Eco-Sustainable Catalytic System for Green Oxidation of Spirostanic Alcohols Using Hypervalent Iodine (III) Tempo-4-n-Acetoxyamine System

Abstract

The oxidation of the 3β-hydroxy group in the steroidal substrates obtained from naturally occurring sources, i.e., solanaceae steroidal sapogenins, is an important process in the preparation of ecdysteroid analogs. The need for selective green oxidation methodologies for steroidal alcohols (spirostenols, diosgenine, and derivatives) avoid the use of toxic Cr (VI) derivatives, without the isomerization of the double bond at 5,6 position and also without the oxidative cleavage of the spirocetal moiety is of great methodological significance. Herein, we report the oxidation of spirostanic steroidal alcohols to their carbonyl analogs using hypervalent iodine (III)/TEMPO-4-N-acetoxyamine system. The present method is simple, eco-sustainable, efficient, and high-yielding process for the oxidative transformation of secondary steroidal alcohols without any over-oxidation, isomerization of the double bond, or oxidative cleavage of spirocetalic fragment in different substrates. Therefore, this method does not involve toxic heavy metals and is expected to have wide utility in the oxidation process of these compounds.