Synthesis Characterization and Stereostructures of the Pyridazino[6,1-b]Quinazolinones

The title compounds pyridazino[6,1-b]quinazolinones wereprepared in five steps from succinic anhydride in good yield withoutthe need for chromatography. the barrier to rotation around the n-nbond and concurrent ring-inversion in 7 and 15, was so low at roomtemperature by comparison with 3-diacylaminoquinazolinone. thepreferred geometries have been determined by a hartree-fock anddensity function theory calculation [rhf/6-31g**(d), b3lyp/6-311g**(d)].