quinolines 2a–e , on reaction with ethyl acetoacetate, diethyl malonate, and ethyl cyanoacetate 3a–c by microwave irradiation in the presence of piperidine. Synthesized compounds were evaluated for antimicrobial activities. Among the compounds tested, 7-chloro-2-oxo-2H-thiopyrano[2,3-b]quinoline-3-carbonitrile 6d and 7-nitro-2-oxo-2H-thiopyrano[2,3-b]quinoline-3-carbonitrile 6e were highly active against S. aureus and M. roseus.

Keywords:

• Antimicrobial agent
• diethyl malonate
• ethyl acetoacetate
• ethyl cyanoacetate
• microwave irradiation
• thiopyrano[2,3-b]quinolines

The authors are thankful to Professor and Chairman, Department of Chemistry and Industrial Chemistry, Kuvempu University, Karnataka, India, for providing laboratory facilities. The authors are also thankful to the head, RSIC, Indian Institute of Science, Bangalore, for spectral data.