Processes for preparing and purifying carbostyril compounds such as aripiprazole and 7-(4-halobutoxy)-3,4-dihydro-2(1H)-quinolinones

An improved process for preparing aripiprazole (7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butoxy}-3,4-dihydro-2(1 h)-quinolinone) or a pharmaceutically acceptable salt thereof wherein the first step comprises reacting 7-HQ with a 1,4-disubstuted-butane in a single-phase solvent and in the presence of a base or in a water-immiscible organic solvent optionally with addition of substantial amount of water to form an heterogeneous biphasic reaction mixture, in the presence of a water-soluble base and optionally a tetra-alkyl ammonium phase transfer catalyst and a reaction promoter, for a period of time sufficient to completely convert 7-HQ to a 7-(4-halobutoxy)-3,4-dihydro-(1H)-quinolinone (7-HBQ);

• and the second step comprises reacting a 7-HBQ and 1-(2,3-dichlorophenyl)piperazine or an acid addition salt thereof preferably in a biphasic reaction mixture that comprises water and a water-immiscible solvent, in the presence of a water-soluble base and optionally also a phase transfer catalyst and a reaction promoter.