5-Methyl-1H-indole-2,3-dione (12.85 g) in dry DMF (50 ml) at 0° to 5° C. was treated with sodium hydride (80% dispersion in mineral oil, 2.53 g). The mixture was allowed to warm to room temperature and after a further 10 minutes 1-(2-chloroethyl)-4-(phenylmethyl)piperazine (20 g) in dry DMF (70 ml) was added. The mixture was heated at 70° C. for 3 hours and then evaporated under reduced pressure. The residue was subjected to flash chromatography on silica gel to afford the title compound (17.75 g). Treatment with ethanolic HCl then gave 5-methyl-1-[2-[4-(phenylmethyl)-1-piperazinyl]ethyl]-1H-indole-2,3-dione dihydrochloride (16.8 g), m.p. 270°-275° C. (dec.).
