Secondary amine mediated ring-opening of tetrahydromidazo[1,5-b] [1,2,4]oxadiazol-2(1H)-ones

Abstract

5,6,7,7a-Tetrahydroimidazo [1,5-b][1,2,4]oxadiazol-2(1H)-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 arnines 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.