Scheme 4From: Identification, synthesis, and characterization of potential genotoxic impurities of sildenafil citrate drug substanceSynthetic scheme of sildenafil sulfonyl isopropyl ester 8. Reagents and conditions: (a) trimetyl orthoformate, isopropyl alcohol, and dichloromethane and (b) pyridine, isopropyl alcohol, and dichloromethaneBack to article page