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

A series of novel substituted thiopyrano2,3-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-thiopyrano2,3-b]quinoline-3-carbonitrile 6d and 7-nitro-2-oxo-2H-thiopyrano2,3-b]quinoline-3-carbonitrile 6e were highly active against S. aureus and M. roseus.