Reactions of 4beta,5-epoxy-5beta-androstan-3-ones with hydrogen fluoride in pyridine.

4beta,5-Epoxy-5beta-androstane-3,17-dione (1a), 17beta-hydroxy-4beta,5-epoxy-5beta-androstan-3-one (1b) and 17beta-acetoxy-4beta,5-epoxy-5beta-androstan-3-one (1c) were treated with anhydrous hydrogen fluoride in pyridine (70% solution) at 55 detrees and yielded the corresponding 4-en-4-ols, e.g. 4-hydroxy-4-androstene-3,17-dione (2a). As the reaction temperature was lowered each epoxide formed a second product which, at -75 degrees, was the major component of the reaction mixture and was identified as the 5alpha-fluoro-4alpha-ol derivative of the parent enone, e.g. 4alpha-hydroxy-5-fluoro-5alpha-androstane-3,17-dione (3a). These fluorohydrins are thermally unstable, losing hydrogen fluoride. The acetates of -he fluorohydrins were also prepared, characterized, and shown to be more stable than the parent alcohols.