Steroidal δ-Alkenyl Oximes as Ambident Nucleophiles: Electrophile- Induced Formation of Oxazepane Derivatives in the Bis-Estrone Series

Electrophile-induced cyclization of steroidal δ-alkenyl oximes and oxime ethers and subsequent hydride reduction of the cyclic nitrones led to new halogenated or selenylated N-hydroxy- or N-benzyloxy-aza-D-homo-estrones. Starting from a 13β-D-secoestrone oxime or oxime ether, steroidal dimers were isolated in intermolecular 1,3-dipolar cycloaddition of the cyclic nitrone to the C=N double bond of the oxazepine intermediates.