Structure–activity relationship studies on 4-(4-(4-chlorophenyl)-1, 4-diazepan-1-yl)-1-(4- fluorophenyl) butan-1-one (SYA 013), a homopiperazine analog of haloperidol has resulted in an understanding of the effect of structural modifications on binding affinity at dopamine and serotonin receptor subtypes. Further exploration, using bioisosteric replacement strategies has led to the identification of several new agents including compounds 7, 8, 11 ...