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This paper describes the facile synthesis of sildenafil citrate (1) and its related compounds through an improved chlorosulfonation reaction using chlorosulfonic acid and thionyl chloride. This synthesis results in pure sildenafil with high yield. The structures of the compounds were determined with infrared (IR), 1H-NMR and 13C-NMR spectroscopic methods, and high resolution mass spectroscopy (HRMS) analysis.

Lisinopril is a drug of the angiotensin-converting enzyme (ACE) inhibitor class that is primarily used in the treatment of hypertension. During the scale-up of the lisinopril process, one unknown impurity was observed and is identified. The present work describes the origin, synthesis, characterization, and control of this impurity. This paper also describes the synthesis and characterization of three other impurities listed in the European Pharmacopoeia 8.4 (Impurity C, D, and F).

A simple, efficient and environmentally benign method for the three component, one-pot synthesis of spirooxindoles using ionic liquid tetrabutylammonium acetate as an inexpensive catalyst as well as reaction medium.