PRODUCTION OF PYRAZOLO[4,3-D]PYRIMIDIN-7-ONES AND THEIR INTERMEDIATE

PROBLEM TO BE SOLVED: To obtain the subject compound useful as a therapeutic agent for male erection function incompetence, etc., more advantageously than a conventional method by using a new intermediate and carrying out a substitution reaction and a ring closure in the same container so as to reduce synthesis processes. SOLUTION: A compound of formula I (X is a leaving group) is reacted in the presence of a compound of the formula, OCH2CH3 to give the objective compound of formula II (sildenafil). Or the compound of formula III is reacted in the presence of a compound of the formula, OHCH2CH2CH3 to give the objective compound of formula IV. Preferably the reaction is carried out in the presence of an auxiliary base. A tertiary 4-6C alcohol metal salt such as Na salt of t-butanol, etc. are preferable as the auxiliary base. The intermediates of formulas I and III are new compounds. The intermediate of formula I is obtained by reacting a reaction product between chlorosulfonic acid and a substituted benzoic acid with N-methylpiperazine to give a new intermediate and reacting the intermediate with 4-amino-1-methyl-3-propyl-1H-pyrazole-5- carboxamide.