STEROIDAL ALLYLIC FLUORINATION USING DIETHYLAMINOSULFUR TRIFLUORIDE -A CONVENIENT METHOD FOR THE SYNTHESIS OF 3-BETA-ACETOXY-7-ALPHA-FLUOROANDROST-5-EN-17-ONE AND 7-BETA-FLUOROANDROST-5-EN-17-ONE

This paper discusses our findings regarding fluorination of the diaste reomeric 3 beta-acetoxy-7-hydroxyandrost-5-en-17-ones (3 and 4) at the allylic 7-hydroxyl group using diethylaminosulfur trifluoride under v arious experimental conditions. The reaction led to the formation of a llylic 7 alpha- and 7 beta-fluoro derivatives, 6 and 7, contaminated w ith small amounts of 3 beta-acetoxy-5 alpha-fluoroandrost-6-en-17-one (8), the rearrangement product, and 3 beta-acetoxyandrosta-4,6-dien-17 -one (9), the elimination product. However, synthesis of 3 beta-acetox y-7 alpha-fluoroandrost-5-en-17-one (6) and 3 beta-acetoxy-7 beta-fluo roandrost-5-en-17-one (7) has been achieved in high isomeric purity by careful manipulation of the experimental conditions. Also included he rein is a convenient chemical synthesis of pure 3 beta-acetoxy-7 alpha -hydroxyandrost-5-en-17-one (4) and 3 beta-acetoxy-7 beta-hydroxyandro st-5-en-17-one (3), the starting materials for the present fluorinatio n reaction. The structure of a degradation product, 3 beta-acetoxy-5 a lpha-hydroxyandrost-6-en-17-one (5), has been established by X-ray dif fraction analysis to ascertain unambiguously its absolute configuratio n.