STRUCTURES OF 3,4-TETRAHYDRO-6H-PYRIMIDO[2,1-B]-QUINAZOLIN-6-ONE AND ITS HYDROCHLORIDE

C11H11N3O, m.p. 243 degrees C, P2/n, Z = 4, a = 5.843(2), b = 14.241(3 ), c = 11.102(1)Angstrom, beta = 93.30(2)degrees, R = 0.046; C11H11N3O .HCl.H2O, Pca2(1), Z = 8, a = 18.640(2), 6 = 8.894(2), c = 14.404(2)An gstrom, R = 0.062. The molecules of the free base are in 1H-tautomeric form. N(1)-H N(11) hydrogen bonds join molecules of the free base int o dimers, which enable tautomeric rearrangement (not observed in this study) also in the solid state without any changes in molecular packin g. The quinazoline system deviates slightly from planarity and benzene pi electrons are partially localized at C(7)-C(8) and C(9)-C(10) bond s as seen from their lengths of about 1.375 Angstrom, while other bond s in the benzene ring are at least 0.02 Angstrom longer.