Reaction of 2 , 5 - Disubstituted - l , 3 , 4 - oxadiazoles

Some 5-aryl-2-mercapto-1,3,4-oxadiazole (I) reacted with maleic anhydride, maleic acid and p-benzoquinone affording 2-(5-aryl-1,3,4-oxadiazol-2-ylthio)succinic anhydrides (II), 2-(5-aryl-1,3,4-oxadiazol-2-ylthio)succinic acids (III) and 2-(2,5-dihydroxyphenylthio)-5-aryl-l,3,4-oxadiazoles (IV), respectively. Treatment of 2-methylthio-5-phenyl-l,3-oxadiazole (V) with amines gives 2-[(alkyl or aryl)-amino]-5-phenyl-l,3,4-oxadiazoles (VI). Compound VIe condensed with aromatic aldehydes to give 2-(4-cinnamoylanilino)-5-phenyl-l,3,4-oxadiazoles (VII) which on bromination afforded the dibromo derivative VIlI and on treatment with hydroxylamine afforded 2-[4-(5-aryl-2-isoxazolin-3-yl)anilino]-5-phenyl-1,3,4-oxadiazoles (IX). Reacting VII with hydrazine hydrate gave 2-[4-(5-aryl-2-pyrazolin-3-yl)anilino]-5-phenyl-l,3,4-oxadiazoles (X), while on treatement VII with acetylacetone and ethylacetoacetate afforded 2[4-(4-acetyl or carbethoxy-5-phenyl-l-cyclohexen -3-one-1-yl)anilino]-5-phenyl-l,3,4-oxadiazoles (XIIa, b), respectively.