Preparative chemical methods for aromatization of 19-nor-Δ4-3-oxosteroids

Article abstract of DOI:10.1016/0039-128X(94)90017-5

Two preparative chemical methods for aromatization of 19-nor-Δ⁴-3-oxosteroids are described.The first method consists of an oxidative aromatization of 19-nor-Δ⁴-3-oxosteroids with iodine-ceric ammonium nitrate in methanol to give a mixture of 3-methoxy ring-A aromatized derivatives consisting of the desired product, the Δ^9,11 derivative, the 6-oxo derivative as well as some ring-A iodinated material.Conversion of this material to a mixture of the 3-methoxy ring-A aromatized derivative and its 6-oxo derivative was achieved by catalytic hydrogenation.Finally, reduction of the 6-oxo function with triethylsilane in trifluoroacetic acid gave the 3-methoxy-17-trifluoroacetate ring-A aromatized derivative as a single product.In the second method, reaction of 19-nor-Δ⁴-3-oxosteroids with copper(II) bromide in acetonitrile at room temperature resulted in aromatic steroids in a single step in excellent yields.The second method was used in the first practical chemical synthesis of a 6-dehydroestrogen from a 19-nor-Δ^4,6-3-oxosteroid. - Keywords: copper(II) bromide; ceric ammonium nitrate; iodine; aromatization; 19-nor-Δ⁴-3-oxosteroids