Some alternative pathways leading to the aromatization of ring A of steroids

Abstract

In contrast to 3β,17β-diacetoxy-4,5-epoxyandrostanes, 3β,17β-diacetoxy-4,5-epoxyoestrane undergoes aromatization in hydrobromic acid–glacial acetic acid without the intervention of a spiro-intermediate. Under these conditions 3β,17β-diacetoxy-4α,5α-epoxy-2,2-dimethylandrostane gave a small amount of an aromatic steroid, possibly 17β-acetoxy-2,3,9-trimethyloestratriene, together with 17β-acetoxy-2,2-dimethylandrost-5-en-4-one and 17β-acetoxy-2,2-dimethylandrost-4-en-3-one. 3β,17β-Diacetoxy-4,5-epoxy-4-methylandrostanes gave 17β-acetoxy-1,4-dimethyloestratriene by a pathway involving a C-10 to C-1 methyl migration, together with 17β-acetoxy-4-methylandrost-4-en-3-one; 17β-acetoxy-3,4-dimethyloestratriene was a minor product.