After dissolving 1.01 g of 1-(4-benzylpiperazin-1-yl)-7-chloroisoquinoline as synthesized in above Step 1 in 30 ml of tetrahydrofuran, 20 mg of palladium acetate, 48 mg of 2-(di-tert-butylphosphino)biphenyl, 450 mg of sodium-tert-butoxide and 5 ml of 2.0 M dimethylamine-tetrahydrofuran solution were added to the solution and sealed in a tube. This mixture was stirred at 80° C. for 16 hours. Removing the insoluble matter by filtration, the solvent was distilled off under reduced pressure and the residue was purified on silica gel column chromatography (methanol:chloroform=1:19) to provide 261 mg (25%) of 1-(4-benzylpiperazin-1-yl)-7-dimethylaminoisoquinoline.
