Synthesis and Ring Opening Reactions of Tetrahydroimidazo[1,5- b ][1,2,4]oxadiazol-2(1 H )-thiones

Abstract

Dipolar cycloaddition of imidazoline 3-oxides 1 with methylisothiocyanate proceeds regio-and diastereoselectively to give tetrahydroimidazo[1,5-b][1,2,4]oxadiazol-2(1H)-thiones 3 in high yields. The cis configuration of the adducts was proved by our double cis elimination test as well as by NOESY experiments. Adducts 3a-c undergo ring opening at reflux in acetonitrile to give imidazoles while 3d-e undergo retro dipolar cycloaddition to give the starting nitrones 1d-e. The imidazooxadiazol-2-thiones 3a-e were treated with concentrated HCl in ethanol at 50 • C to give the corresponding 4H-[1,2,4]oxadiazole-5-thione only in cases in which the substituent at C-6 is an aryl.

Supramolecular architecture of phenylcarbamoylated acetone oxime 1,1-diisopropyl-3-phenylurea] complex

“…Although examples of 2-substituted-1,2,4-oxadiazolidin-5-ones and -thiones [3][4][5][6] and tetrahydroimidazo [1,5-b] [1,2,4]oxadiazol-2(1H)-ones [7,8] and thiones [9,10] are known in the literature, examples of 2-unsubstituted-1,2,4-oxadiazolidin-5-ones are absent. Lycoposerramine-A, is a recently reported alkaloid which has a 4-unsubstituted-1,2,4-oxadiazolidin-5-one residue in the molecule [11].…”

A green synthesis of nitrones from diamino glyoxime using aldehydes and ketones

“…Thermal cycloaddition reactions of nitrones with multiple bond systems is an efficient strategy for providing various heterocyclic five-membered ring systems [2][3][4][5]. On the other hand, they are source of new heterocyclic compound via ring opening reactions [6][7][8]. Under facial concerted [ g 4 s ?…”