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.