Condensation of 5-nitroindole (I) with 1-methyl-4-piperidone (II) in the presence of KOH produced tetrahydropyridinyl indole (III). Subsequent catalytic hydrogenation of (III) over Pd/C gave the 5-amino-3-piperidinylindole (VI). In a related procedure, 5-aminoindole (IV) was condensed with piperidone (II), and the resulting tetrahydropyridine (V) was hydrogenated to yield (VI). Aminoindole (VI) was finally condensed with 4-fluorobenzoyl chloride (VII) to produce the corresponding amide, which was isolated as the fumarate salt.
Acylation of 4-nitroaniline (I) with 4-fluorobenzoyl chloride (II) affords benzanilide (III). Catalytic hydrogenation of the nitro group of (III) employing Pt/C then gives amine (IV). Diazotization of (IV), followed by reduction with SnCl2 leads to hydrazine (V). Reaction of 5-chloro-2-pentanone (VI) with dimethylamine yields the amino ketone (VII). Finally, the title compound is obtained by Fisher indole synthesis from aryl hydrazine (V) and ketone (VII) under acidic conditions.