The selective protection of the 3-ketone functions of steroids as heptafluoro-p-tolyl enol ethers

Abstract

Conjugated and unconjugated 3-ketone functions in steroids react with octafluorotoluene at above 100 °C in the presence of caesium fluoride to give heptafluoro-p-tolyl enol ethers. The related but unusually reactive Wieland–Miescher ketone (11) reacted at room temperature in the presence of tetra-n-butylammonium fluoride. Enones were regenerated from their derivatives by acidic hydrolysis. Hydrolysis of the derivative (10) of 4,5α-dihydrotestosterone was sluggish but sodium methoxide regenerated the parent steroid. The methods have been applied in a synthesis of deuterium-labelled testosterone.