Secondary Amine Mediated Ring-Opening of Tetrahydroimidazo[1,5- b ][1,2,4]oxadiazol-2(1 H )-ones


Abstract: 5,6,7,7a-Tetrahydroimidazo [1,5- b ][1,2,4]oxadiazol-2(1 H )-ones 1a-g converted to imidazoles in the presence of secondary amines. cis-Imidazooxadiazolones 1d-g gave the imidazoles 4d-g when treated with secondary amines, while the treatment of these compounds with tertiary amines afforded imidazoline 3-oxides 5d-g. In case of 1a-c, where R^1 is a hydrogen, tertiary amines induced elimination to give imidazoles 4a-c. In the case of 1a-c, probable trans elimination caused by triethylamine and pyridine and in the case of 1d-f, a concerted double cis elimination mediated by secondary amines is discussed.


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