Abstract

Synthesis of Sildenafil by the O-alkylation of 5-[2-hydroxy-5-(4-methylpiperazin-1-ylsulphonyl)phenyl]-1- methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo-[4,3-d]pyrimidin-7-one 8 proved difficult because concomitant alkylation of the pyrimidine moity also occurred. The selective O-alkylation was carried by DCC assisted decarboxilative etherification of the carbonate 9.

Keywords: Decarboxilative etherification, sildenafil citrate, process impurities, piperazine, cyclic guanosine monophosphate, phenol, O-alkylation, silica gel, chromatography, alkylarylcarbonates