Abstract The structures of imidazo [1, 2-c] quinazolines were reexaminated and established by spectroscopic studies with the aid of high-field 1 H and 13 C nmr and mass spectra. In acidic media, 3 reacts to give the products of electrophilic substitution reaction and ring opening compound 5, leading to the imidazo [1, 2-c] benzo [e]-[1, 2, 3] triazine ring.