Method for synthesizing rolapitant intermediate

The invention discloses a method for synthesizing a rolapitant intermediate. The method comprises a recrystallization method for preparing a target product through recrystallization of 1,7-diazaspiro[4.5] decyl-2-ketone hydrochloride hydrate shown by a formula VIII into a target product; the salt compound shown by the formula VIII is suspended in an EtOH-isopropanol-water-HCl storage solution; heating and backflow are performed; until the clear solution is obtained; slow cooling is performed; when the clear solution starts to become turbid, inoculation, stirring and crystal growing are performed; a system subjected to the stirring and crystal growing is continuously cooled to 0 DEG C; then, vacuum suction filtration, washing and drying are performed to obtain the target product. The method provided by the invention has the advantages that the suction filtration is fast and convenient; the use time is short; the problem of time cost waste is solved.