Design, synthesis, and discovery of 3-piperazinyl-3,4-dihydro-2(1H)-quinolinone derivatives: a novel series of mixed dopamine D2/D4 receptor antagonists

3-Piperazinyl-3,4-dihydro-2(1H)-quinolinone derivatives (δ-lactams) were designed, synthesized, and identified as a new series of mixed dopamine D2/D4 receptor antagonists. To further the structure–activity relationship (SAR) study, 3-piperazinyl-indolin-2-ones (γ-lactams) and 3-piperazinyl-3H,4H,5H-benzo[f]azepin-2-ones ( -lactams) were also prepared and examined.