A Facile Green Synthesis of 16-Dehydropregnenolone Acetate (16-DPA) From Diosgenin

Chromium and MnO₂ free green synthesis of industrially important steroidal drug intermediate 16-dehydropregnenolone acetate (16-DPA) starting from diosgenin is reported. The reaction sequence involves three steps – acetolysis followed by acetylation, oxidation, and hydrolysis. In the first step, Ac₂O was used both as reagent and solvent in combination with a Lewis acid (AlCl₃), which led to considerable reduction of high temperature and pressure requirements of earlier processes. The oxidation step was made catalytic with the use of KMnO₄(5 mol%) in presence of co-oxidant NaIO₄ leading to lowering of the waste generation (Chromium, MnO₂ etc.). Minimization of the temperature, pressure, time consumption, and use of nontoxic solvents makes the process very handy and simple.