A Scalable Process to the Key Intermediate of Cilazapril, (S)‑1-Benzyloxycarbonylhexahydropyridazine-3-carboxylic Acid, Through a Novel Cascade Course

A novel and efficient manufacturing technology is disclosed in the present work for the preparation of (S)-1-benzyloxycarbonylhexahydropyridazine-3-carboxylic acid, which is a key intermediate of cilazapril. The whole process includes only three steps; the first two steps were conducted in one pot, followed by a novel selective removal of a Cbz group in a cascade course.