2,4-diaminothiazoles: Tautomeric structures and acetylation-substitution studies

NMR investigations on the hydrohalides of 2,4-diaminothiazole, 1, and on its 5-methyl and 5-phenyl derivatives, 2 and 3 respectively, show that they exist as a single nonaromatic tautomer with C-5 tetrahedral. This is also true for the free base 1, whereas 3 has C-5 trigonal. The di- and triacetyl derivatives of 1–3 are shown to be N,N′-di- and N,N,N′-triacetyl derivatives. Ethyl 2-cyano-3-ethoxyacrylate and 2-cyano-3-ethoxyacrylonitrile react with 1 at C-5.