Mononuclear heterocyclic rearrangements. Part 11. Rearrangements of 1,2,4-oxadiazoles, isoxazoles, and 1,2,5-oxadiazoles involving a sulphur atom

Abstract

The reactions of 3-amino-5-methyl- and 3-amino-5-phenyl-1,2,4-oxadiazoles, 3-amino-5-methylisoxazole, and 3-amino-4-methyl- and 3-amino-4-phenyl-1,2,5-oxadiazoles with phenyl isothiocyanate have been investigated, and the reactivity of phenylthioureido-derivatives (3) of these ring systems towards rearrangement have been studied. The presence of a sulphur atom in the side-chain sequence (1; XYZ = NCS) greatly enhances the reactivity of the systems under consideration towards rearrangement. The tendency of the three heterocycles to rearrange decreases in the order 1,2,4-oxadiazole > isoxazole > 1,2,5-oxadiazole.