الفهرس 
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Abstract
The aim this part was to discuss the ptropetries and the methods for the synthesis of the five membered ring comopounds having three hetero atoms tw nitrgen and one oxygen or sulfur in the ring Generally methds for he synthesis of the 1,3,4 oxadiazole ring could be divided into two groups according to the starting meterial the first grup makes use of such a ring the react with synthons introducing to that structure another carbaon atom the most popular synthns here are aromatic aldehydes carboxylic acids and orthoesters.