Alkylation of phenothiazine (I) with 1-bromo-3-chloropropane (II) in the presence of NaH in DMF at room temperature afforded chloropropyl compound (III), and then reaction of this compound with 1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one (IV) and K2CO3 in refluxing dioxan yielded the title compound.