| abstract |
The present invention relates to a process for the preparation of sildenafil, i.e. 5- [2-ethoxy-5- (4-methylpiperazin-1-ylsulfonyl) phenyl] -1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole [4,3-d] pyrimidin-7 -one of formula (I), consisting in reacting 2-ethoxy-5- (4-methylpiperazin-1-ylsulfonyl) benzaldehyde of formula (II) with 4-amino-1-methyl-3-n-propylpyrazole-5 -carboxyamide of formula (III). The starting compound and the intermediate compound used in this process are new. |