Oxadiazoles saturated

Figure 3 Typical IR spectra (wave numbers, KBr) for saturated 1,2,4-oxadiazoles. Source <6IAP(294)765,...

The belief that ring transformations of 1,2,4-oxadiazoles require an vinyl substituent in the 3-position had to be abandoned when it was found that compounds like (47) with saturated side chains undergo smooth ring transformation to 4,5-dihydropyrazoles (Scheme 16) <79JCR(S)64, 79JCR(M)801>. 

Oxadiazoles are numbered by designating the heteroatoms as shown in Scheme 1. The position of the double bond in partially reduced rings is designated as A2- or A4- with the terminal ending -oline. The fully saturated ring is described by the terminal ending -olidine. Substituents may be referred to as occupying positions C-3 (R), N-4 (R ) or C-5 (R"). 

The oxadiazole ring was added onto 1 on stirring a saturated solution in methanol with sodium nitrite and hydroxylamine hydrochloride to give dioxime 235. On treatment with sodium carbonate it gave furazan oxide... 

A base-induced conversion of 1,2,4-oxadiazoles to isoxazolines has been found to occur via a three-atom rearrangement that involves a saturated CCO side chain at C(3) of the oxadiazole. ... 

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