Hydroxy-steroids. Part X. The preparation and properties of A-homo-5α-cholestan-4-one

Abstract

The formation of A-homo-5α-cholestan-4-one from 5α-cholestan-3-one and diazomethane (N. A. Nelson and R. N. Schut, J. Amer. Chem. Soc., 1959, 81, 6486) was re-investigated. Using pre-formed diazomethane in ether–methanol the reaction was very slow. However, in the presence of potassium hydroxide ring expansion occurred smoothly to give a mixture from which the A-homo-4-ketone was readily isolated.

It was confirmed that base-catalysed condensations occur at position 3 of the A-homo-ketone. The 3-bromo-derivative is dehydrobrominated to a mixture of the non-conjugated and conjugated ketones A-homo-5α-cholest-1- and -2-en-4-one, the former of which is the more stable.