Reaction of trimethylsilylimidazole with 5,10 beta-epoxy-3-ketosteroids: enolization and aromatization of the A-ring.

The reaction of trimethylsilylimidazole (TSIM) and 3-keto-5,10-epoxy-nor-19-methylandrostanone 3 and its 17-acetate analog 4 was examined at two different temperatures. In both compounds, reaction at 90 degrees C gave predominantly a delta 3-silyl-enol ether plus a minor product as a result of the epoxide ring opening. Under reflux conditions, besides the aforementioned products, aromatization of the A-ring was observed as a major process. The results suggest the potential use of silylation reactions with epoxyketones towards the synthesis of aromatic compounds.