Patent ID: 7279581

Claim:
Process for preparing a pharmaceutically active compound, rizatriptan, or a pharmaceutically acceptable salt thereof, which comprises the following steps: a) Preparation of the diazonium salt of the aniline hydrochloride of formula (II) followed by reduction and acidification to give the hydrazine of formula (III): b) In situ reaction of the hydrazine hydrochloride of formula (III) with α-keto-δ-valerolactone, to give the hydrazone of formula (IV): c) Fischer indole reaction of the hydrazone of formula (IV), to give the pyranoindolone of formula (V): followed optionally by hydrolysis to give the product of formula (VI): d) Transesterification of the compound of formula (V) or esterification of its hydrolysis product of formula (VI), to give a compound of formula (VII): where R represents a straight or branched C1-C4 alkyl chain; e) conversion of the hydroxyl group of the compound of formula (VII) into dimethylamino, to give the indolecarboxylate of formula (VIII): where R has the same meaning as defined above; f) Saponification of the 2-carboalkoxy group of the compound of formula (VIII), to give the indolecarboxylic acid of formula (IX): g) Decarboxylation of the indolecarboxylic acid of formula (IX), to give rizatriptan, and eventually, the preparation of a pharmaceutically acceptable salt thereof.