Synthesis of potent antibacterial agents derived from 5-[1-(phenylsulfonyl) piperidin-4-yl]-1,3,4-Oxadiazol-2-thiol

Due to pharmacological importance of 1,3,4-Oxadiazole derivatives, a new series of Ssubstituted derivatives, 4a-v, of 5-[1-(phenylsulfonyl)piperidin-4- yl]-1,3,4-Oxadiazol-2-thiol (1) was synthesized. The reaction of benzenesulfonyl chloride with ethyl isonipecotate yielded ethyl 1-(phenylsulfonyl)piperidin-4- carboxylate (1), which was further converted into 1-(Phenylsulfonyl) piperidin-4-carbohydrazide (2) by hydrazine hydrate and then 2 into 5-[1-(phenylsulfonyl)piperidin-4-yl]-1,3,4-Oxadiazol-2-thiol (3) in the presence of CS2 along with KOH. The target compounds (4a-v) were synthesized by treating 3 with various electrophiles in DMF and NaH. The proposed structures of compounds, 4a-v, were corroborated through IR, ¹H-NMR & EI-MS spectral data. Further these were evaluated for antibacterial activity against Gram-positive and Gram-negative bacteria. It was observed that the substitution at sulfur of thiol group influenced the antibacterial activity significantly and so varied from moderate to excellent level.