Synthesis of New 2-(Aminomethyl)-4-phenylpyrrolo[1,2-a]-quinoxalines and their Preliminary In-vivo Central Dopamine Antagonist Activity Evaluation in Mice

In the search for antipsychotic agents that are not associated with extrapyramidal side effects, efforts have been focused on finding selective D4‐receptor antagonists and investigating their pharmacology. Our laboratory has developed a synthesis program for new pyrroloquinoxalines with therapeutic potential. We have described the synthesis of some new pyrroloquinoxalines with substituted arylpiperazino or aryltetrahydropyrido chain at position 3 of the quinoxaline ring (2‐(4‐phenylpiperazin‐1‐ylmethyl)‐4‐phenylpyr‐rolo[1,2‐a]quinoxalinium oxalate (3a), 2‐[4‐(2‐methoxyphenyl)piperazin‐1‐ylmethyl]‐4‐phenylpyrrolo[1,2‐a]quinoxalinium oxalate (3b), 2‐[4‐(3‐trinuoromethylphenyl)piperazin‐1‐ylmethyl]‐4‐phenylpyrrolo[l,2‐a]quinoxalinium oxalate (3c), 2‐[4‐(4‐chlorophenyl)piperazin‐1‐ylmethyl]‐4‐phenylpyrrolo[1,2‐a]quinoxalinium oxalate (3d), 2‐(4‐pyridin‐2‐ylpiper‐azin‐1‐ylmethyl)‐4‐phenylpyrrolo[1,2‐a]quinoxalinium oxalate (3e), and 2‐(4‐phenyl‐1,2,3,6‐tetrahydropyridin‐1‐ylmethyl)‐4‐phenylpyrrolo[1,2‐a]quinoxalinium oxalate (3f)). A preliminary pharmacological study of these products was conducted using climbing behaviour induced by apomorphine (2.5 mg kg−1, s.c.) in mice. The derivatives were administered intraperitoneally 30 min before apomorphine. Haloperidol, chlorpromazine and clozapine were used as references. Among this series, 3b, 3c and 3f revealed a central dopamine antagonist activity. The most active derivative was 3b, which exhibited a profile relatively close to clozapine.