Intramolecular michael additions in the pelletierine-benzaldehyde condensation 1

✍ Scribed by James Quick; Richard Oterson

• Book ID: 104243819
• Publisher: Elsevier Science
• Year: 1977
• Tongue: French
• Weight: 221 KB
• Volume: 18
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)92704-2

✦ Synopsis

All of the successful syntheses of the lythraceae alkaloids (e-g,, 1, vertaline)* have utilized the base catalyzed condensation of a substituted benzaldehyde with pelletierine (0 to form a quinolizidinone $,.3 Despite the demonstrated utility of this reaction, there has been only speculation as to its mechanism. 4 Hanaoka, c. al., have suggested the Mannich reaction outlined in Scheme 1 (path a) as the route for this condensation. Since the condensation occurs at high pH (> lo), the formation of the iminium ion appears unlikely. Direct nucleophilic displacements on the carbinolamine. $, or on the B-hvdrol(yketone, k, have also been suggested,4 but are unlikely because of the steric hindrance involved, and because the stereochemical predictions (initial formation of madduct) are not borne out experimentally (vida infra). We suggest an alternate pathway (b) which involves a base-catalyzed Claisen-Schmidt condensation followed by an intramolecular Michael addi-