Scheme 2From: Identification, synthesis, and characterization of potential genotoxic impurities of sildenafil citrate drug substanceSynthetic scheme of sildenafil sulfonyl methyl ester 6. Reagents and conditions: (a) trimetyl orthoformate, methanol, and dichloromethane and (b) pyridine, methanol, and dichloromethaneBack to article page