of Kufa for Chemical Sciences

Abstruct The present work included the synthesis of some new Schiff base derivatives of hydrazine hydrate coupled with ethyl-5-phenyl-2-(1,3,4-oxadiazole thiol) acetate, this role reacted with mercapto-acetic acid to synthesize five-membered ring heterocyclic compound derivatives. The yields of all synthesized compounds were good. All compounds were confirmed by their melting point, FT-IR spectra


Introduction
Oxadiazoles are a monocyclic ring system with multiple applications.Although the 1,3,4oxadiazole ring system was known in 1880, the proper study of its chemistry, structure, physicalproperties, and application of various derivatives began only in 1950 [1] ,N-containing heterocycles, especially five-membered rings, are of great interest as they are found in natural products [2] and used frequently in medicinal chemistry.There are three known isomers:1,2,4oxadiazole, 1,2,3-oxadiazole and 1,2,5-oxadiazole.Amongst oxadiazole isomers, 1,3,4oxadiazole derivatives are known to be the most stable [3].

General
The used chemicals were obtained from Sigma Aldrich.Melting points were recorded by Gallen-Kamp MFB-600 melting point apparatus.The FT-IR spectra were recorded on an FT-IR-8400S-Shimadzu spectrophotometer. 1 H NMR spectra were recorded on Bruker 400MHZ spectrophotometer (Germany), deuterated solvents (DMSO-d 6 ) were used for sample preparation, and tetramethylsilane TMS was used as an internal standard.

Synthesis of 5-phenyl-2-mercapto (1,3,4-oxadiazole) S2
A mixture of phenyl hydrazide (1 g, 0.007 mol) and an excess of carbon disulfide (2.5 mL) in absolute ethanol (25 mL) with an alkaline medium (potassium hydroxide 0.4 gm), The reaction was refluxed for 8 hrs.After checking the finish, all the H 2 S gas stopped by lead acetate was added drops of HCl 10% for neutralization of the base (the precipitate was filtered off and washed with water to afford the desired compounds (potassium chlorides salt) [16].
After that, the mixture was cooled down and the precipitated product was filtrated, washed with cold water, dried, and recrystallized from ethanol [19].

Synthesis of 4-thiazolidinone derivatives S14-S22
A mixture of Schiff bases S5-S13 (0.001mol) and excess of thioglycolic acid (0.002 mol) in ethanol was refluxed for 18-20 hrs.The solvent was evaporated and the residue was neutralized with 5% sodium bicarbonate solution to remove excess of thioglycolic acid.The formed precipitate was filtered, washed several times with distilled water and recrystallized from ethanol [20].

Results and discussion
This work includes synthesis of new heterocyclic ring derivatives