The lability of 6-Bromo-Δ⁴-3-oxosteroids: Observations on the conversion of 6α- and 6β-Bromocholest-4-en-3-one to 5α-Cholestane-3,6-dione

Abstract

Cholesta-4,6-dien-3-one, cholest-4-ene-3,6-dione, 5α-cholestane-3,6-dione, cholest-4-en-6β-ol-3-one, cholest-4-en-2α-ol-3-one, cholest-4-en-4-ol-3-one, and cholesta-2,5-dien-3-ol-4-one, are formed in greater or lesser amounts during chromatography of 6α- and 6β-bromocholest-4-en-3-one over neutral or alkaline alumina. The conversion of 6α- and 6β-bromocholest-4-en-3-one to 5α-cholestane-3,6-dione by the action of methanolic hydrochloric acid has been examined. The use of concentrated hydrochloric acid in this reaction afforded 3,3-dimethoxy-5α-cholestan-6-one in good yield. Under similar conditions, the same ketal was also obtainable from 6β-methoxycholest-4-en-3-one, cholest-4-en-6β-ol-3-one, and 5α-cholestane-3,6-dione. The course of the reactions of the epimeric 6-bromocholest-4-en-3-ones with acidic ethanol, isopropanol, and t-butanol is discussed.