The reaction of 3,4-dimethoxyphenylacetic acid (I) with SOCl2 in methylene chloride gives the corresponding acyl chloride (II), which is treated with aminoacetaldehyde dimethylacetal (III) and triethylamine in methylene chloride yielding N-(2,2-diethoxyethyl)-3,4-dimethoxyphenylacetamide (IV). The cyclization of (IV) by means of HCl in acetic acid atfords 7,8-dimethoxy-1,3-dihydro-2H-3-benzazepin-2-one (V), which is alkylated with 1-bromo-3-chloro propane (VI) by means of potassium tert-butoxide in DMSO to give 3-(3-chloropropyl)-7,8-dimethoxy-1,3-dihydro-2H-3-benzazepin-2-one (VII). The reaction of (VII) with N-methyl-2-(3,4-dimethoxyphenyl)ethylamine (VIII) at 100 C affords 7,8-dimethoxy-3-[3-[N-methyl-N-[2-(3,4-dimethoxyphenyl)ethyl]amino]propyl]-1,3-dihydro-2H-3-benzazepin-2-one (IX), which is finally hydrogenated with H2 over Pd/C in acetic acid.