Pseudopolymorphism and phase stability of 7-piperidino-1,2,3,5-tetrahydroimidazo-[2,1-b]quinazolin-2-one (DN-9693)

The phase stabilities of three pseudopolymorphs of DN-9693 were studied by using thermogravimetry and differential thermal analysis. The thermal dehydration of DN-9693·2HCl·H₂O proceeds by the mechanism of two-dimensional growth of nuclei. The thermal dehydration of 0.5 mol of H₂O per mol of DN-9693·2HCl·2H₂O, and that of 2 mol of H₂O per mol of DN-9693·2HCl·3H₂O, proceed by the mechanisms of three-dimensional diffusion and three-dimensional phase boundary reaction, respectively, but the dehydration followed overlaps with the thermal elimination of HCl. The half-lives for the dehydration at 25°C show that DN-9693·2HCl·H₂O is the most stable form.