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.