Reactivity of Steroidal 1-Azadienes toward Carbonyl Compounds under Enamine Catalysis: Chiral Penta- and Hexacyclic Steroids

The synthesis and reactivity of a steroidal N-sulfonyl-1-azadiene, derived from 16-dehydropregnenolone acetate, toward carbonyl compounds under enamine catalysis is disclosed. An unexpected annulation reaction was observed involving an initial stereoselective conjugate addition of the in situ generated enamine to the steroidal 1-azadiene. The developed diastereoselective synthetic methodology is a novel approach to a new class of chiral pentacyclic and hexacyclic steroids.