Synthesis of new quinoline derivatives as antimicrobial agents

2-hydroxy quinoline-4-hydrazide was condensed with carbon disulfide in ethanolic KOH on cold and by refluxing, the former condition gave 1,3,4-thiadiazoyl-quinoline derivative [II], while the second gave 1,3-4-oxadiazolyl-quinoline derivative [IV]. Reaction of [IV] with formaldehyde and some secondary amines realized Mannich reaction at oxadiazolyl nitrogen moiety. Also, alkyl halides reacted with [IV] and gave S-alkyl derivatives. Replacement of S-alkyl radical by N-R group was also successful via interaction of [VI] with amines. Reaction of [IV] with monochloroacetic acid afforded the S-acetic acid derivative [VII], which on condensation with ethylenediamine gave the tricyclic compound [VIII]