Abstract: A method for preparing pyrazolopyrimidinone derivatives and their pharmaceutically acceptable salts having efficacy on the treatment of impotence, one of male sexual dysfunctions. The method comprises the steps of: a) chlorosulfonating a pyrazolamide compound to obtain a chlorosulfonated compound; b) reacting the chlorosulfonated compound of step (a) with a primary amine to obtain a sulfonamide compound and c) performing an intramolecular cyclization of the sulfonamide compound of step (b) to produce the compound of formula below 1, wherein the steps b) and c) are performed in situ in alcohol by adding a base to the reaction mixture without workup after the step b) is completed.

Abstract: The present invention relates to the method for preparing pyrazolopyrimidinone derivatives and their pharmaceutically acceptable salts having efficacy on the treatment of impotence, one of male sexual dysfunctions. The method according to the present invention comprises the steps of chlorosufonation the pyrazolamide, followed by amination with amine and intramolecular cyclization. The method provides the pyrazolopyrimidinone derivatives and their pharmaceutically acceptable salts with high yield and in an economic manner.