Synthesis of some disubstituted 1,2,4-oxadiazoles and furazans

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Abstract
No Beckmann rearrangement occurs when ω-chlorophenylglyoxime is treated with phosphorus pentachloride, and the steam-volatile product is 3-chloro-4-phenylfurazan (II; R = Cl), not, as previously reported, 3-chloro-5-phenyl-1,2,4-oxadiazole (I; R = Cl). The reported conversion of dialkyl benzoyliminothiocarbonates (III) into 3-phenyl-5-alkoxy-1,2,4-oxadiazoles by hydroxylamine has been confirmed, and the oxadiazolone (V) has been prepared by cyclodehydration of the urea (VI; R = Me). 3-Hydroxy-5-phenyl-1,2,4-oxadiazole (I; R = OH) has been prepared similarly from the urea (VI; R = H) and also from the amine (I; R = NH2). Dialkyl benzoyliminodithiocarbonates (VII) react with hydroxylamine to give 3-alkylthio-5-phenyl-1,2,4-oxadiazoles. The sulphide (I; R = SEt) is converted by hydrogen peroxide into the sulphoxide (I; R = SOEt) and by permanganate into the sulphone (I; R = SO2Et). The sulphone (I; R = SO2Et) reacts with sodium hydroxide to give 3-hydroxy-5-phenyl-1,2,4-oxadiazole. The thiourea (VIII) is converted by sulphuric acid into the disulphide (IX).

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