Synthesis of 2-Substituted-2,3-dihydro-9-phenyl-1H-pyrrolo[3,4-b]quinolin-3-ones as Potential Peripheral Benzodiazepine-receptor Ligands

Two synthetic routes to the achievement of the title compounds are described. 2-Chloromethyl-3-ethoxycarbonyl-4-phenylquinoline (4) was transfomed into the corresponding lacton (5) which in two steps was converted into its isomeric lacton (7. Aminolysis of 7gave γ-hydroxyamide (8) which was in turn transformed into γ-chloroamide (9). Cyclization of 9 with sodium hydride in presence of oxygen led to the oxidized compound (10). while by carrying out the cyclization reaction under inert atmosphere, 2-benzyl-2,3-dihydro-9-phenyl-1H-pyrrolo[3,4-b]quinolin-3-one (3a) was obtained. Autoxidation of anion at 1-position of compound (3a) was considered to account for these results and a mechanistical interpretation was given. A simplier and more versatile route to obtain the title compounds was also developed. © 1994.