7-​[4-​(4-​Benzo[b]​thien-​4-​yl-​1-​piperazinyl)​butoxy]​-​1-​[4-​[(1,​2,​3,​4-​tetrahydro-​2-​oxo-​7-​quinolinyl)​oxy]​butyl]​-2(1H)​-​quinolinone is an intermediate in synthesizing O-[4-((2-Oxo-1,2-dihydroquinolin-7-yl)oxy)butyl] Brexpiprazole (O855355), a derivative of Brexpiprazole (B677385) which is a drug candidate useful in treatment and prevention of mental disorders including CNS disorders.