Sir: The steroid nucleus has been the target of numerous, often ingenious, synthetic schemes.] We recently reported the co- balt-catalyzed one-step synthesis of tricyclic ring systems B via cooligomerization of diynes A with bis(trimethylsily1) acetylene (BTMSA) in the presence of C ~ CO ( CO ) ~ ~ ... I). In this reaction five new carbon-carbon bonds are formed with control of stereochemistry to result in what one might envisage to constitute the ABC-ring portion ...
