Thermal rearrangement and other reactions of 3β-acetoxy-5α-chlorocholestan-6β-yl nitrate

Abstract

The nitrate esters of steroid 5α,6β-chloro- or -bromo-hydrins can be prepared directly from the Δ⁵-compounds by reaction with chlorine or bromine nitrate–pyridine complexes. Pyrolysis of 3β-acetoxy-5α-chlorocholestan-6β-yl nitrate in chlorobenzene gives the rearranged compounds, 3β-acetoxy-5α-chloro-19-nitrocholestan-6β-ol, though in low yield. When pyridine or β-picoline is present, 6-ketone is the principal product, but addition of suitable one-electron oxidants such as cupric or ferric chloride or acetylacetonates, or iodine, results in the formation of 6β,19-epoxide. With the cuprous chloride–β-picoline complex the nitrate ester undergoes an induced decomposition yielding the 5α,6β-epoxide. Mechanisms for these reactions are considered.