Steroidal allylic and homoallylic rearrangements during halogenation with triphenylphosphine and carbon tetrachloride
Abstract
Treatment of 3β-hydroxyandrost-5-en-17-one with triphenylphosphine and carbon tetrachloride under various conditions affords 3α- and 3β-chloroandrost-5-en-17-one, 3α,5-cycloandrost-6-en-17-one, and minor amounts of 17-dichloromethylene derivatives. In contrast, 4β-acetoxy-3β-hydroxyandrost-5-en-17-one affords 4β-acetoxy-3α-chloro- and 3β-acetoxy-4α-chloro-androst-5-en-17-ones. 3β-Acetoxy-4β-hydroxyandrost-5-en-17-one affords 3β-acetoxyandrost-4,6-dien-17-one and minor amounts of the 3β-acetoxy-4α-chloro-5-ene and 3β-acetoxy-6α-chloro-4-ene.