Synthesis of 2,10-Diphenyl-2H-pyridazino[4,5-b]quinolin-1-one and 2,3-Dihydro-9-phenyl-2-phenylamino-1H-pyrrolo[3,4-b]quinolin-1-one Derivatives as Peripheral-type Benzodiazepine Receptors Ligands

The reaction of 2-chloromethyl-3-ethoxycarbonyl-4-phenylquinoline with phenylhydrazine, afforded 2,3-dihydro-9-phenyl-2-phenylamino-1H-pyrrolo[3,4-b]quinolin-1-one derivatives 2 along with a major amount of 3-ethoxycarbonyl-4-phenylquinoline-2-carboxaldehyde phenylhydrazone 4a. The geometric isomers of phenylhydrazone 4a, displaying solvent-dependent E-Z isomerism, were isolated, characterized by H-1-nmr and mass spectra, and the Z-form easily cyclized to pyridazino[4,5-b]quinoline derivative 5a. Analogously, compounds 2b, 2c, 4b, 4c, 5b and 5c were obtained. The title compounds were tested as potential ligands for central and peripheral-type of benzodiazepine receptors, and the results are reported.