REACTION OF STEROIDAL 17-ACETYLENIC ALCOHOLS WITH DIETHYLAMIDOSULFUR TRIFLUORIDE AND THE STRUCTURAL ASSIGNMENTS OF 17-FLUOROSTEROIDS

Reaction of diethylamidosulfur trifluoride (DAST) with C-17 tertiary a lcohols of A-ring-fused steroids, such as Danazol(1), did not furnish the stereochemically coveted C-17 beta-fluoro derivatives. The C-17 al pha-fluoro compounds were isolated as the predominant component of the reaction mixture along with the rearrangement and elimination product s. It is postulated that the attack of fluoride ion to the intermediar y carbonium ion occurs from the least hindered side of the steroid to provide only the a-fluoro derivatives. The formation of rearrangement and elimination products supports the proposed mechanism for the DAST reaction. Reaction products are definitively characterized by one- and two-dimensional (1D and 2D) NMR methods.