Methods for preparing brexpiprazole intermediate and brexpiprazole with cheap metal copper

Methods for preparing a brexpiprazole intermediate and brexpiprazole with cheap metal copper are disclosed. The method for preparing the brexpiprazole intermediate includes dissolving 4-halogen benzo[b]thiophene and piperazine into a solvent under nitrogen protection, and adding an alkali, a ligand and a copper-based catalyst; stirring and reacting the mixture until TLC detection shows that the reaction is finished; after the reaction is finished, subjecting the system to extraction with ethyl acetate or dichloromethane; combining organic phases, and spin-drying the mixture; adding methanol todissolve solid; adding dropwise a hydrochloric acid methanol solution with a concentration of 2M to adjust the pH to 1-7 so that a target product forms a salt and then is precipitated; performing suction filtration to obtain white solid; and drying the white solid to obtain 4-piperazinyl benzothiophene hydrochloride. The methods have advantages of few side reactions, high product quality, low production cost, and the lik