Cobalt-catalyzed one-step assembly of B-ring aromatic steroids from acyclic precursors

Because of their varied physiological activity, steroids are important testing grounds on which to explore the utility of novel synthetic methodology. In this study cobalt, in the form of CpCo(CO)/sub 2/ is used as a matrix around which to assemble natural and unnatural polycyclic products, including the steroid nucleus. In this way, the total synthesis of A-ring aromatic systems of the estrone type was achieved via the D ..-->.. ABCD and A ..-->.. ABCD strategies. An approach is reported here in which all four rings are assembled (0 ..-->.. ABCD) in one step to give B-ring aromatic derivatives with complete control of the crucial stereochemistry of the C,D-ring juncture. This strategy has been accomplished previously only by employing biomimetic cyclizations and not en route to the rate target class of compounds which has never been constructed by total synthesis. 13 references, 1 table.