Ethyl 2-amino-4-tert-butyl-1,3-thiazole-5-carboxylate and 6-methylimidazo[2,1-b]thiazole-2-amino-1,3-thiazole (1/1).

The structure of ethyl 2-amino-4-tert-butyl-1,3-thiazole-5carboxylate, C10H16N2O2S, (I), and the structure of the 1:1 adduct 6-methylimidazo[2,1-b]thiazole±2-amino-1,3-thiazole (1/1), C6H6N2S C3H4N2S, (II), have been determined. The molecules in (I) associate via a hydrogen-bonded R2(8) dimer consisting of NÐH N interactions, with the hydrogenbonding array additionally involving NÐH O interactions to one of the carboxylate O atoms. The 2-aminothiazole molecules in (II) also associate via an NÐH N hydrogenbonded R2(8) dimer, with an additional NÐH N interaction to the Nsp atom of the imidazothiazole moiety, creating hydrogen-bonded quartets.