Total Synthesis of (±)-Lennoxamine and (±)-Aphanorphine by Intramolecular Electrophilic Aromatic Substitution Reactions of 2-Amidoacroleins

Abstract

Intramolecular electrophilic aromatic substitution reactions of 2-amidoacroleins constitute the key steps in the total syntheses of lennoxamine and aphanorphine. The aldehyde moiety of one cyclization product was transformed to a double bond, which was then engaged in a radical cyclization to produce the complete ring system of lennoxamine. The aldehyde functionality of the other cyclization product was converted to the corresponding mesylate, which underwent intramolecular displacement by a lactam enolate to furnish the ring system of aphanorphine. [reaction: see text]