초록 ▼

PROBLEM TO BE SOLVED: To obtain the subject compound especially useful in the therapy of male erectile function insufficiency and having a purity sufficient for administration to man by subjecting a specific bisamide to a ring-closing reaction. SOLUTION: This method for producing sildenafil of formu

PROBLEM TO BE SOLVED: To obtain the subject compound especially useful in the therapy of male erectile function insufficiency and having a purity sufficient for administration to man by subjecting a specific bisamide to a ring-closing reaction. SOLUTION: This method for producing sildenafil of formula II comprises subjecting a compound of formula I to a ring-closing reaction in the presence of a base and, if necessary, further in the presence of hydrogen peroxide or a peroxide salt preferably in a solvent and, if necessary, neutralizing the reaction mixture. The base is especially selected from sodium ethoxide, sodium t-butoxide, potassium t-butoxide and sodium hydride. The solvent is especially selected from ethanol, t-butanol, t-amylalcohol and tetrahydrofuran. The compound of formula I can be obtained by a conventional method using a compound of formula III as a starting substance. A process for purifying the objective compound can thereby be not necessitated.

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