In loving memory of my grandfather, S. J. Jalani
An efficient one-pot synthesis of 1,2,4-oxadiazol-3-amines from simple starting materials,
isothiocyanates, amidines/guanidines, and hydroxylamine, is described. The reaction
is facilitated by metallic-thiophile-assisted desulfurization of in situ formed amidino-
or guanidinothiourea to give chemoselectively N-hydroxyguanidine intermediates that give exclusively various 1,2,4-oxadiazol-3-amines
in good to excellent yields. The reaction mechanistic pathway may proceed through
an intramolecular 5-exo-trig cyclization.
Key words
1,2,4-oxadiazol-3-amine - metallic thiophile - chemoselectivity -
N-hydroxyguanidine