Cleavage of steroidal α-hydroxy acetals with methylmagnesium iodide

Abstract

The four isomeric α-hydroxy acetals 17, 19, 21 and 22 undergo reaction with methylmagnesium iodide under forcing conditions to afford a variety of products, some arising by direct cleavage of the acetal ring, and some by processes which involve skeletal rearrangement with participation of the neighbouring hydroxy group. The structures of the products have been established and their mechanisms of formation are discussed.